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AQA GCSE Biology B2 Unofficial Markscheme 2017

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Grade boundary predictions from myself (they are slightly high) : Test was out of 80
A* - 51 marks
A - 43
B - 33
C - 24
D - 13

Reply 581

Moltenmo

Original post by Jake Dunkley

Grade boundary predictions from myself (they are slightly high) : Test was out of 80
A* - 51 marks
A - 43
B - 33
C - 24
D - 13

Out of 80? These seem high. Generally, A* is about 45.

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Reply 582

Anonimy

Original post by Anikayesthatsme

Guys post your answers here!

Epithelial tissue - to cover the inner and outer surfaces of the stomach
SOURCE:
http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/tissues_organs/organs_in_animalsrev2.shtml

Reply 583

JR11

The type of cell division was meitosis. The cell had divided 4 times and it was a 1 in 4 chance from the genetic diagram. I also got a 20% increase for the calculation on the graph.

Reply 584

Yasminkoski

Original post by mickss

What didn't everyone get for the calculation question?

20% ...is that right?

Reply 585

the9-1labrat

Original post by Anikayesthatsme

Guys post your answers here!

For question 2). I did all of the same, as well as I said that a random quadrat should be placed in area without any plants and soil pH should be recorded and repeated for both areas to get an average... I also said how a range would be found and to make sure its valid they should compare results with someone else that's doing the exact same experiment to see if the results are the same/similar :smile:

Reply 586

Moltenmo

WAS IT RANDOM PLACEMENT OF QUADRATS OR PLACEMENT OF QUADRATS ALONG A LINE TRANSECT?

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Reply 587

silentlystudying

Original post by moltenmo

was it random placement of quadrats or placement of quadrats along a line transect?

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i did random but i think you can have either, idk i might be wrong

Reply 588

Btstrash

Original post by MediaROCKS

It will pick up- don't worry think about when you do maths exams

thabk

Reply 589

Badmaths

Original post by Emmzy04

Would I get the mark for saying 23 PAIRS of chromosomes?

Yes you'll get the mark, was on a paper before and accepted it

Reply 590

Moltenmo

Original post by notgonnasaymisha

i did random but i think you can have either, idk i might be wrong

See...I put random but I am losing hope in this answer. I think it is using a line transect, even though the question didn't actually provide a tape measure. :Confused:

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Reply 591

Y-NR

Note that the last question mentioned the extinction of dinosaurs, and how they used to eat birds. The question did have to do with speciation (which should be in second half of your answer) but I think we had to somehow relate how the birds became flightless. Less/no predators - can come on the ground and no longer need for flight to evade dinosaurs (predators). Then, we can talk about how that one flightless bird became into many (speciation). For similar features, you could refer to common ancestor or similarities in environments, although it was Africa, Australia, and South America so I think common ancestor would be more valid.

Reply 592

Classof2017

Original post by Nathnoodle

Most likely not as it asked for chromosomes ;/

In past papers they have allowed both answers :smile:

Reply 593

Ameerahs

Original post by Ahmed257

1a)What is the function of the epithelial tissue in human cells?
The epithelial tissue helps cover the surface of the cells. Covers the surface of organs. (2 marks)
1b)What is A and C in the epithelial cell?
Cytoplasm, Cell membrane (2 marks)
1c)What is the function of Ribosomes?
Protein synthesis (1 mark)
1d)What is diffusion?
Diffusion is the spreading out of particles from a high concentrated area to a low concentrated area. (2 marks)
2a)How could the students use quadrants and a Ph meter in this experiment?
Place quadrants randomly to obtain more accuracy.
Count every plant in each quadrant
Repeat this to obtain valid data.
place quadrants in different areas to compare the distribution.
work out averages.
Use PH meter in different areas randomly to avoid biased results. (6 marks)
3a)Complete the equation of Amylase.
Amylase-Starch-Sugar (glucose) (1 mark)
3b)Suggest what happens to the enzyme when the ph levels is lowered
The amylase enzyme will be affected by the ph levels as it would become denatured. (2 marks)
3c)What was the percentage increase from 4 to 6 minutes?
25% increase (2 marks)
3e) word equation for photosynthesis?
Carbon dioxide +water=(light) glucose +oxygen (2marks)
3e)why is it important for the cyclists to undergo a placebo?
So the results are more accurate as without a placebo the test would be affected due to the person's expectations. (2 marks)
3f)use the graph to show the validity of the conclusion?
Cyclist in session one had a better performance as the point on the graph for this session was going up which shows that there is a relationship between glucose levels and performance.
Cyclist in session 2 had point going downwards which suggests that the lower the glucose, the worse the performance.(4marks)

