Objectives 17.3 The Process of Speciation -Identify the types of isolation that can lead to the formation of new species. -Describe the current hypothesis about Galápagos finch speciation.

Evolutionary Terms Homologous structures – structures that are shared among different species but indicate a shared evolutionary relative. Analogous structures – structures that are similar in function but do NOT indicate a shared relative. (Example: wings of an insect and wings of a bird)

What is Speciation? Speciation is the formation of a new species. A species is a population whose members can interbreed and produce fertile offspring.

Reproductive Isolation… Reproductive isolation occurs when a population splits into two groups and the two populations no longer interbreed. 3 types of Reproductive Isolation are…

Behavioral Isolation Behavioral isolation occurs when two populations that are capable of interbreeding develop differences in courtship rituals or other behaviors.

Geographic Isolation Geographic isolation occurs when two populations are separated by geographic barriers such as rivers, mountains, or bodies of water.

Temporal Isolation Temporal isolation happens when two or more species reproduce at different times.  

What happened to the Galapagos finches…? It is believed that over time the finches’ beak size and shape became an adaptation to their specific food source. Competition and Natural Selection required them to adapt or die out from lack of resources as a direct result of competition.  

Natural Selection and Distribution Types Directional Selection ~ extreme phenotypes are favored. Stabilizing Selection ~ the intermediate phenotype is favored.