2-1 speciation - SPECIAT ION LIFE 23-23.3 | KLUG pg 604-652...

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Unformatted text preview: SPECIAT ION LIFE 23-23.3 | KLUG pg. 604-652 23.1.1 We can recognize and identify many species by their appearance- morphological species concept : members of many of the groups that he classified as species by their appearance look alike because they share many of the alleles that code for their body structures 23.1.2 Species form over time- speciation is thus the process by which one species splits into two or more daughter species , which thereafter evolve as distinct lineages. The gradual nature of most speciation guarantees that in many cases, two populations at various stages in the process of becoming new species will exist- reproductive isolation : If individuals of a population mate with one another, but not with individuals of other populations , they constitute a distinct group within which genes recombine; that is, they are independent evolutionary units—separate branches on the tree of life- biological species concept : species are groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups 23.1.3 How do new species arise?-If two populations are isolated from each other, and sufficient differences in their genetic structure accumulate during the period of isolation, then the two populations may not exchange genes when they come together again 23.2.1 Allopatric speciation requires almost complete genetic isolation- Speciation that results when a population is divided by a physical barrier is known as allopatric speciation ( allo , “different”; patris , “country”) or geographic speciation-A physical barrier’s effectiveness at preventing gene flow depends on the size and mobility of the species in question 23.2.2 Sympatric speciation occurs without physical bar riers-a partition of a gene pool without physical isolation is called sympatric speciation- some form of disruptive selection is required in which certain genotypes have high fitness on one or the other of two different resources-most common means of sympatric speciation is polyploidy , the production within an individual of duplicate sets of chromosomes . Polyploidy can arise either from chromosome duplication in a single species ( autopolyploidy ) or from the combining of the chromosomes of two different species ( allopolyploidy ) 23.3 What happens when newly formed species come together?...
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2-1 speciation - SPECIAT ION LIFE 23-23.3 | KLUG pg 604-652...

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