AQA Biology B2 - Unofficial Mark Scheme

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wasnt it supposed to be 1 min? since the heart rate stays high for a bit after u exercise, before it decreases?

I thought it just levelled off at 1.5 and carried on for a bit and then reduced but as it it climb higher than 1.5 I though the athlete was just paying back the oxygen debt

Reply 161

Certified

Original post by WrightKe

So why was the answer Mitosis? I'm so confused, maybe I misread the question.

Process in the image was Meiosis. The zygote divides many times by mitosis to form an embryo (which is what the bottom question asked).

Reply 162

AK45HSR

Original post by Certified

Process in the image was Meiosis. The zygote divides many times by mitosis to form an embryo (which is what the bottom question asked).

I swear it said how's does a fertilised egg replicate it self?

Reply 163

Certified

Original post by Cakes717

That's what I got? But everyone is saying something about converting...

This is roughly what I got. I now realise the size of the quadrat was in cm :frown:

Reply 164

Wisbey

Thoughts on grade boundaries?

Reply 165

jjjppp272727

Doing 20/10
only found the mean amount of plantains per 0.625m^2 not per m^2 which was why the answer per metre^2 was 3.2 I think

(edited 7 years ago)

Reply 166

ellielouxse

I didn't put any values for the 6 marker, i just talked about the same intervals and stuff.. Agh

Reply 167

lilyflowerxoxo

Original post by Door105

I got 2 whats the right answer

I put 1

Reply 168

emilyphillips17

Original post by Edgerulezs

Sameee 😂😂 we're either smart for doing that or overthought things 😭

I'm hoping you're smart because I put 1 too 😂😂 it said that lactic acid built up so I thought it'd remain the same for a little while to pay back the oxygen debt?

Reply 169

Certified

Original post by Blahblahblah7

I swear it said how's does a fertilised egg replicate it self?

A zygote is a structure that forms when a sperm fertilises an egg. A zygote containing eight identical cells. The zygote then divides many times by mitosis to form an embryo. The first division of the zygote forms two cells, the next four, the next eight, and so on. Up to the eight-cell stage, all of the cells are identical. They are called embryonic stem cells. It is possible for embryonic stem cells to develop into any other specialised type of cell that the growing embryo needs - for example, nerve cells, blood cells and muscle cells. However, once the embryonic stem cells become specialised, they can't change into any other type of cell.The specialised cells can form all the different types of tissue that the embryo needs.

Reply 170

GCSE_core

Original post by goldenusername

wait there was one for enzymes??

The only question I saw on enzymes was 'what is an enzyme'- don't know why people are putting advantages and disadvantages?

And then there was the advantages and disadvantages of hydrogen peroxide and catalyst which gave the the text to answer from. Is this correct?

Reply 171

username2312801

Any thoughts for Grade boundary

Reply 172

Naco88

Original post by Wisbey

Thoughts on grade boundaries?

I was wondering this so put the poll at the top. Looks like people are pretty confident so they will be quite high.

Reply 173

Mr revision

Wait was was the answer for question 7 than, was it mitosis or meiosis

Reply 174

k0chia

1a. without (sufficient) oxygen
1aii. ran for 1.5 minutes
1b. The amount of lactic acid produced increased. Lactic acid is a product of only anaerobic respiration.

3. what is an enzyme?
A biological catalyst that speeds up chemical reactions by lowering the activation energy needed for the reaction to take place, without being changed or used up during the reaction.

circle question - cytoplasm

5. Chance of getting polydactyly was 50%
the mass of the gametes:
a - 6.6
b- 13.2
c and d - 6.6
the ones at the end of telophase II - 3.3

6. Advantage: Reaction can take place at lower temperatures - less energy used so lower heating costs
Disadvantage: Doesn't kill pathogens/ catalase then contaminates the milk

8. The foxes could mate successfully and they have similar physical features

The foxes may have been isolated into different populations due to higher sea levels. The conditions on each island may have been different. All the foxes in each population would have shown genetic variation (due to sexual reproduction and mutations). Natural selection would have acted differently in the different populations. Foxes with favourable alleles passed on these alleles to the next generations, Eventually the different populations would not be able to mate to produce fertile offspring - speciation had occurred.

Reply 175

Miz9

Original post by Lolol786

Unofficial marks scheme (may not be correct ) not in order
Anerobic - incomplete breadown of glucose
How can u tell ?- athlete produces lactic acid
Athlete and blood flow to muscles - oxidation of co2 and lactic acid , faster transportation of oxygen into blood streem , causes muscles to contract , athlete then anerobicly respires which decreases blood flow to muscles - muscle fatigue

Epithelial - covers and protects stomach from acid
Muscular contracts and churns up food
Glandular secretes hormones and digestive juices to increase breakdown of food
Fox question - isolation, adaption,natural selection , mutation, unable to breed
Can't Remeber anymore

What was the answer to the genetic diagram question?