What does the theory of natural selection state

The theory of natural selection was proposed by Charles Darwin, which states the mechanism of biological evolution by explaining adaptation and speciation. There was five observation of the theory of natural selection.

1) The population produces more offspring than there are adults, in each generation.

2)  The population does not continue to grow in size.

3) Food and many other resources are limited.

These three observations interfere that individuals compete for resources within a population.

4) Individuals within all populations vary.

5) Many variations are heritable.

He also assumed from these two observations that individuals inherit some characteristics that give a better chance of surviving and reproducing.

These observations and interpretations helped him to propose the theory of natural selection. The theory tells the heritable characteristics in a population change over  time become more adapted in generation after generations.