Lecture 7A

Lecture 7A - 1/29/09 Lecture 7 Speciation Reading Text Ch....

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1/29/09 1 Lecture 7 Speciation Reading Text Ch. 24 Speciation: the divergence of a lineage to create new species “The mystery of mysteries” How are adaptation and speciation different? Why does life come in discrete units? Overview I. How many species are there? II. What is a species? A. Biological species concept 1. How does reproductive isolation occur? a. Prezygotic barriers b. Postzygotic barriers 2. Problems with the biological species concept B. Morphospecies concept C. Phylogenetic species concept III. How do species arise? A. Allopatric speciation 1. Vicariance 2. Dispersal B. Sympatric speciation 1. habitat differentiation 2. polyploidy in plants IV. Is reproductive isolation a byproduct or an adaptation? I. How many species are there? 1.8 million named 20 - 100 million suspected “Speciescape” the size of the multicellular organism is proportional to the number of described species in the higher taxon it represents (Wheeler, 1990) II. What is a species? A. Biological species concept : group whose members have the potential to interbreed in nature and produce viable, fertile offspring
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1/29/09 2 Endangered Species Act of 1973 What unites a species? Gene flow What differentiates a species? Reproductive isolation - barriers that prevent different species from producing viable offspring II. What is a species? A. Biological species concept (Mayr) 1. how does reproductive isolation occur? a. Prezygotic barriers: individuals never mate (no zygote) b. Postzygotic barriers: mating occurs but offspring (zygote) not viable or fertile Chrysoperla plorabunda Example of prezygotic isolation Two species of green lacewings that are morphologically indistinguishable Were thought to be same species Chrysoperla johnsoni Produce low frequency songs by vibrating abdomen Chrysoperla plorabunda Chrysoperla johnsoni http://www.eeb.uconn.edu/people/chenry/Cryptic_songs.html - http://
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This note was uploaded on 04/29/2009 for the course BILD BILD 2 taught by Professor Schroeder during the Spring '08 term at UCSD.

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Lecture 7A - 1/29/09 Lecture 7 Speciation Reading Text Ch....

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