Thomas Malthus, a political economist, showed that the human population would outstrip available resources unless kept in check by other factors such as famine, war, and disease. How did Charles Darwin apply this principle to his theory of evolution by natural selection?A. Darwin used this as a contrast to plant and animal populations, which live in balance with their available resources.B. Darwin used this to illustrate that because food supply remains relatively the same, plant and animal populations show little variation in size.C. Darwin realized this also applied to plant and animal populations, and this struggle for existence resulted in an opportunity for natural selection to act on differences within populations.D. Darwin used this to illustrate that as food supplies increase, populations increase.

C. Darwin realized this also applied to plant and animal populations, and this struggle for existence resulted in an opportunity for natural selection to act on differences within populations.

Step-by-step explanation:

Thomas Malthus in his Malthusian theory of population concluded that since population increases geometrically and resources only increase arithmetically, there will reach a point in time when the resources will be not be able to sufficiently cater for the population.

The Charles Darwin theory of Evolution is based on five key observations and conclusions drawn from them. These observations and inferences are summarized as:

Species are more fertile. They birth more offspring than can grow to adulthood.
Populations remain fairly stable with miniscule fluctuations.
Food resources are limited, but are relatively constant most of the time.

Based off these observations, it is seen that there will be a struggle amongst the members of the specie for the limited resources.

In sexually reproducing species, generally no two individuals are identical. Variation is rampant.
Much of this variation is heritable.

From the last two observations, the species that survive then pass on their traits to their offspring and the cycle repeats itself with each subsequent generation being better evolved than the previous ones.

Thus, Darwin discovered that the Malthusian theory of population also applies to plant and animal populations where scarcity of resources gives room for natural selection to take place due to the variation within populations.