What is an allele? (1 marks)?
- Different versions of the same gene.
What is meant by recessive? (1 mark)?
- It heterozygous allele or it is not dominant or it is two different alleles

What is meant by heterozygous (1 mark)?
- It is recessive allele or it is not dominant or it is two different alleles

Name the type of cell division that happened in step two ( 1 mark)
Meiosis because it was sexual reproduction
How many divisions does the cell go through to get 16 copies? (1 mark)
4
Give one ethical objection to embryo screening. [1 mark]
- may lead to damage to embryo / may destroy embryos / embryo cannot give consent
Give one reason in favour of embryo screening. [1 mark]
- prevent having child with the disorder / prevent future suffering / reduce incidence of the disease

Parents are planning to have a child.

Use a genetic diagram to find the probability that the new child will have PKU.
Use the following symbols in your answer:
N = the dominant allele for not having PKU n = the recessive allele for PKU.

Label the diagram.

genetic diagram including:
Parental gametes: N and n and | N and n derivation of offspring genotypes:
NN Nn Nn nn identification:
NN and Nn as non PKU
NN free from PKU
Nn carrier of PKU
nn as affected by PKU

Correct probability only: 0.25 / ¼ / 1 in 4 / 25% / 1 : 3

(4 marks)

What is a species (2 marks)?
- A group of offsprings
- That are able to produce fertile offsprings

you also need to put:
how do we use fossils to see how simple bodied organisms evolve
and 6 marker on speciation
how many chromosomes in a cell
why farmers shouldn’t use more than 0.08%
describing breathing rate, heart rate and concentration of glucose increasing when exercising
Control variables of starch and improvements to the experiment.
i think that is everything needed

Reply 594

RamoyCashHarris

Original post by Charlotte1478

What did everyone put the Ph3 question with the amylase . I put the reaction would be slower as amylase works better with a PH of 7 and there was no starch produced so the reaction would be slower

It's actually because the pH is too acidic therefore the enzyme denatures so it wouldn't be able to produce a result

Reply 595

Btstrash

Original post by AdilB

my friends, my friends I have memorised all. Iam going through the answers with a group of qualified teacher as we speak.
Meanwhile please send any questions you remember in case the questions i memorised were incorrect.

Can u send me the link

Reply 596

number0

Original post by Moltenmo

See...I put random but I am losing hope in this answer. I think it is using a line transect, even though the question didn't actually provide a tape measure. :Confused:

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I think they mainly wanted a random quadrat answer, but you could still probably get marks for transect.

Reply 597

Classof2017

Original post by Moltenmo

See...I put random but I am losing hope in this answer. I think it is using a line transect, even though the question didn't actually provide a tape measure. :Confused:

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You can use a quadrat at regular intervals along a line, like a transect. This is what I said, I thought that this way I would get more of a variety of PH readings. All my friends put random sampling though, I'm hoping you can put either!!

Reply 598

RamoyCashHarris

Alleles are different variations of the same gene
Heterozygous means having two different alleles
There was a 25% chance as there was only one nn

Reply 599

the9-1labrat

Original post by gwen_hughes

The division question was worded badly, it said 16 cells from a single cell - surely that could be one cell splitting into two 8 times or one cell splitting into 2 cells which then create 2 each etc? One cell can split more than once