Population Studies In Ecology: Definition, Factors Affecting And Methods Of Population Studies


  • Meaning Of Population Studies
  • Factors Affecting Population
  • Methods Of Population Studies

Population Studies
Definition: Population is defined as the total number of organisms of the same species living together in a given area at a particular time. In an ecosystem, the community is made up of many populations of different species.
In population studies of a habitat, the following are usually studied:
1. Types Of Organisms: This involves the listing of the various types of populations that are found in the particular habitat. It helps to determine the relationships that exist between the various organisms (plants and animals) in a habitat.
2.Dominance: Dominance refers to those species that exert a greater influence or a major controlling effect on the other members of the community. The relative importance of a species in the community is expressed by dominance.
Dominance could be expressed in terms of (i) their number (ii) occupation of largest portion of space (iii) possession of the highest biomass and (iv) the largest contribution to the energy flow in the habitat.
3. Population Characteristics: These characteristics include:
1. Population Size: This refers to the total number of the species of the same king in a given area.
2. Population Density: Population density is defined as the number of individual organisms per unit area or volume of the habitat. Population density can be use to estimate the total number of individuals of a population or population size.
3. Population Frequency: This refers to the number of times an organism occurs within a given area of a habitat.
4. Percentage Cover: This refers to the area or space covered or occupied by a given species in its habitat and it is expressed in percentage.
5. Population Growth Rate: This refers to the net result of the influence of natality (birth rate) and mortality (death rate) of organisms in a given habitat.
Factors Affecting Population
Factors which may affect the population of organisms in a given habitat include:
1. Natality (Birth Rate): This refers to the rate of give birth to new organisms. This generally (be it plants or animals) leads to increase in population.
2. Mortality (Death Rate): This refers to the rate at which organisms die in a habitat. Mortality generally leads to a decrease in population.
3. Immigration (Dispersal): This is the movement of organisms from different habitats into a new habitat. This tends to increase the population of the new area.
4. Emigration: This is the movement of organisms out of a habitat due to either scarcity of food or unfavourable conditions or for breeding purposes. This, however, reduces the population of a habitat.
5. Availability Of Food: The availability of food in a given habitat tends to increase the population of that habitat through rapid rate of reproduction and other organisms coming in to feed.
6. Seasonal Climatic Changes: Unfavourable climatic changes may result in the decrease of population since most organisms may die or migrate out of the habitat while the reverse is the case when the conditions are favourable.
7. Breeding Periods: Most organisms move out of a habitat during the breeding period or season, thereby reducing the population of the habitat. For example, population decreases during the breeding season in fish, toad, termite, etc.
8. Natural Disasters: Natural disasters like fire, drought, floods, earthquakes, etc may lead to a decrease in population as many organisms may die or move out of that habitat to a new area.
Methods Of Population Studies
1. Population Studies By Sampling Method
Population studies can easily be carried out in a habitat especially in terrestrial habitat by sampling method, making use of an instrument called the quadrat.
A quadrat is made of a square or rectangular wire, plastic, wooden or metal frame with predetermined area.
2. Estimation Of Population Using The Transect Method
The tape should be stretched with markings at intervals. The plants 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.