The Theory of Evolution

Let’s Look at What Darwin was Thinking

What is Evolution?

• Evolution is….

How Long is “A Change Over Time”?

•

• Individuals ____________ evolve.

• Populations ___________ evolve.

Who was Darwin?• Started medical school• Attended seminary• Met up with a botanist; sailed on the HMS Beagle at

the age of 23

Volcanic Islands

http: Galapagos Island video

Darwin’s Tortoises

• Why do they look different on different islands?

Darwin’s Finches

• Why do they look different on different islands?

Darwin was Influenced by Others

• James Hutton: Earth has to be more than just a few thousand years old!!

Darwin was Influenced by Others

• Charles Lyell

Darwin was Influenced by Others

• Thomas Malthus: The human race will grow faster than the supplies needed to support it

Darwin was Influenced by Others• Lamarck, 1809: Inheritance of Acquired Characteristics

1. Living organisms acquired characteristics that helped them adapt and survive.

2. Organisms then passed these characteristics on to the next generation

Lamarck’s Giraffes

Darwin was Influenced by Others

• Alfred Wallace, 1859: Came to the same conclusions that Darwin did.

Darwin was Influenced by Others

• Wallace studied the Malay Archipelago

Darwin’s “The Origin of Species”

• Published in 1859

• 3 Important Observations– 1. Members within a species vary. They are not

all the same.– 2. Much of this variation is inheritable.– 3. There is a “struggle for existence.” More

members of a species are born than can be supported by the environment.

Darwin’s 2 Important Conclusions

• 1. Because of the variations, some organisms are better able to survive to reproductive age and have offspring. (They are ‘fit.’)

• 2. Characteristics that make an organism “fit” will tend to accumulate over time.

Natural Selection

• The traits being selected for contribute to an organism’s fitness in its environment

• What drives natural selection?

• What makes natural selection possible?

Evolution: Descent with Modification

• Each living species has descended, with changes, from other species over time.

• Darwin called this “descent with modification.” We now call it Evolution.

Darwin’s Realizations• All of these birds from the Galapagos were actually

finches• They had all likely descended from a single species

originally from Ecuador

Darwin’s Realizations

• These similar looking animals are found in widely different locations.

• It is most likely they evolved from different ancestors but accumulated similar adaptive features

Artificial Selection: Man’s Involvement in Evolution

Evidence for Evolution1. Fossil record

Evidence for Evolution2. Homologous Structures

• Similar bone structure suggests a common ancestor

Evidence for Evolution2. Homologous Structures

• Vestigial Structures

Evidence for Evolution2. Homologous Structures

• Human Vestigial Structures

Evidence for Evolution3. Similarities in Embryology

• It is scary how much we look like other animals!

Human Embryo

A Summary of Darwin’s Theory

• Individual organisms differs; some of these differences are inheritable.

• Organisms produce more offspring than can be supported.

• Organisms compete for limited resources.• Individuals best suited for their environment

survive and reproduce.• Those characteristics that help an organism

survive and reproduce are passed on to future generations.