Speciation Formation of New Species

Formation of Species Formation of new species is called speciation.Formation of new species is called speciation. Two or more new species arise from a previous species.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. –The same population cannot interbreed with other populations successfully. Leopards Panthera uncia Panthera pardus

Isolating Mechanisms Speciation begins with separation and isolation of a single population into two separate populationsSpeciation begins with separation and isolation of a single population into two separate populations

Geographic isolation A physical separation.A physical separation. Referred to as a barrierReferred to as a barrier –Canyons –Rivers –freeways California Newt, 3 subspecies separated by mountains and waterways What other types of animals might be geographically isolated?

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 habitatEcological isolation: same region different habitat Temporal isolation: Mate during different seasonsTemporal isolation: Mate during different seasons Behavioral isolation: different mating ritual (bird song, dance, pheromones)Behavioral isolation: different mating ritual (bird song, dance, pheromones)

TemporalEcological Behavioral

Postzygotic Isolation –Fertilization occurs but zygote does not survive or offspring cannot reproduce. –Offspring cannot compete successfully for resources. Horse DonkeyMule

Summary review 1.What is speciation? 2.Give your own examples of geographic isolation and prezygotic isolation and explain how they can lead to speciation. 3.What is postzygotic isolation? 4.What kind of speciation is shown in the cartoons below?