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General Biology: 16.3: Speciation

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Celeste Nicholas

on 17 May 2012

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Transcript of General Biology: 16.3: Speciation

The Process of Speciation 3. Behavioral Isolation 1. Geographic Isolation 2. Temporal Isolation 3 types of reproductive isolation "Temporal" = relating to time

TEMPORAL ISOLATION occurs when two populations reporduce at different TIMES.
GEOGRAPHIC ISOLATION occurs when two populations are separated PHYSICALLY by geographic barrier.

Ex. rivers, mountains, or stretches of water, lava, ISLANDS.

Ex. Galapagos finches! different islands, ultimately different species

Ex. The kaibab squirrel lives on the north side of the grand CANYON and the abert squirrel lives on the south side!

Ex. Bonobos are also known as "left bank" chimpanzees.
Chimpanzees are "right bank" chimps. They are separated by the Congo RIVER.

How did the pollenpeepers in the PBS activity become geographically isolated? BEHAVIORAL ISOLATION occurs when two populations have differences in COURTSHIP rituals or BEHAVIORS that prevent them from interbreeding. These are "ISOLATING mechanisms" that could lead to speciation.

Isolating = SEPARATING

They could EVOLVE to become so GENETICALLY different that they can no longer breed and produce fertile offspring.

So, even if they were brought together in a zoo, they still couldn't have fertile offspring.

Ex. Their chomosomes cannot form homologues in meiosis. Example: eastern and western meadowlarks will not mate with each other because they use different SONGS to attract mates.

Ex. Two species of tree frogs that live side-by-side in the southeastern U.S. have different MATING CALLS. Ex. 3 similar species of orchid live in the same rain forest
They release pollen only on a single day
They release pollen on DIFFERENT DAYS so they cannot pollinate each other

Ex. There are 4 groups of Chinook salmon who spawn at different times of the year along California's central coast: winter, spring, summer and fall. The populations who breed in one SEASON never breed with those in another SEASON. A SPECIES is a group of similar organisms that can potentially BREED and produce FERTILE offspring.

Why "fertile?"

So what is the difference between a species and a population?

-A POPULATION is a group of individuals of the SAME species that interbreed and reproduce.

SPECIATION is the formation of NEW species.

Speciation is the ultimate consequence of EVOLUTION! Enough change over time occurs that related organisms can no longer breed and produce fertile offspring. = NEW SPECIES

REPRODUCTIVE ISOLATION occurs when formerly interbreeding species or populations separate so that they cannot produce fertile offspring.

How do you think reproductive isolation can occur? How does isolation lead to speciation? Organisms that are isolated respond differently to NATURAL SELECTION and have different GENE POOLS.
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