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Formation of Species Speciation Define the following: Gene pool Gene flow Genetic drift The concept of species New species are discovered and others become extinct Existing species are essentially changed versions of older species What is a species? A single kind of organism Morphologically similar (look alike) Can interbreed to produce fully fertile offspring Speciation Speciation is the process of when a new species is formed = species formation How do species give rise to other different species? Speciation begins with isolation Results when two interbreeding populations stop breeding Isolation: Two Types 1. Geographic Isolation when a physical separation of the members of a population occurs Original habitat becomes divided Geographic Isolation Barriers can be formed by: – Canons, mountain ranges, bodies of water, or other features organisms can not cross Allopatric Speciation A result of geographic isolation Gene pool begins to differ because of genetic drift and natural selection Isolation: Two Types 2. Reproductive Isolation Results from barriers to successfully breed between populations in the same area Organisms begin to diverge Reproductive Isolation Can be caused by: The evolution of different mating location, mating time, or mating rituals: Different species of bowerbird construct elaborate bowers and decorate them with different colors in order to woo females. The Satin bowerbird (left) builds a channel between upright sticks, and decorates with bright blue objects, while the MacGregor’s Bowerbird (right) builds a tall tower of sticks and decorates with bits of charcoal. Evolutionary changes in mating rituals, such as bower construction, can contribute to speciation. Sympatric Speciation Occurs because of reproductive isolation Two subgroups of the same population Competing individuals of a population adapt to different food sources to ensure survival They may no longer interbreed Rates of Speciation Gradualism – speciation occurs at a gradual stable rate Punctuated equilibrium – speciation occurs in bursts – sudden changes
