a2 2:

CCEA Exemplar Scheme of Work: GCE Biology

A2 2:Biochemistry, Genetics and

Evolutionary Trends

1


Unit A2 2: Biochemistry, Genetics and Evolutionary Trends Specification Section 5.1: Respiration

5.1 Respiration

Spec Ref Learning Outcomes

Teaching Strategies Additional Notes (Resources, risk assessment, practical)

5.1.1 Recognise the nature and function of ATP

Show the structure of ATP on a simple diagram which shows the component structures – adenine, ribose and phosphate.

Explain the conversion of ATP to ADP and the consequent release of energy from the final phosphate high energy bond within the structure. Link this to the process of respiration that it is the process by which cells release energy through the utilisation of the energy stored in ATP.

Conversion of ATP to ADP. Give pupils various examples where ATP is used in active transport e.g. mineral uptake, absorption of amino acids in the proximal convoluted tubule of the kidney nephron.

LINK – 1.1.3 Recognise the occurrence, structure and function of carbohydrates

LINK – 2.1.2 Understand the features of exchange surfaces which aid passive and active transport

LINK – 4.1.2 Describe the function of the nephron

Time required: 1/2 weeksBased on approx 4.5 hours teaching time

per week(Guidance only)

2




5.1.2 Understand glycolysis Definition of glycolysis – the ‘splitting of sugar’.

Underline that glycolysis is a common process to both aerobic and anaerobic respiration. Idea shower the features of aerobic and anaerobic respiration, based on GCSE knowledge.

Using diagrams of cell ultrastructure show that glycolysis takes place in the cell cytoplasm.

Use a flow diagram, possibly a cut and stick exercise, to show the conversion process of glucose to the final pyruvate 3C structure.

Highlight that there is only a small yield of ATP (2) from glycolysis - at this stage introduce a summary table for ATP yield which can be filled in as the topic progresses.

LINK – 1.5.3 Understand the structure and function of eukaryotic cell components

3




5.1.3 Understand aerobic respiration

Show pupils the equation for aerobic respiration and ask them to explain the inputs, process and outputs. Their explanation can then be expanded to A2 level following the process below. Highlight the relevance of the equation and at all times refer back to the equation throughout the explanation.

Show a composite diagram of all 3 reactions i.e. glycolysis, Krebs cycle and electron transport chain to show that each reaction is linked to the next.

Design a flow diagram to show the stages of glycolysis enhanced with the use of the animation. Note enzyme activity.

Demonstrate that the product of glycolysis (pyruvate) is used in the Krebs cycle via the ‘Link Reaction’.

Add in to the initial diagram the location of each reaction in the mitochondria.

www.qcc.cuny.edu/BiologicalSciences/Faculty/DMeyer/respiration.html

programs.northlandcollege.edu/biology/Biology1111/animations/glycolysis.html

4

http://programs.northlandcollege.edu/biology/Biology1111/animations/glycolysis.html



http://www.qcc.cuny.edu/BiologicalSciences/Faculty/DMeyer/respiration.html






5.1.4 Understand anaerobic respiration

Show pupils the equation for anaerobic respiration and ask them to explain the inputs, process and outputs. Their explanation can then be expanded to A2 level following the process below. Highlight the relevance of the equation and at all times refer back to the equation throughout the explanation.

State the main defining feature of anaerobic respiration – that glycolysis occurs followed by further reactions which regenerate the co-enzyme NAD+

Highlight that the net yield of ATP will be 2 since only glycolysis is occurring.

State that ethanol and carbon dioxide are produced in plants and microorganisms – relevance to production of beer and bread.

State that lactate is the product in animals – relevance to muscle cramp during exercise and ‘paying back your oxygen debt’.

LINK – 1.2.1 Understand the structure of enzymes

www.instruct1.cit.cornell.edu/Courses/biomi290/MOVIES/GLYCOLYSIS.HTML

5

http://www.instruct1.cit.cornell.edu/Courses/biomi290/MOVIES/GLYCOLYSIS.HTML






5.1.5 Understand Krebs cycle Make pupils aware that in different textbooks that the Krebs cycle may be referred to as the citric acid cycle or TCA cycle.

Understand that the Krebs cycle is oxidative decarboxylation, in simple terms the removal of carbon atoms from carbon substrates.

Show the cycle as a circular diagram encompassing various carbon substrate molecules, producing NADH (+H+), FADH2 and ATP. Use the analogy of a ferris wheel – the seats representing the carbon substrate molecules with differing numbers of carbon atoms.

Produce another summary table of the net yield of co-factors – NADH +H+ etc.

Use animations to enhance diagrams.

Mention the use of different respiratory substrates – carbohydrate, protein and fat and the consequential energy release – this can be inserted into the summary table previously

www.wiley.com/legacy/college/boyer/0470003790/animations/tca/tca.htm

www.wiley.com/college/pratt/0471393878/student/animations/citric_acid_cycle/index.html

6

http://www.wiley.com/college/pratt/0471393878/student/animations/citric_acid_cycle/index.html



http://www.wiley.com/legacy/college/boyer/0470003790/animations/tca/tca.htm






mentioned as a method of structuring revision.

