Mutation and Variation in Population (Natural Selection)

First condition is that of variation in traits. For example, there are many different kinds of
physical colour for beetles such as green and brown, and white and black traits in
population of moths.

Second condition is that of the differences in the hereditary reproduction. Not only can
the population not expand limitlessly but also can it extend the full use of the ability for
hereditary reproduction and therefore there emerges differences in the hereditary
reproduction in the population of organisms. In this example, because of the visibility of
green beetles, they became prey to the birds and so the ability for the hereditary
reproduction is comparatively less than the brown beetles.

Third condition. Traits have genetically inherited nature. For example, brown beetles
reproduce brown offspring and green beetles reproduce green offspring because these
characteristics have genetic basis.

Consequently, organisms with traits that give them an advantage over their competitors
are more likely to pass on their traits to the next generation than those with traits that do
not confer an advantage thereby spreading within the population. The whole organisms
in the population turn into the population with such traits. And if there are variations in
traits within the population and that there are variations in the reproduction of each
organism of the population, traits having genetically inherited nature, then consequently
it follows that evolution occurs through the means of natural selection.