RP12: Effect Of Different Variables On Species Distribution

Question 1

List 3 abiotic factors

Answer 1

Light intensity

Temp

Water supply

Nutrient supply

Humidity

Wind speed

Day length

Rainfall

Question 2

List 3 biotic factors

Answer 2

Competition for resources

Predation

Disease

Question 3

How is % 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 % of squares the species is present in

Question 4

Outline 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 results be used to determine relationship between chosen factor and % cover

Answer 5

Use statistical test

E.g. person’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 formula for mark-release-recapture method

Answer 7

Population size =

No. In 1st sample X no. In 2nd sample
——————————————————
No. Marked in 2nd sample

Question 8

State assumptions when using mark-release-recapture method

Answer 8

No births, deaths or immigrations

Random mixing of marked individuals with population

Marking does not affect behaviour of individuals or make them more vulnerable to predators