If a question asks for two examples and you list three, does this limit you from getting full marks? Cause on the assessors report a concern was "Some students gave more than two answers."
It's okay, but a) they will not consider the third b) wastes time (albeit a little) and c) if the third is incorrect, then you'll probably lose marks on the whole question. I think VCAA usually advises to put your best answers first.
in a speciation question, when you say variation existed in the original population, would it be correct to say phenotypic variation, or would you just stick to variation?
I'd stick with "genetic variation existed in the original population/before selection pressure as... etc." It's probably good to mention the actual variation that existed (e.g. there were already resistant bacteria before the use of penicillin).
A question of my own:How does the immune system recognise 'self'? Obviously this would include both cells and any kind of protein molecule.
So would it be correct to say that "immune cells have specific receptors that are able to distinguish between different kinds of protein markers (e.g. MHC on cells). If the protein marker is the same as the ones on B and T cells, then the molecule is identified as 'self'. "
But wouldn't other non-specific cells of the immune system (NK cells, macrophages, neutrophils etc.) be able to detect such 'non-self' molecules in the same fashion? Or would it better to stick to the umbrella term of "immune cells'?
And if I wanted to be more specific, would the following be accurate:
"All cells have specific protein markers on their cell membranes. If it is specifically complementary (?) to the Major Histocompatibility Complex (MHC) marker of an immune cell, then it is identified as 'self' cell. If not, then it is identified as 'non self' and a foreign antigen which triggers an immune response."
Surely, the same procedure would be applied to any protein molecule?
Thanks