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Population is the total number of organisms of the same species living together in an area at a certain time.

Community is made up of many population of different species.Terms to consider in studying population in an habitat are: •Types of organisms: deals with different species of organisms present in an habitat. •Dominance:species of organisms that exert greater influence. •Population characteristics: in a given area,a large population can withstand disaster e.g fire, disease e.t.c. •Population density:is given as;total population/population size÷area of habitat. Population size=population density×area of habitat. Factors affecting population.

These include the following; *Natality (birth rate). *Mortality (death rate). *Immigration (increase in population). *Emigration (dispersal). *Availability of food. *Seasonal climatic changes. *Breeding period. *Natural disaster. Method of population study. On terrestrial habitat population study can be carried out using the following methods; *Sampling method. *Transect method. °Sampling method: can be done by using an instrument called QUADRAT.A quadrat is made up of a square of rectangular wire,plastic, wooden/metal frame with predetermined area.e.g, the area of a quadrat maybe 1•5m^2 or it may have the size of 25cm,as shown below: DIAGRAM OF QUADRAT.

A quadrat is made from a length of stout wire. ∆How to conduct population study. Population size and density of a particular species in a terrestrial habitat can be estimated by the following procedures:

*Choose and locate the sample plot.

*Then identify the species in the plot.

*Measure the area with a measuring tape to know the area of habitat.

*Throw/toss the quadrat randomly at intervals for up to 10times.

*After each throw the number of species within the area of quadrat is recorded.

*The density of species is calculated by dividing the average no of time the species occurs within the quadrat by the area of quadrat.

°Transect method: the tape should be stretched with marking at intervals.the plant within the various intervals are recorded.This procedure is repeated a number of times until an accurate estimate of the number and types of plants in the habitat are obtained.

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