7




5.1.6 Understand the electron transport chain

The products of the Krebs cycle – NADH + H+ and flavoproteins (FADH2) enter the electron transport chain. This is the reaction during which the greatest net yield of ATP is produced.

Explain the electron transport chain in terms of carriers which pass on electrons. These carriers are arranged at progressively lower energy levels – as in a staircase. As each energy level is reached, excess energy is released. This process can be demonstrated using a tennis ball, pupils are arranged in descending order of the electron carriers and the tennis ball is then passed between them – other pupils can then be used to represent the release of energy bound in ATP.

Draw the electron transport chain as a simple staircase diagram – mark on this diagram the points at which ATP is synthesised, the final hydrogen acceptor and the net yield of ATP for NADH (+H+) or reduced flavoprotein (FADH2).

8




Insert these values into the ATP yield summary table.

Emphasise that oxygen is the final hydrogen acceptor in the electron transport chain, it combines with oxygen to form water – highlight the significance of this step with reference to the equation, water is a product of respiration.

Use animations to consolidate information.

www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/oxidative/oxidativephosphorylation.html

www.wiley.com/legacy/college/boyer/0470003790/animations/electron_transport/electron_transport.htm

www.highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter9/animations.html#

5.1.7 Compare aerobic and anaerobic respiration

Summary table of aerobic and anaerobic respiration – stages involved, substrates involved, products produced; emphasis on larger yield of ATP from aerobic than anaerobic respiration.

The significance of anaerobic respiration in the provision of ATP

9

http://www.highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter9/animations.html#



http://www.wiley.com/legacy/college/boyer/0470003790/animations/electron_transport/electron_transport.htm



http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/oxidative/oxidativephosphorylation.html






without the use of oxygen. Provide relevant examples of the

use of anaerobic respiration – training athletes, peat bogs etc.

Focus on anaerobic respiration as the production of lactic acid in animals – this results in an oxygen debt which is repaid after exercise – apply to context of training athletes.

10




5.1.8 Understand the respiratory quotient

RQ value as the ratio of carbon dioxide produced to oxygen consumed in a respiring organism.

Demonstration of simple respirometer measuring oxygen consumption with potassium hydroxide present. Measuring the net difference between carbon dioxide production and oxygen consumption with no potassium hydroxide present. Determine carbon dioxide production and the RQ value.

Give various equations for pupils to work out the RQ value. Use RQ value found to determine respiratory substrate (e.g. carbohydrate = 1) and in detecting anaerobic respiration (greater than 1).

Risk Assessment – KOH corrosive

5.1.9 Practical Work Simple Respirometer showing rate of respiration/uptake of oxygen

Demonstrate the use of hydrogen acceptors using indicators e.g. methylene blue.

LINK – 2.1.8 Practical Work Risk Assessment – KOH

corrosive

11


Unit A2 2: Biochemistry, Genetics and Evolutionary Trends Specification Section 5.2: Photosynthesis

5.2 Photosynthesis



5.2.1 Describe the sites in the chloroplast where the reactions of photosynthesis occur

Diagrams of the chloroplasts in increasing detail showing the structures involved and the reactions which take place in situ.

Define the light-dependent stage and where it occurs in the chloroplast.

Define the light-independent stage, where it occurs in the chloroplast – refer to the past usage of the ‘dark’ reaction and Calvin cycle.

LINK – 1.5.3 Eukaryotic Cell Components



12


Spec Ref

Learning Outcomes Teaching Strategies Additional Notes (Resources, risk assessment, practical)

5.2.2 Understand the light-dependent stage of photosynthesis

Use the equation for photosynthesis as a starting point for pupils to highlight the important factors involved in the process. This can also be used to come back to at different stages throughout the topic to reiterate and highlight specific points. Based on GCSE knowledge this will aid their understanding of this new material.

Introduce pupils to a simple diagram of the core principles of this reaction.

Use a cut and stick activity for pupils to make the light-dependent reaction – this should be done using the full extent of the page in order for pupils to visually understand the changes in energy levels involved. This technique can then be further enhanced with the inclusion of more detail at later stages.

Define terms used such as photophosphorylation by using the technique of breaking the word into its constituents; this enables pupils to think about the processes involved.

LINK – 2.1.5 Understand gas exchange in plants

LINK – 2.1.8 Practical Work

www.highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter10/animations.html

www.cst.cmich.edu/users/baile1re/

13

http://www.cst.cmich.edu/users/baile1re/bio101fall/enzphoto/photoanima.html


http://www.highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter10/animations.html




Spec Ref


Emphasis on the products of this light-dependent stage – reduced NADP (NADPH) and ATP which are then used in the light-independent stage.

The dissociation of water to release oxygen.

Refer back to the initial reference to the equation for photosynthesis, emphasise the following – light is required for the photoactivation of PSI, water is required to replace electrons in PSII through its dissociation to release oxygen. Highlight that the other events in the equation are mentioned in the light-independent stage.

