7Chapter 15

Theory of Evolution

Section 1

History of Evolutionary Thought

Charles Darwin

1809 - 1882

Darwin’s theories became the basis for the way evolution is explained today.

Ideas of Darwin’s time:

18th century- all species are permanent and unchanging

Earth is thousands (not billions) of years old

Darwin and the Galapagos Islands

Spent 5 years traveling to study animals; noted for excursion to the Galapagos Islands

He noticed:

1) Groups of animals varied from island to island (tortoises, for example)

2) Also noticed that there were similarities and differences between animals in other parts of the world

The Galapagos Islands

His findings led him to believe that organisms change over time…

Evolution- the development of new types of organisms from preexisting types of organisms over time

Geology ideas of the time… Scientists begin to

study rock strata- layers of rock

Inferred that the rock layers on the bottom are older than the rock layers on the top- the principle of superposition

Georges Cuvier

Studied fossils in rock layers to determine:

1) organisms from the past are different than organisms living today

2) some organisms have become extinct

Explained this with the idea of

catastrophism

Catastrophism

The idea that sudden geologic events caused the extinction of large groups of organisms

Charles LyellUniformitarianism

Believed that geologic processes that have changed the earth in the past still change the earth today

Ex. erosion

If the earth could change over time…

…why couldn’t living things?

Cuvier and Lyell’s ideas supported Darwin’s theory about organisms changing over time.

Jean Baptiste Lamarck * inheritance of

acquired characteristics-

Individuals could acquire traits during their lifetime and then pass those traits on to their offspring

1744-1828

Lamarck’s theory explained how organisms changed BUT that they changed in a lifetime.

He also thought simple organisms could arise from nonliving matter.

Darwin once accepted Lamarck’s theory but changed his mind

Inheritance of Acquired Characteristics

If a person developed muscles during their lifetime, their child would be born with muscles

One giraffe stretches its neck more to reach leaves. Over time, the neck becomes longer and then the babies are born with longer necks as well.

Theory of Use and Disuse