Speciation

Harrisi a a leucurus new species can also arise within

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Unformatted text preview: harrisi A. A. leucurus New species can also arise within the New same geographic area as the parent species species In sympatric speciation • New species may arise without geographic New isolation isolation Many plant species have evolved by polyploidy • Multiplication of the chromosome number due to Multiplication errors in cell division errors Zygote Parent species Meiotic error Offspring may be viable and self-fertile Selffertilization 4n = 12 Tetraploid 2n = 6 Diploid O. lamarckiana Unreduced diploid gametes O. gigas Polyploid plants clothe and feed us Many plants, including food plants such as bread Many wheat wheat • Are the result of hybridization and polyploidy Adaptive radiation may occur in new or newly vacated habitats newly In adaptive radiation, the evolution of new In species • Occurs when mass extinctions or colonization Occurs provide organisms with new environments provide Island chains • Provide examples of adaptive radiation Cactus-seed-eater (cactus finch) A 1 B 2 B B C B 3 C4 C C D Tool-using insect-eater (woodpecker finch) Seed-eater (medium ground finch) CD 5 D The tempo of speciation can appear steady or The jumpy jumpy According to the gradualism model • New species evolve by the gradual accumulation of New changes brought about by natural selection changes Time The punctuated equilibrium model draws on The the fossil record the • Where species change the most as they arise from Where an ancestral species and then change relatively lit...
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