EVOLUTIONEVOLUTIONAccumulation of inherited changes within a population over time

2 types of evolution2 types of evolution

Microevolution Macroevolution

Pre-Darwinian IdeasPre-Darwinian IdeasDarwin was not 1st to propose

theory of evolution

Aristotle (4th century BC)◦Life extended from simple to complex

◦Imperfect but moving toward perfection

◦No mechanism for HOW

Jean Baptiste de Lamarck (1744-1829)

◦1st to propose that organisms undergo change over time as a result of natural phenomena

◦Use and disuse

◦Theory of acquired characteristics

◦LAMARCK WAS WRONG IN MECHANISM

Influences on DarwinInfluences on DarwinCharles Lyell and James Hutton

◦Earth much older than people thought

Voyage of the Beagle – 1831

Thomas Malthus

Breeders - artificial selection

Darwin’s Theory of Evolution by Darwin’s Theory of Evolution by Natural SelectionNatural SelectionIn struggle for survival, favorable

traits preserved, unfavorable ones eliminated◦Adaptation

Natural Selection – best adapted organisms survive and pass on their traits, population changes over time◦Fitness

4 aspects of natural world on 4 aspects of natural world on which Darwin based his theory:which Darwin based his theory:

Overproduction

Variation

Limits on population growth

Differential reproductive success

What Natural Selection is What Natural Selection is NOT:NOT:Natural Selection is not a CHOICE

Natural Selection is NOT BASED ON NEED

Natural Selection is not a MUST

Modern SynthesisModern SynthesisMendel’s work (1860s) not

recognized until 20th century

1930s-40s – biologists combined Mendelian inheritance with Darwinian Evolution◦Mutations are source of variation◦Continue to try to understand causal

processes of evolution

Some new perspectives on Some new perspectives on Evolution…Evolution…EvoDevo

Epigenetics

What is the role of What is the role of chance??chance??Chance is probably not much of a

factor in natural selection

Some scientists think chance plays a more significant role in macroevolution