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# Edexcel Biology IGCSE 2B Unofficial Mark Scheme 10th June 2016 watch

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1. (Original post by rcmack)
im pretty sure that you just said that the roe was a lot longer that the sika, which had the same mass of 45kg (i think). this means, as the result does not fit the general pattern of results, so the embryo had to remain inactive
i have no idea, i just don't think the answer of roe makes sense tbh
I'm pretty sure writing consumer is correct because they never said the insect must feed off the plant. Take an example, the fly trap can eat a preying mantis, but the preying mantis is an insect that feeds off other insects, so in this case it would be a tertiary consumer.
No because it is impossible for the consumer to be the primary or the tertiary as it doesn't feed on plants and insects eat just producers as they are not carnivores (the type it mentioned)
3. .125? 50% i think
4. (Original post by y64654)
.125? 50% i think
No because there is a .5 probability of getting it, so in order for 3 to have gotten it you do 0.5x0.5x0.5.
5. Does anyone know about the question with the heterozygous nd homozygous. The number of homozygous resessive and dominant????
6. Really good actually
7. (Original post by Igcse_student)
Does anyone know about the question with the heterozygous nd homozygous. The number of homozygous resessive and dominant????
homozygous recessive was 11, homozygous dominant was 0
No because there is a .5 probability of getting it, so in order for 3 to have gotten it you do 0.5x0.5x0.5.
Each time you clone something the probability is the same of getting a certain outcome because the Genotype of the parents doesn't change no matter how many children they have. Therefore if you have a million children all with the disease then then the probability of this is still 50%- it isn't mathematics and you overthought the question
9. (Original post by escg)
i have no idea, i just don't think the answer of roe makes sense tbh
Every single person I know put Roe
It was Roe and it was an easy question
10. (Original post by y64654)
Each time you clone something the probability is the same of getting a certain outcome because the Genotype of the parents doesn't change no matter how many children they have. Therefore if you have a million children all with the disease then then the probability of this is still 50%- it isn't mathematics and you overthought the question
the probability of getting one with FH is 50%
the probability of getting one with FH and then getting another is not the same as the probability of just getting one, so it is 50% x 50% x 50%.
11. (Original post by y64654)
Each time you clone something the probability is the same of getting a certain outcome because the Genotype of the parents doesn't change no matter how many children they have. Therefore if you have a million children all with the disease then then the probability of this is still 50%- it isn't mathematics and you overthought the question
also say the probability of getting heads on a coin flip is 50%,
the probability someone flips heads is not the same as the probability that one person flips heads 100 times in a row
12. (Original post by rcmack)
isnt that oestrogen and progesterone that do that?
Yeah, which is produced by the placenta after two months of pregnancy, and I guess it helps in the development of the embryo

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13. would 12.5% instead of .125 be ok? if you're talking about the percentage chance after all
14. (Original post by rcmack)
i believe the rod and cone cells are in the retina and fovea, but im not sure
Would you get the mark for saying fovea?
15. Taking into account both papers, has biology been easier or harder than previous years?
16. (Original post by rcmack)
also say the probability of getting heads on a coin flip is 50%,
the probability someone flips heads is not the same as the probability that one person flips heads 100 times in a row
The whole point of the question is that they are un-related results. It's a principle in genetics for biology. I know how probability works but the whole point is that say you had 1 with and 2 without instead of all- This would still be 50x50x50 if what you are saying is correct (which it isn't). You have to know that the syllabus teaches that no-matter how many children you have it's till a 50% chance. The fact that one has already been a boy makes no difference to weather or not the next will be. Its the same as the question about male and female which came up in the past. (0.125) isn't even a percentage by the way so even if your method was correct you still didn't get the mark as it asked for a percentage and gave the % units.
17. I got that genetic probability question wrong. Can someone actually explain how having 3 children with the disease is more unlikely than having 1? I might be overthinking, but I thought it was 50%.
18. (Original post by jshwan)
I got that genetic probability question wrong. Can someone actually explain how having 3 children with the disease is more unlikely than having 1? I might be overthinking, but I thought it was 50%.
You got it correct- the point of the question is to identify the fact that no matter how many children you have the probability resets. Well done
19. Sika is the name of the deer
20. (Original post by y64654)
You got it correct- the point of the question is to identify the fact that no matter how many children you have the probability resets. Well done
Sorry mate but i think you're digging a hole. If the question was something like 'What is the possibility that a 4th child would have the disorder?' the answer would have been 50%, but it was asking what is the possibility of having the first three children with the disease (0.5^3)

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Updated: June 14, 2016
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