Post Exam Discussion AQA A2 Biol4 25th January 2012

me too lol

I thought the question stated that pigs could survive at temperatures above 35 degrees, but you had to give a reason why they didn't continue raising the temperatures???

Reply 41

EffKayy

16

Original post by alexremix

I thought the question stated that pigs could survive at temperatures above 35 degrees, but you had to give a reason why they didn't continue raising the temperatures???

Yeah there would be no point raising the temperature as the biomass/percentage efficiency or whatever was the same from 30 and 35. so timeconsuming etc

Reply 42

baldybolstridge

Question 6) C) i) what did people put, it was the question where if you increase the flow of the human sewage the concentration of nitrates at point a decreases, but surly if your push the sewage through faster, another limiting factor will mean that not all of the nitrates will be absorbed, so conc should increase ! ?

Reply 43

Lukeeee

I really liked this paper. :biggrin:

Reply 44

Yosemite80

@ baldy, That was what I initially thought too...

But because sewage needs to be converted to NH4, then NO2, then NO3 by at least three different types of bacteria, there wouldn't be enough time for the bacteria species to convert sewage to NO3 if rate of flow was increased, therefore NO3 at point A decreased, because the concentration of all those intermediate products would increase.

Reply 45

swiftylol

OP

18

Got the paper, if anyone needs a question then just ask.

Reply 46

cricketmaniac

What was the very last question? On why plants need to photosynthesise and respire???

Reply 47

swiftylol

OP

18

Original post by cricketmaniac

What was the very last question? On why plants need to photosynthesise and respire???

"Plants produce ATP in their chloroplasts during photosynthesis. They also produce ATP during respiration. Explain why it is important for plants to produce ATP during respiration in addition to during photosynthesis. (5 Marks)"

Reply 48

Yosemite80

That one was kinda tricky O.o

1. Seed formation requires a lot of ATP?
2. ATP is used in photosynthesis as well as produced?
3. They cannot move so must obtain more energy so more ATP needed?
4. I think I didn't get this one, but probably because photosynthesis doesn't take place at night and plants need ATP at night too?
5. Plants need to grow and synthesise biomass in addition to seed formation?

(edited 12 years ago)

Reply 49

Lukeeee

Original post by Yosemite80

That one was kinda tricky O.o

1. Seed formation requires a lot of ATP?
2. ATP is used in photosynthesis as well as produced?
3. They cannot move so must obtain more energy so more ATP needed?
4. I think I didn't get this one, but probably because photosynthesis doesn't take place at night and plants need ATP at night too?
5. Plants need to grow and synthesise biomass in addition to seed formation?

I just spoke about point 4 really and spoke about the whole light independent side etc.

Reply 50

Yosemite80

*by point 3 I mean they cannot obtain food for energy by chasing around their "prey", to clear any confusion

Reply 51

Renn

1

This probably isn't right but for 8(c) I basically based my answer on respiration being important in producing ATP when the production of ATP from photosynthesis is insufficient cos of limiting factors like light intensity: during the night & cloudy weather
I also mentioned how most of the Sun's energy doesn't get transferred to the plant because it's reflected back/wrong wavelength/doesn't fall on the chlorophyll molecule

Reply 52

kpmarshall

Why is the answer to the genetic cross 1/4?

I know that 1/4 comes from taking into account that gender is 1/2, but the actual question didn't ask for a specific gender, so surely it's just 1/2?

Reply 53

Yosemite80

The only hairless offspring in that cross was *one* male. Also remember that the allele is sex-linked i.e. on the X chromosome. The cross was X(H)X(h) vs X(H)Y. The result was X(H)Y, X(H)X(h), *X(h)Y* and X(H)X(H). Therefore the answer is 1/4. Because the allele is sex-linked this takes into account of gender automatically, if that makes sense.

edit: H refers to allele for hair and h the allele for no hair

(edited 12 years ago)

Reply 54

cricketmaniac

Original post by swiftylol

"Plants produce ATP in their chloroplasts during photosynthesis. They also produce ATP during respiration. Explain why it is important for plants to produce ATP during respiration in addition to during photosynthesis. (5 Marks)"

Mate what was the total marks available for the question on genetics

Reply 55

Yosemite80

First part (show the allele was recessive) was 2 marks I think, then 2nd part (show it was sex-linked) was 1, then the actual cross may have been 3-4 marks, maybe 5. I would estimate 7 in total.

Reply 56

Roxas

16

OMG I mucked up so much in this exam! I have just realise i did X(h)Y as the parent male on the cross, so my WHOLE cross is wrong, noo! -4 marks!

I got the whole reed sewage question wrong too D:

boo.

Reply 57

swiftylol

OP

18

Original post by cricketmaniac

Mate what was the total marks available for the question on genetics

Use the evidence to explain that:

Harlessness is caused by a recessive allele (2 marks)

That hairlessness is caused by a gene on the X chromosome (1 mark)

Complete the genetic diagram etc.... (4 marks)

Reply 58

sunnybacon

12

Original post by PumdogMillionaire

Did nobody find the pigs over 35 degrees question mildly entertaining/pointless "pigs can't survive at more than 35 degrees, why did the scientists not test above this temperature" - i kinda put 'because they're not cruel bastards' in obviously more eloquent biological speak...