Evolution

Page
5

Each Species Struggles For:

Food

Living Space

Mates

Slide 47

Population Growth

Malthus Reasoned That If The Human Population Continued To Grow Unchecked, Sooner or Later There Would Be Insufficient Living Space & Food For Everyone

Death Rate Will Increase To Balance Population size & Food Supply

Slide 48

Population Growth

Darwin Realized Malthus’s Principles Were Visible In Nature

Plants & Animals Produce Far More Offspring Than Can Be Supported

Most Die

If They Didn’t – Earth Would Be Overrun

Slide 49

Darwin’s Theory of Evolution

Organisms Change Over Time

Slide 50

Common Descent with Modification

Darwin proposed that organisms descended from common ancestors

Idea that organisms change with time, diverging from a common form

Caused evolution of new species

Slide 51

.

Natural Selection

Driving force for evolution

During the struggle for resources, strongest survive & reproduce

Idea that at least some of the differences between individuals, which impact their survival and fertility, are inheritable

Slide 52

Origin of Species

Darwin Presents His Case

Slide 53

Publication of “On The Origin of Species”

Upon His Return To England, Darwin Developed His Observations Into The Theory of Evolution

But He Did Not Publish For 25 Years –

Why?

Slide 54

Publication of “On The Origin of Species”

Darwin Knew That His Theory Would Be Extremely Controversial And Would Be Attacked

His Theory Challenged Established Religious & Scientific Beliefs, Particularly About The Creation Of Man

Slide 55

Publication of “On The Origin of Species”

He Refused To Publish Until He Received An Essay From Alfred Wallace

Fellow Naturalist

Independently Developed The Same Theory

After 25 Years, Someone Else Had Come To The Same Conclusions From Their Observations Of Nature

Slide 56

Wallace’s Contribution

Alfred Russel Wallace Independently came to same Conclusion as Darwin that species changed over time because of their struggle for existence