AQA A2 Biol4 January 2012 pre- exam discussion

You are told that is very rare --> so likely to be reccessive, and because you have to have two copies of a recessive allele for it to be present in the phenotype, its going to be homozygous recessive.

So 48% --> ''rr' we'll call it.
So 'r' = square root of 0.48 (same as 48%)
Therefore r is 0.693.
1- 0.693 = 0.307, because R (dominant allele) and r (recessive allele) MUST equal one.
So R = 0.307, r = 0.693.

Use the equation

p^2 + 2pq + q^2 = 1
Where 2pq is for the heterozygous. So you do (0.693*0.307)*2 = 0.43 which is 43%. Hope this is correct haha

The allele for the disorder is Dominant, it says so in the question. I'm confused.

Oh, let me add your retarded line: 'lol at you'.

....
I didnt read the dominant bit.. so yeah lol at me..
awkward haha

Bold = relevant information to question.

So, you know 48% of the population are either HH or Hh, so 52% are hh.

Need to work out allele frequency. h = sqrt(0.52) = 0.72, so H = 0.28.

Heterozygous is 2Hh = (2*0.72*0.28)*100 = 40.32%

1) ATP is a better source of energy than glucose. Give one reason why (1)
2)Explain why photolysis of water is needed in the light dependent stage (1)
3) Give one way in which the rate of photosynthesis can be measured (2)
4) After succession, a climax community is made. Explain the advantage of this in terms of food chains/webs (1) (old spec question)
5) State the units for which:
Pyramids of Biomass (2)
Pyramids of Energy (1)
is measured
6) Explain one disadvantage of using chemical pesticides (1)
7) In intensive rearing of livestock, the food intake is controlled. Explain why (2)
8) Describe what is meant by:
A genotype (1)
A phenotype (1)
A recessive allele (1)
9) Explain the effect of combustion of fossil fuels towards the environment (2)
10) Explain how leaching can occur (1)
11) On the death of animals, saprobionts break down large organic molecules into smaller ones and absorb these via diffusion. They also contribute towards climate change. Explain how (3)


GO GO GO

You arent going to attempt my wonderful questions on the previous page? haha

I know the answers, so it'd be a waste of time.

You arent going to attempt my wonderful questions on the previous page? haha

hey i answered them!

1) ATP can be formed in one simple step: ADP + Pi --> ATP, and because it's released in short bursts less is wasted as heat.
I wouldnt credit the bit about it being formed in one step, however you can say it can be hydrolysed in a single step reaction. But the short bursts one would score credit, not sure though.. you gottta specify that it releases a small amount of energy.
2) photolysis of water is needed to lyse the water into o2 and electrons, so that the electrons can be passed along the electron transfer chain, it provides electrons to replace those that are lost from photosystem 2, which help ATP generation.
V. good.
3) the rate of photosynthesis can be measured by measuring the volume of oxygen produced from a plant. so for example by doing an experiment with a plant underwater with a funnel over it, and then counting the number of bubbles coming out of the funnel. i'm not sure, i have no idea
1/2 - remember to say divided by per unit time
4)
5) pyramids of biomass is measured in g/m2
For area --> gm^-2, then for volume its gm^-3
pyramids of energy is measured in kcal ?
kjm^-2year^-1
6) one disadvantage is that they can be leached if it rains, and this can lead to eutrophication
v good.
7) food intake is controlled because for example, in a battery farm the animals are all confined to a very small space and hence they cannot move around which leads to them losing less energy, so they don't need to eat as much food. this is useful for the farmer because he doesn't need to spend loads of money on feeding the animals in excessive amounts
0 marks. You gotta say food is given which contains high protein, etc for good digestability/maximum growth.
8) a genotype is the genetic makeup - the specific allele makeup of the individual
a phenotype is the visible characteristics/ the observable behaviour, they result from the genotype
v good.
9) combustion of fossil fuels leads to accumulation of greenhouse gases which lead to global warming: this causes the earth to warm up and affects the environment.

10) leaching can occur w
hen there is rainfall and this causes pesticides or fertilizers to be washed away into lakes or reservoirs.
rainwater dissolves the fertilisers.
11) saprobionts, i have no idea, they are decomposers that break down the dead organisms. they contribute to climate change because they do respiration so they release co2 into the atmosphere which is a greenhouse gas which can lead to global warming ?
V good - but you gotta say extracellular digestion - enzymes etc

I know the answers, so it'd be a waste of time.

By the way this is *KINDA*ish portraying you as over-confident....

6) one disadvantage is that they can be leached if it rains, and this can lead to eutrophication

i just can't get in the mood to study unit 4 bio.... arghhhhhhhh

Sorry I've asked this before as well, but does anyone have the June 09 paper?

Sorry I've asked this before as well, but does anyone have the June 09 paper?

All the old spec papers are here: http://www.aqa.org.uk/qualifications/a-level/science/biology/biology-6416-materials