Use animations to show pupils a moving visual image of the stages in the reaction.

bio101fall/enzphoto/photoanima.html

5.2.3 Understand the light-independent stage in photosynthesis

Begin with reference to the equation.

Carbon dioxide fixation i.e. the use of carbon dioxide in the reactions of carbon substrates e.g. ribulose bisphosphate.

The use of NADPH, from the light-dependent stage, to reduce

LINK – 4.4.14 Explain the cycling of carbon in the ecosystem

14




Spec Ref


glycerate phosphate The use of ATP, again from the

light-dependent stage, to facilitate the reactions occurring.

Emphasis on the recycling nature of the substrates involved, they are not lost, simply regenerated in the process.

The final stage of the synthesis of the C6 sugars.

Animations to show the stages.

www.faculty.nl.edu/jste/calvin_cycle.htm

.www.web.virginia.edu/gg_demo/movies/figure18_12b.html

15

http://www.web.virginia.edu/gg_demo/movies/figure18_12b.html



http://www.faculty.nl.edu/jste/calvin_cycle.htm

http://www.faculty.nl.edu/jste/calvin_cycle.htm


Spec Ref


5.2.4 Appreciate that light is absorbed by chlorophyll and associated pigments

Begin with an emphasis on the fact that chlorophyll is not the only photosynthetic pigment. Increase pupils understanding of this concept by showing them the light spectrum – there are several different wavelengths of light so it therefore makes sense that plants will do their best to optimise their usage of light available to them by having more than one pigment.

Use website to show absorption spectra and action spectrum. Highlight the difference between these two spectra – absorption spectra is the action of the pigments within plants, the action spectrum is the wavelengths of light.

16


Spec Ref


5.2.5 Understand the external factors limiting the rate of photosynthesis

The rate of photosynthesis is measured by carbon dioxide uptake or oxygen production as shown in the equation previously.

Define the terms gross and net photosynthesis and compensation point. Compensation point can be further examined using the web link.

Table to show external factors which could limit the rate of photosynthesis – let pupils develop these factors themselves. Use a case study scenario of a market gardener and pupils can put the factors into context. Include in the table information on each factor and an example of the graph which would be produced.

www.tomatosphere.org/EngManual/activity9a.html

5.2.6 Practical Work Refer to the use of the Audus apparatus.

Paper chromatography of plant pigments to illustrate the presence of more than one pigment present in plants. Include the calculation of Rf values.

Demonstrate the role of hydrogen acceptors using redox indicator

LINK – 2.1.8 Practical Work LINK – 1.1.8 Practical Work

17

http://www.tomatosphere.org/EngManual/activity9a.html




Spec Ref


such as DCPIP.

18


Unit A2 2: Biochemistry, Genetics and Evolutionary Trends Specification Section 5.3: DNA as the Genetic Code

5.3 DNA as the Genetic Code

Spec Ref


5.3.1 Understand the nature of the genetic code.

Recall information from Module 1 that a gene is a sequence of bases on a strand of DNA.

The specific sequence of the bases will determine which amino acids join together to form a polypeptide.

Animation of DNA structure. Introduce the concept of codes as a

shortened way of carrying a large volume of information e.g. Morse code.

Specify that the genetic code is a non-overlapping, degenerate code of three bases i.e. a codon.

Define the terms non-overlapping and degenerate.

Give examples of codons and the amino acid that they code for.

LINK – 1.1.6 Recognise the occurrence, structure and function of nucleic acids

LINK – 1.1.5 Recognise the occurrence, structure and function of proteins

www.johnkyrk.com/DNAanatomy.html

Time required: 2 weeksBased on approx 4.5 hours teaching time


19

http://www.johnkyrk.com/DNAanatomy.html

http://www.johnkyrk.com/DNAanatomy.html


Spec Ref


5.3.2 Understand the process of transcription in the synthesis of proteins.

Explain transcription using the analogy of writing down information in order for it to be transferred from one location to another.

Explain transcription in the context of the writing down of the genetic information involving the unpairing of bases in one region of the DNA followed by the synthesis of a strand on mRNA which carries a triplet code sequence which is complementary to the DNA. Emphasise that the DNA is a template for the mRNA, this is the messenger which allows the genetic info in the form of the triplet code to be carried from one location in the cell to another.

Animation showing transcription.

www.learn.genetics.utah.edu/units/basics/transcribe

www.library.thinkquest.org/20465/g_DNATranscription.html

20

http://www.library.thinkquest.org/20465/g_DNATranscription.html



http://www.learn.genetics.utah.edu/units/basics/transcribe/

http://www.learn.genetics.utah.edu/units/basics/transcribe/


Spec Ref


5.3.3 Understand the process of translation in the synthesis of proteins.

Explain translation as the de-coding or ‘reading’ of the triplet message on the mRNA.

The codon, 3 bases, has a natural complementary sequence of 3 bases, this is referred to as the anticodon. This set of 3 bases is attached to a specific tRNA molecule which carries and transfers a specific amino acid. Note that specificity of amino acid is determined by the sequence of the triplet code and anticodon as explained in 5.3.1.

