Paper 3 Exam Questions

Question 1

ecologists captured insects from a number of sites on an island. suggest how they decided where to take their samples.

2 marks

Answer 1

1. they drew a grid on the area on a map
2. randomly selected coordinates to take samples from

Question 2

give two assumptions made when using the mark-release-recapture method

2 marks

Answer 2

two from:
1. no immigration
2. no losses to predation
3. marking does not affect survival
4. birth rate and death rate are equal

Question 3

describe how you would make a temporary mount of a piece of starch tissue to use with an optical microscope

4 marks

Answer 3

1. add a drop of water to the slide
2. obtain thin section of plant tissue and place on slide
3. stain with iodine
4. lower cover slip using mounted needle

Question 4

what sugar would you expect to be produced during human chewing? give reason for your answer.

2 marks

Answer 4

1. maltose
2. salivary amylase breaks down starch

Question 5

what is the function of the chloroplast? 1 mark

Answer 5

site of photosynthesis

Question 6

what is the function of the nucleus?
1 mark

Answer 6

contains genetic information

Question 7

what is the equation linking magnification, image and actual size?
1 mark

Answer 7

image size = actual image x magnification

Question 8

explain why in an experiment testing the effect of fungus on plants the seeds were steralised and the soil was heated to 85 degrees for 2 days
2 marks

Answer 8

1. to kill any bacteria on the surface of the seeds
2. so only the added fungus has any effect

Question 9

explain why in an experiment testing the effect of fungus on plants the soil could not contain any mineral ions useful to the plants
1 mark

Answer 9

so only fertiliser affects growth

Question 10

when drying plants samples over 3 days what should the scientist do to ensure all the water has been removed?
2 marks

Answer 10

1. weigh samples at intervals during drying
2. to see if weight becomes constant

Question 11

Describe how behavoiur of female fish could lead to sympatric speciation

3 marks

Answer 11

1. not geographically isolated
2. leading to reproductive isolation
3. changes in allele frequency

Question 12

name the type of competetion between two different species

1 mark

Answer 12

interspecific

Question 13

Suggest how a virus that once was only able to infect one frog species became able to infect other species of frog.

2 marks

Answer 13

1. Mutation in the viral DNA
2. Altered (tertiary structure of the) viral attachment protein
3. Allows it/attachment protein/virus to bind (to receptors of other species)

Question 14

Name two techniques scientists may have used when analysing viral DNA to determine 2 viruses are closley related.

1 mark

Answer 14

genome sequencing
gentic fingerprinting

Question 15

Determining the genome of a virus can allow scientists to develop a vaccine. Explain how

2 marks

Answer 15

1. could identify proteins (that
   derive from the genetic code)
2. (They) could (then) identify potential antigens to use in the vaccine

Question 16

Decribe how B lymphocytes respond to vaccination against a virus.

3 marks

Answer 16

1. B cell (antibody) binds to (viral) complementary antigen
2. B cell clones
3. Plasma cells produce (monoclonal) antibodies
4. plasma cells produce memory cells

Question 17

A high concentration of sodium in the bood can affect blood volume and cause hypertention.
Suggest how high concentration of sodium affects blood volume

3 marks

Answer 17

1. sodium ions lower water potential
2. water would move into blood via osmosis
3. increasing blood volume

Question 18

Describe the advantage of the Bohr effect during intense exercise

2 marks

Answer 18

1. increased dissociation of oxygen
2. for aerobic respiration at the muscles