The concept of the Malthusian Trap was proposed by Thomas Robert Malthus in 1798. The Malthusian Trap or Malthusian Theory argues that gains in food production lead to an increase in population, which results in food shortages as the ever growing population takes over land meant more crop production.

: advocating control of population growth (as by contraception)

In An Essay on the Principle of Population (1798), Thomas Robert Malthus posited that an increase in a society’s cost of living was linked to the inability of its population to produce enough food and to maintain a level of economic stability. It is known as the “Malthusian Trap”.

The Demographic Transition Model (DTM) is based on historical population trends of two demographic characteristics – birth rate and death rate – to suggest that a country’s total population growth rate cycles through stages as that country develops economically.

Two modes of population growth. The Exponential curve (also known as a J-curve) occurs when there is no limit to population size. The Logistic curve (also known as an S-curve) shows the effect of a limiting factor (in this case the carrying capacity of the environment).

Explain the difference between S and J Curves. S curves (sigmoidal curve) is a population growth curve that shows an initial rapid growth (exponential growth) and then it slows down as the carrying capacity is reached. J Curve is a population growth curve that shows only exponential growth. It shows postive feedback.

Logistic growth is commonly observed in nature as well as in the laboratory (Figure 6), but ecologists have observed that the size of many populations fluctuates over time rather than remaining constant as logistic growth predicts.

In the real world, with its limited resources, exponential growth cannot continue indefinitely. Exponential growth may occur in environments where there are few individuals and plentiful resources, but when the number of individuals becomes large enough, resources will be depleted, slowing the growth rate.

Limiting factors are resources or other factors in the environment that can lower the population growth rate. Limiting factors include a low food supply and lack of space. Limiting factors can lower birth rates, increase death rates, or lead to emigration.

Given a large enough supply of nutrients, the number of bacteria in a colony will tend to grow exponentially, but eventually the model will fail, because the bacteria will run out of room or nutrients to grow.

Could any species undergo exponential growth forever? No, such growth will eventually exceed the carrying capacity of any environment.

Exponential growth is a pattern of data that shows greater increases with passing time, creating the curve of an exponential function.

In these simple models of exponential growth, birth and death rates stay the same through time, regardless of population size. They are density-independent.