The complementary triplets on mRNA and tRNA will pair together in ribosomal sites (peptidyl and aminoacyl) – ribosomes situated in the cell cytoplasm hence the need for mRNA and tRNA.

When 2 amino acids are side by side, at the 2 sites on the ribosome, a condensation reaction will occur and a peptide bond will form between them.

Animation showing translation.


www.biostudio.com/demo_freeman_protein_synthesis.htm

www.wisc-online.com/objects/index_tj.asp?objID=AP1302

1.1.6 Recognise the occurrence, structure and function of nucleic acids

21

http://www.wisc-online.com/objects/index_tj.asp?objID=AP1302



http://www.biostudio.com/demo_freeman_protein_synthesis.htm




Spec Ref


Cut and stick exercise to show both transcription and translation on one page – highlighting the processes and their locations.

Outline the structure and function of tRNA and ribosomes.

22


Spec Ref


5.3.4 Explain the one gene/one polypeptide theory.

Emphasise that one gene codes for a specific polypeptide - enzyme, hormone, antibody etc. This can be enhanced by demonstrating fictitious examples of base sequences leading to amino acid chains etc – emphasis on the sequence of the bases determining the sequence of the amino acids and hence the polypeptide.

The importance of enzymes in controlling all cell reactions and metabolic pathways.

LINK – 1.2 Enzymes

23


Unit A2 2: Biochemistry, Genetics and Evolutionary Trends Specification Section 5.4: Gene Technology

5.4 Gene Technology

Spec Ref


5.4.1 Explain the stages involved in gene transfer

Explain an overview of gene technology, its uses, benefits and drawbacks. Use relevant examples to engage pupils e.g. ‘Dolly the sheep’, ‘Flavr Savr’ tomatoes, embryo technology, designer babies etc.

Explain the stages involved in gene technology as a flow diagram which can be expanded into fully detailed notes – obtaining donor DNA with use of enzymes, use of DNA probes, incorporation into donor genes using vectors, transformation of recipient cells and use of markers to check success of recipient cells.

Define all or any terms which pupils may find difficult, this is most easily done by developing a genetics vocabulary list which can be updated as the topic progresses.

Explain why recipient cells are

www.present.udel.edu/biotech/rDNA.html

www.pbs.org/wgbh/nova/genome/sequencer.html#



24

http://www.pbs.org/wgbh/nova/genome/sequencer.html#

http://www.pbs.org/wgbh/nova/genome/sequencer.html#

http://www.present.udel.edu/biotech/rDNA.html

http://www.present.udel.edu/biotech/rDNA.html


Spec Ref


chosen e.g. rapid life cycle etc. Show pictures of recipient cells and pupils can use this as a visual tool for memory skills.

Use analogies to enhance explanation and link the information covered here to the theory previously covered in other modules, highlighting the fact that this topic involves the application of theory covered into industry etc.

Use animations.5.4.2 Appreciate the range of

substances produced by genetically engineered micro organisms

Highlight that micro organisms are used as recipient organisms due to their rapid life cycle.

Detail the process of the production of the important chemicals using a flow diagram, this puts the theory covered in 5.4.1 into the context of each chemical studied – insulin, human growth hormone, enzymes, adhesives, lung surfactant protein etc.

Highlight that this method of highered.mcgraw-

25

http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter16/animations.html#


Spec Ref


production is highly efficient and effective and also necessary in modern pharmaceuticals and medicine.

Where possible link the use of these products to the topics studied at AS and A2 to further place them into context e.g. lung surfactant links to Respiratory systems in mammals in 2.1.6

Website

hill.com/sites/0072437316/student_view0/chapter16/animations.html#

26




Spec Ref


5.4.3 Appreciate the role of transgenic animals and plants

Definition of a transgenic organism. Possible topic for discussion and

pupil research using topical issues – newspapers etc.

Table of examples of transgenic plants, brief description, their products, benefits, drawbacks etc.

Table of examples of transgenic animals, brief description, their products, benefits, drawbacks etc.

Use newspaper articles and/or topical television news reports or documentaries to inform pupils and to inspire interest in this field e.g. Channel 4 ‘Animal Farm’ 2007.

Website

www.learner.org/ channel/courses/biology/units/gmo/images.html

27

http://www.learner.org/channel/courses/biology/units/gmo/images.html




Spec Ref


5.4.4 Explain gene therapy, showing an appreciation of advantages and problems

This is an opportunity for pupils to research this topic and present back information to the class – emphasis on advantages and disadvantages etc.

Define the need for gene therapy as a treatment for genetic disease caused by an absence of a gene or a faulty gene.

Treatment through the introduction of a functional gene to restore normal functioning e.g. treatment of CF through the use of an inhaler which contains lipid droplets each of which contains the functional gene to correct the CF condition. These droplets are inhaled into the lungs and the lipid droplet fuses with the lipid bi-layer of the membrane so releasing the functional gene into the lung cells.

