1. 8.3 Population Ecology

2. What is meant by population
ecology?
 A branch of ecology that studies the structure
and dynamics of population.
 Population density – number of organism per
unit area of habitat
 Affected by abiotic and biotic factors, birth
rate, death rate, immigration and emigration.

3.  Direct counting – method to estimate the size
and density of population (impractical due to
the size of ecosystem, the number of plants
involved and the movement of the animal).
 Sampling technique – more practical way,
enable us to estimate the total population
size of the organism.

4. The quadrat sampling technique
 Used in estimating the size of plant
population and immobile animal.
 A quadrat – metal, wooden frame or PVC
pipe frame which form a square of a known
area (1 m2
).
 Placed randomly in an ecosystem where
sampling is carried out.

5. The quadrat sampling technique

6.  Used to determine:
(a) Frequency – number of times a particular
species is found present when a quadrat is
thrown a certain number of time
The quadrat sampling technique

7. (b) Density – the mean number of individuals of
species per unit area
(c) Percentage coverage – an indication of how
much the area of quadrat is occupied by a
species
The quadrat sampling technique

8. The capture, mark, release and
recapture technique
 Used to estimate mobile animals (small
mammals, butterflies, birds and insects)
 Procedure:
1. Animal sample is captured
2. Marked
3. Released
4. Second sample captured & number of
marked animal recorded.

9.  Population size of the animal in the area can
be estimated using the formula below:
The capture, mark, release and
recapture technique

10. The abiotic factors which influence the
distribution of an organism
 What are abiotic factors?
 How the abiotic factors influence the
distribution of an organism?

11. Exercise
 Do Focus Practice 8.3 on page 188 in the
textbook.