Evolution through
Natural Selection

Several Insights Led to Darwin’s Theory

After his voyage on the Beagle, Darwin spent more than ______years conducting research, thinking about how evolution occurs.

Though he had traveled the world, many things at home also influenced him.

Describe what influenced Darwin’s theory of Evolution in England:

Darwin used this line of thinking to come up with his theory of evolution through a mechanism he called: ______

For natural selection and thus evolution to occur in a population, ______requirements (or tenets) were needed.

The Tenets of Biological Evolution

This leads to a ______for ______in which some individuals survive and some die.

  1. Natural Selection

•The better adapted individuals tend to survive and ______more than the less well-adapted individuals.

The better adapted individuals ______their______ to more offspring than the less well adapted.

–The ______of natural selection therefore ______.

–As one generation follows another, the characteristics of the species ______.

Darwin & Wallace

Darwin conceived his theory of evolution by natural selection in ______but spent the next 20 years conducting research to ______it.

He was writing up his theory in 1858 when he received an essay from ______describing basically the same idea.

They decided to publish their theory together in July of 1858. Wallace unfairly is often forgotten.

Darwin wrote a book on his observations a year later called, ______. It is now considered the ______of evolutionary biology.

Revisiting Lamark

Describe or draw how Lamark would have explained the long trunks found in Elephants:
Describe or draw how Darwin/Wallace would have explained the long trunks found in Elephants:

Evolution and Populations:

It is important to note that biological evolution refers to ______and not to individuals and that the changes must be ______to the next generation.

In practice this means that evolution is a process that:

In other words: ______evolve, not ______.

Our Evolving Definition of Evolution:

The ______of ______in the ______traits of a ______. Evolution describes the changes in ______in the ______of a species over time.

These changes are the result of:

•______

•______

•______

How Does Variation Arise?

In the DNA: - ______In the Environment: -______

-______

Source of Variation / Role in Promoting Variation
In the DNA- Sexual Reproduction
In the DNA- Mutations
The Environment- Genetic Drift
Explain why Variation is Random / Explain why Natural Selection is not Random

Differential Survival:

The result of differential survival is that the individuals best ______to a ______environment will survive to reproduce.

  • They will get the most ______.
  • Find the best ______.
  • Not be ______by other species.
  • Find a ______.
  • ______and care for their ______.

Remember it is ultimately ______that matters. Once an organism passes on its ______its biological “______” in life is done. This is why many creatures die after mating.

Of course those are creatures whose offspring can survive ______after being born.

Some offspring need parents around to help them grow and develop.

Speciation:

If environments ______(either gradually or suddenly), what traits are considered the “best adapted” may also change.

This process can lead to changes in the species.

When two populations of a species are in different environments they cannot ______.

If the ______pressures are different in these respective environments, these populations will eventually become different ______(speciation).

How do animals and plants even get to ______from the mainland?

Birds and insects may ______, but plants and animals get to islands most likely from ______that carry them there.

This is known as the ______.

There are many types of speciation, but ______speciation is where a geographical ______separates two populations and prevents interbreeding.

Extinction:

Environmenst are constantly ______and if a species cannot ______, they may go ______.

The ______an environment changes, the less time a population has to adapt to these changes.

Example: ______couldn’t adapt to the ______climate.

Their place was taken by ______.

Not all dinosaurs went extinct. Some also evolved to become ______-blooded ______.

There have been ______major extinction events during the history of life on Earth.

The ______(65.5 MYA) extinction is probably the most well known, as it killed off all ______. ______% of all species went extinct.

That wasn’t even the largest though. That honor goes to the ______extinction (251 MYA) which caused the extinction of ______% of all marine species and ______% of all land species.