OCR Gateway Biology B1,2,3 25/05/2016 unofficial markscheme

what are the grade boundaries

Please comment if you think these are wrong/you know some questions I missed etc.

1. a) A=iris, controls the amount of light entering the eye
B=retina, where the image is focused, detects the light rays [2]

b) cornea, lens [2]

c) They each receive different alleles from the parents so their phenotypes are different from having different recessive/dominant alleles [possibly 2]

d) The 2 eyes see images which overlap and the brain compares the two to judge distance - seeing how similar/different the images are [2]

Total: 8

2. a) auxins [1]

b) Charlotte - the roots are growing towards gravity so are positvely geotrophic [2]

Total: 3

3. a) 33g [1]

b) She also needs protein for the growing foetus - her EAR would increase [1]

a) f f (mother) F f (father) = 50% [2]

b) f f (mother) F f (father) = 50% [2]

Total: 6

4. a) stimulant because increasing the amount of neurotransmitters [2]

b) 6 mark - describe the graph and explain why a placebo is used eg reduces psychological effects, fairer test, accurately see if the drug has any effect [6]

Total: 8

5. a) The tigers have a lack of habitats so fewer reliable food sources, possible mating partners etc. [3]

b) As the numbers of predator increase, the numbers of prey decrease. There is cyclical fluctuation - the predators and prey have similar graphs but a time difference. [2]

Total: 5

6. a) Phylum, Order, Genus [3]

b) They evolve with different gene pools and eventually their DNA becomes so different they are considered different species [2]

Total: 5

7. a) they compete with other organisms eg. bees for the nectar [1]

b) Their habitat and role in that habitat - they both play the same role of feeding on the nectar in their habitat [1]

c) They have evolved to feed from oak trees instead of bushes so have different mouth parts to allow them to do this [1]

Total: 3

8. a) 1940-1980 [1]

b)

c) The gradient of the line - there will probably be a range for this as the graph was a little ambiguous so 0.5-0.7/80 = 0.00625-0.00875 [2]

d) With a hugely increasing population, it will become harder to think about the future when developing because there will be more people now to consider or something like that [2]

Total:

9. The controversial 6 mark - 2 or 5%? (I put 2). The energy is lost by egestion, excretion and respiration. There is not enough energy left for another trophic level because the efficiency is so low - most of the energy at each stage is used for things other than growth. [6]

Total: 6

10. a) D because it has a thicker wall to allow for higher pressure blood to travel to the body and is the mirror image of a normal heart [2]

b) I'm not sure [how is the transplant surgery different]- I put the vessels eg. vena cava would be on the opposite side to normal [2]

c) 6300 [1]

d) ad: the doctors need to know if someone has it to carry out treatments, quite a few people are affected by it,

dis: not that many people are affected by it, could be expensive, could cause harm to the foetus, parents may disagree [2]

Total: 7

11. a) 6 marks, advantages and disadvantages of Aspen wood cloning:
ads: every organism is genetically identical so know characteristics, supported structure
dis: a genetic illness could affect all organisms, all are male so cannot reproduce with a female [6]

b) Plant cells continue to have the ability to differentiate (become other cells) as the plant ages, whereas animal cells lose this ability OR animal cloning raises more ethical questions and moral issues for most people than plant cloning (I don't know which it is) [1]

c) ads: more accurate
dis: requires killing the organism [2]

Total: 9

12. a) the amount of oxygen needed to oxidise the amount of lactic acid which has built up [1]

b) The amount of oxygen which is needed will be the same as the amount taken in - the oxygen taken in is needed to replace the oxygen debt [1]

c) Lactic acid. It steeply increases during exercise because of anaerobic respiration and then gradually decreases after when it's broken down by the liver, until none is left. [2]

Total: 4

13. a) The number x 3 because there are 3 bases coded for 1 amino acid [1]

b)

c) The DNA unzips, allowing free nucleotides to attach to each strand and form 2 new DNA molecules. A-T and C-G. [3]

Total: 6

what are the grade boundaries

For 13)a)

Would it not x2 because it doesn't matter what base pairs it's always two?

Can't remember exactly but that's what I put.

It's 3 bases per amino acid, so it's x3 unfortunately

what are the grade boundaries

Guess we all did good so plus the b456 paper and cause we shall b fine make sure to revise as tht paper is more marks

For 9, I can pretty much confirm it is 2%, as the question asked about grass and sheep, not sheep and humans

what did you guys get for the second last question (13 b)?
it was like "dna polymerase is coded for by a different order of amino acids in some genes than others, why is this?" (really badly paraphrased soz)
i said "because they have different functions" but i wanted to say "because the order of amino acids changes the shape of the dna polymerase and thus active site making it specialised for different substrates" but i ran out of time... ****. any marks for this?

Is this GCSE Biology OCR Gateway?? I'm doing triple science too!

Yes, that is why the thread is called 'OCR Gateway Biology B1,2,3 25/05/2016 unofficial markscheme'

Yes, that is why the thread is called 'OCR Gateway Biology B1,2,3 25/05/2016 unofficial markscheme'