Discuss and summarise the advantages and disadvantages of somatic cell replacement therapy.

28


Spec Ref


5.4.5 Understand genome sequencing projects

Define genome – the complete sequence of DNA on one set of chromosomes in diploid, eukaryotic organisms. Relate the sequence of DNA to the fact that it is the sequence of genes present as determined by the sequence of bases. Hence, the determination of the genetic code.

Look at the sequencing projects which have been undertaken to date via the web e.g. E.coli as the first organism to be fully sequenced etc. Each group of pupils could be asked to research one of the listed organisms and report back to the class on the details found.

Development of the fact that knowledge of the genetic code as discussed above, enables the production of the structure of the proteins that would be produced during expression of the genes.

Discussion of the Human Genome Project using the web address listed.

Highlight that the production of genome sequences enables a library


www.genome.gov/25019879#GetCD

www.sumanasinc.com/webcontent/anisamples/nonmajorsbiology/dnalibrary.html

www.dnalc.org/ddnalc/resources/animations.html

www.dh.gov.uk/en/Publicationsandstatistics/Publications/PublicationsPolicyAndGuidance/DH_4118934

29

http://www.dh.gov.uk/en/Publicationsandstatistics/Publications/PublicationsPolicyAndGuidance/DH_4118934



http://www.dnalc.org/ddnalc/resources/animations.html



http://www.sumanasinc.com/webcontent/anisamples/nonmajorsbiology/dnalibrary.html



http://www.genome.gov/25019879#GetCD

http://www.genome.gov/25019879#GetCD


Spec Ref


to be produced which details genetic disorders etc and will therefore support developments in gene therapy, genetic testing, diagnosis and designer drugs. Give relevant examples which will support this theory e.g. Pre-implantation Genetic Diagnosis, breast cancer and CF treatment.

30


Spec Ref


5.4.6 Appreciate that the inactivation or replacement of genes facilitates the understanding of gene and organism function.

Discuss experimentation using animals, explain that the true functioning of a gene can only be determined when its effects are seen in a similar organism e.g. a mammal. The effects of the gene can be seen when the gene is removed, this allows the genes role in protein production and therefore metabolism to be assessed. The mouse is a useful organism to use for this diagnostic treatment – knockout mouse and knockin mouse (website). This technology is again useful in the development of genetic disorders and drug therapies e.g. Parkinson’s disease, arthritis and diabetes.

www.en.wikipedia.org/wiki/Knockout_mice

31

http://www.en.wikipedia.org/wiki/Knockout_mice

http://www.en.wikipedia.org/wiki/Knockout_mice


Spec Ref


5.4.7 Appreciate social, legal, ecological and ethical issues regarding the benefits and risks of gene technology

This can involve pupil research and the staging of a debate-like class structure. Each pair of pupils can be given an identity within this social debate and they then defend their position e.g. pharmaceutical company, Religious leader, animal rights campaigner, ecological campaigner etc. This will encourage them to research the issues involved and to develop a reasoned view on the subject. Develop a set of questions which you can ask and challenge the pupils which will encourage them to think

Summarise all points in a table of benefits and risks.

Guide pupils to consider the following; safety precautions, limitations of gene transfer, potential dangers of gene transfer and need for legislation. Give examples where applicable.

32


Unit A2 2: Biochemistry, Genetics and Evolutionary Trends Specification Section 5.5: Genes and Patterns of Inheritance

5.5 Genes and Patterns of Inheritance

Spec Ref


5.5.1 Understand the terms genotype and phenotype

Provide pupils with definitions of these two terms.

Use analogies to explain the difference between these terms – e.g. genotype is the genes, phenotype is the outward appearance as determined by the genotype and the environment etc.

Define homozygosity and heterozygosity – if appropriate remind pupils of homo and hetero as prefixes to other words which they may be more familiar with e.g. homologous chromosomes at GCSE.

5.5.2 Understand the relationship between chromosomes, genes and alleles

Develop a vocabulary list of the definitions of each of the terms used.

Enhance this list using diagrams of the structures involved and how they are all related to one another.

Animation to show the relationship

www.sciencenetlinks.com/interactives/dna.swf

www.biostudio.com/demo_freeman_dna_coilin



33

http://www.biostudio.com/demo_freeman_dna_coiling.htm


http://www.sciencenetlinks.com/interactives/dna.swf

http://www.sciencenetlinks.com/interactives/dna.swf


Spec Ref


between the chromosome, DNA and allele.

g.htm

34



Spec Ref


5.5.3 Understand the inheritance of traits showing discontinuous variation

Define various types of variation – show pupils typical graphs of data and ask them to explain the results with regards to characteristics in plants and animals.

Define monohybrid and dihybrid inheritance – mono means one and di- means two traits.

State Mendel’s first law of inheritance.

Explain dominance and recessiveness using examples and analogies.

State Mendel’s second law of inheritance and link both laws to the increase genetic diversity at meiosis, no two individuals are the same.

