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Speciation Formation of New Species Formation of Species • Formation of new species is called speciation. • Two or more new species arise from a previous species. Darwin’s Finches of the Galapagos islands Morphological Concept of Species – Based on similar structures (morphology) – Older definition of species. – Not used today. how many species do you see? Biological Concept of Species – A population of organisms that can successfully interbreed. Panthera uncia – The same population cannot interbreed with other populations successfully. Leopards Panthera pardus Isolating Mechanisms • Speciation begins with separation and isolation of a single population into two separate populations Geographic isolation • A physical separation. • Referred to as a barrier – Canyons – Rivers – freeways What other types of animals might be geographically isolated? California Newt, 3 subspecies separated by mountains and waterways Reproductive Isolation – Reproductive barriers prevent portions of a population from interbreeding. – Prezygotic isolation: sperm and egg cannot reach each other. • Ecological isolation: same region different habitat • Temporal isolation: Mate during different seasons • Behavioral isolation: different mating ritual (bird song, dance, pheromones) Temporal Ecological Behavioral Postzygotic Isolation – Fertilization occurs but zygote does not survive or offspring cannot reproduce. – Offspring cannot compete successfully for resources. Horse Donkey Mule Summary review 1. 2. 3. 4. What is speciation? Give your own examples of geographic isolation and prezygotic isolation and explain how they can lead to speciation. What is postzygotic isolation? What kind of speciation is shown in the cartoons below?
