What does Darwin’s theory of evolution explain about the natural world

1). All living organisms are constantly involved in 'a struggle for existence'.

2). In a population, those that tend to survive and reproduce are the individuals whose variations gives them competitive advantage over the rest.

Explanation:

Darwin, thus, identified environmental pressures as the main cause of natural selection. They cause favourable variations to accumulate and unfavourable ones to be weeded out. Over thousands of generations, favourable variations, naturally selected by he environment, accumulate sufficiently to give rise to new species from ancestral species. Therefore, according to Darwin, natural selection, acting through environmental pressure, is the driving force behind evolutionary change in the natural world.

pregnancy happens more and more