Chapter 14: The Origin of Species

Three questions about the chapter:
1.What is taxonomy?
Taxonomy is the branch of biology that names and classifies species and groups them into broader categories.
2.How many types of reproductive barriers are there?
There are two types of reproductive barriers - prezygotic and postzygotic.
3.Who were the people who most recently studied the evolution of Darwin's finches?
Peter and Rosemary Grant were the most people who studied the evolution of Darwin's finches most recently.

Five main facts about the chapter:
1.The origin of species is the source of biological diversity.
2.There are several ways to define a species.
3.Reproductive barriers keep species separate.
4.In allopatric speciation, geographic isolation leads to speciation.
5.Most plant species trace their origin to polyploid speciation.
 

Diagram:

This diagram shows the evolution of wheat.



















 Link: http://www.flickr.com/photos/monado/sets/72157625811571540/detail/


Summary:
The introduction of the chapter talked about the rise and fall of cichlids, who live in Lake Victoria. Biologists often define a species as a group of organisms whose members can breed and produce fertile offspring, but who do not produce fertile offspring with members of other groups. Speiation is the emergence of a new species-is the bridge between microevolution and macroevolution. Next the chapter talked about that the origin of species is the source of biological diversity. There are sevral ways to define a species. Taxonomy is the branch of biology that names and classifies species and groups them into broader categories. The biological species concept was described in 1942 by biologist Ernst Mayr. It defines a species as a group of populations whose members have the potential to interbreed in nature and produce fertile offspring. Members of different species do not usually mate with each other. And, if members of one species do mate with members of anther species, the offspring will probably not be fertile. In effect, reproductive isolation prevents genetic exchange and maintains the gap between species. Other definitions of species are the morphological species concept, which has been used to identify most of the 1.8 million species that have been name to date, the ecological species concept, and the phylogenetic species concept. Reproductive barriers keep species separate. There are two main types of reproductive barriers - prezygotic, which prevent mating or fertilization between species, and postzygotic, which operate after hybrid zygotes are formed. In allopatric speciation, geographic isolation leads to speciation. In sympatric speciaton, speciation takes place without geographic isolation. New species formed in this way are polyploid. Most plant species trace their origin to polyploid speciation. Reproductive barriers may evolve as populations diverge. Hybrid zones provide opportunities to study reproductive isolation. Peter and Rosemary Grant study the evolution of Darwin's finches on Galapagos. Adaptive radiation may occur when new opportunities arise. Speciation can occur rapidly or slowly. 

Key Terms:
1.Species - a group of organisms whose members can breed and produce fertile offspring, but who do not produce fertile offspring with members of other groups.
2.Speciation - the emergence of new species.
3.Taxonomy - the branch of biology that names and classifies species and groups them into broader categories.
4.Biological species concept - defines a species as a group of populations whose members have the potential to interbreed in nature and produce fertile offspring.
5.Reproductive isolation - prevents genetic exchange and maintains the hap between species.
6.Reproductive barrier - a biological feature of the organism itself to prevent individuals of closely related species from interbreeding when their ranges overlap.
7.Prezygotic barriers - prevent mating or fertilization between species.
8.Postzygotic barriers - operate after hybrid zygotes are formed.
9.Adaptive radiation - the evolution of many diverse species from a common ancestor
10.Hybrid zones - regions in which members of different species meet and mate, producing at least some hybrid offspring.