One of the main reasons for the evolution of everything that exists on this planet is caused by natural selection. Natural selection, a theory scientifically tested and made acceptable by a man named Charles Darwin, explained how species evolved and changed over time. According to Darwin, all organisms in their species group exhibit some form of variation. Because of this difference in variation he concluded that the organisms that best adapted to their environment would survive and live to reproduce and pass on their genes to their offspring. Those small variations would then spread to the rest of the population over time as the genes of those who are less fit would die or become less frequent. The way Darwin came to this realization was by observing the birds of the Galápagos Islands also known as Galápagos finches. Through observation he came to realize that birds that had beaks best suited to the food available in the environment were more competent at mating than others, such as those birds that had beak shapes best suited to obtaining nectar from flowers or eat hard seeds. The fact that birds had an advantage over others of the same species is a key component in understanding how nature helps better-adapted varieties survive and reproduce. Another key component to understanding how evolution works in the web of life is coevolution. Coevolution describes the relationship in which different species influence each other's evolution. This form of evolution is very likely to occur in nature, especially when there is a close relationship between species. Keep this in mind when thinking about the role hummingbirds have with the flowers from which they obtain nectar. This is an important component of their DNA (Wang et al. 2014) Hummingbirds of the family Trochilidae have gone through a huge wave of evolutionary divergence with more than three hundred and thirty species classified in over one hundred genera, making hummingbirds one of the most diverse birds. This reflects the amount of morphological and physiological adaptations that are correlated with nectar feeding attributes (Bleiweiss et al. 1997). Due to the hummingbird's wide range of adaptations over years and years of evolution, there is now obvious sexual dimorphism between male and female. female hummingbirds, mostly in non-hermit species residing in the Andes and orogeny. Sexual dimorphism is a phenotypic difference between males and females. One of the phenotypic differences between female and male hummingbirds is beak length associated with plumage and reproductive behaviors.