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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
1.
This leads to a ________________________ for ___________________________ in which some individuals survive and some die.
2. Natural Selection
Definition:
•The better adapted individuals tend to survive and ____________________________ more than the less well-adapted individuals.
3.
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
In the DNA- Sexual Reproduction
In the DNA- Mutations
The Environment- Genetic Drift
Role in Promoting Variation
Explain why Variation is Random
Explain why Natural Selection is not Random
Differential Survival:
Define 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.
From the movie clip- explain/draw how the pocket rock mouse shows speciation in response to
changes in its environment:
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).
Explain how the Galapagos Finches
are examples of 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.