B7: RP - SAMPLING

Question 1

What are some environmental factors affecting distribution of plants?

Answer 1

-mineral ions in soil
-seed dispersal/wind
-light intensity
-predators
-human impact/physical factors
-water in soil
-pollution

Question 2

What are 2 ways of studying distribution?

Answer 2

-random sampling (and percentage cover)
-measuring how distribution changes across an area using a transect line

Question 3

What are the 2 equations you can use to estimate population size?

Answer 3

(total area/sample area (area of all quadrats)) x no. of organisms counted
or
(total area/area of 1 quadrat) x mean no. of organisms per quadrat)

Question 4

Random sampling: method

Answer 4

-lay 2 20m tape measures out at a right angle to create a grid (total area that you are sampling)
-use a random number generator to randomly choose 2 numbers/coordinates
-place the quadrat (0.5m x 0.5m) at the random coordinates
-count all the organisms of the species that you are sampling in the quadrat
-repeat steps 2-4 for at least 10 quadrats
-calculate mean no. of organisms per quadrat
-estimate population size using equations: (total area/ sample area) x no. of organisms counted or (total area/area of quadrat) x mean no. of organisms per quadrat

Question 5

Why use random sampling?

Answer 5

-uneven distribution
-more representative/valid
-avoid bias
-more accurate/precise mean

Question 6

Percentage cover

Answer 6

-used if you can’t count individual organisms
-only count squares more than 1/2 covered

Question 7

Percentage cover equation

Answer 7

(no. of squares covered by organism/total no. of squares in quadrat) x 100

Question 8

Investigating the effect of a factor (light intensity) on plant distribution using a transect line: method

Answer 8

-lay a 20m tape measure out from a tree (transect line)
-place quadrat along transect line at regular intervals
-count all the organisms in each quadrat
-measure light intensity of each quadrat

Question 9

How could you improve the method for investigating the effect of a factor (light intensity) on plant distribution using a transect line?

Answer 9

-repeat with more transects around the tree in different direction
-repeat with other trees
-smaller intervals for sampling