Population Growth: Definition, Type & Causes

The modern man appeared about \(25000\) million years ago. Now how come we see so many people around us? We see war and conflicts everywhere among us? Why are these happening? Why did rules and regulations come into existence? Yes, population growth is the main problem for various things which are currently happening in the world.

The drastic rise in population affected the living condition, agricultural and technological advances and a decline in the occurrence of many diseases. Population Growth refers to the increase or decrease in the size of a population over time, depending on the balance of births and deaths. If many people die, the world’s population will expand slowly, if at all, and may even shrink. Absolute and relative population growth are both measured.

So, in this article, let us learn more about population growth, causes, effects, etc, which need to be controlled in future generations. Continue reading to know more.

What is Population?

The Population is defined as the total number of individuals of a species present in a particular area at a given time. A species has many populations living in different regions.

Define Population Growth

Population Growth is defined as the increase in the number of individuals in a population is called population growth.

Three factors determine population growth, and they are:

1. Natality: The number of births in a given period of time in a population. Various indices have been used to express natality:
   (a) Crude Birth Rate: Ratio between the number of births(usually one year) and total population for the same year.
   (b) Standardized Birth Rate: It involves the calculation of what the birth rate for a region would have been if its age composition had been the same as that of the country as a whole.
   (c) General or Total Natality Rate: The ratio between the number of births and the number of women in the reproductive age group usually defined as \(15 – 45\) or \(15 – 49\).
   
2. Mortality: It is used to describe the occurrence of deaths among a defined population.
   Various indices have been used to express Mortality:
   (a) Crude Mortality Rate: Ratio between the number of deaths and total population for a year.
   (b) Infant Mortality Rate: The number of children dying under one year of age divided by the number of live births that year.
   (c) Maternal Mortality Rate: Number of deaths assigned to pregnancy-related causes during a given time interval, divided by the number of live births during the same time interval.
   (d) Standardized Mortality Rate: It involves the calculation of what the death rate for a region would have been if its age composition had been the same as that of the country as a whole.
   
3. Migration: It is defined as the movement of people from one place to another in order to live and work in a specific period of time. This can be Immigration or Emigration.
   (a) Immigration: It is the number of individuals of a given species that have come into the habitat from some other habitat during the time period under consideration.
   (b) Emigration: It is the number of individuals of the population that leave their habitat and go somewhere else during the time period under consideration.

Learn Examples on Population Growth

Types of Population Growth

The population has characteristic patterns of increase, which are called population growth forms.
There are mainly two types of population growth:
1. \(S\)-shaped growth curve.
2. \(J\)-shaped growth curve.

1. \(S\)-shaped or Sigmoid or Logistic Growth Curve

This type of growth curve is shown by the yeast cells under laboratory conditions. It is also shown by the population of most organisms. It has \(5\) phases: lag phase, positive acceleration phase, exponential phase, negative acceleration phase, and stationary phase.

(a) Lag phase: In the beginning, the small population of yeast cells adapts itself to the new environment. There is little or no increase in population.

(b) Positive acceleration phase: Increase in population starts and occurs at a slow rate in the beginning.

(c) Exponential phase: The increase in the population becomes rapid and soon attains its full potential rate. This is due to the constant environment, the availability of food and other requirements of life in plenty, to no predation and interspecific competition, and no serious intraspecific competition so that the curve rises steeply upward.

(d) Negative acceleration phase: The growth rate finally slows down as environmental resistance increases. Environmental resistance is due to many factors, such as more competition for food, less space, and greater mortality.

(e) Stationary phase: Finally, the population becomes stable because the number of new cells produced almost equals the number of cells that die. Every population tends to reach a number at which it becomes stabilized with the resources of its environment. A stable population is said to be in equilibrium or at saturation level. This limit in population is a constant \(K\) and is imposed by the carrying capacity of the environment.

