BILD 3 Chapter 24

BILD 3 Chapter 24 - Chapter 24: The Origin of Species...

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Chapter 24: The Origin of Species Speciation – The origin of new species; the focal point of the evolutionary theory because the appearance of new species is the source of biological diversity. Macroevolution – Refers to evolutionary change above the species level. Species – A group whose members possesses similar anatomical characteristics and has the ability to interbreed. Biological Species Concept – Defines a species as a population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but are unable to produce viable, fertile offspring with members of other populations. Reproductive Isolation – existence of biological factors (barriers) that impede members of two species from producing viable, fertile hybrids. Prezygotic Barriers – “before the zygote”; impede mating between species or hinder the fertilization of the ova if members of different species attempt to mate. Postzygotic Barriers – “after the zygote”; Prevent the hybrid zygote from developing into a viable, fertile adult. Habitat Isolation – Two species that occupy different habitats within the same area may encounter each other rarely, if at all, even though they are not isolated by obvious physical barriers such as mountain ranges; a prezygotic barrier. Temporal Isolation – Species that breed during different times of the day, different seasons, or different years cannot mix gametes; a prezygotic barrier. Behavioral Isolation – Courtship rituals that attract mates and other behaviors unique to a species are effective reproductive barriers, even between closely related species; a prezygotic barrier. Mechanical Isolation – Morphological differences can prevent successful mating; a prezygotic barrier. Gametic Isolation – Sperm of one species may not be able to fertilize the eggs of another species;
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This note was uploaded on 10/24/2008 for the course BILD 3 taught by Professor Wills during the Spring '07 term at UCSD.

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BILD 3 Chapter 24 - Chapter 24: The Origin of Species...

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