Species are composed of populations. What does this term mean? A population is a certain group of individuals of one biological species inhabiting a certain space, partially isolated from other similar communities. A relatively stable population can reproduce itself over several generations.
The size of the territory occupied by different populations is not the same. They depend on the size of the body and its lifestyle. Bacteria, a fraction of a micron in length, select very small areas for their populations. For large mammals, habitat is measured in square kilometers.
Why do species exist as populations?
The relationships between members of the same group are diverse. Often they depend on each other. Why do species exist as populations? The answer is simple: because it is easier to survive.
In some cases, members of the population can compete and even fight for certain environmental factors (light, mineral nutrition in plants, territory in animals). But more often they help each other. This is especially pronounced in colonial nesting birds and ungulates leading a herd lifestyle.
Gene exchange and inheritance transfer
Answering the question why biological species exist in the form of populations, the facilitated process of reproduction should be recognized as perhaps the most important factor. It provides the exchange of genes, the transfer of hereditary properties from parents to descendants. These connections are somewhat weakened in populations where parthenogenetic reproduction predominates. This is characteristic of some insects, such as aphids. For many plants vegetative propagation is characteristic. Such are the slippers that dwell in deciduous forests and the slipper venus, wheat grass creeping in the meadows. Some species of animals vegetatively reproduce - corals, sponges.
Structure
A population exists in space in the form of a specific biological pattern. Its character, worked out by the mechanism of natural selection, makes it possible to economically use the ecological resources of the territory and maintain biologically necessary contacts between the individuals that make up the population. This makes it possible to understand why species exist in the form of populations and subspecies.
The spatial distribution of the group depends on the size of the food sites in animals or on the required nutritional area in plants. This process may be accompanied by increased competition. Often, it leads to the death of the weakest individuals in plants, the expulsion of those in animals. Many animals mark occupied areas with urine, odorous secretions of special glands, and sound signals. The latter is especially common in birds. Many animals demonstrate their right to the territory or actively defend it with their behavior.
There are many reasons why biological species exist in the form of populations, but the main ones are: mutual assistance, facilitated reproduction, and more efficient use of resources.