Speciation, Investigating Populations and Succession

Question 1

Describe the process of succession (6)

Answer 1

1. Pioneer species
2. Pioneers cause change in environmental abiotic / biotic factors
3. Pioneers make the environment less hostile for new species
4. New species make conditions less suitable for previous species
5. Increase in biodiversity
6. Stability increases
7. Climax community

Question 2

Explain how succession results in a wide variety of fish living on coral reefs (2)

Answer 2

1. Increase in number of species
2. More habitats and niches

Question 3

Describe random sampling
[estimation of population density] (5)

Answer 3

1. Use a grid
2. Use random number generator to generate random coordinates
3. Count number of plants in a quadrat
4. Large sample (20+ quadrats) AND Calculate mean
5. Valid method of calculating total number of ……… e.g. mean number of plants per quadrat multiplied by number of quadrats in wood

Question 4

Describe systematic sampling (3)

Answer 4

1. Transect (from one side of the dune to the other)
2. Place quadrats at regular intervals along the line
3. Count plants

Question 5

Describe how you would determine the mean percentage cover for beach grass on a sand dune. (3)

Answer 5

1. Use random number generator to generate random coordinates
2. Large number of quadrats (min 20)
3. Divide total percentage by number of quadrats

Question 6

Describe a method that could be used to determine the mean percentage cover of algae on coral reef (3)

Answer 6

1. Use random number generator to generate random coordinates
2. Large number of quadrats (min 20)
3. Divide total percentage by number of quadrats

Question 7

Describe the mark, release, recapture technique (4)

Answer 7

1. Capture sample, mark and release
2. Appropriate method of marking suggested / method of marking does not harm fish
3. Take second sample and count marked organisms
4. No in Population = No in sample1 × No in sample2
   divide
   Number marked in sample2

Question 8

The mark release recapture method can be used to estimate the size of a fish population. Explain how. (4)

Answer 8

1. Capture sample, mark and release
2. Appropriate method of marking suggested / method of marking does not harm fish
3. Allow time for fish to randomly redistribute before collecting second sample
4. No in Population = No in sample1 × No in sample2
   divide
   Number marked in sample2

Question 9

Suggest why the mark release recapture method can produce unreliable results in very large lakes (2)

Answer 9

1. Fish may congregate
2. Unlikely fish distribute randomly

Question 10

Describe how you would determine how many quadrats to use when investigating a habitat. (5)

Answer 10

1. Calculate running mean
2. When enough quadrats, this shows little change
3. Enough to carry out a statistical test
4. A large number to make sure results are reliable
5. Need to make sure work can be carried out in the time available

Question 11

Describe what is meant by allopatric speciation (6)

Answer 11

1. Geographical isolation
2. Separate gene pools
3. Variation due to mutation
4. Different biotic/abiotic factors
5. Selection for advantageous alleles
6. Differential reproductive success
7. Leads to change in allelic frequency
8. Can’t breed to produce fertile offspring

Question 12

Describe what is meant by sympatric speciation (6)

Answer 12

1. Not geographical isolation
2. Leads to reproductive isolation
3. Separate gene pools
4. Selection for advantageous alleles
5. Differential reproductive success
6. Leads to change in allelic frequency / can’t breed to produce fertile offspring

Question 13

What is meant by the term genetic drift, otherwise known as bottleneck? (1)

Answer 13

1. Random increase or decrease in allelic frequency

Question 14

What is meant by the term gene flow, otherwise known as the founder effect? (1)

Answer 14

1. Change in allelic frequency is due to migration of fertile individuals