RP12 Effect Of Different Variables On Species Distribution

Question 1

List abiotic factors

Answer 1

Light intensity

Temperature

Water supply

Nutrient supply

Humidity

Wind speed

Day length

Rainfall

Question 2

List biotic factors

Answer 2

Competition for resources

Predation

Disease

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 o 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 chose species.
5. At each coordinate, a measure of independent variable should be taken. E.g 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 pearsons linear correlation, spearman’s rank.

Question 6

Why should a random generator be used?

Answer 6

To avoid bias in random sampling.

Question 7

State the formula for mark-release-recapture method.

Answer 7

Population size= no. In first sample x no. In second sample

Question 8

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

Answer 8

• no births, deaths or migration
• random mixing of marked individuals with population.
• marking doesn’t affect behaviour of individuals or make them more vulnerable to predators.