Work out various examples using the genetic diagram as a standard format – teach pupils how to display their work using a punnett square where applicable.

Teach pupils the test cross method of determining the genotype of an unknown organism.

Use various examples to explain and enhance the theory e.g. monohybrid

www.science.nhmccd.edu/biol/monohybr/monhybr.html

www.science.nhmccd.edu/biol/dihybrid/dihybrid.html

www.science.nhmccd.edu/biol/monohybr/test.html

www.biologica.concord.org/webtest1/web_labs_mendels_peas.htm

35

http://www.biologica.concord.org/webtest1/web_labs_mendels_peas.htm



http://www.science.nhmccd.edu/biol/monohybr/test.html

http://www.science.nhmccd.edu/biol/monohybr/test.html

http://www.science.nhmccd.edu/biol/dihybrid/dihybrid.html



http://www.science.nhmccd.edu/biol/monohybr/monhybr.html




Spec Ref


tall and short pea plants, codominance in flower colour, multiple alleles for blood groups and chicken combs, lethal alleles etc. Use the animations available to increase understanding.

36


Spec Ref


5.5.4 Understand sex determination and sex linkage

Define the difference between autosomes and sex chromosomes.

State the determination of sex in mammals through XX and XY – study different karyotype diagrams and ask pupils to identify the sex of the individual – this will revise previous knowledge.

Dominant and recessive characters can be sex linked – carried on the X chromosome e.g. Haemophilia, colour blindness etc.

5.5.5 Gene interaction Explain what gene interaction is and give examples – the characteristics of both genes which affect each other e.g. sweet pea plant, 2 white flowered parents can produce purple and white flowered offspring.

Give examples of the inheritance of traits showing gene interaction e.g. sweet pea plants, chinchilla coat colour etc.

5.5.6 Understand the inheritance of traits showing continuous variation (polygenic inheritance)

Definition of continuous variation using the typical graph to explain any data.

In its most basic form polygenic inheritance means more genes

37


Spec Ref


therefore more phenotypes therefore continuous variation –organisms belong to neither one category or the other.

Emphasis on the environment as a contributing factor to continuous variation.

38


Unit A2 2: Biochemistry, Genetics and Evolutionary Trends Specification Section 5.6: Mechanism of Change

5.6 Mechanism of Change

Spec Ref


5.6.1 Understand the concept of the gene pool

Define the term gene pool – the total sum of the alleles of genotype and allele frequencies of a gene in a population at a given time.

Look at genotype frequencies. Look at phenotype frequencies. Allele frequencies. Apply these terms to examples.



39


Spec Ref


5.6.2 Understand the Hardy-Weinberg equation and apply it to calculate allele and genotype frequencies in an outbreeding population

Vocabulary list. Explain that the Hardy-Weinberg

principle allows us to predict numbers of expected genotypes in a population. The principle tracks the proportion of two different alleles in the population.

State the Hardy-Weinberg equation – p2 + 2pq + q2 = 1 where the allele frequencies are denoted by p and q for the alleles A and a.

p2 represents the homozygous dominant condition.

2pq represents the heterozygous condition.

q2 represents the homozygous recessive condition.

Use of the equation to calculate allele frequencies from various examples

The Hardy-Weinberg principle is the situation in which a genetic equilibrium is maintained and in which alleles combine randomly at fertilisation.

Summarise the conditions for the application of Hardy-Weinberg equilibrium in a table e.g. non-

www.ncbi.nlm.nih.gov/disease/EVC.html

40

http://www.ncbi.nlm.nih.gov/disease/EVC.html

http://www.ncbi.nlm.nih.gov/disease/EVC.html


Spec Ref


random mating as applied to wind pollinated grass flower; migration leading to gene flow – in the Amish population this gene flow is missing (website); mutations; natural selection as highlighted by Ptarmigan plumage moult and large finally population size.

Apply this theory to relevant examples and encourage pupils to apply this information to their general knowledge of the natural world.

41


Spec Ref Learning Outcomes Teaching Strategies Additional Notes (Resources, risk assessment, practical)

5.6.3 Understand the source and maintenance of genetic variation

Vocabulary list. The heterozygote individual as that

which is a reservoir of genetic variation within a population due to the fact it is the individual with 2 alleles of one gene. This condition maintains the occurrence of disadvantageous alleles in the population whereas the homozygote recessive for this allele is eliminated due to the disadvantages delivered to the phenotype e.g. failure to reproduce.

Mutations as a source of variation in that a mutation leads to a change in structure or amount of DNA. This will then lead to the production of different proteins which will result in increased variation within the population; somatic cell mutations will affect the organisms phenotype and therefore their survival but will not influence evolution. Mutation can be further studied in terms of gene mutation which will lead to one individual characteristic changing and then chromosome mutation (aneuploidy and polyploidy) which will lead to the inheritance of the mutant

www.ygyh.org

42

http://www.ygyh.org/



characteristic by the offspring. Polyploidy organisms are often associated with extremely advantageous features such as size, hardiness, disease resistance etc, discuss and note the significance of this with regards to plant breeding for successful/desirable characteristics.

