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Lesson 1, Topic 8
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# Population and Population Studies

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The total number of individuals of a given species in a given place is called a population or population size while the total area occupied by the population is called population area and the number of individuals per unit area is called population density.

Population density is calculated using the formula,

â‡’ $$\scriptsize Population\: Density = \normalsize \frac{Population \: Size}{Population \: Density}$$ Â

The unit of measurement is population size/unit area.

For example, if the population size of ants is 400 over an area of 200cm2, the population density can be calculated thus;

â‡’ $$\scriptsize Population\: Density = \normalsize \frac{Population \: Size}{Population \: Density}$$ Â

â‡’ $$\scriptsize Population\: Density = \normalsize \frac{400}{200} \\ \scriptsize = 2 \: ants/cm^2$$ Â

Meanwhile, an instrument called a quadrat can be used, to estimate the number of plants and animals in a habitat. A quadrat is a rectangular or square frame made from thick wood. The quadrat is thrown at random several times on specific areas and the area thus covered is studied.

### Factors Affecting Population:

Some factors can cause the population in a given area to increase or decrease, these are:

1. Natality (Birth rate)

2. Mortality (Death rate)

3. Food.

4. Migration â€“ Immigration and Emigration.

Evaluation Questions:

1. Define the following terms

(a) Habitat
(b) Ecology
(c) Ecosystem
(d) Adaptation
(e) Population
(f) Biome

2. State 2 ecological factors and give two examples of each of the ecological factors.

a. list three (3) adaptations of terrestrial plants to their habitat.
b. list three (3) adaptations of terrestrial animals to their habitat.

3. Explain the following interactions in the ecosystem

a. Saprophytism
b. Mutualism Â  Â
c. Predation

4. List 4 (four) factors affecting the population in a given area?

Reading Assignment:

Spectrum Basic Science for Junior Secondary School, Book 2. Pages 25 â€“ 29

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