Difficult Questions Thread - Biology

[Owlbird83]

Modelled on Artydreams' chemistry difficult questions thread, I'll also be posting some old past VCAA questions that less than 50% of people got correct in the exam. Please use a spoiler to hide your answers from others reading when you post. Hopefully by participating you'll be get some extra bio revision!

From 2002 VCE biology exam 1:

1. A plant wilted but later recovered. During the time the leaves were wilted, the rate of photosynthesis decreased because
A. enzymes in the leaf cells were denatured.
B. chlorophyll in the wilting leaves was broken down.
C. the amount of light reaching the plant was reduced.
D. the amount of carbon dioxide entering the leaf decreased.

2. Question 7
Some people have allergic responses to particular compounds or foods. For example, asthma attacks, in which a person has difficulty breathing, may be due to an allergic response. Cells of the immune system, including mast cells, are involved in these allergic responses. A summary of the action of mast cells is shown below.


a. Where are mast cells found in the body? (1 mark)

b. Name the following structures (2 marks)
-Structure X
-Structure P

c. Name compound Z. (1 mark)

The release of compound Z results in inflammation of the surrounding area.
d. What is the importance of inflammation? (1 mark)

Treatment is sometimes given to people with an allergy to reduce the chance of future reactions. Treatment can involve the injection of particular kinds of antigens.
e. Explain how this treatment reduces the chance of a future allergic reaction. (1 mark)

3. A group of students designed a series of experiments to investigate factors affecting the rate of photosynthesis in plants. The plants were enclosed in clear plastic boxes and kept in the dark for ten minutes. The plants in their boxes were then exposed to light for ten minutes. The students measured the oxygen concentration in the air surrounding the plants.
The results of their experiments are shown in the graph below.


a. i. Write a balanced chemical equation for the process of photosynthesis. (2 marks)
ii. By referring to your balanced equation, explain why the oxygen concentration in the air surrounding the plants can be used as a measure of the rate of photosynthesis. (1 mark)

b. Explain why the oxygen concentration in the air surrounding the plants decreased during the first 10 minutes of the experiment (1 mark)

[Billuminati]

Spoiler

https://drive.google.com/file/d/1TiG74tg7ALjY9DHWST3CHoNuhtM07odl/view?usp=drivesdk

Welp I guess immunology is certainly one of those things you learn, forget then repeat. Don't think I BSed 2e properly because the allergen probably can't suddenly grow "self" markers in subsequent exposures. They mentioned subsequent exposures so it must have something to do with the adaptive immune system. Which means I probably need to do some emergency studying right now for BMS2052 which will be my microbio + immunology unit next sem

[biology1234]

Can someone explain codominance in a easy manner? I get confused  when they say dominant allele masks recessive allele?

[Billuminati]

Can someone explain codominance in a easy manner? I get confused  when they say dominant allele masks recessive allele?

Codominance is where 2 or more alleles are both dominant and when both present, do not mask each other. The easiest example to visualise this is blood types

Say you have a father with genotype I^Ai (phenotype= type A blood) and a mother with genotype I^Bi (phenotype= type B blood). If you do a Punnett square, you'll see their children will be 25% I^AI^B (type AB), 25% I^Ai (type A), 25% I^Bi (type B) and 25% ii (type O). While both the I^A and I^B alleles are dominant, they coexist in people with AB type blood and do not mask each other. However they both mask i (recessive allele for O-type blood) so people with O type blood must be homozygous for the recessive allele in order for their phenotype to be expressed