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Darwin, Evolution and Natural Selection Lecture (Part 2)Textbook Reference: Chapter 21 in Biology How Life Works (2nd ed.)
Sections 21.4 – 21.6; pp.432 to 441
Importance of evolution?
What does it explain? How organisms have arisen and diversified from earlier
organisms
What is evolution? The change over time in allele frequencies in a population of
organisms
Importance? The theory is a foundation of modern biology, genetics and ecology
Darwin’s Theory: Descent with Modification by Natural Selection
• Why didn’t Darwin introduce his theory publicly. Why?
Controversial
• Who is Alfred Russel Wallace and why was he important?
Had a theory of natural selection similar to Darwin’s.
Darwin Challenged Traditional Views
• On the Origin of Species by Means of Natural Selection (Nov. 24 1859) stressed
two major points:
1. Current species are descendants of ancestral species (ancestral species differ
from modern species)
2. Natural Selection provided a mechanism for this evolutionary change
• At start of 19th century, the general belief was:
- The earth was young (6000 years old)
- Species remained unchanged since their creation
- But there were a few doubts about this
- Darwin really rocked the boat
-
• Darwin challenged these beliefs
Prevailing Views Before Darwin
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, • Aristotle (384-322 B.C)
- Opposed evolution
- Species fixed and unchanging
- Scala naturae
• Old Testament of the Bible
- Species individually designed by Creator and perfect
- Seemed to corroborate Aristotle’s views
- Many scientists of 1700s believed that creator had designed each species for a
specific purpose
• Carolus Linnaeus (1707-1778)
- Binomial naming system
- Classified species into hierarchy- increasingly complex, nested categories
- Similarity between species reflected pattern of creation rather than evolution
relatedness
Other Scientists Influenced Darwin
• Paleontology = study of fossils in sedimentary rock in layers or strata
• Cuvier opposed idea of gradual evolutionary change but observed extinctions in
fossil record
• Catastrophism – opposed evolutionary change, which advocated a
catastrophism
• Repopulation via immigration
• Other scientists suggested change via cumulative effect of slow but continuous
processes
– Geologist James Hutton (1726-1797)
o Perceived that changes in earth’s surface can result from slow,
continuous, gradual mechanisms still operating today
– Geologist Charles Lyell (1797 – 1875)
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