U4L1 Early Theories of Evolution

Georges-Louis LeClerc

believed that humans and apes have a common ancestor and that

species changed over time

Largely influenced by religion and philosophy

Georges Cuvier

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 areas

Sir Charles Lyell

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

Principle of Uniformitarianism

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

Jean Baptiste Lamarck

first to suggest that environment plays a role in this change

Individuals adapt to environmental conditions (Use and Disuse) and pass adaptations on to offspring (Inheritance of Acquired Traits)

Lamarck’s Hypothesis

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)

Charles Darwin

observed that living things show great diversity in morphology

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

Malthus

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

Alfred Wallace

independently arrived at same conclusion as Darwin

Together they developed Theory of Natural Selection

Darwin/Wallace Hypothesis

For any trait there is variation in population

When environmental conditions change, individuals that

possess a favoured trait enjoy differential survival and

reproduction (trait becomes more common in next generation)