SS1 Biology Lesson Note on Population Growth and Food Supply

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POPULATION GROWTH AND FOOD SUPPLY

Population can be defined as the total number of organisms of the same species living in a habitat over a period of time. Food supply affects population growth both positively and negatively, based on availability or unavailability of food in a habitat.

If food is adequately available organism will be well fed, give birth to new ones; death rate reduces and population rises. When there is inadequate supply of food, the organism is malnourished, there is competition for the limited food, birth rate reduces, death rate increases and there is a decline in population of the organism. The number of organisms migrating out of the habitat increases and cannibalism may set in.

Factors affecting population growth include the following:

1. Reproduction (birth rate)
2. Migration (movement of organism)
3. Death (death rate)
4. Availability of food
5. Availability of space
6. Availability of water
7. Natural disaster
8. Famine
9. War

Experiment to demonstrate effect of food on population

Aim: to show the effect of food on mice population.

Method:  some mice or rodents are kept it two cages. Those in cage 1 are provided with a lot of food and water at the beginning of the experiment. Those in the second cage are supplied with enough food and water continually. The mice left for some time.

Observation: the number of mice continues to increase in the cage with food continuous supplies of food. The population of mice in the cage with food supplied only once will increase for a while when there is no food most of them start to die.

Conclusion: the population of mice tends to increase when there is plenty of food, while their population tends to decrease when there is no food.

EVALUATION

1. Define population.
2. State three factors that influence population of an habitat
3. List three effects of inadequate food supply on population
4. Describe an experiment that shows the effect of food supply on population.

SUB-TOPIC 3: RELATIONSHIP BETWEEN AVALABLE FOOD AND HUMAN POPULATION

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