Chapter 6: Speciation and Evolution of Populations (Microevolution)
- Page ID
- 94610
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- Define species and describe how scientists identify species as different
- Describe genetic variables that lead to speciation
- Identify prezygotic and postzygotic reproductive barriers
- Explain allopatric and sympatric speciation
- Describe adaptive radiation
- Explain the two major theories on rates of speciation
- 6.1: Species Defined
- A biological species is defined as a group of individuals that, in nature, are able to mate and produce viable, fertile offspring. There are other definitions of species but, according to the biological definition, one species is distinguished from another when, in nature, it is not possible for matings between individuals from each species to produce fertile, living offspring.
- 6.2: Speciation
- Speciation is an event in which a single species may branch to form two or more new species.
- 6.3: Rates of Speciation and Extinction
- Scientists around the world study speciation, documenting observations both of living organisms and those found in the fossil record. As their ideas take shape and as research reveals new details about how life evolves, they develop models to help explain rates of speciation. In terms of how quickly speciation occurs, two patterns are currently observed: the gradual speciation model and the punctuated equilibrium model.
- 6.4: Evolution of Genomes
- Processes that change the genes and genetic information of an organism can result in evolution if this mutation becomes fixed in the population. Technologies that allow us to compare the genomes of different species allows us to establish the degree to which they are related, and therefore, how far apart they have evolved.
- 6.5: Evolution in Populations
- The Hardy-Weinberg law argues that the gene frequencies and genotype ratios in a randomly-breeding population remain constant from generation to generation. Evolution involves changes in the gene pool, while a population in Hardy-Weinberg equilibrium shows no change. Hence, populations are able to maintain a reservoir of variability so that if future conditions require it, the gene pool can change.