Edexcel 6BIO2 ~ 3rd June 2013 ~ AS Biology

so S phase is okay?
and check my answer to the last question please

It was X is metaphase and Y is anaphase. Then the cell Z was in interphase as the nucleus was so large although pic not clear. Um btw for the mcq in ques one there was a question of which cell bacterial, animal or plant has an sER i wrote two of them as plant and animal are eukaryotes. Am i rite???
paper wasnt so bad. So far losing a few marks only. That woese question threw me. Lol
praying for high A.
Anyone doing chem today??

For the last question I wrote :
1)Reintroduce the species far away from each other to reduce the competition
2) Introducing a new prey will help to increase their survival chances
3) I forgot what I wrote here :/

So what u thnk of the first 2 points? any one please

I can't say for sure because the cell was already bigger.. they may give you the mark though

you could also suy it was interphase though because most of the cells were in that stage


two of them was correct
good luck!
and yep got chem2 later on


I don't know whether 1 would get the mark because you wouldn't want to isolate them
I don't know whether that would get the mark either because they told you that they prey on prairie dogs, so you should probably assume that's the only thing they eat

Yes thanx sooo much!! Goodluck. Im quite siked for chem
x

no problem and thank you, I hope I've at least got a B since I only need a B for an A overall. Yeah chemistry is the subject I find the easiest as well (well not easiest but I always do better in it)

For the mitosis question

X- prophase- it cannot be metaphase as they are not lined up at the equator
Y- anaphase/metaphase not too sure as the spindle may either have contracted or not.

The last question is cytokinesis - reason there's a cellplate, 2 cells are attached together if you look at any other cell in the picture all the cells with the nucleus present are seperate, non of the others are attached as is the case here.

The prevention of polyspermy one is- the fusion of the cortical granules etc, which I'm sure is the answer to the question, you could have also put change in ion concentrations within the cell making it positive so repelling the positive sperm but I'm not sure if that's in the syllabus.

Heu guys, I'm going to try get started on an unofficial mark scheme, I think I remember quite a few of the questions. My answers may be wrong. I have a Chemistry exam in a few hours, so I'll start of with a few of the questions first, then after my exam, I'll try and update the mark scheme. Personally, I found the paper okay, it wasn't too hard, but there were a few odd questions here and there. The multiple choice at the beginning was confusing. Apologies in advance if my mark scheme confuses anyone or if it's wrong.

Ferrets question

Explain how zoos have the captive breeding programme (5 marks)
Allow ferrets to mate with individiuals different to previous mating
Allow only those with different genes to mate
Keep a record book of which ferret has mated with which
Afterwards, reintroduce them back into the wild

From the graph, explain why no ferrets were released before 1991 (I think it was 2 marks)
The number of births was quite low before 1991, therefore if they were released back into the wild they would be endangered and threatened and at risk of extinction

Comment on the effectiveness of the breeding programme from 1991-2000
Overall increase, so must have been effective, even though there were a few years where the births were decreasing. In 1997 (i think it was), highest number of ferrets born.

Explain factors on survival (can't remember exactly how it was worded)
If the dogs are killed by poison, easier for ferrets to catch them, but population may reduce because more ferrets will die, because they will be poisoned (probably wrong answer)
Competition with other species within the area will affect its chances of survival (competing for food and territory)
Most of area disturbed by human activity, therefore, loss of natural habitat (e.g. roads being built), and hunting, so more difficult to adapt.

Meiosis

Explain after acrosome reaction what egg cell does (Can't exactly remember how it was worded)
Acrosome ruptures and digestive enzymes are released which break down zona pellucida layer. This allows sperm to get through to egg. Sperm head fuses with cell membrane. Egg cell releases cortical granules into space between zona pellucida and cell membrane. Zona pellucida thickens, so that only 1 sperm reaches fertilised egg.

Explain how meiosis brings about genetic variation.
Crossing over occurs. The 2 chromatids are wrapped/twisted around each other. Bits of 1 chromatid break and join bits of the other chromatid (on chiasmata).This leads to a combination of different alles in the 4 daughter haploid cells produced. Independent/random assortment also occurs. This is when any number from 0 to all 23 from the maternal or paternal chromatids are distributed into the gametes (hence offspring) completely at random.

I'll be able to add to the mark scheme when after my exam today. If anybody else wants to add to it, or correct anything which is wrong, please feel free to.

What do people reckon the grade boundaries on this paper are going to be?

Yup all I could think about was the zona pellucida hardening and then the sperm nucleus only entering ..

And then I threw in that they fuse and make a zygote in hope of desperate marks,

What did u put for reintroduction into the wild?

And also, the Zoo question was specifically asking about genetic diversity wasn't it? .. Oh ****


Posted from TSR Mobile

I put interphase at first, but changed to cytokinesis, because there was a cell plate forming

Am I the only one who wrote down the multiple choice answers they put down?
C
D
C
D
C-this one is wrong i think, endoplasmic reticulum question
D
A
C

Nahhh it was definitely
Metaphase
Anaphase
Interphase: nucleus present, chromosomes decondensed/ separate chromatids not visible, the cell is not dividing therefore not cytokinesis

It was definitely metaphase!

Compared to some other cells they were definitely aligned at the equator

Posted from TSR Mobile

I put that the ferrets may eat the dead poisoned animals which can cause the ferrets to die and cause a decline in the ferret population. Do you think I would get the mark for that

Does anyone remember the question about ferrets and something about not releasing them (2 marks) before 1991

I said (cant remember that much):

- Cannot release, as population of ferrets are low ---> can lead to extinction
- If ferrets are released, they may not be able to adapt quick enough (due to NS) and stuff on advantageous allele (cant remember :L)


Another question was on taxonomy (3/4 mark i think)

I said (y):

- Taxonomy is when organisms are grouped together by looking at their similarities and differences
- If two organisms have the same role within an ecological niche they are in the same species
- If two organisms can produce fertile offspring, they are in the same species.
- Two organisms have similar evolutionary backgrounds, they are in the same genus/species
- DNA profiling can be used to determine whether two species are related with each other, to see whether they have similar base structures.

Can someone verify if they have something similar to this or correct me