1. Read through the following passage on the structure of prokaryotic cells, then write on the dotted lines the most appropriate word or words to complete the account.

Bacteria, such as Escherichia coli, are prokaryotic organisms. One of the main

differences between prokaryotic cells and eukaryotic cells is that in a prokaryotic cell,

the bacterial chromosome is not surrounded by a ............................................. .

Prokaryotic cells store carbon compounds in the form of .............................................

and ................................................. and they may also contain one or more small circular

DNA molecules, known as ................................................ . E. coli cells are motile due

to the presence of a......................................................... .(Total 5 marks)

2. The photograph below shows a section through a mitochondrion as seen using an electron microscope.

A

C BProf. R. Bellairs/Wellcome Photo Library

(a) Name the parts labelled A, B and C.

A ................................................................................................................................

B ................................................................................................................................

C ................................................................................................................................(3)

1

(b) Describe the role of mitochondria.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................(2)

(Total 5 marks)

3. The diagram below shows the structure of a chromosome as it might appear at the end of prophase of mitosis.

AB

(a) Name the parts labelled A and B.

A .................................................................................................................................

B .................................................................................................................................(2)

(b) During metaphase of mitosis, the chromosomes become attached to the equator of the spindle. Name the stage of mitosis that follows metaphase and describe the events that occur in this stage.

Stage ...........................................................................................................................

Events occurring ........................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................(3)

2

(c) Explain the significance of the stage you have named and described in (b).

....................................................................................................................................

....................................................................................................................................(1)

(d) Mitosis forms part of the cell cycle. Name one other stage of the cell cycle and state what occurs in the stage that you have named.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................(2)

(Total 8 marks)

4. The table below refers to three organelles commonly found in eukaryotic cells. Complete the table by writing the name of the organelle, its description or one function, as appropriate, in each of the five boxes provided.

Name of organelle Description One function

Golgi apparatus

Cylindrical organellesmade up of microtubules

Involved in spindleOrganisation during celldivision in animal cells

Rod-shaped structureswith a double membrane,the inner one folded toform cristae

(Total 5 marks)

5. (a) The table below describes some of the key events that occur during mitosis Complete the table by writing the name of the stage of mitosis next to its description.

3

Key events Stage

Chromatids separate and move to opposite poles of the dividing cell.

Chromosomes shorten and thicken. The nuclear envelope breaks down and the spindle forms.

The spindle fibres break down, the nuclear membrane re-forms and the chromosomes elongate.

Chromosomes line up on the equator of the cell, attached to spindle fibres by their centromeres.

(4)

(b) The graph below illustrates the change in DNA content during the cell cycle

6

5

4

3

2

1

00 2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4 2 6

T im e / h o u rs

M a ss o f D N A /a rb itra ry u n its

C D

1G

A B

4

(i) Calculate the percentage of the cell cycle time spent in G1.

Answer...................................................................(3)

(ii) At which point, A, B, C or D, does chromosome replication (the S phase) begin? Explain your answer.

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(2)

(Total 9 marks)

5

6. The photomicrographs show a transverse section through a leaf of Ammophila, which is a xerophyte. The large photomicrograph shows details of the tissues inside the box.

Describe three ways in which this leaf is adapted to reduce water loss.

1............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

2............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

6

3............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................(Total 6 marks)

7. A freshwater stream was sampled over a distance of 4.0 km to determine the abundance of an aquatic invertebrate. The oxygen concentration of the water was measured over the same distance. The results are shown in the graphs below.

1 0 0

5 0

00 1 .0 2 .0 3 .0 4 .0

D is ta n ce / k m

N u m b er o f o rg an ism s fo u n dat eac h sam p lin g s ta tio n

0 1 .0 2 .0 3 .0 4 .0D is ta n ce / k m

O x y g en co n ce ntra tio n

(a) Name one aquatic invertebrate that might show this distribution along the stream.

.....................................................................................................................................

.....................................................................................................................................(1)

7

(b) Suggest two adaptations that would enable an invertebrate to thrive between 0.2 and 1.0 km along the stream. In each case state how the adaptation assists survival.

1...................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

2...................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(4)

(Total 5 marks)

8. The table below refers to features of prokaryotic and eukaryotic cells. If the feature is usually present, place a tick ( ) in the appropriate box and if the feature is absent, place a cross (X) in the appropriate box.

Feature Prokaryotic cell Eukaryotic cell

Cell surface membrane

Plasmids

Ribosomes

Mitochondria

(Total 4 marks)

8

9. The drawing below shows an animal cell, magnified × 1000, undergoing mitosis.

(a) Give two features that help to identify this as an animal cell.

1 .................................................................................................................................

2 .................................................................................................................................(2)

(b) Name the parts labelled A and B.

A ................................................................................................................................

B ................................................................................................................................(2)

(c) Name the stage of mitosis shown in the drawing.

....................................................................................................................................(1)

9

(d) Calculate the actual maximum diameter of this cell. Show your working.

Answer ...........................................................(2)

(Total 7 marks)

10. A procedure was carried out to separate the major organelles within liver cells. This involved breaking up (homogenising) liver tissue in an ice-cold salt solution which had the same water potential as the cell cytoplasm.

Ultracentrifugation was then used to separate the organelles. Ultracentrifugation is a process that separates materials of different densities by spinning them in a tube at different speeds. The denser materials are forced to the bottom of the tube as a pellet, while less dense materials remain nearer to the top of the tube in liquid known as the supernatant.

10

The flow chart below summarises the steps involved in this procedure.

L iv er tis su e b ro k en u pin ice -co ld sa lt so lu tion

C en trifu g ed a t lo w sp e ed fo r1 0 m in u tes

S u p e rn a tan t c en trifu g ed a t m ed iu msp ee d fo r 2 0 m in u te s

S u p ern a ta n t ce n tr ifu ge d a t h ig hsp ee d fo r 3 0 m in u te s

F in a l su p ern a ta n t

P e lle t A

P e lle t B

P elle t C

(a) Suggest why it was necessary for the salt solution to have the same water potential as the cell cytoplasm.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................(2)

11

(b) This procedure separated mitochondria, nuclei and ribosomes into the three pellets, A, B and C. Complete the table below to show which one of these organelles would be found in which pellet.

Pellet Organelle

A

B

C

(2)

(c) Suggest two components of the cell, other than water, that might be present in the final supernatant.

1 .................................................................................................................................

2 .................................................................................................................................(2)

(d) In the space below, draw and label a diagram to show the structure of a mitochondrion.

(4)

12

(e) Explain why large numbers of mitochondria are found in liver cells.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................(2)

(Total 12 marks)

11. The diagram below shows the structure of a bacterium, a typical prokaryotic cell.

A

B

C

(a) Name A, B and C as labelled on the diagram.

A ...............................................................................................................................

B ...............................................................................................................................

C ...............................................................................................................................(3)

13

(b) Complete the table below to show three differences between a prokaryotic cell and a eukaryotic cell.

Prokaryotic cell Eukaryotic cell

1

2

3

(3)(Total 6 marks)

12. The diagram below shows cells from a root tip, prepared by the root tip squash method.

14

(a) Describe how you would prepare a root tip squash so that mitosis can be studied.

………………………………………………………………………………………..

………………………………………………………………………………………..

………………………………………………………………………………………..

………………………………………………………………………………………..

………………………………………………………………………………………..

………………………………………………………………………………………..

………………………………………………………………………………………..

………………………………………………………………………………………..(4)

(b) State which of the cells labelled A–E is in:

(i) metaphase ...................

(ii) anaphase .....................(2)

(c) State two events that take place during interphase.

1. ……………………………………………………………………………………..

2. ……………………………………………………………………………………..(2)

(Total 8 marks)

15

13. The diagram below shows a germinating pollen grain as seen using a light microscope.

A

(a) Name the parts labelled A and B.

A ...............................................................................................................................

B ...............................................................................................................................(2)

(b) Describe the roles of the two male nuclei during fertilisation.

……………………………………………….……………………………………..

……………………………………………….……………………………………..

……………………………………………….……………………………………..

……………………………………………….……………………………………..

……………………………………………….……………………………………..

……………………………………………….……………………………………..

……………………………………………….……………………………………..

……………………………………………….……………………………………..(4)

16

(c) An investigation was carried out into the effect of sucrose concentration on the germination of pollen grains from two species of plants, Bauhinia purpurea and Camellia japonica. The results are shown in the graph below.

3 0

2 5

2 0

1 5

1 0

5

00 1 0 2 0 3 0 4 0

S uc ro se co n ce n tra tio n (% )

G e rm in a tio nra te (% )

B . p u rp u rea

C . ja p o n ica

Graph J. B. E. Summer 2001, p. 150

(i) What is the optimum concentration of sucrose for the germination of pollen grains from both species?

………..……………………………….………………………………………(1)

(ii) Compare the germination rate of these two species as the concentration of sucrose increases from 20%.

………..……………………………….………………………………………

………..……………………………….………………………………………

………..……………………………….………………………………………

………..……………………………….………………………………………

………..……………………………….………………………………………

………..……………………………….………………………………………(3)

(Total 10 marks)

17

14. The diagram below shows a midge larva, Chironomus. This is a species which is adapted to live in fresh water with a low concentration of dissolved oxygen.

1 c m

Describe two ways in which invertebrates such as Chironomus are adapted to live in water with a low concentration of dissolved oxygen.

..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................(Total 4 marks)

15. The diagram below shows part of a transverse section at high magnification through a seminiferous tubule in human testis.

18

(a) Identify cells B and C.

B .............................................................................................................................….

