01:119:115 Lecture Notes - Lecture 21: Garter Snake, Reproductive Isolation, Species Problem
18 Oct 2016
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Document Summary
Evolutionary theory must explain how populations evolve and how new species originate. Microevolution -> changes in allele frequency in a population over time. Macroevolution -> broad patterns of evolutionary change above the species level. Group of populations whose members can interbreed in nature and produce viable, Do not exchange genes with different species -> reproductively isolated. Speciation = process by which one specie splits into 2 or more species -> yielded tremendous diversity of life ~1. 8 million have been identified. New species that result share many characteristics because they descended from a common ancestor. The concept of biological species based on reproductive isolation. Mechanisms to prevent two different species from interbreeding and producing viable, fertile offspring hybrids = offspring of crosses between different species. Different types of reproductive barriers to fertilization: prezygotic: before zygote is formed, postzygotic after zygote is formed. Occur before zygote is formed -> prevent fertilization from taking place.
