It is known to all of us that life of organisms could not exist on earth without interactions. Ecology is the study of the interaction of organisms in an area with their environment. This interaction constitutes an overall adaptation of the organisms to their environment which also includes the continuity of species. There is not a single habitat which is solely occupied by a single species. Within an ecosystem, organisms live in a group and they share or compete for resources. They grow as a population. Let us discuss the attributes of the population in an ecosystem in detail.
Organisms and Population
A population could be defined as the set of all organisms of the same species existing in a geographical area which is capable of interbreeding. Both sexual and asexual reproductions contribute to the population. Rats in an abandoned dwelling, teak wood trees in a forest tract, bacteria in a culture plate, are all examples of a population. The environmental conditions are variable and populations of a particular region learn to adapt to its environmental conditions. Evolution through natural selection also had a role in shaping the populations.
There is a line of difference between being a part of a population and an organism. Populations have some features that as an organism, a species lacks. Birth and death rates, sex ratio, age distribution and population density are certain attributes of populations. These attributes could be statistically measured for a population but not for an organism. This is because an organism has birth and death but not birth rate and death rate. Birth and death rates are the per capital births and deaths in a population respectively. In other words, the birth rate is calculated by dividing the total number of births by the total population in a given period of time. These rates vary as per the number of members in a population.
Thirdly we have sex ratio which calculates the ratio of male to female individuals of a population. Next population attribute is age distribution. A population may constitute of different age groups such as pre-reproductive, reproductive and post-reproductive age groups. This age distribution is graphically represented by an age pyramid. The age pyramids indicate whether a population is growing, stable or declining.
Finally, we have a population density which tells us the size of a population. This attribute is the reflection of the condition of a habitat. More density indicates that the habitat provides a more favorable living conditions. Hence, we can summarise that the population attributes provide a lot of information about an ecosystem and thus help in population ecology.
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