what is characteristics of population ?
Answers
Answer:
Demography is the study of a population, the total number of people or organisms in a given area. Understanding how population characteristics such as size, spatial distribution, age structure, or the birth and death rates change over time can help scientists or governments make decisions.
Explanation:
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Answer:
Some of the most important characteristics of population are as follows:
1. Population density
2. Natality
3. Mortality
4. Population growth
5. Age distribution of population
6. Population fluctuations.
Explanation:
1. Population Density:
Population density refers to the size of any population in relation to some unit of space. It is expressed in terms of the number of individuals or biomass per unit area or volume, as for example, 500 teak trees per hectare; 40 lions per 100 km2, 5 million diatoms per cubic meter of water. Population density is seldom static and it changes with time and space.
2. Natality:
Natality refers to the rate of reproduction or birth per unit time. It is an expression of the production of new individuals in the population by birth, hatching, germination or fission.
Natality is calculated by the following formula:
Birth rate or Natality (B) = Number of births per unit time/Average population.
The maximum number of births produced per individual under ideal conditions of environment is called potential natality. It is also called reproductive or biotic potential, absolute natality or maximum natality.
Natality varies from organism to organism. It depends upon the population density and environmental factors. It is a general rule that if the population density is usually low, the birth rate is also low. This is so because the chances of mating between males and females are low. If population density is unusually high, the birth rate may also be low due to poor nutrition or physiological or psychological problems related to crowding.
The maximum or absolute natality is observed when the species exists under ideal ecological and genetic conditions. The actual number of births occurring under the existing environmental conditions is much less as compared to absolute natality. It is referred to as ecological natality or realized natality. It is not constant for population and may vary with the size of population as well as with the time.
3. Mortality:
Mortality refers to the number of deaths in population per unit time.
Mortality rate = D/t where D is the number of deaths in the time t.
Mortality can be expressed in the following two ways:
(i) Minimum or Specific or Potential Mortality:
It represents the minimum of theoretical loss of individuals under ideal or non-limiting condition. Thus, even under the best conditions individuals of a population would die of old age determined by their physiological longevity. So it is constant for a population.
(ii) Ecological or Realized Mortality:
It refers to the death of individuals of a population under existing environmental conditions. Since it varies with environmental conditions, it is never constant. The maximum mortality occurs at the egg, larval, seedling and old age. Mortality is affected by a number of factors, such as, density, competition, disease, predation and environment. Death rates vary among the species and are correlated with birth rates. When the rate of natality is equal to the rate of mortality the population is stationary.
4. Population Growth:
The growth is one of the dynamic features of species population. Population size increases in a characteristic way. When the number of individuals of population is plotted on the y-axis and the times on the x-axis, a curve is obtained that indicates the trend in the growth of population size in a given time. This curve is called population growth curve.
5. Age Distribution:
Age distribution is another important characteristic of population which influences natality and mortality. Mortality, usually varies with age, as chances of death are more in early and later periods of life span. Similarly, natality is restricted to certain age groups, as for example, in middle age-groups in higher animals. According to Bodenheimer (1958), the individuals of a population can be divided into pre-reproductive, reproductive and post-reproductive groups. The individuals of pre-reproductive group are young, those of reproductive group are mature and those in post-reproductive group are old.
6. Population Fluctuations:
The size and density of natural population show a changing pattern over a period of time. This is called population fluctuation.