DARWINIAN REVOLUTION

Alfred Russel Wallace

Alfred Russell

Charles Darwin

History

Darwin's Five Theories

Multiplication of species

Evolution per se

Common descent

this process is now called “speciation”.

every group of organisms has descended from a common ancestor.

the world is steadily changing and populations of

organisms are transformed over time.

Natural selection

Gradualism

most evolutionary change occurs slowly

this was Darwin’s mechanism for how evolutionary

change occurred.

The origin of Species

• focused biologists’ attention on the great diversity of organisms.

Ideas from The Origin of Species

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Darwin explained three broad observations about life:

• The unity of life.
• The diversity of life
• The match between organisms and their environment.

Theory of Evolution

AGAIN

• A process of Natural Selection in which only the fittest would survive. (Reference: STS book)

• This Theory emerged at a time when most of the population believed and accepted the biblical version of Earth's creation, because of this conflict the people were divided. some believed the theory explained the origin of life, but the religious and the faithful strongly refuted it.

Evolution

AND AGAIN

• Change through time

• The process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth.

• And can be defined by Darwin’s phrase descent with modification

• Evolution can be viewed as both a pattern and a process

Artificial Selection

Darwin noted that humans have modified other species by selecting and breeding individuals with desired traits, a process called artificial selection

Darwin argued that a similar process occurs in nature:

AND AGAIN

e.g In organisms that reproduce sexually, two adults that possess a desired trait — such as two parent plants that are tall — are bred together.

Adaptation

LASTLY!

In reassessing his observations, Darwin perceived adaptation to the environment and the origin of new species as closely related processes.

From studies made years after Darwin’s voyage, biologists have concluded that this is what happened to the Galápagos finches.

SUMMARY

SUMMARY

On the Origin of Species (or more completely, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life), published on 24 November 1859, is a work of scientific literature by Charles Darwin which is considered to be the foundation of evolutionary biology.

Darwin's book introduced the scientific theory that populations evolve over the course of generations through a process of natural selection. It presented a body of evidence that the diversity of life arose by common descent through a branching pattern of evolution. Darwin included evidence that he had gathered on the Beagle expedition in the 1830s and his subsequent findings from research, correspondence, and experimentation.

CONCLUSION