And adaptations

Natural selection1

Charles darwin

• His theory of evolution by natural selection explained:• Where all of the astonishingly diverse kinds of living things

came from• How they became exquisitely adapted to their particular

environments.

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What is natural selection?

• Natural Selection is the process where organisms that have traits that better enable them to adapt to specific environmental pressures (ex. predators, climate change, competition for food and mates, etc.) will tend to survive and reproduce in greater numbers than others of their kind, thus ensuring those favorable traits will get passed on.

HUH??????

• Advantageous traits get passed on• More likely to survive and reproduce

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You need babies to pass on genes

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Natural Selection

1. There is genetic variation (different traits).

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Example: Two green beetle parents reproduce and they have green and brown beetle offspring

Natural Selection

2. There is an overproduction of offspring to ensure survival.

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Example: green beetles tend to get eaten by birds and survive to reproduce less often than brown beetles do.

The environment cannot support unlimited population growth because there are not enough resources

Not all offspring will live and get to reproduce because of various environmental pressures, so parents often overproduce to ensure at least some survive

Natural selection

3. There is a struggle for existence.

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Example: The surviving brown beetles have brown baby beetles because this trait has a genetic basis and gets passed on

There are natural pressures that exist in an organism’s environment that make it difficult to survive: predators, climate change, competition for food, mates and territory, etc.

The organisms that have the characteristics that allow them to overcome these pressures survive and can then live and reproduce

Natural selection

4. End result: new species

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The organism with the advantageous traits lives and reproduces, passing along those genes

Over several generations, a new species arises, made up of all the advantageous traits passed on from their ancestors

Example: the favorable brown color trait gets passed down several generations until all of the beetles are brown, creating a new brown-beetle species

Galapagos Island Finches

• In the case of the finches on the Galapagos Islands, the 13 different species are believed to all be descendants from a common ancestor in South America• The original species of finch ended up on the

Galapagos Islands and the finches adapted to a particular niche in order to survive• As the finches adapted to the different niches on

the islands, they evolved into a unique types of finches over time

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Crushing Food (e.g. Seeds)

Getting Food from inside a tree

How organisms adapt

• Adaptations are characteristics that enable organisms to better survive and reproduce

• There are three types of adaptations:

• Structural – physical feature

• Physiological – physical or chemical event

• Behavioral – what an organism does

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Structural adaptations

• A physical feature of an organism that allows it to survive• Example: Polar bears have white fur to help

camouflage them in the white snow

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Physiological adaptations

• A physical or chemical event that occurs in the organism’s body that help it survive• Example: snakes produce poisonous venom to

protect itself against predators

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Behavioral adaptations

• Refers to what an organism does to survive in the unique conditions of its environment• Example: Possums play “dead” to avoid predators

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The end. Sort of

• So, now that we know what organisms do to survive, what happens to those that don’t or eventually grow old and pass on?

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