C .............................................................................................................................….(2)

(b) (i) Give the letter of one cell with the haploid (n) number of chromosomes.

…………………………………………………………………………………(1)

(ii) Explain how meiosis results in the production of haploid cells.

…………………………………………………………………………………

…………………………………………………………………………………

…………………………………………………………………………………

…………………………………………………………………………………

…………………………………………………………………………………

…………………………………………………………………………………

…………………………………………………………………………………

…………………………………………………………………………………(4)

(c) Give two features of a spermatozoon that enable it to carry out fertilisation. Explain in each case how these features assist in fertilisation.

………………………………………………………………………………………..

………………………………………………………………………………………..

………………………………………………………………………………………..

………………………………………………………………………………………..(2)

(Total 9 marks)

19

16. Some bacteria were grown in a culture with radioactive amino acids. They used the labelled amino acids to synthesise proteins which were incorporated into their cells.

The bacteria were then washed thoroughly and mixed with some white blood cells. The amount of radioactivity taken up by the white blood cells was measured at intervals of two hours for 24 hours.

The white blood cells were phagocytic and engulfed (took up) the bacteria by a process called phagocytosis. Phagocytosis is a form of endocytosis. This process is illustrated in the diagram below.

B ac te riu mM em b ra n e e x te n s io n s P h ag o so m e

(p h ag o cy tic v a cu o le)

W hite b lo o d ce ll

N u cle us

Lysosomes then fuse with the phagosome and release their contents into it.

The table below shows the level of radioactivity found inside and outside the white blood cells during the 24 hour period.

Time after mixing cells together/hours

Radioactivity inside white blood cells/arbitrary units

Radioactivity outside white blood cells/arbitrary units

024681012141618202224

01648617072727143211085

80643219108893759707275

(a) (i) Describe the structure of a lysosome.

20

………………………………….…….………………………………………

………………………………….…….………………………………………

………………………………….…….………………………………………

………………………………….…….………………………………………(2)

(ii) Describe the roles of lysosomes.

………………………………….…….………………………………………

………………………………….…….………………………………………

………………………………….…….………………………………………

………………………………….…….………………………………………(2)

(b) Describe the changes in the level of radioactivity found inside the white blood cells during the period of 24 hours.

……………………………………………….………………………………………

……………………………………………….………………………………………

……………………………………………….………………………………………

……………………………………………….………………………………………

……………………………………………….………………………………………

……………………………………………….………………………………………(3)

(c) Suggest what is happening to the bacteria inside the phagosomes between 10 and14 hours.

……………………………………………….………………………………………

……………………………………………….………………………………………

21

(d) Explain why the amount of radioactivity increases outside the white blood cells after 14 hours.

……………………………………………….………………………………………

……………………………………………….………………………………………

……………………………………………….………………………………………

……………………………………………….………………………………………(2)

(e) Suggest why the white blood cells did not take up all the radioactivity.

……………………………………………….………………………………………

……………………………………………….………………………………………(1)

(Total 11 marks)

17. Give an account of the process of meiosis and its significance in the production of gametes in humans.

(Allow three lined pages)(Total 10 marks)

22

18. (a) The flow diagram below shows the sequence in spermatogenesis leading to the formation of spermatozoa.

C ell A

P rim a ry sp erm a to c yte

S ec on d a ry sp erm ato cy te

S pe rm atid

S pe rm ato zo o n

(i) Name cell A.

……….……………………………….………………………………………(1)

(ii) On the flow diagram, write the letter M to indicate where the second division of meiosis occurs.

(1)

(b) The diagram below shows the structure of a spermatozoon.

23

Name the parts labelled A, B and C.

A …………………………………………….………………………………………

B …………………………………………….………………………………………

C …………………………………………….………………………………………(2)

(c) Describe how the spermatozoa are transferred into the female.

……………………………………………….………………………………………

……………………………………………….………………………………………

……………………………………………….………………………………………

……………………………………………….………………………………………

……………………………………………….………………………………………

……………………………………………….………………………………………

……………………………………………….………………………………………

……………………………………………….………………………………………

……………………………………………….………………………………………

……………………………………………….………………………………………(5)

(Total 9 marks)

24

19. The flow chart below shows the sequence in which some cells are formed during spermatogenesis in the mammalian testes.

S p erm a to g o n iu m

C ell A

S eco n d a ry sp erm a to c y te

C ell B

S p e rm ato zo o n

(a) State the part of the testis where spermatogenesis occurs.

................................................................................................................................(1)

(b) Name cells A and B.

Cell A .....................................................................................................................

Cell B .....................................................................................................................(2)

(c) Explain the importance of meiosis in the formation of spermatozoa.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(3)

(Total 6 marks)

25

20. The diagrams below show two invertebrates found in freshwater habitats. Rat-tailed maggots are found in stagnant or slow moving water. Stonefly nymphs live in fast flowing streams.

1 cm

R at-ta ile d m ag g o t 1 cm

S to n efly n y m p h

(a) Suggest how rat-tailed maggots are adapted to their habitat.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(4)

26

(b) Suggest what adaptations stonefly nymphs might have for living in fast flowing water.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(2)

(Total 6 marks)

21. Distinguish between each of the following pairs of terms.

Tissues and organs

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(Total 2 marks)

27

22. The diagrams below show four stages of mitosis.

A

C

B

D

(a) (i) Write the letters of the stages in the sequence in which they occur during mitosis.

........... .......... .......... ...........(1)

(ii) Name stage D.

.................................................................................................................................(1)

28

(b) The graph below shows how the quantity of DNA varies with time in a cell cycle.

4

3

2

1

00 5 1 0 1 5 2 0 2 5

Tim e /h o u rs

Q u an tity o f D N A/ a rb itra ry u n its

(i) Explain the changes in the quantity of DNA that take place:

between 10 to 15 hours

.....................................................................................................................................

.....................................................................................................................................

at 20 hours

.....................................................................................................................................

.....................................................................................................................................(2)

29

(ii) What is happening- in the cell between 15 and 20 hours?

.....................................................................................................................................

.....................................................................................................................................(1)

(iii) What is the minimum length of time that interphase would occupy in this cell cycle?

.....................................................................................................................................(1)

(Total 6 marks)

30

23. The photograph below-shows part of an animal cell, as seen using an electron microscope. The magnification is ×5000.

(a) Name the structures labelled A and B.

A............................................................................................................................................

B............................................................................................................................................(2)

31

(b) Calculate the actual length of the structure labelled B in m. Show your working.

Actual length of B .................. m(3)

(c) Describe how proteins synthesised on the rough endoplasmic reticulum are processed and transported out of the cell.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(5)

(Total 10 marks)

24. (a) The diagram below shows a stage in the division of a cell taken from the testis of an animal. The diploid number of chromosomes of the animal is 4.

32

Identify the stage of meiosis shown in the diagram.

...............................................................................................................................................(2)

33

(b) The life cycle of a human can be represented by the diagram below.

S p e rm

O v u m

A d u lt Z y g o te

E m b ry o

The diploid number of chromosomes in a human cell is 46.

State the number of chromosomes present in each of the following.

(i) Sperm ………...........................................................................................................

(ii) Zygote ……..............................................................................................................

(iii) A cell in the embryo …..…......................................................................................(3)

34

(c) Describe spermatogenesis in humans.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(5)

(Total 10 marks)

35

25. The photograph below shows a group of cacti, plants which are adapted to living in hot deserts.

Suggest how each of the following features helps a cactus to survive in desert conditions.

(a) A shallow, extensive root system.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

36

(b) Fleshy stems, containing large, thin-walled cells.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

(c) Leaves reduced to spines.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

(Total 7 marks)

37

26. The siting of a new sewage treatment works and the discharge of its effluent need careful consideration in order to minimise ecological damage. Figure 1 shows two possible sites for a new sewage works near to the coast in North Devon.

Figure 1 – Plan of proposed sites for sewage treatment works, undergroundpipelines and marine discharge pipelines

Site 2 p = field Site 1 a = fieldq = field b = conservation arear = fields = cliff grasslandt = rocky shore

This development would involve the permanent siting of the buildings for the main sewage treatment plant, an underground pipeline and a marine discharge pipe. A strip of land 10 metres wide would need to be removed during the laying of the underground pipeline. The land would be returned to its previous condition after the work is completed.

An ecological assessment must be carried out before any development can go ahead. The assessment compares the possible effects of the development on the terrestrial areas of the two sites. The first stage is to assign each area to a particular ecological category, using the criteria in Figure 2.

Figure 2 – Criteria for assigning ecological categories to an area

Criteria

38

Very high species diversity and highest number of different habitats or rare habitats

———►

Very low species diversity and lowest number of different habitats or rare habitats

Ecological category

5 ———► 1

The second stage is to calculate the impact of the proposed development within each area using the following formula:

area (m2) × ecological category = units of damage

Finally, consideration is given to whether the damage is reversible or irreversible. Figure 3 shows the results of this ecological assessment survey for Site 1 and Site 2.

Figure 3 – A comparison of the results of the ecological assessment survey for Site 1 and Site 2

Site 1

Area Type ofdevelopment

Area/m2 Ecologicalcategory

Units ofdamage

Reversibledamage

Irreversibledamage

a Building 10 500 2 21 000 – 21 000

b* Pipeline 150 000 5 750 000 750 000 –

Totals 771 000 750 000 21 000

Site 2

Area Type ofdevelopment

Area/m2 Ecologicalcategory

Units ofdamage

Reversibledamage

Irreversibledamage

p Building 21 000 2

q* Pipeline 2 500 1

r* Pipeline 3 000 1

s* Pipeline 500 5

t* Pipeline 2 000 5 10 000

Totals

* involves laying of underground pipeline only.

