The Theory of Gradualism and the Punctuated Equilibrium

Theory by Niles Eldridge and Stephen Jay GouldPresentation by Mark Van Lierde

Gradualism Gradualism is a universal theory that has been

applied to many other sciences aside from biology. Gradualism has been applied to geography Gradualism has been applied to linguistics, or

language Gradualism has even been applied to the political

science

Gradualism Continued

Put plainly, gradualism is the theory that change occurs over time

To use large words, gradualism is a theory proposed by a man named James Hutton in 1795 that states profound change is the product of cumulative change.

It is more often than not contrasted with catastrophism.

Catastrophism It’s a simple theory that states large, catastrophic

events changed the Earth, and got species to where they are today.

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More Gradualism (Little Bit)

Sometime after the theory was proposed by James, it was incorporated into a theory by a man called Charles Lyell.

His theory was uniformitarianism, which stated that that changes within the earth’s crust were caused by cumulative change.

Uniformitarianism is also contrasted with catastrophism.

Evolutionary Theory and Gradualism

Charles Darwin THE FATHER OF EVOLUTION was influenced by Charles Lyell’s book on the subject.

He even incorporated it into his famous theory. Charles had first read Lyell’s first book: Principles of

Geology

Gradualism Today Gradualism is often confused with phyletic

gradualism, which is a biology specific term. Phyletic gradualism is a term that was created by

two scientists (Niles Eldredge and Stephen Jay Gould) to contrast with their own model.

The model of evolution created by Eldredge and Gould is called the punctuated equilibrium.

The Punctuated Equilibrium

The punctuated equilibrium is a theory on how species evolve proposed by Eldredge and Gould in 1972.

Their theory states that throughout time there will be very little to no change in a species, this period of time is called stasis.

When there is large change in a species occurs, it is called cladogenesis.

Cladogensis is when species splits into two species as opposed to just turning into another.

Lol explanations

Lol more explanations

The Men Behind It Niles Eldrege and Stephen Jay Gould are a couple of

paleontologists. They created the theory and applied it to their fossil

records. It was supposed to help explain the fossils that are

similar, but at the same time are different.

Stephen Jay Gould Lived from 1941-2002 American Paleontologist Taught at Harvard, worked at various museums, also

taught biology at New York University Died during his second fight with cancer

Niles Eldredge Was born in 1943 American Paleontologist Works in a museum as a curator Likes to play jazz music

The Punctuated Equilibrium

The punctuated equilibrium is a way to explain how species change

It is very similar to the tree-like diagram but seems more modern

The straight section is when a species is in stasis

When a line splits the species becomes two separate species

Differences Between the Punctuated Equilibrium and

Gradualism The differences between the two are very obvious. Gradualism says that it is cumulative change that

changes a species. The punctuated equilibrium shows that change

occurs quickly, and in short periods of time

Example of Gradualism One good example would be the turtles found on the

Galapagos Islands. They changed slowly to fit into their respective

environments.