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We can’t define a species by looks alone!

If we defined a species If we defined a species as looking similar, these as looking similar, these

would ALL be two would ALL be two separate species!separate species!

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We can’t define a species by just We can’t define a species by just producing offspring, either!producing offspring, either!

Cannot Reproduce (sterile)

Cannot Reproduce (sterile)

““Beefalo”Beefalo”Cannot Reproduce (sterile)

Cannot Reproduce (sterile)

MulMuleeLigeLige

rrCannot Reproduce (sterile)

Cannot Reproduce (sterile)

The offspring have to be fertile or it doesn’t count!!

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A species is: A group of interbreeding populations Reproductively isolatedisolated (kept apart) from other such

groups Organisms must be able to mate and produce fertile

offspring (This is why mules, ligers, and beefalo aren’t new

species! No fertile offspring!)

When you can mate and and produce fertile offspringproduce fertile offspring, you are in the same gene pool! Because they can Because they can

mate and produce mate and produce a fertile puppy, the a fertile puppy, the

Beagle and Pug Beagle and Pug share a gene pool!share a gene pool!

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Reproductive isolationReproductive isolation: when members of two populations cannot mate and produce fertile offspring

Isolation

1. Behavioral2. Geographic3. Temporal

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Two species could interbreed but have different courtship rituals Example: Different bird songs

Western Meadowlark Eastern Meadowlark

Sounds Sounds similarsimilar, , but different but different

enough to keep enough to keep them separatethem separate

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Rivers, mountains, etc… keep populations apart Separates into two separate gene

pools Many “abiotic” factors

Abiotic = not livingAbiotic = not living

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Alpheidae (Snapping Shrimp) around Panama

Panama CanalPanama Canal

= closest relative •What does this mean?What does this mean?•Isthmus of Panama formed ~3MYAIsthmus of Panama formed ~3MYA•7 Species of shrimp split into 14 species!7 Species of shrimp split into 14 species!

Gene pools have been separated!!

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Species reproduce at different times Not seen in humans, more in other species Some animals have periods where they are

in “heat” Animals that reproduce at different

times of the year might as well be separated by a geographic barrier

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Collected from what islands? Galapagos islands

Why are they special? Darwin thought they were

differentdifferent types of birds Blackbirds, grossbeaks, finches, etc…

ALL finches 13 new species, never seen before

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1. Founders arrive Birds blown hundreds of miles off of the

mainland Survive & reproduce on island

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2. Islands separate populations Finches do not like to travel over open water Geographic (“abiotic”) isolation No longer can breed with each other

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Lonesome Lonesome GeorgeGeorge

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3. Changes in gene pool Populations adapted to local environment Different plants on each island means different

food for birds Large seeds require large beaks to crack them open Small beaks better at opening small seeds

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4. Reproductive isolation If birds were somehow able to come in contact

with each other again, they would be too alien now

Finches are attracted to birds with the same size beak

They are now separate species

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Process of isolation, genetic change, and reproductive isolation has repeated itself many times

13 species of finch found nowhere else on planet

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1. Founders arrive2. Separation

(Geographic, behavioral, temporal)

3. Changes in gene pool4. Reproductive Isolation

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