The Evolution of a Theory

Darwin and Evolution

Outline• History of Evolutionary Thought• Darwin’s Theory of Evolution

– Occurrence of Descent– Biogeography

• Natural Selection and Adaptation• The Evidence of Evolution

– Fossil– Biogeographical– Anatomical– Biochemical

Scientific view prior to Darwin

• strongly tied to religion, in fact, its purpose was to verify religious dogma.

Some guiding ideas in science

• Special creation of the fixity of all species

• The Scala Naturae

Mid-Eighteenth Century

• Taxonomy -- important endeavor during mid-eighteenth century.–Linnaeus –Count Buffon.

Late Eighteenth Century

• Cuvier --comparative anatomy Founded Paleontology

• Proposed Catastrophism

Natural Theology

• The Rev. William Paley – looking for perfection

• precursor to scientific creationism

• Precursor to ID?

Life’s a Struggle

• The Rev. Thomas Malthus – life is a struggle. Populations limited by:

–Drought

–Famine

–Pestilence

–War?

Late Eighteenth Century•Lamarck was first biologist to believe evolution occurs and to link diversity with environmental adaptation.

–Concluded more complex organisms are descended from less complex organisms.

PROPOSED:

Inheritance of Acquired Characteristics

Darwin’s Theory of Evolution

• The theory of evolution is also called descent with modification.

• Darwin’s Influences:– Charles Lyell

• Uniformitarianism

– Thomas Malthus– Reverend Paley

Galapagos Islands-Darwin’s Lab

Galápagos Tortoises and Finches

Driving Force of Evolution?NATURAL SELECTION

–Preconditions• Heritable variation• Struggle for resources• Variations in fitness

–Consequences• Population better adapted to local

environment

Artificial Selection

Preconditions

• Organisms Have Variations

• Organisms Struggle to Exist

• Organisms Differ in Fitness

Result

• Populations Become Adapted

What is the evidence for evolution?

• Fossil

• Biogeographical

• Anatomical

• Embryological

• Biochemical

Evolution of the Horse

Biogeography

Comparative Anatomy

Comparative Anatomy 2

• Homologous Structures are anatomically similar

• Analogous Structures serve the same function

• Vestigial Structures

Comparative Embryology

Biochemical Evidence

Models of Evolution

Summary• History of Evolutionary Thought• Darwin’s Theory of Evolution

– Occurrence of Descent– Biogeography

• Natural Selection and Adaptation• The Evidence of Evolution

– Fossil– Biogeographical– Anatomical– Embryological– Biochemical