animals with the intermediate characteristic will tend to disappear. Natural selection can also cause extinction in almost the same way. Species that produce numerous offspring will consequently produce more varieties, which may be favored at one time or another. Rare species will take more time in modifying (adapting), and therefore they will be, "beaten in the race for life". Any species in low abundance will always run the risk of extinction in variable habitats.Evidence of Evolution , SpeciationDarwin's extensive studies on the finches of the Galapagos Islands provide sufficient evidence that evolution does indeed exist. The varying birds were once the same species, but due to natural selection and the inability to disperse, they evolved into different species. Darwin also provides evidence that suggests organisms have common ancestors; through the fossil record, the geological time scale, and geological distribution. In the fossil rocks, the most primitive species were on the bottom, and the more complex on top, showing that the older organisms gave rise to the new ones. In his book he provides a diagram (phylogenetic tree) to describe how species diverge from common predecessors. Divergence of character, which has already been discussed, is a simple explanation. The varying species of finches also provide evidence. Many generations ago, these finches were all within the same species, but after being separated for so long, they could no longer reproduce with each other, therefore speciation occurred. Speciation is the creation of new species as a direct result of evolution through natural selection. But evolution does not always form new species. In a habitat where seasonal changes bring about harsh times, evolution might act against one particular phenotype, and then later that same phenotype might be favored. Evolution is the change in the genetic pool or genetic make-up of populations over generations, so for a...