(f) The growth rate is given as:
\(\frac{{dN}}{{dt}} = rN\left( {K – \frac{N}{K}} \right)\)
Where \(N = \) Population density at time \(t;r = \) Intrinsic rate of natural increase; \(K = \) Carrying capacity

2. \(J\)-shaped Growth Curve

This type of curve was shown by a small population of reindeer experimentally reared in the natural environment with plenty of food but no predators. There are only two phases in this curve: The lag phase and the exponential phase.

(a) Lag phase: There was no significant increase in the population of reindeer for some time in which the animals became adapted to their environment.

(b) Exponential phase: On becoming adapted to their environment, the reindeer started reproducing rapidly. Rapid multiplication continued as long as enough food was available. An increase in the population of reindeer resulted in a corresponding decrease in the amount of food available to them. Finally, the food supply was exhausted, and this led to mass starvation and mortality.

(c) The growth rate is given as
\(\frac{{dN}}{{dt}} = \left( {b – d} \right) \times N,\) and if \(\left( {b\,\, – \,\,d} \right) = r,\) then, \(\frac{{dN}}{{dt}} = rN\)
Where \(\frac{{dN}}{{dt}} = \) rate of change of population size,
\(r = \) intrinsic rate of natural increase,
\(N = \) Population size,
\(b = \) Birth rate,
\(d = \) Death rate.

Population Growth Diagram

What is the Population Growth Rate?

The population growth rate is defined as the ratio between the annual increase in the population size and the total population for that year.

Causes of Population Growth

1. The decline in the death rate and an increase in the birth rate due to advanced medical facilities.
2. Agricultural Advancements
3. Technological Advancement in Fertility Treatment
4. Immigration
5. Lack of Family Planning
6. Poor Contraceptives Use
7. Orthodoxy
8. Child Labour
9. Lack of Strict Population Control Laws

Factors of Population Growth

There are mainly four factors that affect population growth:

1. Lack of education leads to an increase in population.
2. Traditional faith: The child is considered as ‘God’s gift’ in a major part of our population. As a result, no efforts are made to adopt a family welfare program.
3. Economic reasons: Poverty is the main reason for population growth. Children are considered helping hands. So, people, at least in the low-income group, consider children as a source of income.
4. Emigration: Emigration is the permanent outward movement of individuals from a population for setting into a new area. It decreases the local population.
For example, it does not occur in plants as the same is fixed. In animals, emigration occurs due to natural calamity, scarcity of food, shelter and mate.

Effects of Population Growth

1. Depletion of Natural Resources
2. Degradation of Environment
3. Conflicts and Wars
4. Rise in Unemployment
5. High Cost of Living
6. Malnutrition, Starvation and Famine
7. Water Shortage
8. Lower Life Expectancy
9. Increased Global Warming and Climate Change
10. Extinction
11. Increased Intensive Farming

Summary

Growth in the population indicates an increase in demand and many changes in human activities. Many ecologists put the blame for the environmental crisis on the rapid growth in the world population, which by placing increasing demands on scarce resources, is degrading the global ecosystem. To avoid the rise in population, we should educate people about reproductive health and family planning and make them aware of population growth and its effects.

Frequently Asked Questions

We have provided some frequently asked questions here

Q.1. What are the two types of population growth?
Ans: There are mainly two types of population growth:
1. \(S\)-shaped growth curve.
2. \(J\)-shaped growth curve.

Q.2. What are the causes of Population Growth.
Ans: The causes of population growth are:
1. The decline in the death rate and an increase in the birth rate due to advanced medical facilities.
2. Agricultural Advancements
3. Technological Advancement in Fertility Treatment
4. Immigration
5. Lack of Family Planning

Q.3. What is the population growth rate definition?
Ans: The population growth rate is simply defined as the ratio between the annual increase in the population size and the total population for that year.

Q.4. What is population growth based on?
Ans: The population growth is based on few factors, and they are:
1. Birth Rate (Natality)
2. Migration
3. Mortality

Q.5. What are the \(4\) main challenges of population growth?
Ans: The \(4\) main challenges of population growth are:
1. Depletion of Natural Resources
2. Climate change and global warming
3. High Cost of Living
4. Conflicts and Wars

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