Hey all!
Congratulations on finishing Bio!! Huge!
What did you think of the exam? Let me know below!OVERALL THOUGHTS: Overall a fair exam. They tested your understanding of a whole lot of concepts, which will have rewarded you if you'd studied a bit of everything! A few questionable MCQs, and a tricky 8-marker at the end - like always, a combination of the work of scientists + new technology. MCQs:
1. C (homeostasis)
2. D (nervous)
3. D (frank macfarlane burnet)
4. A (they fight infection)
5. B (comparative anatomy)
6. C (phagocytosis)
7. A (urea)
8. C (pH decreases, acidity increases)
9. B (experiment = 5mL starch + 1mL amylase, control = 5mL starch)
10. B (10µm - I don't have a ruler pls take this with a grain of salt.
11. C (both T and B cells have ways of recognising antigens)
12. B (Tt x tt)
13. D (a tricky one! could have been A or D, depending on how you interpreted the wording "newly made strand")
14. C (fungi have cell walls, protozoans are unicellular and do not)
15. D (codominance)
16. B (osmosis is a passive process of water moving from high to low concentrations)
17. A (Rosalind Franklin discovered DNA’s double helix shape)
18. C (accuracy = proximity of findings to theoretical findings)
19. A (44 chromosomes/2 + 62 chromosomes/2 = 53 overall. Tricky and IMO not in the syllabus)
20. D (the concentration of the substrate is decreasing)
SAQ:21. Enzyme diagramA = enzyme, B = substrate (substrate is destroyed, enzyme remains)
(2m)22. The disease question. (6m)a. Examples of infectious/non-infectious disease. You’d have your own examples here. ˝ a mark for each part of the table.
b. Drinking water question (4m). Just pick two examples and explain how they reduce risk of infection
- Chlorine +- ammonia added to drinking water in order to kill/deactivate microbes, leaving a residue that prevents recontamination
- pH adjusted with lime and caustic soda to create an inhospitable environment for certain pathogens.
23. The blood vessel question (5m)- Vessel 1 = artery: thick muscular walls allow them to push oxygenated blood at high pressures from the heart to tissues in need.
- Vessel 2 = vein: valves to prevent backflow of deoxygenated blood to tissues – allowing it to travel to the lungs for re-oxygenation.
24. Genes and homologous chromosomes (7m)a. Crossing over (2m)i. Before: Aa Bb Gg
ii. After: Aa Bb GG and Aa Bb gg
b. Effect of independent assortment on the genotype of the offspring (2m)
Define independent assortment then quickly explain that it means that those chromatids could be sorted with any combination of genes from other chromosomes
c. Isolation and evolution (3m)I would have defined evolution in a nice quick sentence, and explained how geographic isolation allows that population to evolve specific adaptations best suited to their unique environment
25. Urine concentration of marine fish and freshwater fish (4m)I would have drawn a table here.
- Marine fish = surrounded by salt water = lose water to their environment = very concentrated urine to maintain a steady state.
- Freshwater fish = surrounded by fresh water = gain water from their environment = very dilute urine to maintain a steady state.
26. Substrate/enzyme question (4m)a. Independent variable = substrate concentration
b. Trends: as substrate concentration increases, so does the rate of reaction. Eventually a plateau is reached. This is because the enzymes’ active sites are saturated and reactions cannot be catalysed at a faster rate.
27. Plants question (5m)a. Transverse sections of xylem and phloem. Something you would have wrote-learned.
b. Transport of sugars through a plant: ‘Pressure flow theory’: sugars are loaded actively into the ‘source’, and water follows by diffusion. This allows the sugars to move passively by diffusion to areas of the plant in need – the ‘sink’ – where they are actively unloaded.
28. PENDING! The photocopy of the exam I received was missing this page. 29. 'Justify the change in emphasis from treatment to prevention of a named disease’ (5m).
You could have named any disease – ideally one with some good methods of prevention! Vaccines etc.
You then had to explain why this change was beneficial. The answer is pretty much the same for any disease; prevention addresses problems before they occur (allowing for greater quality of life in the population), saves the government and individuals money (public health programs for prevention are much cheaper than treating patients), and prevention – particularly in the case of vaccine-preventable diseases - allows for herd immunity which protects the vulnerable.
30. Immune response question (6m)a. The role of ONE T-cell (2m)eg. Suppressor T-cells; to suppress the immune response once the antigen is cleared.
b. Benefit/limitation of immunosuppression in organ transplant patients (4m)
eg. BENEFIT: prevents organ ‘rejection’ when the implanted organ is recognised by the body’s immune cells as foreign and lodges an immune response against it
LIMITATION: renders the patient vulnerable to all infectious diseases, as their immune response must be suppressed for the rest of their life.
31. ‘Assess the importance of the work of Beadle and Tatum to the ability to produce a specific transgenic species’ (8m)So your job here is to:
1) explain what the work of Beadle and Tatum was, and its significance
2) define transgenic species
3) name a specific transgenic species and give about a sentence of detail about it
4) link the two; explaining where Beadle and Tatum’s findings come into play and ‘assessing’ their importance. Here I’d say ‘very’. It is possible to argue that there were other significant scientists also. You can have named them in addition to discussing B + T.
5) Have some kind of concluding statement.
As a rough guide:
Beadle and Tatum applied controlled mutation by UV rays to neurospora crassa (bread mould) – finding that mutations to specific genes resulted in the mould being unable to produce specific proteins. They therefore concluded that one gene is responsible for the production of one protein (later amended to one polypeptide).
Transgenic species are species that contain inserted genetic material that is not normally present, for example – ‘Cold Strawberries’ contain a gene from salmon that allows them to survive the cold.
Beadle and Tatum’s work was clearly extremely significant in the origination of transgenic species; which exist on the premise that inserting specific genes will lead to the production of specific, desired proteins. The example of Cold Strawberries requires an understanding of the characteristic desired, the protein that facilitates that characteristic, and the genes that code for that protein – all derivatives of Beadle and Tatum’s findings.
Clearly, the work of other scientists was also significant. For example, the structure and nature of DNA – discovered largely by Franklin, Watson, Crick and Chargaff – is important too.
Beadle and Tatum’s work built on the findings of scientists before them; using new technology available to them. The same is true for the creation of transgenic species; the creators of which built on the findings of Beadle and Tatum, along with other scientists. An understanding and appreciation of the work of others is essential for new discoveries in biology.
And... that's it! Great job team!! Hopefully you've got the time to give yourself a well-deserved break.
If you'd like to join in the discussion but don't have an account - you can make one
right here and it'll take you less than a minute.
Home
Help
Search
Login
Topic: Biology Exam Discussion (and suggested answers!) (Read 43398 times)