Variation and adaptation- Darwin knew that individuals have natural variations among their heritable traits. He hypothesized that some of those variations are better suited to life in their environment than others.
Survival of the fittest- fitness describes how well an organism can survive and reproduce in its environment. Individuals With adaptations that are well suited for their environment can survive and reproduce and are said to have high fitness. Organisms that are not suited for their environment gradually die if there is no adaptation.
Natural selection-process by which organisms with variations most suited to their local environment survive and leave more offspring.
In both artificial and natural selection, only certain individuals in a population produce new Individuals. But in natural selection the environment influences fitness.
Natural selection occurs in any situation in which individuals are born than can survive, there is natural heritable variation, and there is visible variation in fitness.
Biogeography- is the study where organisms live now and where they and their ancestors lived in the past.
Closely related but different- over time natural selection produced variations in populations that resulted in different, but closely related species.
Distantly related but similar- similarities among animals provide evidence that similar selection pressures has caused distantly related species to develop similar adaptations.
Age of the earth- half a century after Darwin has published his theory, however, physicists radioactivity. Geologist now use radioactivity to establish the age of certain rocks and fossils.
Recent fossil finds- many recently discovered fossils form a series that trace the evolution of modern species from extinct ancestors.
Homologous structures-structures that are shared by related species and that have been inherited from a common ancestor.
Evolutionary theory explains the existence of homologous structures adapted to different purposes as the result of descendent with modification from a common ancestor.
Analogous structures- body parts that share common function, not structure.
Vestigial structures- inherited from ancestors, but have lost much or all of their original function due to different section presses acting on the dependent.
Embryology- similar patterns of embryological development provide further evidence that organisms have descends form a common ancestor.
At the molecular level, the universal genetic code and homologous molecules provide evidence of common descent.