Mutagenic agents can be discussed with regards to pupil’s own knowledge – reference can be made to the Chernobyl disaster and the research carried out into the increased occurrence of Leukaemia in people who live close to electricity pylons. This can then lead into a table of the different mutagenic agents e.g. X-rays, UV light, Cyclamate – pupils will be able to relate some of these to experiences in real context (lead vests for nurses who carry out X-rays in hospitals).

Sexual reproduction is the basic method of maintaining variation due to cross fertilisation of gametes carrying different genetic information.

43



5.6.4 Understand selection and its contribution to the maintenance of polymorphic populations and evolutionary change in populations

Vocabulary list defining selection, polymorphic and evolutionary change.

Discuss natural selection in respect to Darwin and build on their general knowledge and knowledge from GCSE.

Examples – natural selection as illustrated by antibiotic resistance in bacteria and Darwin’s finches etc.

Stabilising selection as illustrated by the length of hind legs in rabbits and birth weight in human babies. Include typical graph.

Directional selection as illustrated by peppered moth and ear length in hares. Include graph.

Polymorphic populations are used to investigate both types of selection mentioned above due to the occurrence of many different individuals.

44


Spec Ref


5.6.5 Understand the concept of species and the process of speciation

Definition of species. Ask pupils to think about why all

birds are not the same, why all frogs are not the same. This will encourage them to see that within one genus of animals/plants there are several different species each with its own defining characteristic. Possibly even introduce the research on the various different species of human being – Homo habilis, Homo neanderthalensis etc.

Types of speciation which occur – table format; sympatric speciation between 2 groups in the same environment; allopatric speciation due to geographical isolation as with Darwin’s finches/Tilapia in Kenyan lakes leads to genetic divergence.

Study genetic divergence as the product of reproductive isolating mechanisms which prevent the new mutations in the isolated group being transferred to the original group – behavioural isolation, ecological isolation, temporal isolation, mechanical isolation and

45


Spec Ref


hybrid isolation giving appropriate examples.

Significance of polyploidy in plant speciation e.g. Spartina species – the sterile hybrid would not be able to carry out normal meiosis hence reproductive isolation.

46


Unit A2 2: Biochemistry, Genetics and Evolutionary Trends Specification Section 5.7: Kingdom Plantae

5.7 Kingdom Plantae

Spec Ref


5.7.1 Describe the form (level of organisation) and life cycle in Division Bryophyta

Provide pupils with flow diagram showing the classification of Kingdom Plantae into different divisions and classes etc. Give various examples of the organisms belonging to these divisions to provide pupils with a relevant link to the theory.

Bring in a sample of the specimen e.g. moss and use it in an idea showering session focusing on the form, differentiation, features, structures etc. Introduce a diagram of the moss and use this to introduce technical names e.g. gametophyte, archaegonium and antheridium etc.

Provide pupils with a vocabulary list defining the scientific terms for the structures and develop a memory scheme for remembering the structures and their functions.

LINK – 2.3.8 Appreciate the 5 kingdom system of classification

LINK – 2.3.6 Understand the other taxa within which species can be grouped



47


Spec Ref


Table on form of Bryophyta. Emphasise the nature of the structure and its function and the role it plays in alternation of generations.

Life cycle displayed as a diagram using labels and pictures of structures involved in each stage. Colour code the sections of the sporophyte and gametophyte to effectively show the alternation of generations. Emphasise the importance of water for the transfer of sperm; spores formed by meiosis; gametes by mitosis.

48


Spec Ref


5.7.2 Describe the form (level of organisation) and life cycle in Division Tracheophyta

Definition of Tracheophyta as multicellular plants with vascular system divided into 2 sub-divisions – Pteridophytes and Spermatophytes.

Provide classroom specimens of Pteridophytes and Spermatophytes and identify features and structures.

Show pupils pictures of examples. Introduce diagrams of specimens

and label the structures – providing a vocabulary list where appropriate to aid understanding e.g. prothallus etc. Highlight that spermatophytes are more complex and advanced as they are not dependent upon water for reproduction – they produce pollen instead of spores.

Life cycle diagrams as with Bryophyta – colour coded to show alternation of generations etc. Emphasise the sporophyte is dominant over the gametophyte, spores produced by meiosis, gametes by mitosis.

LINK – 2.1.13 Understand the movement of water (and dissolved ions) through xylem

LINK – 2.1.14 Understand the translocation of organic solutes through phloem

5.7.3 Compare the divisions of Plantae

Repetition of flow diagram to highlight classification.

Review of features studied in each

49


Spec Ref


specimen. Place these observations and notes

into a table which details the characteristics and specific features of each division.

Highlight the increasing level of complexity and level of organisation from Bryophyta to Pteriodophyta to Spermatophyta.

50


Unit A2 2: Biochemistry, Genetics and Evolutionary Trends Specification Section 5.8: Kingdom Animalia

5.8 Kingdom Animalia

Spec Ref


5.8.1 Describe the body form and feeding in Phylum Cnidaria

Flow diagram showing classification of animals into phylum etc.