Data adapted from JBE Vol 32 Number 2 Summer 1998

39

(a) Suggest why some damage is considered to be reversible and some damage is considered to be irreversible.

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................(2)

(b) Complete the data for Site 2 in Figure 3.(3)

(c) Using the data in Figure 3, compare the ecological effect that the development of the sewage treatment works would have at Site 1 and Site 2.

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................(3)

(d) State what is meant by species diversity.

............................................................................................................................................

............................................................................................................................................(1)

40

(e) The ecological impact on the marine environment also needs to be considered. Using information from Figure 1, suggest three factors affecting the marine environment that should be considered when comparing Site 1 with Site 2.

1 ………………………………………………………………………………………...

2 ………………………………………………………………………………………...

3 ………………………………………………………………………………………...(3)

(f) Suggest why an accidental discharge of raw sewage from the treatment works might lead to an increase in the numbers of carnivorous fish around the discharge pipe.

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................(4)

(Total 16 marks)

41

27. The electronmicrograph below shows part of a cell.

(a) (i) Give one piece of evidence that this is a eukaryotic cell.

...........................................................................................................................

...........................................................................................................................(1)

(ii) Name one type of organism that is a prokaryotic cell.

...........................................................................................................................(1)

(b) (i) Name the structure labelled A.

...........................................................................................................................(1)

(ii) State the function of the structure labelled A.

...........................................................................................................................

...........................................................................................................................(1)

42

(c) Name the parts of the mitochondrion labelled B and C.

B ..................................................................................................................................

C ..................................................................................................................................(2)

(Total 6 marks)

28. (a) Describe two features of a human sperm cell and explain how they allow it to carry out Leave its role in fertilisation. blank

Feature 1 ......................................................................................................................

.....................................................................................................................................

Explanation..................................................................................................................

.....................................................................................................................................

Feature 2 ......................................................................................................................

.....................................................................................................................................

Explanation..................................................................................................................

.....................................................................................................................................(4)

(b) Name the type of nuclear division by which sperm cells are produced, and which introduces variation through random assortment.

.....................................................................................................................................(1)

43

(c) In his lifetime a man produces many millions of sperm cells and yet he is most unlikely to have more than ten children. Suggest a biological advantage of producing such vast numbers of sperms.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 7 marks)

29. Plant cells have a cell wall made of cellulose, whereas animal cells do not have a cell wall.

(a) State three other structural features found in plant cells but not in animal cells.

1 ..................................................................................................................................

.....................................................................................................................................

2 ..................................................................................................................................

.....................................................................................................................................

3 ..................................................................................................................................

.....................................................................................................................................(3)

44

(b) The photograph below shows a transverse section through the stem of a stinging nettle (Urtica dioica), as seen through a light microscope. Diagrams P and Q show some cells from two regions of the section.

Alfred Pasieka /Science Photo Library

(i) Name the type of cell found at P and at Q.

P ........................................................................................................................

Q ........................................................................................................................(2)

45

(ii) Explain how the structure of the cell walls found at P and Q provides the strength to help support the whole plant.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(3)

(c) Stinging nettles can be grown on land unsuitable for crops.

(i) Suggest one possible use of harvested nettle stems.

...........................................................................................................................(1)

(ii) Explain how crops of nettles could be used as a sustainable resource.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(Total 11 marks)

46

30. The following table refers to organelles found in eukaryotic cells. Complete the table by writing the name of the organelle, two features of its structure or one function of the organelle in each of the four empty boxes as appropriate.

Name of organelle Two features of structure One function

1. Stack of curved cisternae

2. Surrounded by many vesicles

Modificationof proteins

Rough endoplasmicreticulum

1.

2.

Chloroplast

1.

2.

Site ofphotosynthesis

(Total 6 marks)

47

31. The flow diagram below shows a method for preparing and staining cells in order to study stages of mitosis.

Trea t p lan t m a te ria l w ith h y d ro ch lo ric ac id

P lace in s ta in an d w arm

B reak o p en p lan t m a te ria l

M o u n t o n s lid e

S q u ash g en tly

(a) Name a suitable part of a plant to use, giving a reason for your choice.

……………………………………………………………………………………………

……………………………………………………………………………………………

……………………………………………………………………………………………(2)

(b) (i) Explain why staining is necessary in this preparation.

………………………………………………………………………………………

………………………………………………………………………………………(1)

(ii) Name a suitable stain for this technique.

.....................................................................................................................................(1)

48

(c) Explain why it is necessary to squash the preparation.

……………………………………………………………………………………………

……………………………………………………………………………………………(1)

(Total 5 marks)

32. The table below refers to some features of prokaryotic and eukaryotic cells.

Complete the table by writing a tick if the feature is present or a cross if the feature is absent. Do not leave any boxes empty. The first line has been done for you.

Prokaryotic cell Eukaryotic cell

Ribosomes present

Cell diameter usually more than 20 m

Cells may contain plasmids

DNA combined with protein into chromosomes

Nuclear membranes present

Cell wall always present

(Total 5 marks)

49

33. Read through the following account relating to some carbohydrates in plants, then write on the dotted lines the most appropriate word or words to complete the account.

Starch is made from the monosaccharide ....................................... whereas cellulose is

made from the monosaccharide ....................................... . Polysaccharides are formed

when ....................................... monosaccharides join together using .......................................

bonds.

Starch is ....................................... in water and can therefore be used to store

....................................... . Cellulose molecules are held together in parallel groups by

....................................... bonds.(Total 7 marks)

34. (a) Describe how the structure of a xylem vessel helps it to carry out the function of water transport in plants.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

50

(b) Explain how water moves through xylem vessels in the transpiration stream.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(4)

51

(c) Mineral ions are carried in the transpiration stream. State the importance of each of the following ions for plant growth.

(i) Calcium ions

...........................................................................................................................

...........................................................................................................................

(ii) Magnesium ions

...........................................................................................................................

...........................................................................................................................

(iii) Nitrate ions

...........................................................................................................................

...........................................................................................................................(3)

(Total 9 marks)

52

35. (a) The diagram below shows the results of two different types of cell division, A and B, in an animal cell with six chromosomes.

A

B

A n im a lce ll

N ew sk ince ll

G am e te

Name the types of cell division indicated by A and B.

A ..................................................................................................................................

B ..................................................................................................................................(2)

(b) The diagram below shows the fusion of two gametes.

G am ete

G am ete

(i) Name the process by which gametes fuse.

...........................................................................................................................(1)

(ii) Name the type of cell formed by this process.

53

...........................................................................................................................(1)

(c) The diagram below shows a sperm cell.

X Y Z

Name the organelles labelled X, Y, and Z.

X ..................................................................................................................................

Y ..................................................................................................................................

Z ..................................................................................................................................(3)

(Total 7 marks)

36. Garlic is known to contain an antibacterial substance called allicin.

(a) Suggest an advantage to a plant in producing antibacterial substances in its cells.

.....................................................................................................................................

.....................................................................................................................................(1)

54

(b) The presence of antibacterial substances in garlic can be demonstrated by grinding garlic in ethanol to produce an extract. A sample of this extract is then applied to a small disc of filter paper.

(i) Describe how you would demonstrate that this disc contained an antibacterial substance.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(4)

(ii) A newly discovered rainforest plant is thought to contain a powerful antibacterial substance. Explain how you would compare the effectiveness of this new substance with allicin in garlic.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(3)

55

(c) Suggest how this newly discovered plant substance might have a useful application which does not involve genetic modification.

.....................................................................................................................................

.....................................................................................................................................(1)

(Total 9 marks)

56

37. One of the roles of zoos is to conserve endangered animals. For example, some populations of tigers are under threat of extinction and a group of zoos in the USA is developing breeding programmes to maintain the species.

Renee Lynn/Science Photo Library

These zoos have an overall population of around 150 tigers, and the animals are regularly moved between zoos for breeding. It is estimated that one new pair of tigers will need to be introduced to the programme every seven years in order to maintain 90% of the genetic diversity of the tiger population in these zoos.

57

(a) Suggest two factors which might lead to the extinction of tigers in the wild.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(b) Suggest why it is necessary to introduce new tigers to the breeding programme.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(c) Explain the importance of maintaining at least 90% of the genetic diversity in the zoo population for the successful reintroduction of tigers into the wild.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(4)

(Total 9 marks)

58

38. Read through the following account of mitosis in an animal cell, then write on the dotted lines the most appropriate word or words to complete the account.

During prophase, the ................................................ breaks down and the

................................................ migrate to opposite poles of the cell.

During ................................................, the chromosomes are visible as pairs of

chromatids, lined up along the equator of the cell. Spindle fibres extend from the poles

of the cell and attach to the ................................................ .

In ................................................, the spindle fibres contract, pulling the chromatids

apart.(Total 5 marks)

39. The diagram below shows the structure of a bacterial cell as seen using an electronmicroscope.

C ell w a ll S to rag e g ran u le B

A

X Y

(a) (i) Name the parts labelled A and B.

A ............................................................................................................................

B ............................................................................................................................(2)

59

(ii) Name the carbohydrate present in the storage granules.

...............................................................................................................................(1)

(iii) Describe how the cell wall in this bacterial cell differs from that in a plant cell.

...............................................................................................................................

...............................................................................................................................(1)

(b) The diagram has been magnified 6000 times. Calculate the actual length of thebacterial cell between X and Y. Show your working, and give your answer inmicrometres.

Answer ............................. µm(3)

(Total 7 marks)

40. Eukaryotic cells contain organelles, many of which are bound by a membrane. Some organelles have a double membrane, often called an envelope.

