Chapter 15: Darwins Theory of EvolutionSection: 15 3: Darwin Presents His Case

Key Concepts:How is natural selection related to a species fitness? What evidence of evolution did Darwin present?

A. Publication of On the Origin of Species In 1859, Darwin published the results of his work. It was called On the Origin of Species In this book Darwin proposed NATURAL SELECTION - a mechanism for evolution. The theory of natural selection takes into account several ideas about a species survival.

B. Evolution by Natural SelectionDarwin said that organisms must compete for resources (food, water, shelter, mates, etc.). He called this STRUGGLE FOR EXISTENCE. Darwin then said that in this struggle for existence that the stronger animal survived; the one more suited for its environment. He called this the FITNESS ADAPTATION

These ideas are combined into what is known as The Survival of the Fittest Individuals that are better suited to their environment (better adaptations) survive and reproduce most successfully. Natural Selection results in changes in the inherited characteristics of a population. These changes increase a species fitness in its environment.

C. Evidence of evolutionFossil Record Darwin said that comparing fossils showed how organisms have changed over time. Geographic Distribution of living Things Similar organisms lived in similar habitats in different parts of the world

Geographic Distribution of Living SpeciesBeaver NORTH AMERICAMuskratCapybaraSOUTH AMERICACoypuSection 15-3Beaver MuskratBeaver and MuskratCoypu CapybaraCoypu and Capybara

Homologous Structures limbs that have the same basic bones, but vary in form and function

Homologous Body StructuresTurtleAlligatorBirdMammalAncient lobe-finned fishSection 15-3

Embryology The early stages of vertebrate animals are very similar in structure.

Concept MapSection 15-3includesEvidence of Evolutionwhich is composed of which indicateswhich implieswhich implies