B123 OCR unofficial markscheme 2017 NEW. Watch

yhyh123
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1a) male phenotype - testes
male genotype - XY
female genotype - XX
female phenotype- ovaries

1b) the presence of the Y chromosone means the protein called tetesterone is produced which creates the male reproductive organ called the testes. The absence of the Y chromosone on the female means the embryo just develops ovaries.

- tick box question on phytoplankton
- decomposition of plants and respiration

PH question -
(stated at the top that the PH increases when carbon dioxide levels decrease)
therefore carbon dioxide is a non-living indicator and can be used to measure environmental change in the water. if the ph of the water increases then this shows that carbon dioixde levels are low , therefore minimises the risk of global warming. OR , if the ph level is low , this indicates that c02 levels are high and global warming may occur.


- Efficiency question was 0.2( 1 significant figure)

why is it unlikely for an owl to have a predator?
because the owl consumed a small amount of energy (16) therefore its unlikely for it to have a predator as it would not have a lot of energy to take in by the owl.( around them lines)

definition of negative feedback-
used to maintain a constant internal environment with the receptor,processing centre and effector.

why are males more at risk to have haepho(whatever the disease was called) than women ?
because the recessive allele for haepho(whatever the disease was called) is X , and men have XY chromosones therefore only need one. whereas females have XX and would need two.
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