Speciation Pt 1 -Species – a group of organisms that can continue to interbreed with each other and where their offspring are fertile (meaning, the offspring can have offspring as well)   -organisms are considered separate species if they are unable to breed with each other -evidence: different species of fishes found in smaller ponds produced after a lake dried up; tigers and lions – can interbreed to produce ligers, but ligers are sterile

Speciation Pt 1 How does speciation occur? -Genetics becomes too dissimilar that they can no longer produce fertile offspring -These barriers occur in two ways: Prezygotic – “Before Fertilization”: factors that occur before fertilization such as separation by geography, differences in mating seasons, or incompatible genitalia Postzygotic – “After Fertilization”: factors that occur after fertilization such as infertile offspring

Speciation Pt 1 Two ways for reproductive barriers to occur: Sympatric: isolation from within the same habitat -ex: flies mating originally on hawthorns, then some started to mate on apples – flies continue to mate on the fruit they grew up in Allopatric: geographic isolation -ex: Northern Spotted Owl, located in Northwestern US, and Mexican Spotted Owl, located in Southwestern US and Mexico – similar in genetics and appearance, yet unable to breed together -ex. experiment with fruit flies fed different foods and isolated from each other led to flies that preferred flies that ate same food