(a) (i) Describe two structural differences between the double membrane surrounding a mitochondrion and the double membrane surrounding a nucleus.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(2)

60

(ii) Name one other organelle that has a double membrane.

................................................................................................................................(1)

(b) Centrioles are an example of organelles that are not membrane-bound. Describe the structure and function of centrioles.

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................(3)

(Total 6 marks)

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41. The diagram below shows the sequence of stages in meiosis.

Te lo p h ase II

A n ap h ase II

M e tap h ase II

P ro p h ase II

Te lo p h ase I

A n ap h ase I

M e tap h ase I

P ro p h ase I

(a) Describe what is happening to the chromosomes during the following stages.

(i) Prophase I

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(2)

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(ii) Metaphase I

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(2)

(iii) Anaphase II

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(2)

(b) Meiosis in humans results in the production of gametes. Name the type of cell produced by each of the following stages.

(i) Meiosis I in oogenesis.

................................................................................................................................(1)

(ii) Meiosis I in spermatogenesis.

................................................................................................................................(1)

(Total 8 marks)

63

42. The photograph below shows a transverse section through part of a leaf of Nymphaea, as seen using a light microscope. Nymphaea is a hydrophyte (a plant which lives in water).The upper epidermis and air spaces are labelled.

(a) Suggest one function of the tissue labelled A, giving an explanation for your answer.

Function ........................................................................................................................

Explanation ...................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................(3)

(b) Suggest two functions of the large air spaces in this leaf.

1 ...................................................................................................................................

......................................................................................................................................

2 ...................................................................................................................................

......................................................................................................................................(2)

64

(c) Suggest why stomata are found only in the upper epidermis of this leaf.

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................(2)

(Total 7 marks)

43. The biodiversity of tropical rainforests in the Central American country of Honduras is being investigated, and changes in the use of land are being recorded.

(a) Explain what is meant by biodiversity.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(b) Describe two ways in which a taxonomy of living organisms is of benefit to the process of measuring biodiversity.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

65

(c) The table below gives estimates of the total rainforest cover in Honduras over a period of eight years.

Year Area of cover / km2

1992

1994

1996

1998

2000

56250

55660

55080

54480

53820

Calculate the percentage change in forest cover between 1992 and 2000. Show your working.

Answer ............................(2)

66

(d) Lack of adequate regulations in Honduras has encouraged traditional slash-and-burn farming, extensive grazing, forest fires and illegal clearance of the rainforest.Suggest reasons why the government of Honduras might not want to introduce regulations for the control of changes in land use, and suggest reasons why conserving the rainforests should be encouraged.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(5)

(Total 11 marks)

44. Agrostis tenuis is a grass that grows near old copper mines in North Wales. Copper is usually very toxic to plants, but some Agrostis plants can tolerate copper in the soil and grow on the waste tips from the copper mines.

(a) Suggest a method for measuring tolerance to copper in a sample of Agrostis plants.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

67

(b) Agrostis plants were sampled from three sites close to a copper mine. Site B was on the waste tip from the mine, Site Awas up-wind of the tip and Site C was down-wind, as shown below. The tolerance to copper of each of the samples was measured and the results are shown in the graph below.

M ain w in d d irec tio n

H ig h

To le ran cetoC o p p er

L o w

S ite A S ite B S ite C

S ite A S ite B S ite C

U p -w in d s iteN o co p p e r p re sen t in so il

C o p p e r m in e w as te tipC o p p e r p re sen t in so il

D o w n -w in d s iteN o co p p e r p re sen t in so il

Suggest an explanation for the difference in tolerance between plants in the up-wind site (A) and plants in the down-wind site (C).

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

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(c) Samples of tolerant and non-tolerant plants were grown in three trays of soil that contained no copper. Tray 1 contained only tolerant plants, Tray 3 contained only non-tolerant plants and Tray 2 had a mixture of equal numbers of both types. The total dry mass of the plants in each tray was measured. The arrangement of the plants and the results are summarised below.

Tra y 1A ll to le ran t p lan ts

Tra y 2M ix ed to le ran t an dn o n -to le ran t p lan ts

Tra y 3A ll n o n -to le ran t

p lan ts

Total dry massof tolerant plants 46 g 12 g ___

Total dry massof non-tolerant ___ 30 g 47 gplants

Suggest an explanation for the results obtained in Tray 2.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(4)

(d) Suggest and explain how the abundance of copper-tolerant Agrostis plants would be likely to change if the copper were removed from the soil on the mine waste tip (Site B).

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

69

(Total 11 marks)

45. The diagrams below show the structures of a leaf palisade cell and a bacterial cell, as seenusing an electron microscope.

Leaf palisade cell Bacterial cell(Magnification × 100000) (Magnification × 18000)

(a) Name the parts labelled A, B and C.

A ...................................................................................................................................

B ...................................................................................................................................

C ...................................................................................................................................(3)

(b) Give one difference between the cell wall of a leaf palisade cell and the cell wall of a bacterial cell.

......................................................................................................................................

......................................................................................................................................(1)

(c) Describe the function of part D.

......................................................................................................................................

70

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................(2)

(Total 6 marks)

46. An investigation was performed to determine the length of time that a cell in an onion root tip spends in each stage of mitosis.

A growing root from an onion was selected and a root tip squash was made. This was examined under a light microscope and the percentage of cells in each stage of mitosis was determined.

The results are shown in the table below.

Stage of mitosisPercentage of cells in this

stage

Prophase 2.43

Metaphase 1.40

Anaphase 0.70

Telophase 2.78

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(a) Describe how you would prepare a root tip squash so that mitosis could be studied.

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................(4)

(b) The percentage of cells in a stage of mitosis is proportional to the duration of that stage. Use this information to compare the duration of each stage of mitosis in these root tip cells.

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................(3)

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(c) The duration of each stage of mitosis can be calculated using the equation below.

Duration of a stage = 100

timecycle cell stagein that cells of Percentage

The cell cycle time for these cells is 1200 minutes.Describe how you would use this data to determine the total duration of mitosis.

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................(2)

(Total 9 marks)

47. (a) Draw and label a diagram to show the structure of the Golgi apparatus as seen using an electron microscope.

(3)

73

(b) The process of protein synthesis in cells and the secretion of proteins from the cells was investigated using radioactively labelled amino acids.

The cells were incubated with radioactive amino acids for 30 minutes. The cells were then removed and washed thoroughly to remove any radioactive amino acids on the cell surfaces.

The washed cells were then incubated with non-radioactive amino acids for 120 minutes. Every 20 minutes a sample of cells was removed and the level of radioactivity in the rough endoplasmic reticulum and in the secretory vesicles was determined.

The graph below shows the levels of radioactivity in the rough endoplasmic reticulum and the secretory vesicles.

8 0

7 0

6 0

5 0

4 0

3 0

2 0

1 0

00 2 0 4 0 6 0 8 0 1 0 0 1 2 0

In cu b a tio n tim e / m in

L ev e l o frad io ac tiv ity/ a rb itra ryu n its

S ec re to ryv esic le s

R o u g hen d o p la sm icre ticu lu m

(i) Describe and explain the changes in the level of radioactivity in the rough endoplasmic reticulum during the first 40 minutes of the incubation period.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(2)

(ii) Explain the shape of the curve for the secretory vesicles between 0 and 40 minutes.

74

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(3)

(Total 8 marks)

48. The diagram below shows a stage in the division of a cell from the male part of a flower.The diploid number of chromosomes for this plant is 14.

(a) State the exact location of such a cell in the male part of a flower.

......................................................................................................................................(1)

75

(b) Identify the stage of meiosis shown in the diagram.

......................................................................................................................................(2)

(c) Fertilisation in a plant involves different types of cells and nuclei.State the number of chromosomes present in each of the following in this plant.

A pollen tube nucleus ..........................

A female gamete (egg cell) .................

A zygote nucleus .................................

An endosperm cell ...............................(4)

(Total 7 marks)

49. (a) The diagram below shows some of the stages during the development of a human ovum.

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(i) On the diagram, write the letter M to show when the first division of meiosis is complete.

(1)

(ii) Name structure Q, shown in the diagram.

...............................................................................................................................(1)

(iii) After ovulation, structure Q develops to form a corpus luteum. Name two hormones that are secreted by the corpus luteum.

1 .............................................................................................................................

2 .............................................................................................................................(2)

(b) Describe the process of fertilisation in humans.

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................(3)

(Total 7 marks)

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50. Cell A in the diagram below has two pairs of chromosomes. Cell B is one of four cells that were produced from cell A by cell division.

(a) State the type of cell division which has occurred to produce cell B, and give a reason for your answer.

Type of cell division .....................................................................................................

Reason ..........................................................................................................................

......................................................................................................................................(2)

(b) Explain what happened during this cell division which resulted in the different appearance of chromosome P.

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................(3)

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(c) Give the exact location in a human male where this type of cell division occurs.

......................................................................................................................................(1)

(Total 6 marks)

51. Write an essay on the following topic:

The uptake, transport and roles of mineral ions in flowering plants.

Marks will be awarded for scientific content, coverage of the topic, and the quality of written communication. You should include in your answers any relevant information from the whole of your course. You may include diagrams if you wish, but make sure that they are relevant to your essay and add extra information to it.

(Total 15 marks)

52. The table below lists some features of a typical plant cell and a typical animal cell.

Complete the table with a tick ( ) if you would expect the feature to be usually present or a cross ( ) if you would expect it to be absent.Do not leave any boxes empty.The first line has been done for you.

