Required Practical 12

Question 1

List 3 abiotic factors.

Answer 1

Light intensity, Temperature, Water supply

Additional abiotic factors include Nutrient supply, Humidity, Wind speed, Day length, and Rainfall.

Question 2

List 3 biotic factors.

Answer 2

Predation, Competition for resources, Disease

Additional biotic factors include specific species interactions.

Question 3

How is percentage cover calculated?

Answer 3

Use a quadrat with squares. Count how many squares the required species is present in. Only count a square if more than half of the square is covered. Calculate the percentage of squares the species is present in.

Question 4

Outline the procedure to this practical.

Answer 4

1. Choose an area to take samples from. Use a random number generator to
   generate 10 sets of random coordinates.
2. Use two tape measures to create a set of axes off which coordinates can be
   read.
3. Place the quadrat at each of the coordinates, placing the bottom left corner on
   the coordinate every time.
4. Record the percentage cover for the chosen species.
5. At each coordinate, a measure of the independent variable should be taken.
   Eg. record light intensity using a photometer at each location

Question 5

How can the results be used to determine the relationship between the chosen factor and the percentage cover?

Answer 5

Use a statistical test e.g. Pearson’s linear correlation, Spearman’s rank.

Question 6

Why should a random number generator be used?

Answer 6

To avoid bias in random sampling.

Question 7

State the formula for the mark-release-recapture method.

Answer 7

Population size = no. in 1st sample x no. in 2nd sample / no. marked in 2nd.

Question 8

State the assumptions when using the mark-release-recapture method.

Answer 8

1. No births, deaths or immigrations.
2. Random mixing of marked individuals with population.
3. Marking does not affect behaviour of individuals or make them more vulnerable to predators.