WHAT IS POPULATION IN ECOLOGY?

WHAT IS POPULATION?

In ecology, population is defined as the total number of organisms of the same species living together in a given area at a particular time.A population is a subset of individuals of one species that occupies a particular geographic area and, in sexually reproducing species, interbreeds. The geographic boundaries of a population are easy to establish for some species but more difficult for others.

For example, plants or animals occupying islands have a geographic range defined by the perimeter of the island. In contrast, some species are dispersed across vast expanses, and the boundaries of local populations are more difficult to determine. A continuum exists from closed populations that are geographically isolated from, and lack exchange with, other populations of the same species to open populations that show varying degrees of connection.

In an ecosystem, the community is made up of many different species.
In population studies of habitat, the following are usually the areas of studies

1.

TYPES OF ORGANISMS:

this involves the listing of the various types of population that are found under the population. It helps to determine the relationship that exists between the various organisms that co-exist within the community
2.

DOMINANCE:

the dominance refers to those species who exert a greater influence or control on the other members of the community. So the relative importance of a specie in a community is expressed by dominance. So dominance could be expressed in terms of, (i) their number (ii) their occupation of the largest area in the community (iii) possession of the Biomass and (iv) the largest contributor to the energy flow in the habitat. For a species to be dominant, it should possess some of these attributes

CHARACTERISTICS OF POPULATION

The characteristics of population simply the underlying factors by which a population is recognized. These characters are follows

POPULATION SIZE:

population size refers to the total number of the species of the same kind in given area or habitat. A large population stands a better chance of surviving dangerous and unfavourable conditions such as fire, diseases, etc. while a small population can easily be wiped out.
ii.

POPULATION DENSITY:

population density is defined as the number of individual organisms per unit area or volume of the habitat. So mathematically, population density is equal to total population all over Area of habitat. Population density can be used to estimate the total number of a population or population size
iii.

POPULATION FREQUENCY:

this refers to the number of times an organism occurs within a given area of a habitat
iv.

PERCENTAGE COVER:

this refers to the area or space covered or occupied by a given species in its habitat and is expressed in percentage
v.

POPULATION GROWTH RATE:

this refers to the result of the influence of natality (birthrate) and mortality (death rate) of organisms in a given habitat

FACTORS AFFECTING POPULATION

Factors which may affect population of organisms in a given area include
1.

NATALITY (birth rate):

this refers to the rate at which organisms give birth to new ones. This aspect of population, either plant or animals, lead to increase in population
2.

MORTALITY (death rate):

this refers to the rate at which organisms die in a habitat. Mortality generally lead to decrease in population
3.

IMMIGRATION (dispersal):

this is the movement of organisms from one habitat to another new habitat. This type of factor increases the population of the new area

4.

EMMIGRATION:

this the movement of organisms from a habitat due to food shortage or unfavourable conditions and sometimes can be for breeding purposes too. This however reduces the population of a habitat
5.

AVAILABILITY OF FOOD:

the availability of in a given habitat tends to increase that habitat through rapid 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 condition are favourable
7.

BREEDING PERIODS:

most organisms move out of the habitat during the mating or breeding seasons in search of mates or partners
8.

NATURAL DISASTERS:

natural disasters like fire, drought, floods and earthquakes may lead to decrease in population as many organisms would have died out or move out to a new habitat for safety

METHODS OF POPULATION STUDIES

There are practically two ways by which a population of a place can be determined. They are
1.

SAMPLING METHOD OF POPULATION STUDIES: this type or method of population studies is mainly or especially used in terrestrial habitat by making use of a gadget called QUADRAT

A quadrat is made of a square or rectangular wire, plastic, wooden or metal frame with predetermined area
2.

THE TRANSECT METHOD OF ESTIMATION OF POPULATION IN POPULATION STUDIES:

this involves the use of tape. The tape should be stretched with markings at intervals. The plants within the various intervals should be recorded. This procedure should be repeated a number of times until an accurate estimate of the number and types of plants in the habitat are obtained. The transect tape method of population studies is used specially to determine the total of trees or plants in a given community or habitat

HOW TO CONDUCT POPULATION STUDIES

The population size or total population and population density of a particular species in a terrestrial habitat can be estimated by the following procedures
1. Choose and locate the sample plot
2. Then identify the species in the plot
3. Measure the area with a measuring tape to know the area of the habitat
4. Throw the quadrat randomly at intervals for up to ten times
5. After each throw, the number of species within the area of quadrat is recorded
6. The density of population is by the average number of times the species occurs within the quadrat. They are thus written like these
i. Frequency of species=X
ii. Number of tosses= Y/10
iii. Average number of species per quadrat== X/Y/10=Z
iv. Area of quadrat ==1m
v. Density ==Z

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