Intro to Evolution

A Short History

Aristotle

Envisioned – scala naturae Fixed species occupied allotted rungs on

an increasingly complex ladder of life

Linnaeus – Devised a hierarchy for classification

King Phillip Came Over For Grape Soda

Pre-Darwinian View

Cuvier –

Believed that catastrophic extinctions explained unique sets of fossil species between successive strata

James Hutton & Charles Lyell Proposed that profound changes in the

earth’s surface can result from slow, continuous actions

Pre-Darwinian View

Jean Baptiste Lemark

Inheritance of Acquired Characteristics Proposed the theory of evolution where

increasing complexity & more perfect adaptations result from inheritance of characteristics acquired by organisms interacting w/ the environment

However, there is NO evidence for inheritance of acquired characteristics

Pre-Darwinian View

Darwin

Proposed the idea that new species originate from ancestral forms by the gradual accumulations of adaptations

Alfred Wallace Independently arrived at the theory of

Natural Selection soon after Darwin

Pre-Darwinian View

Darwinian view of life has 2 parts:

Descent with Modification

Natural Selection

Dual Meaning of Darwinism

Survival of the Fittest The driving force of Evolution Based on differential success in

reproduction Individuals best adapted to the local

environment leave more offspring = thereby pass on their adaptive characteristics more frequently

Natural Selection

Fact 1:

All species’ population size would increase exponentially if all individuals that are born reproduce successfully

Fact 2 Most populations are normally stable

in size, except for seasonal fluctuations

Fact 3 Natural resources are limited

5 Facts of Nature

Fact 4

Individuals of a population vary extensively in their characteristics; no 2 individuals are exactly alike

Fact 5 Much of this variation is inherited

5 Facts of Nature

Darwin’s 1st Inference/Conclusion:

Production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, w/ only a fraction of offspring surviving each generation

Darwin’s Conclusions

2nd Inference/Conclusion:

Survival is a struggle that depends on the inherited characteristics of the individual. Surviving individuals will produce more offspring

3rd Inference/Conclusion: Unequal ability to survive and reproduce

will lead to gradual change in a population

Biogeography of species

First suggested common descent – island species are more closely related than those on distant shores

Chronological fossil record This supports and is compatible w/ other

lines of evidence Taxonomic hierarchy

reflects common descent

Signs of Evolution

Homologous structures

testify to an evolutionary remodeling process

Embryonic Development Reveals homologies not apparent in adult

species Closely related species show

unmistakable similarities in their DNA and Proteins

Signs of Evolution Cont.

Tree of Life - Cladogram