Chapter 17 Speciation process that produces splits among lineages in tree of life divergence of biological lineages emergence of reproductive isolation between lineages Morphological species concept individuals look alike Cryptic species two or more species that morphologically same but do not interbreed Reproductive isolation two groups of organisms can no longer exchange genes Biological species concept species interbreed and can produce offspring concept does not apply to asexually reproducing organisms lineage species concept tree of life one species to two or more daughter species Speciation requires interruption of gene flow More genetic divergence more reproductive isolation Allopatric speciation population divided by physical barrier geographic barrier divergence of sub population establishment of reproductive barrier s species diverge and cannot reproduce new species Sympatric speciation speciation without physical isolation may occur with disruptive selection preference for distinct microhabitats where mating takes place takes place mostly in plants meitoc errors in plants cause sympatric speciation common means of sympatric speciation is polyploidy duplication of sets of chromosomes within individuals autopolyploidy chromosome duplication in single species allopolyploidy combining of two different species Prezygotic isolating mechanisms prevent hybridization Temporal isolation breeding seasons Mechanical isolation inability to breed due to reproductive organs Behavioral isolation preference for mate Gametic isolation sperm cannot attach to egg Habitat isolation species evolved due to habitat and no contact with other species Postzygotic isolating mechanisms reduce fitness of hybrid offspring Low hybrid zygote viability zygotes do not mature Low hybrid adult viability hybrid offspring has low survivability hybrid infertility infertile adults Adaptive radiation formation of many related species from single common ancestor Sexual reproduction new combos of genes and produces gene variety Disadvantages meiosis males and mating Advantages sexual selection escape from parasites changing environments