investigating populations

Question 1

sampling methods are used to investigate this

Answer 1

1. choose an area to sample - a small area within the area being investigated
2. samples should be random to avoid bias eg split area into a grid and use a number generator to select co-ordinates
3. use an appropriate technique for eg - quadrat transect mark release capture
4. repeat process
5. number of individuals for the whole area can be estimated by taking mean and multiplying it by the size of the whole area

Question 2

quadrats

Answer 2

square frame usually divided into 100
quadrats are placed at different points on the ground
randomly generated
measure: species frequency , number of individuals , percentage cover

Question 3

transect

Answer 3

rope used to find out how many plants are distributed across an area eg how species change from a tree towards the middle of the field

Question 4

belt transect

Answer 4

quadrats are placed next to eachother along the transect

Question 5

interrupted belt transect

Answer 5

allows longer distance to be covered more quickly
quadrats are placed at intervals

Question 6

mark release recapture

Answer 6

1. capture a sample of species and count them
2. mark them in a harmless way
3. release them back into the population
4. after some time the trapping is repeated and the second sample is captured
5. number of marked and non marked are recorded

Question 7

mark release recapture

Answer 7

P= N1 x N2 - divided by R
(number in sample 1 x number in sample 2)
divided by the number of marked recaptures in sample 2

Question 8

what are the assumptions of this

Answer 8

• the marked sample has enough time to mix back into the population
  -marking hasnt affected individuals chances of survival
  -marking hasnt rubbed off
  -no changes in population due to births , deaths , migrations