Highlight that animals are divided into phyla while plants are classified into divisions.

Develop a reference page for this topic which will include diagrams of radial and bilateral symmetry in body form; diploblastic/triploblastic; ectoderm; endoderm; mesoglea etc. and a vocabulary list to detail and explain such terminology as coelomate and aceolomate.

Concentrate on Phylum Cnidaria as radially symmetrical, diploblastic animals with little differentiation e.g. Hydra. Give diagram of Hydra highlighting the body features (mesoglea, hydrostatic skeleton etc.) and providing pupils with the opportunity to relate the structures present to the feeding habits and

LINK – 1.1.6 Understand the mechanisms by which substances move across membranes



51


Spec Ref


life cycle of the Hydra.

Emphasise that initial digestion is extracellular with the final phase intracellular by endocytosis. Encourage pupils to understand the use of tentacles etc in the feeding process. This could be enhanced using video clips from such T.V. documentaries as the ‘Blue Planet’.

52


Spec Ref


5.8.2 Understand the body form and feeding in Phylum Platyhelminthes

Platyhelminthes as triploblastic, acoelomate animals showing tissue differentiation e.g. Planarian.

Show pupils diagrams of the body structure of Planarian from external views and also transverse and longitudinal sections with labels.

Show pupils pictures of Planarian to link the diagrammatic representation to ‘real life’

Introduce some outside interest with reference to the parasitic Platyhelminthes such as Liver Fluke etc.

Emphasise non-cellular mesoglea from Phylum Cnidaria becomes the cellular mesoderm which supports the body hence the organism retains its shape at all times unlike the jelly-like Cnidaria.

Differentiation in feeding habits from detritivores to active predators. Primitive digestive system – 1 opening to body with simple gut running throughout the body. Most of the digestive process is carried out intracellularly.

Direct pupils thought processes

53


Spec Ref


towards realising that there is an increase in complexity between the 2 phyla studied so far.

At this stage start developing a summary table which focuses on the main features of each Phyla – this will guide thought processes to make links between Phyla and will also aid the learning process.

54


Spec Ref


5.8.3 Describe the body form and feeding in Phylum Annelida

Annelida as triploblastic animals with a body cavity and tissue differentiation.

Highlight the following – first animal so far to have a body cavity and true tissue differentiation – increasing complexity. Encourage pupils to suggest reasons for this body cavity and tissue differentiation and to predict the feeding habits of the annelids.

Introduce the example of the earthworm using a diagram clearly labelled with defining features.

From this diagram move on to discuss body form – labelling the 3 body layers and the coelom. Highlight the well differentiated digestive system etc.

Note the bilateral symmetry and the segmentation of the body form – extrapolate to discuss other segmentation in other animals and this can be linked to the process of evolution from one common ancestor. Note that segmentation provides a hydrostatic skeleton for movement. Show a video clip of

55


Spec Ref


earthworm movement to explain how this hydrostatic skeleton works – again a good source would be ‘Life on Earth’ etc.

Highlight that earthworms are detritivores with a specialised gut and extracellular digestion.

56


Spec Ref


5.8.4 Describe the body from and feeding in Phylum Chordata

Idea shower names of organisms that pupils think are chordates, from these initial ideas direct pupils to idea shower the characteristics of body form and feeding of the animals they have suggested. Encourage them to use the vocabulary introduced in this topic and try to reach a final stage of developing a few sentences to describe Chordates as has been done for them with other Phyla studied.

Chordates as triploblastic, coelomate animals with the defining feature of an internal skeleton using any example of a small mammal - mouse, rat etc.

Detail on form should focus on the variety of systems present due to complex differentiation of tissues. The nature of these systems means that chordates are bilaterally symmetrical, segmented and at some stage of development have a post-anal tail – show pictures of the human foetus in early stages of

57


Spec Ref


development when a small tail is evident to generate interest.

Defining feature of the internal skeleton is the stiff dorsal rod which gives the body structure and therefore a true back and front unlike Phylum Cnidaria. This skeleton is made from jointed calcified bones. Encourage pupils to make comparisons between the Phyla studied and this will enable them to remember the features of each.

Discuss the variation in feeding habits – the differentiation in systems and complexity in body form enables chordates to be active predators, omnivores or herbivores.

Look at the mammalian digestive system as a sequence of well developed specialised regions where structure and function are closely linked as previously studied. Highlight that digestion is extracellular in the spaces within the system e.g. stomach and duodenum.

Finish by completing the summary

58


Spec Ref


table linking the features together and highlighting the increase in complexity for each Phyla and the consequences that has on feeding and lifestyle for organisms within that classification. Throughout the topic encourage pupils to think of their own examples as this will aid their learning process.

5.8.5 Practical Work Study appropriate living and preserved specimens, prepared slides and photographs.

59

a2 2:

Documents

krebs cycle

structure of atp

atp yield

ccea exemplar scheme

conversion of atp

edubi glycolysis

risk assessment

respiration time