Ch23_Lecture

Ch23_Lecture - 23 Species and Their Formation 23 Species...

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Unformatted text preview: 23 Species and Their Formation 23 Species and Their Formation 23.1 What Are Species? 23.2 How Do New Species Arise? 23.3 What Happens when Newly Formed Species Come Together? 23.4 Why Do Rates of Speciation Vary? 23.5 Why Do Adaptive Radiations Occur? 23.1 What Are Species? Species literally means kinds. We recognize most species by their appearance. Many species change little over large geographic ranges. 23.1 What Are Species? Linnaeus described species based on their appearancethe morphological species concept . Members of species look alike because they share many alleles. He originated the binomial system of nomenclature. 23.1 What Are Species? But males and females may not look alike. Immature individuals may not look like their parents. Other types of information must be used to determine species. 23.1 What Are Species? Species can be thought of as branches on the tree of life. Speciation : The process by which one species splits into two or more daughter species, often gradually. 23.1 What Are Species? Speciation involves reproductive isolation when individuals of a population mate with each other, but not with individuals in another population, they are a distinct evolutionary unit. 23.1 What Are Species? The biological species concept : proposed by Ernst Mayr: Species are groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups . This does not apply to asexually reproducing organisms. 23.2 How Do New Species Arise? Allopatric speciation occurs when populations are separated by a physical barrier. Also called geographic speciation ....
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This note was uploaded on 05/10/2008 for the course BIOL 120 taught by Professor Hasek during the Spring '08 term at LSU.

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Ch23_Lecture - 23 Species and Their Formation 23 Species...

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