Typical plant cell Typical animal cell

Cellulose cell wall

Chloroplasts

Cell membrane

Large central vacuole

Chromosomes

Centrioles

Cytoplasm

Stored starch

(Total 7 marks)

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53. The diagrams below show cells from a garlic plant at five different stages of mitosis as seen using a light microscope. These stages are in the wrong order.

A B C D E

(a) Give the correct order in which the five stages take place by using the letters A–E.

1st stage ............ 2nd stage ............ 3rd stage ............

4th stage ............ 5th stage ............(2)

(b) (i) Name the part of a garlic plant which is used to prepare a slide showing the stages of mitosis.

...........................................................................................................................(1)

(ii) Name a stain which is used to make the chromosomes easy to see.

...........................................................................................................................(1)

(c) Name the process which must occur in the genetic material before the chromosomes become visible.

(i) Name of the process .........................................................................................(1)

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(ii) State what happens to the genetic material during this process.

...........................................................................................................................

...........................................................................................................................(1)

(Total 6 marks)

54. Complete the following by filling in the spaces with the most appropriate word or words.

Plant cell walls are largely made up of cellulose. Cellulose molecules consist of

.................................... molecules joined together in very long chains. These

cellulose molecules lie parallel, bound together by .................................... bonds

making up ..................................... A xylem vessel is a tube which forms when a

long row of cells dies and the end walls of the cells break down. As well as

containing cellulose the walls of xylem vessels contain lignin, which makes them

.................................... and .....................................(Total 5 marks)

55. The diagrams below show some cells in different stages of mitosis.

A

B

C

D

81

(a) Name the stages of mitosis shown by the cells labelled A, B and C.

A .................................................................................................................................

B .................................................................................................................................

C .................................................................................................................................(3)

(b) Describe the events that occur in the stage of mitosis shown by cell D.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(c) Explain the significance of the stage shown by cell D.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(1)

(Total 6 marks)

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56. The table below refers to the first and second divisions of meiosis.

If the statement is correct, place a tick ( ) in the appropriate box and if the statement is incorrect, place a cross ( ) in the appropriate box.

Statement First division ofmeiosis

Second division of meiosis

Pairing of homologous chromosomes occurs.

Each chromosome consists of a pair of chromatids during prophase.

Crossing over occurs and chiasmata are formed.

Independent assortment of chromosomes occurs.

(Total 4 marks)

57. The diagram below shows a mayfly nymph, an invertebrate which lives in freshwater streams.

83

(a) Give two features, visible in the diagram, which show how mayfly nymphs are adapted for living in an aquatic habitat. In each case, explain how the feature helps the mayfly nymphs to live in water.

1 ..................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

2 ..................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(4)

(b) Freshwater streams may be polluted with organic effluents. One of the effects of an organic effluent is to reduce the concentration of dissolved oxygen in the water. The graph below shows the distribution of larvae of Chironomus, a freshwater invertebrate, at increasing distances downstream from the source of an organic effluent.

N u m b ers o f

la rv a eC h iro n o m u s

D istan ce d o w n stre am fro m e fflu en t

P o in t a t w h ic h e ff lu en te n te rs th e s tre am

84

(i) Suggest and explain two ways in which Chironomus larvae could be adapted to living in water with a low concentration of dissolved oxygen.

1 ........................................................................................................................

...........................................................................................................................

...........................................................................................................................

2 ........................................................................................................................

...........................................................................................................................

...........................................................................................................................(4)

(ii) Immediately after the point at which the effluent enters the stream, numbers of Chironomus larvae decrease and then increase.

Suggest an explanation for this increase in the numbers of Chironomus larvae.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(Total 10 marks)

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58. Although zoos have changed considerably since London Zoo first showed imported animals to the public, their role in animal conservation is criticised by some.

(a) Describe two activities of zoos which can be used to justify keeping animals in captivity.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(4)

(b) The small numbers of animals typically found in zoos can be a problem for maintaining populations of healthy captive animals over several generations.Describe and explain steps taken to avoid such problems.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 6 marks)

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59. In the space below, draw a diagram to show the structure of the bacterium Escherichia coli. On your diagram label three structures not found in a liver cell.

(Total 4 marks)

60. The photograph below shows a chloroplast as seen using an electron microscope. It has been magnified 5000 times.

Magnification × 5000

(a) Name the parts labelled A, B and C.

87

A ..................................................................................................................................

B ..................................................................................................................................

C ..................................................................................................................................(3)

(b) The magnification of this chloroplast is ×5000. Measure the width of the chloroplast between points X and Y on the photograph.

Calculate the actual width of the chloroplast, expressing the answer in m (micrometres). Show your working.

Answer ............................. m(3)

(c) Name two types of cells which contain chloroplasts and are found in a leaf.

1 ...................................................................................................................................

2 ...................................................................................................................................(2)

(Total 8 marks)

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61. The diagram below shows the stages in the cell cycle of a plant root cell.

C y to k in e s is

Te lo p h ase

A n ap h a se

M eta p h ase

P ro p h ase

In te rp h a se

(a) The cell had 2 arbitrary units of DNA at the start of interphase. State the number of arbitrary units of DNA in this cell in each of the following stages.

(i) at the end of prophase

...........................................................................................................................(1)

(ii) during anaphase

...........................................................................................................................(1)

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(b) Describe how you would prepare a root tip squash to observe the stages of mitosis.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(5)

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(c) Two onion bulbs were grown to obtain some roots. One onion bulb was grown in water, the other in a solution of a drug called vincristine, as shown below.

O n io n b u lb

R o o ts

S o lu tio n o fv in c ris tin e

W ate r

Vincristine is a drug used in the treatment of cancer. It prevents spindle formation during mitosis. The result of a root tip squash on the roots grown in a solution of vincristine showed an increase in the percentage of cells found in one of the phases compared with roots grown in water.

(i) Suggest in which phase of mitosis this increase occurs.

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(ii) Give an explanation for your answer.

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(Total 10 marks)

62. The photograph below shows four germinating pollen grains, as seen using a light microscope.

Maginification ×100

(a) Name the part labelled A.

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(b) Part A contains a tube nucleus and two male nuclei. Describe the roles of the two male nuclei in the process of fertilisation in a flowering plant.

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(c) An experiment was carried out to investigate the effect of sucrose concentration on the germination of pollen grains from Camellia flowers. The results graph below.

3 0

2 5

2 0

1 5

1 0

5

00 5 1 0 1 5 2 0 2 5 3 0

S u c ro se co n cen tra tio n (% )

P e rcen ta g eg e rm in a tio no f p o lleng ra in s (% )

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(i) From the graph, find the expected percentage germination in a 16% sucrose concentration.

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(ii) Describe the relationship between the percentage germination and the sucrose concentration, as shown in the graph.

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(Total 8 marks)

63. The photograph below shows a cell from an insect testis, undergoing meiosis.

Magnification ×1000

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(a) Name the stage of meiosis shown in the photograph and give a reason for your answer.

Name of stage .............................................................................................................

Reason ........................................................................................................................

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(b) In a species of butterfly, the diploid (2n) number of chromosomes is 360. State the number of chromosomes present in each of the following cells.

(i) A butterfly sperm ...........................................................

(ii) A butterfly zygote ..........................................................(2)

(c) Explain the importance of meiosis in the formation of gametes.

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(Total 7 marks)

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64. The diagrams below show some of the stages of meiosis I in an animal cell.

(a) State the diploid (2n) number of this cell.

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(b) Write the letters in the correct order to show the sequence of stages in meiosis I.

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(c) Explain the importance of meiosis in spermatogenesis.

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(d) Semen contains about 100 million sperm per cm3. Suggest why the chances of

fertilisation are significantly reduced if this number falls below about 30 million per cm3.

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65. (a) Distinguish between the terms gene and allele.

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(b) Marfan’s Syndrome is a rare genetic disease which affects the eyes, heart and bones. The family tree below shows how this disease was inherited through three generations of a family.

A B

C D E F G H

J K L M N

u n affec te d fe m a le

u n a ffec te d m a le

fem a le w ith M arfa n ’sS y n d ro m e

m a le w ith M arfan ’sS y n d ro m e

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(i) Male A is an unaffected homozygous individual. State whether the allele for Marfan’s Syndrome is dominant or recessive. Explain your answer.

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(ii) Using the symbols of D for dominant allele and d for recessive allele, show the genotype for the following individuals.

B ......................................................

F ......................................................

J ......................................................(2)

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(iii) Individuals C and D have one affected child. Use a genetic diagram to determine the probability of their next child being affected.

(3)

(c) A genetic disease can suddenly appear in a family with no previous history of the disease. Suggest how this could be possible.

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(Total 11 marks)

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66. The table below refers to starch and cellulose molecules. Complete the table by placing a tick () in the appropriate box if the statement is correct or a cross ( ) if the statement is incorrect.

Do not leave any boxes empty.The first line has been done for you.

Starch Cellulose

Molecule with branchesattached by 1-6 linkages

Molecules always longand straight

Formed from α glucosemolecules

Form microfibrils byhydrogen bonding

Major component ofplant cell walls

Stored in amyloplasts

(Total 5 marks)

67. Read through the following account relating to sexual reproduction. Write on each dotted line the most appropriate word to complete the account.

A sperm is produced by a special kind of nuclear division called......................................

In this type of division the chromosome number of the normal body cell is

..................................... The chromosomes are .................................... assorted which

increases genetic variation.

