Population ecology studies the structure and dynamics of populations. Factors like birth rate, death rate, and immigration affect population density. Direct counting of populations is impractical, so sampling techniques like quadrat sampling and capture-mark-recapture are used instead. Quadrat sampling involves using frames to estimate plant and immobile animal population frequencies, densities, and percentages. Capture-mark-recapture involves capturing, marking, releasing, then recapturing animals to estimate total population size using a specific formula. Abiotic factors like temperature and light influence where organisms can live.

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.