gcse b2 unofficial markscheme aqa

Question 1

What is the function of the epithelial tissue in human cells (1 mark)?The epithelial tissue covers the surface of organs such as the stomach

What is A and C in the epithelial cell (2 marks)?- Cytoplasm
- Cell membrane

What is the function of Ribosomes (1 mark)?Protein synthesis

What is diffusion (2 marks)?
- Net Movement of particles
- From a High concentration to a low concentration

Question 2
A student noticed that in a Marshland there were "more Heath plants in areas with high PH levels." Using diagram 6 ( a picture of a quadrant and a PH indicator) explain a method how the student could test the hypothesis. Explain how he would make the test reliable. (6 marks).

- Quadrat placed randomly, non biased location, and student counts amount of the plant in a section, then takes the soil pH.
- Does this in multiple locations to see the distribution of these plants, comparing them to pH levels.
- Record results in table and plot on graph to see correlation
- Can be repeated so results are accurate

Question 3
What is the word equation for Photosynthesis (1 mark)?
Carbon dioxide + Water -- (Sunlight) --> Oxygen + glucose

Complete the equation (1 mark)?
Starch --(Amylase)--> Sugars

Students were seeing the effect of the rate of carbon dioxide concentration to photosynthesis
Give two control variables the students used in the investigation (2 marks)
- Same volume of amylase
- Same volume of Starch

What was the arbitrary units at 0.04%?
16

The student reached a conclusion that PH7 was the best working condition. The conclusion is not accurate give 2 reasons how they can improve their experiment ( 2 marks).
- Smaller PH interval
- Repeat experiment again

Starch is checked for presence by adding iodine
Brown colour = Starch present
Yellowish colour = No starch present
What is the colour of the leaf:
at PH6 0.04% = Brown colour (1 mark)
at PH6 0.08% = Yellow colour (1 mark)

Explain what will happen to the Amylase at PH3 (2 marks)?
- Amylase denatures/ Active site changes shape/ Substrate cannot bind
- No production of starch

Question 4
What is the percentage increase between 0.04% to 0.08% (2 marks)?
20/16 = 1.25
answer = 25%

Why can't the farmer use more than 0.08% (2 marks)?
- The rate of photosynthesis will not change
- There are other limiting factors

Name two other limiting factors (2 marks)?
- Light intensity
- Temperature

Question 5
Why is it important that the cyclists don't know the difference between the placebo and the glucose drink (2 marks)?
- So that the results are controlled
- So the cyclists perform the same under both drugs.

Evaluate the scientist's method of conducting the experiment on the cyclists (4 marks )?
Positives
- A week interval between each session
- A placebo was given so that results could be compared
Negatives
- The cyclists were not monitored during the week: they make have different glucose intake
- Not a large of cyclists only 7 were tested

Explain how the increased heart rate, faster flow of blood and increased breathing rate improve the athlete's performance (4 marks).
- During exercise, more energy is required.
- Increased heartbeat allows more blood to be pumped around the body
- Blood flows faster as it needs to provide oxygen to muscles
- The breathing rate increases so that more oxygen enters the body preventing oxygen debt and lactic acid build up.

Question 7
What is an allele? (1 marks)?
- A form of a 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

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 (4 marks)

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

How many chromosomes is there in a human cell (1 mark)?
46 or 23 pairs

Name the type of cell division that happened in step two(1 mark).Mitosis
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


Question 8
What is a species (2 marks)?
- A group of organisms
- That are able to produce fertile offsprings

How do we use fossils to see how species today have evolved from simple organisms (2 marks)?
- The structure of the bones
- The way they were preserved

The ancestral bird was able to fly. The dinosaurs went extinct 65 million years before. The dinosaurs were meat eaters. Explain how the three different species of flightless birds could have developed to have common characteristics (6 marks).

The ancestral bird populations was separated (by geographical barrier / by land) / were isolated
Genetic variation (in each population) or different/new alleles or mutations occur enabling the bird to adapt
Different environment to adapt
Lack of predators meant that the birds didn't have to use their wings
Natural selection occurs and the favourable characteristics are passed on
Eventually the three types cannot interbreed successfully to produce fertile offspring, thus, a new species id formed with similar characteristics to the other flightless birds.


Name the type of cell division that happened in step two(1 mark).Mitosis

I think the answer to this is Meiosis, not mitosis, since it is the division of cells to create gametes.

Complete the equation (1 mark)?Starch --(Amylase)--> Sugars

I put down glucose instead of sugars, should this be okay?

For the AKU diagram was it not Nn and nn because the disease was caused by a recessive allele
Nn nn
Nn Nn nn nn
so it is 1/2 chance of getting the disease
Someone tell me if i'm correct please.

nope. the disease by dominant allele. If so, the parents would have it too, however we know the younger child wuould, meaning the parents were heterozygous. Therefore they were both Nn Nn. None of the parents had the AKU disease.

what's the most marks I could get?

for drawing the punnet square and getting results from what u have, i'd say 2.

I didn't draw the punnet square- i did the genetic diagram- that will be fine won't it

yes. You might however gain 1 or drop 1 depending on the examiner.

what do you mean 1 mark out of 4 or 0/4?