A sperm can only fertilise an egg by penetrating the jelly surrounding the egg

membrane. The head of the sperm releases .................................... which allow the

sperm to reach the egg membrane. This process is called the ....................................

reaction. Fertilisation produces a diploid cell called a .................................... which

divides by ..................................... to form an embryo.(Total 7 marks)

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68. (a) Identify the organelles (structures inside a cell) which fit the descriptions given in the table below. The first one has been done for you.

Description Name of organelle

iWhere photosynthesis takes place and carbon dioxideis converted into sugar chloroplast

ii Where aerobic respiration takes place

iiiWhere amino acids are joined together to formproteins

ivPackages proteins into vesicles so that they can bereleased from the cell by exocytosis

vA large space inside a plant cell surrounded by atonoplast and helping to maintain cell turgidity

viDivides and organises a spindle in an animal cell as itstarts to undergo mitosis

(5)

(b) Describe the structure of pits in plant cells and explain their function.

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(c) Give two ways in which the structure of a prokaryotic cell differs from a eukaryotic cell.

1 ..................................................................................................................................

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2 ..................................................................................................................................

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(Total 9 marks)

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69. Many plants are grown for their fibres for use in making cloth. For example, nettle fibres can be used for this purpose. In the future nettle fibres may be developed in the United Kingdom as an alternative to imported cotton plant fibres.

A student investigated the strength of plant fibres to find out if they could be made into cloth.

The following method was used.

Step 1. Harvest nettle plants and remove leaves from stems

Step 2. Place stems in buckets and cover with water. Leave for ten days

Step 3. Remove stems and wash fibres under running water

(a) Suggest and explain the changes that take place in the nettle stems during Step 2.

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(b) Describe a reliable method for measuring the strength of these plant fibres.

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(c) Suggest why, in the United Kingdom, cloth made from nettle fibres could be made more cheaply than cloth made from cotton.

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(Total 8 marks)

70. A newspaper recently published the following report.

‘Scientists find gene to halt ovarian cancer’

A gene that can stop the development of cancer of the ovary has been identified. This gene acts as a tumour suppressor. If the gene is switched off then a tumour develops.Scientists have switched the gene back on in mice and the cancer cells stopped developing.

Scientists hope to be able to find a drug to turn this gene back on. This could provide a means of treating ovarian cancer in humans.

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(a) (i) If a suitable drug is found it will have to be carefully tested in clinical trials.Describe the methods that would be used to trial a new drug to treat ovarian cancer.

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(ii) William Withering carried out trials of the digitalis soup which he used to treat patients. Explain why his methods could not be used as part of a modern clinical trial.

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(b) In the future, it may be possible to treat ovarian cancer by transplanting healthy stem cells into a diseased ovary. Some people think that stem cell research should not be carried out.

State whether you are for or against the use of stem cells to treat ovarian cancer.

For or against? ........................

Present an argument to explain why you hold this point of view (for or against) using your biological knowledge of stem cell research and the ethical issues connected with it.

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(Total 9 marks)

71. A study of mammals in West Africa has found that populations have decreased by up to 76% in 41 different species. Some species have become extinct in the area, reducing the biodiversity.

Is lan d o f A g ad ir

A tla n ticO cea n

M A U R ITA N IA

Source: www.news.bbc.co.uk

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(a) Explain why extinction of species reduces biodiversity.

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(b) It is thought that this loss of biodiversity is an indirect result of European legislation which limits fishing in European waters. Rather than lose their way of life, European fishermen now fish off the West African coast, and this has reduced fish stocks dramatically. The highest density of human populations in West Africa is along the coast.

(i) Suggest one reason why fish stocks are important for the human population in West Africa.

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(ii) Suggest reasons why changes in European legislation have had an effect on the wild mammal populations of West Africa.

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(c) With reference to the information given, describe the importance of considering cultural issues when using legislation for conservation of organisms.

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(d) Explain why local legislation is likely to be less effective than international agreements for major conservation projects.

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(Total 10 marks)

72. The table below describes some structures found in eukaryotic cells.

Complete the table below by writing the name of the structure in the box next to its description.

Description Name of structure

Cylindrical organelle made up of microtubules,involved in spindle organisation.

Site where ribosomal RNA is made and thesubunits of the ribosomes are assembled.

Organelle consisting of stacks of cisternae andvesicles, concerned with the modification ofproteins.

Small spherical structures surrounded by a singlemembrane, containing hydrolytic enzymes.

(Total 4 marks)

108

73. The table below refers to structures that may be found in bacterial cells or liver cells.Place a tick ( ) in the box if the structure is found in the cell and a cross ( ) in the box if it is not.

Structure Bacterial cell Liver cell

Ribosomes

Centrioles

Starch grains

Nucleus

(Total 4 marks)

74. The diagram below shows some of the organelles found in a eukaryotic cell.

R ib o so m es A

B

G o lg i ap p a ra tu s

N u c lea r m em b ran e

(a) Name the parts of the Golgi apparatus labelled A and B.

A ........................................................................

B ........................................................................(2)

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(b) Some of the proteins synthesised by ribosomes are transported to the Golgi apparatus.

Describe what happens to these proteins in the Golgi apparatus.

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(Total 5 marks)

75. The tips of three onion roots were cut off and each was used to make a root tip squash.

(a) Name a suitable stain that can be used to show chromosomes in a root tip squash.

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(b) The number of cells observed in each phase of mitosis was counted and these results are shown in the table below.

Root tip Number of cells observed

Prophase Metaphase Anaphase Telophase

1 15 5 3 5

2 23 5 4 9

3 17 6 2 8

The number of cells observed in a phase is directly proportional to the length of that phase. Using these results, put the phases in order starting with the longest phase and ending with the shortest phase.

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(c) The appearance of the chromosomes from part of a root tip squash is shown below.

P 1P 2

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(i) The cells labelled P1 and P2 are both in prophase. Suggest an explanation for the difference in appearance between the two cells.

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(ii) Write the letter A on the illustration to label a cell that is undergoing anaphase.(1)

(iii) Describe what happens during anaphase.

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(Total 8 marks)

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76. (a) The diagram below shows some of the stages and cells involved in the process of spermatogenesis.

S p erm a to g o n ia

S p erm a to zo a

C e lls A

S eco n d ary sp e rm a to cy te s

P rim ary sp e rm a to cy te s

(i) Name Cells A shown in the diagram above.

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(ii) State which of the cells named in the diagram are diploid (2n).

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(b) The graph below shows the changes in the DNA content of cells in the testes, during the formation of spermatozoa.

D N A co n ten t p e r ce ll

4 n

2 n

n

Tim e

Name the type of nuclear division shown by the graph and explain why it is important to reduce the DNA content from diploid (2n) to haploid (n), during the formation of spermatozoa.

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(Total 6 marks)

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77. The photograph below shows a transverse section through a leaf of Ammophila, as seen using a light microscope. Ammophila is an example of a plant with xeromorphic adaptations.

(a) Explain what is meant by the term xeromorphic adaptations.

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(b) Describe and explain two features, visible in the photograph, that show how Ammophila is adapted to its environment.

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(Total 5 marks)

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78. (a) Some people take garlic extracts as they believe that these contain natural chemicals capable of reducing infection.

An experiment was carried out to study the effect of garlic extracts on the growth of Gram negative and Gram positive bacteria.

The 100% extract was obtained by crushing the garlic. This extract was diluted with water to give 4 different concentrations (80%, 60%, 40% and 20%). Small discs of filter paper were then soaked in the 100% extract and the diluted extracts, removed and dried.

A suspension of Gram negative bacteria was spread evenly over a solid medium in a petri dish. One disc from each dilution of the garlic extract was placed on the surface of the medium. The culture was incubated for 48 hours.

This procedure was repeated with a suspension of Gram positive bacteria.

The appearance of the cultures after 48 hours is shown below. The numbers show the percentage concentration of garlic extract used.

D iscs so a k ed ing a rlic ex trac t

Z o n e o f n ob ac te ria l g ro w thG ra m n eg a tiv e cu ltu re

a fter 4 8 h o u rsG ra m p o sitiv e cu ltu re

a fter 4 8 h o u rs

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The diameter of the zone of no bacterial growth was measured for each disc on each plate.The graph below shows these results.

Dia

met

er o

f zo

ne o

f no

bac

teri

al g

row

th /

mm

1 2

1 0

8

6

4

2

00 2 0 4 0 6 0 8 0 1 0 0

C o n cen tra tio n o f g a rlic ex trac t (% )

E ffec t o f g a rlic ex trac t o nG ram n eg a tiv e b ac te riaE ffec t o f g a rlic ex trac t o nG ram p o sitiv e b ac te ria

Describe the effect of diluting the garlic extract on the growth of Gram negative bacteria.

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(b) Suggest how the information shown in the graph supports the following conclusions

118

drawn from this experiment.

(i) The chemicals in the garlic extract do not interfere with the cell wall.

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(ii) The cell wall of Gram negative bacteria is more permeable to the chemicals contained in the garlic extract than the cell wall of Gram positive bacteria.

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(Total 4 marks)

79. Write an essay on the following topic.

Genetic variation and natural selection.

Marks will be awarded for scientific content, coverage of the topic, and the quality of written communication. You should include in your answer any relevant information from the whole of your course. You may include diagrams if you wish, but make sure that they are relevant to your essay and add extra information to it.

(Total 15 marks)

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80. Complete the table below by placing in each box a tick ( ) if you would expect the feature to be present or a cross ( ) if you would expect it to be absent.The first row has been done for you.

Feature Sperm Egg

Tail

Haploid nucleus

Acrosome present

Mitochondria present

Cytoplasm containingmany lipid droplets

Use ATP for movement

(Total 5 marks)

81. This question is about the preparation of a microscope slide that would enable you to see the stages of mitosis.

(a) Name a suitable organism and tissue which could be used to study mitosis.

