Natural Selection What does the word “evolve” mean? To change Does evolution happen quickly or slowly? Very slowly- over thousands or millions of years.

Natural Selection

What does the word “evolve” mean?

To change

Does evolution happen quickly or slowly?

Very slowly- over thousands or millions of years

Does evolution result in new species?

Sometimes

Did humans come from monkeys?

Evolution

Fossil records show that living things have in fact changed over time (evolution)

When we say Evolution, we don’t mean one individual changing over the course of it’s lifetime. We mean a species changing over many many years

Why did they change?

How did they change?

Evolution by Natural Selection

Evolution (change in a species over many years) occurs because of and through a process called natural selection.

Peppered Moths!!!

Peppered Moths

Before Pollution After Pollution

Peppered Moths

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1. More offspring are produced than can survive

1. More offspring are produced than can survive

This means that there is a struggle for existence and not every organism will survive long enough to reproduce

This is caused by competition for food, spaces, and other limited resources

Was this true for the peppered moths?

2. There is an inheritable variation ……

2. There is an inheritable variation ……

This means that there is a variety of inherited traits. Any inheritable trait that helps an organism survive and reproduce is called an adaptation

Examples include body parts like a duck’s foot, colors like a camouflaged insect, or behaviors like how prey avoid being eaten

Was this true for the peppered moths?

3. Survival of the fittest

3. Survival of the fittest

This means that only the individuals that have the greatest fitness survive. Fitness means how well an organism can survive and reproduce in its environment

An example is grasshoppers. They come in two colors: green and yellow. In a grassy environment, the green ones are more “fit” because they are less likely to get eaten and more likely to reproduce

Was this true for the peppered moths?

4. Natural Selection

4. Natural Selection

The process by which organisms with variations most suited to their local environment survive and leave more offspring

This doesn’t make organisms better- it just eliminates organisms who do not have traits that are well suited for that environment

If the environment changes, then perhaps different traits will be better and more likely to be passed down

4. Natural Selection

The process by which organisms with variations most suited to their local environment survive and leave more offspring

This doesn’t make organisms better- it just eliminates organisms who do not have traits that are well suited for that environment

If the environment changes, then perhaps different traits will be better and more likely to be passed down