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Lecture 5

BIOA01H3 Lecture 5: Darwin and Evolution

Biological Sciences
Course Code
Scott MacIvor

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Natural selection does not lead to an absolute optimum
- Instead a competitive optimum (as good or better than alternatives)
- Because…
o Selection can only act on existing variants
o Evolution is limited by historical constraints
o Adaptations are often compromises
Most environments have competing selective pressures
Environments constantly change over time
Vestigial structures
Currently useless evolutionary leftovers
o Chance, natural selection, and the environment all interact
Adaptations lags behind environmental change
- Environments can change quickly, adaptation takes more time
- Traits seen today are the result of natural selection in the past
- Natural selection never anticipates environmental change
Why is evolution controversial
- God has an impact on life as we know it
- People are very spiritual and believe in creation
- Evolution spurred by awe of God
o Seeking to catalog God’s creation
- People questioning vestigial structures
o Shouldn’t everything be perfectly suited to its environment
People became interested in fossils and the history they hold
- Stratification: horizontal layering of rocks
- Paleobiology: study of ancient organisms
- Catastrophism: theory of fossil formation by catastrophe
Jean-Baptiste Lamark
- Hypothesized an incorrect mechanism of evolution
o Use and disuse theory
Plants and animals change over time at their own will
- Made important contributions to evolutionary thought
o Species change with time and pass on changes
o Organisms respond to environment
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