(i) organism .................................................................................................................(1)

(ii) tissue .......................................................................................................................(1)

(b) Name a stain you might use to make the chromosomes visible.

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(c) Explain why the cells are warmed in acid during the preparation of the slide.

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(d) The diagram below shows a chromosome during an early stage of mitosis. Write the names of the parts labelled A and B on the lines provided.

A B

A ....................................

B ....................................

(2)(Total 6 marks)

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82. The diagram below shows the steps needed to produce human tissues from embryonic stem cells. This procedure has not yet been successfully carried out although some scientists hope that it will soon be possible. Perhaps one day new nervous tissue will be produced that will enable people with spinal injuries to walk again.

S tep 1

S tep 2

S tep 3

S tep 4

S tep 5

S tep 6

S tep 7

fe rtilisa tio n

‘sp a re ’ em b ry o

g ro w n to fo rm b la s to cy s t

s tem ce lls iso la ted , rem a in so f b la s to cy s t d isca rd ed

stem ce lls cu ltu red

ce ll d iffe ren tia tio n

h u m an tissu es fo r tran sp lan ta tio n

(a) (i) Describe how scientists might obtain a supply of ‘spare embryos’ (Step 2) to produce tissues.

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(ii) After fertilisation, cells are totipotent but by the time a blastocyst has formed the cells are pluripotent. Explain what is meant by the terms totipotent and pluripotent.

totipotent ..........................................................................................................

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pluripotent .......................................................................................................

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(b) Explain why the following are important in producing tissues from stem cells.

(i) stem cells cultured (Step 5)

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(ii) cell differentiation (Step 6)

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(c) The use of embryonic stem cells to produce tissues in this way is controversial. Some people think that it should be banned, whilst other people think that it would be wrong not to try this technique. State whether you are for or against using embryonic stem cells to produce new tissues.

For or against?.............................................

Use your knowledge of stem cell research issues to justify your view.

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(Total 11 marks)

83. The tolerance of plants to copper ions in the soil is under genetic control. The frequency of an allele, which causes a plant to be more tolerant of copper, was measured at two different sites A and B.

The table below shows the percentage frequencies of the tolerance and non-tolerance alleles in plant populations at the two sites.

Site Percentage frequencies of

Tolerance allele Non-tolerance allele

A 30 70

B 80 20

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(a) Explain what is meant by the frequency of an allele in a population.

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(b) Describe how natural selection could have brought about the different allele frequencies at the two sites.

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(c) Suggest why bacteria often adapt to changing conditions much more quickly than plants.

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(Total 8 marks)

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84. Answer the following essay question.

You are expected to answer in continuous prose. You should use examples from the biology course you have studied but need not restrict yourself to the course content.

You should spend approximately 45 minutes answering this question including planning time.

Marks will be awarded for the following areas:

Breadth: selection of a range of relevant examples (up to 6 marks)

Depth: Further description and discussion of the examples (up to 8 marks)

Balance: Have you answered the question asked; for example have you recognised the advantages and disadvantages or benefits and risks (up to 6 marks)

Style: Coherence, clarity and expression (up to 4 marks)

Some people claim that many medical problems, such as the shortage of suitable organs needed for transplant surgery, may become a thing of the past. The use of stem cells, which may have had a specific gene or genes inserted, could give rise to many new treatments.

Write an essay on: ‘Manipulating stem cells: a miracle cure or a dangerous development?’(Total 20 marks)

85. (a) The cell cycle includes interphase and mitosis. Mitosis has four phases: prophase, metaphase, anaphase and telophase. The photograph below shows plant root cells at various stages of the cell cycle.

(i) Draw a line to indicate a cell in the photograph that is undergoing anaphase and label this line A.

(1)

(ii) Draw a line to indicate a cell in the photograph that is undergoing telophase and label this line T.

(1)

(iii) How many of the cells shown in the photograph are in telophase?

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(b) Give an account of the events that take place during prophase and metaphase of mitosis.

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(Total 8 marks)

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86. (a) In the space below, draw and label a diagram to show the structure of a chloroplast, as seen using an electron microscope.

(4)

(b) The photograph below shows a group of mitochondria in a liver cell, as seen using an electron microscope. The magnification is ×50 000.

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(i) Measure the length of the mitochondrion labelled A between X and Y. Calculate the actual length of this mitochondrion in μm. Show your working.

Actual length of A ......................µm.(3)

(ii) Suggest one other structure that might be visible in the cytoplasm of this liver cell if the magnification used was higher.

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(iii) Suggest one reason why the double membrane is not clearly visible all around the mitochondrion labelled A.

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(Total 9 marks)

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87. (a) Some invertebrates, such as insect larvae, show various adaptations to living in freshwater with a low concentration of dissolved oxygen. Some other invertebrates are adapted to living in fast-flowing water.

(i) Describe and explain two ways in which invertebrates are adapted to living in fresh water with a low concentration of dissolved oxygen.

1 ........................................................................................................................

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2 ........................................................................................................................

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(ii) Suggest and explain one way in which an invertebrate might be adapted to living in fast-flowing water.

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(b) An experiment was carried out to investigate the relationship between temperature and the concentration of dissolved oxygen in freshwater. The results are shown in the table below.

Temperature / °C Concentration of dissolved oxygen / mg dm–3

5 12.8

10 11.3

15 10.2

20 9.2

25 8.2

30 7.5

Describe the relationship between temperature and the concentration of dissolved oxygen, as shown by the data.

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(Total 8 marks)

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88. (a) The diagrams below show some of the stages of meiosis I in an animal cell. The diploid number (2n) of this cell is 4.

A B C

D E

Write the letters in the correct order to show the sequence of stages in meiosis I.

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(b) The diploid number of chromosomes in a human cell is 46. State the number of chromosomes present in each of the following.

(i) A spermatogonium ...................

(ii) A spermatid ..............................(2)

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(c) Describe the process of oogenesis.

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(Total 8 marks)

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89. The table below refers to some cell structures. Complete the table by inserting the correct word, words or diagram in the appropriate boxes. Leave the shaded grey boxes empty.

Name of cell structure Description of cell structure Diagram of cell structure

(1)

1. Darkly-stained region in the nucleus.

2. Where ribosomal RNA is made.

Centriole

(2)

Lysosome

1.

2.

(2)

(1)

1. Hollow cylinders made of protein.

2. Form spindle fibres.

(Total 6 marks)

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90. The graphs below show changes in the DNA content of cells during the cell cycle in two different plants, A and B.

P la n t AD

NA

con

tent

in

each

ce

ll /

arb

itra

ry u

nits

6

3

Tim e / h o u rs

3 63 43 23 02 82 62 42 22 01 81 61 41 21 086420

P la n t B

DN

A c

onte

nt i

n ea

ch

cell

/ a

rbit

rary

uni

ts

6

3

Tim e / h o u rs

3 63 43 23 02 82 62 42 22 01 81 61 41 21 086420

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(a) Compare the cell cycle of plant A with the cell cycle of plant B.

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(b) The DNA content of the cells of plant A doubles between 4 and 8 hours. Give an explanation for this change in DNA content.

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(c) Describe the events that are occurring inside the cells of plant A between 11 and 13 hours.

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(Total 7 marks)

91. The photograph below shows a transverse section through part of a leaf of Ammophila, as seen using a light microscope. Ammophila is a plant which is adapted to living in a dry environment.

Magnification ×100

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(a) Describe and explain three ways in which the leaves of plants, such as Ammophila, are adapted to their environment.

1 ..................................................................................................................................

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2 ..................................................................................................................................

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3 ..................................................................................................................................

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(b) Suggest one way in which the structure of a leaf of a hydrophyte might differ from the structure of a leaf of Ammophila.

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(Total 7 marks)

92. Write an essay on the following topic.

Sexual reproduction and genetic variation in flowering plants.

Marks will be awarded for scientific content, coverage of the topic, and the quality of written communication. You should include in your answer any relevant information from the whole of your course. You may include diagrams if you wish, but make sure that they are relevant to your essay and add extra information to it.

(Total 15 marks)

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93. The table below compares the features of typical plant, animal and bacterial cells.Complete the table by placing a tick ( ) in the appropriate box if the feature is usually present or a cross ( ) if the feature is usually absent.Do not leave any boxes empty.

The first line has been done for you.

Plant(eukaryotic) cell

Animal(eukaryotic) cell

Bacterial(prokaryotic) cell

Cell wall

Chloroplasts

Nuclear membrane

Cell (unit) membrane

Ribosomes

Centrioles

(Total 5 marks)

94. The hormone insulin is a protein. It is produced in certain cells in the human pancreas.Once insulin molecules have been produced they are secreted through the cell membrane into the blood. Describe the sequence of events from when an insulin molecule has been formed until it passes through the cell membrane.

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95. Cellulose and starch are both polysaccharides, made up of glucose molecules condensed together.

(a) Describe how the molecular structure of a cellulose molecule differs from that of a starch molecule.

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(b) In the cell walls of plants, the cellulose molecules are arranged so that they make up cellulose microfibrils. Explain how the arrangement of cellulose molecules in a microfibril give it great strength.

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(c) Xylem vessels are tubes formed when columns of cells die. Their walls are made of cellulose strengthened with other substances, such as lignin. In addition to providing support, xylem vessels also transport water from the roots to the leaves with the help of cohesion. Explain what is meant by cohesion.

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(Total 7 marks)

96. (a) Mammalian gametes are formed by meiosis and have the ability to fuse to form a zygote. Explain why it is important that gametes are produced by meiosis.

