GCSE biology question

[Tree]

Ok i don't know if this is allowed i know it happens in the 11 plus section and if a precedent is set to pose gcse questions here this section could get quite full but i am v frustrated in this mcq question for aqa biology nov08 :

ok there are two snakes one poisonous with stripes the other with similar stripes but not poisonous sneakily surviving on the back of the other snakes poisoness the final question in this section is

extinction of both poisonous and non poisonous snakes could be caused by ...

1 an new predator evolving

2 the non-poisonous snake becoming different in appearance from the poisonous ones.

3 competition between predators of non -poisonous snakes

4 a scarcity of food in their habitat


it seem to me that 1 and 4 are both possible to lead to extinction but only 1 answer is allowed

any ideas is there something i'm missing here

[nigs]

Hi

Not sure if you know that AQA website has past questions and answers to some of their papers.

The answer to your question seems to be (1).

Have a look at this link to the AQA answers on the 2008 paper:

http://store.aqa.org.uk/qual/gcse/qp-ms ... -NOV08.PDF

Also this link to all the Biology papers they have:

http://web.aqa.org.uk/qual/newgcses/sci ... 03&tabid=2

Hope this helps.

[Tree]

thanks Nigs i did have the answer from the website as 1 but i why can't it be 4 ???

[hermanmunster]

reckon that they are most likely to be both wiped out by an external source ie (1) - lack of food could cause the posionous snake to turn on the opposition ie the non poisonous snake, the non posionous one having little defence I suspect.

[Tree]

HM i suppose but it's not that obvious we don't even know if they do eat each other ??

[Tree]

i mean if it had said most likely to have been caused... by then answer 1 would perhaps be more obvious but then how likely is a new predator to evolve that's gonna take millenia isn't it ??

[hermanmunster]

agreed it is not a good question - I suppose they want to first get identified the events that would only affect one of the snakes - so that would eliminate 2 and 3. I suspect that the teaching is that in theb absence of food, competition increases and hence the poisonous snake may do better at killing the few things that there are to eat (+/- killing the other snakes.) - depends how selection is taught really,

[nigs]

My DD (and she is still taking her Biology modules) seems to think that the answer wouldn't be (4) the scarcity of food - because the snakes would look for food elsewhere.

[KenR]

Just showed this to my other half (A Level biology teacher) her comments were as followed.

Just the sort of rubbish that AQA come up with at GCSE, most true Biologists would not be able to answer this type of yesterday.

very bad question. If answer 1 had used the word 'introduced' rather than 'evolving' then that might justify answer - but not with 'evolving'.

You would normally expect the schools and teacher to formaly complain about this sort of question

Incidently this is based on a real life scenario of the coral snake and milk snake

[Tree]

Hi KenR thank your other half for me i'm glad it's wasn't just me it is a bit worrying you often see dodgy questions on practice papers but i was a bit suprised as this was an actual gcse, thanks everyone.