Natural Selection
Natural selection, an idea initially suggested by Charles Darwin, explains why some organisms survive in an environment and others die. Natural selection is essentially "survival of the fittest", explaining how the strongest in the environment would survive while the weakest would die. Then, the survivors would pass on their genes and the cycle of natural selection would continue.
Speciation
Speciation is defined as the creation of a new species as a result of evolution. There are two different types of speciation, allopatric and sympatric. Allopatric speciation is when speciation occurs because of geographic isolation between each half of a population. Therefore, each half adapts differently to their environment. Sympatric speciation is when speciation occurs as a result of a meiosis error,polyploidy, where the chromosome number doubles. Then as a result, self-pollination occurs.
Evidence of Evolution
There are many pieces of evidence supporting evolution. One being fossils. Fossils display old organisms and their relationship with living species. Fossils also show extinction. Another piece of evidence supporting evolution is the presence of vestigial organs. Vestigial organs are organs that are currently without purpose, such as the appendix, but their presence proves that they used to have a purpose. Showing that evolution occurred and put the organ out of use. A third piece of evidence proving evolution is known as convergent evolution, when different species have similar traits. This suggests they may have derived from at common ancestor. Yet key piece of evidence in support of evolution is known as divergent evolution. Meaning, species were once related but now are completely different. Embryology also proves evolution since it shows the similarity of embryos in different organisms. This means that the DNA coding for development is similar within these organisms. A final piece of evidence supporting evolution is homologous structures. Homologous structures are similar bone structures in different organisms, proving they must have derived from a common ancestor. The bone structures aren't completely similar now because the organisms needed to adapt to different environments.