mark scheme p2 (structure)

8/8/2019 Mark scheme P2 (structure)

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2

BIOLOGY

SECTION A

PAPER 2 [4551/2]

No. Marking Criteria / Sample Answers Marks

1 (a) (i) Gills 1

(ii) Tracheal system 1

(b) P : Filaments

Q: Spiracles

1

1 2

(c) (R is ring of chitin which) support the tracheal / prevent the tracheal

from collapsing.

1

(d) Diagram 1.1(b):

P1: The filament have numerous thin-walled lamellae to maximise

the surface area for gaseous exchange.

P2: The gill filaments have thin membrane and covered by a net

work of capillaries to transport respiratory gases.

P3: The surface of the gills is moist which allows the gases to be

dissolved.

Any 1P 1

Diagram 1.2(b)

P1: The large number of tracheoles provides a large surface for the

diffusion of gases.P2: Tip of tracheoles have thin permeable walls and contain fluid in

which respiratory gases can dissolve.

P3:Terminal ends of the tracheol remains moist which allows the

gases to be dissolved.

Any 1P

1

(e) (i) P1:( The gaseous exchange process occurs over the whole body

surface in an Amoeba sp) through simple diffusion.

P2:Higher concentration of oxygen in the water surrounding causes

oxygen to diffuse into the Amoeba.

P3:Higher concentration of carbon dioxide in the cell causes carbondioxide to diffuse out of the Amoeba.

Any 2P

1

1

1

2

(ii) S: Contractile vacuole 1

(iii) P1: Freshwater is hypotonic to the cytoplasmic fluid of Amoeba sp .

P2: Water diffuses into the cell and fill the contractile vacuole by

osmosis

P3: When the contractile vacuole is filled with water to its maximum

size, it contracts to expel its content from time to time.

Any 2P

1

1

1

2


2/5

3

No. Marking criteria/ Sample answers Mark

2 (a) (i) Osmosis 1

(ii) P1 : Sucrose solution is hypertonic / more concentrated.

P2 : Water diffuse from distilled water into the sucrose solutionP3 : The level of sucrose solution in the capillary tube stop rising

at the equilibrium stage / the concentration inside and outside

of the visking tubing is the same / the amount of water

diffuse into and out from the visking tubing is the same.

Any 2 Ps

1

11 2

(b) F- Sucrose molecules are too large

E- The visking tubing is a semi permeable membrane/

which only allows certain substances to pass through.

1

1 2

(c) (i) Y : crenation

Z : haemolysis

1

1 2

(ii) P1- Solution Z is hypotonic compare to red blood cell.

P2- Osmosis occur

P3- water leaves/ diffuses into the cell

P4- Red blood cell expand/ swell and burst.

Any 3P

1

1

1

1

3

(iii) F : No

P1 : Plant cell consists of cell wallP2 : Cell wall is made up of cellulose

// Cell wall able to withstand the pressure.

Any 2

1

11 2

Total 12


3/5

4


3 (a) (i) Absorption / Simple diffusion / facilitated diffusion 1

(ii) F1 thin wall/ one cell thick

E1 increase rate of diffusion of digested food/ nutrients

F2 large surface area/ has microvilli

E2 increase rate of absorption of digested food/ nutrient

F3 has a network of capillaries/ blood vessels

E3 to transport the absorbed nutrients

Any F + E

1

1

1

1

1

1

2

(b) P: hepatic portal vein

Q: lymphatic/lymph vessel/ duct

1

1 2

(c) P1: Deamination.// The amino group is removed (from amino acid)/

converted to ammonia .

P2: (Ammonia) is converted to urea.

P3: urea will be excreted through the kidneys.

Any 2 Ps

1

1

1 2

(d) L1: A major energy reserve in the body//

L2: (phospholipids are) components of the plasma membrane//

L3: Lipids is used as a respiratory substrate//

L4: Excess fats are stored in adipose tissues (under the skin, aroundinternal organs)

Any 1L

A1:Amino acids are used in protein synthesis//

A2:For repair and production of new protoplasm/growth and repair//

A3:Used in the formation of enzymes/ some hormones/protein part of

haemoglobin/ antibodies

Any 1A

G1:Glucose is used as the main respiratory substrate// It is oxidised to

release energy (water and carbon dioxide)//

G2:Excessive glucose is converted to glycogen// Blood glucose level rise / increase.

Any 1 G

1

1

1

1

1

1

1

1

1

3

(e) P1: Diabetes mellitus // Blood sugar level increases// Hyperglycemia

P2: Excess glucose cannot be converted to glycogen.

1

1 2

Total 12


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5


4 (a)

Both arrows correct 1

(b) A Pulmonary artery

B Pulmonary vein

1

1 2

(c) F : Contraction of ventricle / heartE1: generates a (high) pressure

E2 : (to) propel/ force / pump the blood flow from the heart/ ventricle to

vessel A

Any two

11

1 2

(d)(i) Coronary artery 1 1

(ii) P1: Cut the supply of O2/ nutrients to the heart muscle

P2: causing chest pain / angina / heart attack / myocardial infarctionReject Heart problem

1

1 2

(e) (i)

(ii)

P1: platelets break down and release chemicals

P2: to cause platelets to stick to each other

P3: platelets clump together to form a plug to prevent blood loss .

P4: released thrombokinase and other clotting factors

Any 2P

P1 : Fibrinogen is soluble, fibrin is insoluble / not soluble

P2 : Fibrin able to form fibres / meshwork / thread to trap

blood cells, fibrinogen is not able to do so.

1

1

1

1

1

1

2

2

Total 12


5/5

6

No. Marking Criteria / Sample Answers Marks

5 (a) (i) (Transfer/flow of) energy 1

(a) (ii) F : Phytoplankton is an autotrophic organism.P1 : Able to absorb light energy / consists of chloroplast.

P2 : synthesis their own food / carry out photosynthesis

Any 2

11

1 2

(b) F1 : population of small fish increases

P1 : no shark feed on small fish // shark is the predator

F2 : population of plankton decreases

P2 : more small fish feed on the plankton

F3 : Eventually the population of small fish decreases

Any 3

1

1

1

1

1 3

(c) F : Commensalism

P1 : Shark is the host / neither gain any benefit nor harmed.

P2 : Remora benefits

P3 : Remora obtain protection / food / transport from the shark.

Any 3

1

1

1

1 3

(d) P1 : Fertilizer washed away by rain water into the lake

P2 : Nutrient / minerals content in the lake increase.

P3 : alga bloom / alga grow rapidly in the lake.

P4 : eutrophication occur.P5 : Oxygen content in the lake decrease / drop

P6 : Fishes die / population decrease

Any 3 P

1

1

1

11

1 3

Total 12

mark scheme p2 (structure)

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