23.5 measuring the distribution and abundance of organisms

how to measure distribution

• a line or belt transect is used

• both are forms of systematic sampling, a type of non-random sampling

• in systematic sampling, different areas within a habitat are identified which are then sampled seperately

fluctuations in the abundance of organisms

• immigration and births will increase the number of individuals

• emmigration and death will decrease the number of organisms

measuring plant abundance

estimated number in population (m²) = number of individuals in a sample/ area of a sample (m²)

measuring animal abundance

1. capture as many individuals as possible in a sample size

2. mark or tag each individuals

3. release the marked organisms back into the area and allow time for them to redistribute themselves through the habitat

4. recapture as many samples as possible

5. record the number of marked and unmarked individuals individuals presents within the sample

   estimated population size = number of individuals in first sample x number of individuals in the second sample / number of recaptured marked individuals

simpsons diversity index