EVOLUTION

VERY SIMPLY PUT--Evolution is

change in a species over time.

How long did it take to CHANGE?

66 million

years ago

54 million

years ago

37 million

years ago

26 million

years ago

Present Day

There are two models for HOW this change occurs.

Gradualism gradual change over

a long period of time

Punctuated Equilibrium periods of rapid

change in species are separated by periods of little or no change.

We have learned about the origins of evolutionary thought.

1773-Boston Tea Party

1785-James Hutton

1831-Charles Darwin

1809-Jean-Baptiste Lamarck

1798-Thomas Malthus

1787-The U.S Constitution is signed

1861-U.S. Civil War Begins

1859-Darwin publishes The Origin of the Species

1858-Alfred Wallace

1833-Charles Lyell

1850-California Gold Rush

Share out some of the contributions of the scientists that led to today’s model of evolution.

Who was Charles Darwin?

How did Darwin come up with the theory of natural selection?

He collected evidence in the Galapagos Islands that pointed towards his theory of natural selection.

The Galapagos Tortoise

Geological Formation of the Islands

Darwin’s Finches Adapted to their Food Source

What is natural selection?In a nut shell…

Better traits

easier to survive

more likely to reproduce

Over time better traits dominate a population

What type of mouse is more likely to survive to produce offspring?

Biological Fitness Fitness—an organisms ability to reproduce

and pass their genes on to their next generation

Survival of the FittestThose who are more “Fit” will be more likely to survive.

More AttractiveSmarterStronger

More Likely To Survive and Reproduce

Which species is most fit for this exam? Why?

Quick QuestionOrganisms well suited to their environment

a. reproduce at a greater rate than those less suited to the same environment.b. are always larger than organisms less suited to that environment.

c. always live longer than organisms less suited to that environment.

d. need less food than organisms less suited to that environment.

What did Darwin call the

process?

Natural Selection

Natural Selection operates on 4 factors:

Genetic variation: all the genes that make up the population.

Overproduction of offspring: more is better. Struggle for existence: compete for food,

territory, and mate (survival of the fittest) Survival and reproduction: individuals that

are better able to cope or have advantages over another will leave more offspring

AdaptationA trait produced by natural selection that has become common in a population because it provides a selective advantage.

Successful reproduction of the fittest members of a population eventually leads to an adaptation within that population.

Organisms adapt to their environments in many ways…

Storage Adaptations

Conserves water – not stored in hump

Stored fat provides insulation

Reproductive Adaptations

Protection

Camouflage

Owl moth

Wasp moth

Fish

Adaptations to food

Parasite orchids

Carnivorous plants

Specialized beaks

Parasitic

Specialized teeth

Plant adaptations

Wind dispersalWater

dispersal

Animal dispersal

So how do adaptations occur?

Other Mechanisms of Evolution that lead to adaptions.

Mutations Gene flow (migration) Genetic drift

Mutations

They may produce a different phenotype that may be an advantage for a species.

A mutation could cause parents with genes for bright green coloration to have offspring with a gene for brown coloration. That would make the genes for brown beetles more frequent in the population.

A mutation is any change to the genetic material of a cell.

Gene Flow (Migration)

Some individuals from a population of brown beetles might have joined a population of green beetles. That would make the genes for brown beetles more frequent in the green beetle population.

Gene Flow (Migration) The amount of gene

flow within a population varies. Very mobile organisms

have a higher rate of gene flow than organisms that are immobile.

Which would have a higher rate of gene flow?

This is corn.

Effects of Gene Flow on Evolution

Within a population Across populations

When the brown beetle joins the green beetle population, the brown beetle genes enter the populations gene pool.

Can make distant populations genetically similar to one another.

Can introduce genes into a population increasing genetic variation

Genetic Drift

A random change in allele frequencies that occur in small populations. Usually brought on by natural disasters or catastrophic events such as ?

Several green beetles were killed when someone stepped on them and had no offspring. The next generation would have a few more brown beetles than the previous generation—but just by chance.

Genetic Drift

Bottleneck effect Population’s size is

reduced for at least one generation

Reduced variation may affect the ability to adapt to natural selection pressures- climate change, shift in resources.

Founder’s effect A new colony is started

by a few members of the original populations.

Colony will have reduced genetic variation.

Can decrease genetic variation, especially in small populations!

SPECIATIONHow do these changes lead to the

formation of new species? Eventually the gene pools of the populations

become too different. The populations can no longer interbreed.

This is called REPRODUCTIVE ISOLATION.

Why does evolution matter now?

If it happens as a long slow process, how does it affect me?

Tampering with Evolution

Artificial Selection –Humans breed organisms for specific traits

Interbreeding animals that would not normally interbreed in nature to create new species

Cockapoo

Artificial Selection is an example of evolution where humans choose which

plants/animals reproduce to make cuter pets or better crops. We like to call it “breeding”.

Wild tomatoes Tomato crop