5.1 Early Theories of Evolution

Who is this? What Theory did they propose?

• Early belief was Earth and all life on it were immutable (unchanging over time)

• Largely influenced by religion and philosophy

• Believed humans and apes have a common ancestor and that species changed over time

• Earth was 6,000 years old

Who is this? What Theory did they propose?

• studied rock stratum and found that older stratum contained fossils of dissimilar species

  Catastrophism - Earth experiences destructive natural events that kill many species in a region

• Explained reappearance of fossils - species from nearby regions would repopulate affected area

Who is this? What Theory did they propose?

• believed Earth was much older than a few thousand years (closer to billions of years old)

• Based on rate of erosion, Niagara Falls is 35,000 y/o

• Earth is billions of years old

Principle of Uniformitarianism - rate at which geological processes occur today (very slowly) has not changed over time

Who is this? What Theory did they propose?

Jean Baptiste Lamarck

• first to suggest that environment plays a role in this change

Use and Disuse - individuals adapt to environmental conditions

Inheritance of Acquired Traits - the passing adaptations on to offspring

Explain Lamarck’s Hypothesis

Summary: An individual could change its morphology through use of a body part and this change is passed on to its descendants

Supporting Evidence: None

• Genetic traits are passed on through gametes only (changes to body cells do not get passed on)

Who is this? What Theory did they propose?

Charles Darwin

• observed that living things show great diversity in morphology (the study of the forms of things)

• Like Lamarck, he believed that environment was cause, but mechanism was different

• Darwin’s theory built on work of Lyell and Thomas Malthus

Who is this? What Theory did they propose?

Malthus

• “since people reproduce at a greater rate than their available resources = causes a struggle for survival”

• Genetic variation causes some to have traits that allow them to survive, reproduce and pass traits on

Who is this? What Theory did they propose?

Alfred Wallace

• independently arrived at same conclusion as Darwin

• Together they developed Theory of Natural Selection

Explain The Theory of Natural Selection

1. For any trait, there is variation in population

2. When environmental conditions change, individuals that possess a favoured trait enjoy differential survival and reproduction (trait becomes more common in next generation)