The Theory of Evolution

Evolution

• a gradual change in the genetic material of a population.

• (Population = all the animals of the same species living within a region)

Darwin and the Voyage of the Beagle

Charles Darwin- the scientists given credit for the discovery of evolution through natural selection.

Darwin’s Observations• Patterns of Diversity

Darwin’s Observations

• Living Organisms and Fossils

Darwin’s Observations• The Galapagos Islands

An Ancient, Changing Earth

• Previous scientists recognized that Earth is many millions of years old, and the processes that changed Earth in the past are the same processes that operate in the present.

The Earth has changed and is still

changing…

Natural Variation

Individuals, even of the same species,

always contain some differences or

variation. Additional variation

can be added through genetic

mutations.

Evolution by Natural SelectionOrganisms best suited for their surroundings will survive and pass on their genes to the next generations. Overtime, only the best genes will remain.

The Evolution of the Peppered Moth In England a species of moth called the Peppered Moth had two available,

inheritable wing colors- a light color and a dark color. (Dark colored moths had dark colored babies, and vice versa.) Prior to the industrial revolution,

the light color dominated with 99% of the moths displaying this phenotype, because it helped the insect blend in light colored lichens covering the trees.

However, after the factories opened, the light phenotype became almost extinct and the darker color began to dominate. Why do you think this

happened?

Evidence of Evolution

Darwin argued that living things have been evolving on Earth for millions of years. Evidence for this process could be found in the fossil record, the geographical distribution of living species, homologous structures of living organisms, and similarities in early development.

Evidence of Evolution

The Fossil Record

Evidence of Evolution

Geographic Distribution

of Living Species

Evidence of Evolution

Homologous Body Structures

Vestigial Structures

Evidence of Evolution

Similarities in Early Development

Patterns of Evolution• macroevolution: large-scale evolutionary changes (ex:

Reptiles evolving into birds)

• Microevolution: small evolutionary changes (ex: the peppered moth)

• Punctuated Equilibrium: Evolution is not a slow process. It consists of long, stable periods interrupted by rapid and brief periods of change.

Divergent Evolution

• divergent evolution: two related species develop more and more differences– examples:

polar bear – white fur for camouflagegrizzly bear – brown fur to fit in environment

• If the populations are isolated, it leads to speciation – the formation of new species.