What to expect for your Unit 2 exam…

1. What to expect for your Unit 2 exam…

2. It may draw on any of the four principles from Unit 1: • Polymers & polymerisation. • Functions of proteins. • Enzymes (structure & function). • Structure of plasma membranes & the exchange of substances.

3. Did you know that… • It is 105 minutes long & carries 85 marks? • Is worth 47% of the total AS marks? • It has 7-9 short answer questions followed by two longer questions (data-handling & HSW)?

4. The examiners have written it so the early questions and the early sections of the longer questions are E-grade. • The examiners will test your ability to apply your understanding to unfamiliar contexts e.g. how a named cancer drug works by using your knowledge of proto-oncogenes or interpret data on polecats compared to ferrets – you DON’T need to learn about polecats & ferrets!!!

5. Using information from the one-day student conference…Unit 2 could be about the following:

6. DNA: • Structure: • Nucleotides • Bases: ATGC • Replication: • Semi-conservative (HSW) • Heavy nitrogen • Link structure to function: • Codons/introns/multiple repeats

7. Cell Cycle: • Mitosis: • Cell replication (growth & repair). • Know the stages. • Recognise images of each stage. • Link to cancer (HSW).

8. Variation: • Understand: mean, standard deviation, normal distribution, continuous and discontinuous data. • Apply the understanding to unfamiliar scenarios. • E.g. using standard deviation to identify significant differences between data sets.

9. Variation & diversity: • Meiosis: • Crossing over & independent assortment cause variation. • Four haploid nuclei formed. • NOT JUST gamete formation e.g. it can also occur in other stages of algae & fungi life cycle. • Key words: • Homologous • Chromatids • Centromeres • Chromosomes • Bivalent • Chiasma • Recombinant allele

10. Variation & diversity (cont’d): • Genetic diversity: • Affected by bottleneck, founder effect & selective breeding. • Selective breeding ethics (HSW). • Diversity index: know your BIG N from your LITTLE n. • DNA in bacteria: • Antibiotic resistance: • Conjugation. • Transmission (vertical & horizontal). • Immunological studies (HSW).

11. HSW: • If you are asked to “discuss” then you include BOTH sides of the argument so use the word BUT • With ethics there are no fixed correct answers use your knowledge of Unit 1 AND 2 to answer the questions. • Read the passage carefully, everything is there for a reason. • Underline key phrases. • Use the information from the passage to answer the question: be objective.

12. Transport: • Know surface to volume ratio. • Adaptations for insect (tracheal sys), fish (gills), mammalian (blood sys) & plants (xylem). • Circulation of blood & tissue fluid. • Transpiration in plants including apoplastic & symplastic pathways, uptake in roots, root pressure, cohesion-tension theory & factors affecting transpiration. • Conflict between gas exchange & water loss in plants & insects.

13. Handling data: • Can you describe (grade E) OR describe & interpret data (grade A)? • READ: • The question – if it says use the graph or table, do so!!! • The graph axes/table headings. • Check the points – use them in your description or interpretation. If there’s a maximum say so, where is it? • Strong positive correlation etc.? • Use the graph to predict – draw a line (or curve) of best fit.

14. Evaluate = judge the worth of…use the word BUT Find a discrepancy with your observation. E.g. the graph shows that there are more rats in the summer BUT large fluctuations, maybe other species would show different results & sample size may have been too small.

15. HSW: • The large HSW question is worth nearly 20%... It will be based on anything from the course but will involve current issues. It could be about an investigation, trialling drugs, ethical issues or interpreting data.