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

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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

Reply 81

y64654

Original post by conradliebers

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)

.125? 50% i think

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.

Reply 84

Igcse_student

Does anyone know about the question with the heterozygous nd homozygous. The number of homozygous resessive and dominant????

Reply 85

rcmack

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

Reply 86

y64654

Original post by conradliebers

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

Reply 87

Year11Struggles

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

Reply 88

rcmack

Original post by y64654

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%.

Reply 89

rcmack

Original post by y64654

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

Reply 90

Droneon

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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Reply 91

Lrrgolas

would 12.5% instead of .125 be ok? if you're talking about the percentage chance after all

Reply 92

Oreatex

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?

Reply 93

Oreatex

Taking into account both papers, has biology been easier or harder than previous years?

Reply 94

y64654

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.

(edited 7 years ago)

Reply 95

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%.

Reply 96

y64654

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

Reply 97

rmg3000

Sika is the name of the deer

Reply 98

jose99

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)