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(b) Explain how the genetic material from a mammalian sperm cell is able to enter an ovum to bring about the process of fertilisation.

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(c) (i) Calculate the number of cells that will be present in the embryo after the first four

141

mitotic divisions of the zygote.

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(ii) Suggest why, during the first four mitotic divisions, the embryo does not increase in volume even though the total number of cells increases.

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(iii) Outline the events that occur in mitosis from the start of prophase up to the end of metaphase.

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(Total 9 marks)

97. (a) A single stem cell can give rise to many genetically identical cells of different types.There are, for example, adult stem cells in the human brain which are capable of producing the different types of brain cells including nerve cells (neurones).

Scientists are trying to find ways of growing such adult brain stem cells in the laboratory.

(i) Name the type of cell division by which a stem cell can give rise to many genetically identical cells.

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(ii) Explain how cells produced from stem cells can have the same genes yet be of different types.

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(iii) Suggest why it might be useful to keep a supply of live stem cells from your brain in a laboratory.

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(b) Much research remains to be done and so it will be some time before adult stem cell treatments will be available to those who might benefit from them. However, research using embryonic stem cells is much further advanced.

(i) Suggest why research with embryonic stem cells is further advanced than research with adult stem cells.

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(ii) Some people hold the view that research into and the medical use of embryonic stem cells is unethical and that we should await the results of research on adult stem cells.

Are you for or against embryonic stem cell research? .....................................

Using your scientific knowledge and your understanding of the ethical issues associated with embryonic stem cell research, explain why you hold this view.

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(Total 11 marks)

98. (a) The diagrams A and B below show cells from the same organism. Both cells are in the same stage of nuclear division. One cell is undergoing mitosis and the other cell is undergoing meiosis.

A B

Z

(i) Which cell is undergoing mitosis? Put a cross in the correct box.

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A B (1)

(ii) Give the name of the structure labelled Z.

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(iii) Name the stage of mitosis shown.

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(b) Describe how you would prepare cells in order to observe mitosis.

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(Total 7 marks)

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99. (a) Independent assortment and crossing over both result in genetic variation.

(i) Explain how independent assortment leads to genetic variation.

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(ii) Describe how crossing over further increases genetic variation.

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(b) The graph below shows changes in mean height of men in Japan from 1950 to 1980.

1 6 3

1 9 4 5 1 9 5 0 1 9 5 5 1 9 6 0 1 9 6 5 1 9 7 0 1 97 5 1 9 8 0

1 6 4

1 6 5

1 6 6

1 6 7

1 6 8

1 6 9

1 7 0

1 7 1

1 7 2

1 7 3

M ean h e ig h t o f m en aged 20

/cm

Year

Describe the changes in height between 1950 and 1980.

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(c) The graph below shows changes in the major components of the diet of men in Japan over the same period.

1 9 5 0 1 9 6 0 1 9 7 0 1 9 8 0

Year

ca rb o h y d ra te

fa t

an im a l p ro te in

8 0

7 0

6 0

5 0

4 0

3 0

2 0

1 0

0Rel

ativ

e p

rop

orti

on o

f d

ieta

ry c

omp

onen

t /

arb

itra

ry u

nit

s

The evidence from both graphs suggests that a combination of genetic and environmental factors influence the height of men in Japan. Give an explanation for this.

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(Total 10 marks)

100. (a) The diagram below shows a view through a typical animal cell.

The table below lists three organelles. Put a cross in the box to match each organelle with the correct letter shown on the diagram.

Organelle A B C D E

Rough endoplasmic reticulum

Mitochondrion

Golgi apparatus(3)

(b) For some time after the Golgi apparatus was identified, there was doubt as to whether it

148

was a new and separate organelle. Explain how the Golgi apparatus could be confused with other organelles within a cell.

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(c) In an experiment to investigate the role of organelles in protein transport, cells were given radioactively-labelled amino acids for a fixed period of time. The percentage of the radioactivity found in four different organelles was then measured at different time intervals. The table below shows the results.

Time after adding Radioactivity present / %

radioactively-labelledamino acid / min

Roughendoplasmic

reticulum

Golgiapparatus

Secretoryvesicles

Mitochondria

4 67 27 1 3

6 53 39 2 1

20 11 73 10 3

240 11 10 73 2

(i) The data provide evidence that the Golgi apparatus is a separate organelle.Suggest an explanation for this.

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(ii) Explain how the data provide evidence for the sequence of events in the process of protein transport in these cells.

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(iii) Suggest one reason for the presence of some radioactivity detected in the mitochondria.

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(Total 13 marks)

101. (a) Three structures found in mammalian sperm cells are described in the table below.Give the name of each structure being described.

Description Structure

Releases digestive enzymes to penetrate egg

Allows the sperm to swim to the egg cell

Provides the energy required for swimming

(3)

(b) Give the term that describes the ability of a stem cell from an embryo to produce all cell types.

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(c) Describe how a cell loses the ability to produce other cell types and becomes specialised.

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(d) Embryos have been produced from human egg cells which have not been fertilised by sperm. These embryos never survive past a few days. This is because some of the genes needed for development are only active in chromosomes from the sperm.

It has been suggested that there will be less opposition to the medical use of stem cells from these embryos than from normal embryos. Suggest reasons for this.

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(Total 10 marks)

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102. Taxonomy is the branch of biology concerned with the classification of organisms. In the taxonomic system first developed by Linnaeus, organisms are given a two-part Latin name.

(a) State one advantage of the binomial system developed by Linnaeus.

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(b) The table below shows the classification of the blue whale, Balaenoptera musculus together with some of the classification of the fin whale, Balaenoptera physalus.

Complete the table by suggesting appropriate names for the class, order and family of the fin whale.

Classification taxon Blue whale Fin whale

Kingdom Animalia Animalia

Phylum Chordata Chordata

Class Mammalia

Order Cetacea

Family Balaenopteridae

Genus Balaenoptera Balaenoptera

Species Balaenoptera musculus Balaenoptera physalus

(1)

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(c) Below are four features, A, B, C and D, used in the classification of organisms. Put a cross in the box or boxes next to the features which are shared by both blue whales and fin whales.

A – feed by heterotrophism on organic material

B – multicellular

C – cells surrounded by cell wall

D – cytoplasm of cells contain circular DNA(2)

(d) Suggest reasons for the classification of the blue whale and the fin whale within the same genus, Balaenoptera, but as different species.

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(Total 7 marks)

103. (a) State what is meant by the term species richness.

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(b) In a survey, the mean species richness for the vegetation found in roadside verges and hedgerows in England and Wales was measured in 1990 and again in 1998. The results of this survey are shown in the graphs below.

14 .0

14 .5

15 .0

15 .5

16 .0

16 .5

17 .0

17 .5

199 0 1998

R o a d sid e ve rg e s

Sp

ecie

s ri

chn

ess

11 . 5

1 2 . 0

1 2 . 5

1 3 . 0

1 3 . 5

1 4 . 0

1 4 . 5

1 9 9 0 1 9 9 8

H e d g e ro w s

Sp

ecie

s ri

chn

ess

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Compare the species richness shown by the survey for the vegetation in the roadside verges with that of the hedgerows over this study period.

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(c) Other information would be needed, in addition to species richness, to measure the biodiversity of the vegetation in the two types of habitat. Give an explanation for this.

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(d) Seed banks, such as the Millennium Seed Bank Project (MSBP), are an effective means of conserving plant species.

Write a short briefing, intended for a government committee, describing how seed banks work and why their funding should be continued.

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(Total 12 marks)

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104. Sisal is a material used to make rope. It is made from the sclerenchyma fibres found in the leaves of the plant, Agave sisalana.

After extraction of the fibres, the waste leaf material can be used in the production of organic fertiliser.

The four countries that produce most of the world’s sisal are Brazil, Kenya, Tanzania and Madagascar. The table below shows the annual harvest of freshly-cut Agave sisalana leaves together with the total annual production of sisal.

CountryAnnual harvest of freshly-

cut leaves / tonnes × 103Annual production of sisal /

tonnes × 103

Brazil 995 199

Kenya 196 40

Tanzania 145 28

Madagascar 96 20

TOTAL 1432

(a) (i) Complete the table to show the total annual production of sisal.(1)

(ii) Calculate the total percentage of sisal produced from freshly-cut leaves. Show your working.

Answer ..................... %(2)

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(b) Nylon is a synthetic (man-made) fibre which can be used to make ropes. Nylon ropes are lighter and stronger than those made using sisal. Suggest two advantages of using sisal rather than nylon to make ropes.

1 ..................................................................................................................................

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(c) (i) Explain what is meant by the term tensile strength of a fibre.

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(ii) Suggest how you could carry out a practical investigation to compare the tensile strength of sisal and nylon fibres.

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(d) Describe two ways in which the structure of xylem vessels is similar to that of sclerenchyma fibres.

1 ..................................................................................................................................

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(Total 12 marks)

105. (a) Below are four cell structures A, B, C and D. Place a cross in the box next to each

structure found only in plant cells.

A plasmodesmata

B ribosome

C tonoplast

D chromosome(2)

(b) The list below shows some organelles found in eukaryotic cells.

amyloplast centriole chloroplast

lysosome mitochondrion nucleus ribosome

Complete the table by choosing the correct organelle to match each description.

Organelle Description

Has a smooth outer membrane and a folded inner membrane

Contains a starch granule enclosed by a membrane

Spherical sac formed from a single membrane and containing enzymes

(3)

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(c) Describe the structure of a cellulose microfibril.

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(Total 9 marks)

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