8.3 Population Ecology

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.

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.

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.

The quadrat sampling technique

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

(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

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. Released4. Second sample captured & number of

marked animal recorded.

Population size of the animal in the area can be estimated using the formula below:

The capture, mark, release and recapture technique

The abiotic factors which influence the distribution of an organism

What are abiotic factors? How the abiotic factors influence the

distribution of an organism?

Exercise

Do Focus Practice 8.3 on page 188 in the textbook.