Edexcel 6BIO2 ~ 3rd June 2013 ~ AS Biology

any idea on the mark scheme?

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thank you so much thats much easier but i still dont get what "hydrolysed by the digestive enzymes" means

crying, can someone explain the top line? why do they both have crosses, I thought cellulose has H bonds in microfibrils?

Hard Question really can't solve it at all...i didnt understand the ms too ...so any help will be appreciated:

Hard Question really can't solve it at all...i didnt understand the ms too ...so any help will be appreciated:

its not the microfibrils that are held by hydrogen bonds, its the cellulose chains that are held by hydrogen bonds.

Posted from TSR Mobile

This asks for changes, so what happens to the sperm cell and egg cell. so you just describe the steps during fertilisation. Its 3 marks so three points are required:

I would write (well, i haven't looked in the markscheme) something along the lines on:

1) The sperm cell penetrates through the zona pellucida layer and is hydrolysed by the digestive enzymes secreted from the sperm head.
2) After penetration, the zona pellucida then reforms/hardens after a sperm has entered to prevent polyspermy (multiple sperms)
3) Therefore, the process of meiosis is completed.



The nucleus of a cell is responsible for cellular activity including cell division. Blood cells don't divide, they are produced by other cells within bone marrow.

For part a) it asks you a definition of the frequency of an ALLELE, we know that frequency means the total number and alleles are different versions for the same gene, so the definition of a frequency of an allele in a population should be:

a) It is the total number of alleles for one gene in a given area.

For part b) it asks you to explain natural selection in the enviroment and how it leads to adaption, so a suitable answer would be for four marks (give four points):

b) (1) Environment change due to a selection pressure
(2) A mutation occurs
(3) Advantageous allele in that particular environment
(4) Hence, more likely the advantageous allele will be passed onto the offspring of the plant

For part c) a simple 2 marker, we know that bacteria are simple cellular organisms, so to react to the environment we know that:

1) bacteria can mutate much quicker than plants

Also we know that (from the stem of the question) that bacteria can react faster, so it should be easy to say that

2) bacteria has a greater selection pressure than plants if it is to react quickly to the environment.

Hope that answers your question (and hopefully i got this right, P.S what question paper is this and where can i get a hold of the markscheme? )

Ahhh man! Your link is broken dude, any chance of a re-upload ? =3

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it worked for me, but here it is again

Well but the things i didnt understand is part b ...maybe coz i dunno what selection pressure is...so tell me please...
ok i ll post the document and markscheme after a while..i ll arrange it first

Is someone able to explain to me in the easiest way gametogenesis in plants
and Meiosis also

selection pressure is an event or condition that requires a 'useful/advantageous' gene to be passed on for survival such as extreme change in conditions, selectron pressure for a particular gene increases, therefore, said gene is passed on more frequently


pasically, pollen lands on stigma, then the pollen undergoes mitosis forming 2 nuclei, a pollen tube nucleus and a generative nucleus. The pollen tube nucleus (I'll refer to as ptn) is responsible for digesting its way down the style of the plant and attaches to and disintegrates at the ovary. The generative nucleus on its travel through the style undergoes another mitotic division, there are now 2 nuclei. When they reach the ovary, they enter the ovule and one fertilises the egg nucleus forming a zygoe (a diploid structure (2n number of chromosomes) and the other fertialises a pair of polar nuclei which forms the endosperm (a triploid structure (3n chromosome number))

http://www.youtube.com/watch?v=GK3eHNu9zsA this is quite good for getting your head around meiosis although I'd say it's not as accurate as it could be

Alright thanks that was really helpful. You seem to know your stuff! Another thing is all this natural selection business
Please explain it simpler words

hey guys can some one explain me the steps for natural selection including the mutation and variation , its repeated alot in pastpapers but i want the steps so i can memorize them and use them , the mark scheme is quite confusing