Bio II - Chapter 22-part 1

Concept 22.1: The Darwinian Revolution

• Publication: Darwin's The Origin of Species (1859)

• Challenged Traditional Views:

  • The earth is young

  • The earth's surface is unchanging

  • Species are unchanging

  • Humans are not influenced by natural laws

Influential Figures in Evolutionary Thought

• Carolus Linnaeus (1707-1778)

  • Founder of taxonomy; classified organisms by physical characteristics.

  • Believed species were fixed and unchanged over time.

• Georges Cuvier (1769-1832)

  • Developed paleontology; recognized extinction through fossil studies.

  • Proposed catastrophism to explain extinctions: local catastrophic events led to species replacement.

• Geologists James Hutton and Charles Lyell

  • Advocated for uniformitarianism: changes in Earth's surface occur gradually; processes still operational today.

  • Implication: Earth must be older than 4000 years.

• Thomas Malthus (1766-1834)

  • Wrote An Essay on the Principle of Population; examined the relationship between food production and population growth.

• Jean-Baptiste Lamarck (1744-1829)

  • Proposed that species evolve through use and disuse of traits and inheritance of acquired characteristics.

  • Suggested evolution driven by an innate drive towards complexity.

Darwin's Observations as a Naturalist

• Darwin's Education: Studied theology at Cambridge University.

• HMS Beagle Voyage (1831-1836):

  • Collected specimens; observed geological uplift and unique species in the Galápagos Islands.

  • Hypothesis: Species from South America colonized the islands and adapted over time.

Galápagos Islands Observations

• Noticed variation among species such as tortoises and finches on different islands.

• All Galápagos finches likely evolved from a common ancestor in South America.

The Manuscript from Wallace

• In June 1858, received a manuscript from Alfred Russel Wallace, who proposed a similar idea of natural selection.

• Prompted Darwin to publish The Origin of Species in 1859.

Theories from The Origin of Species

• Descent with Modifications: Evolution explained through heritable variations within species.

• Natural Selection: Individuals with advantageous traits survive and reproduce better than others, leading to adaptation.

Comparison of Theories: Lamarck vs. Darwin

• Lamarck:

  • Inheritance of acquired characteristics.

• Darwin:

  • Natural selection as the primary mechanism for evolution and adaptation.

Key Features of Natural Selection

• Major Components:

  • Variation within populations.

  • Heritability of traits.

  • Differential reproductive success.

The Process of Natural Selection

• Individuals vary in traits.

• Traits under genetic control can be inherited.

• More offspring are produced than can survive; thus, some fail to reproduce.

• Inferences from Natural Selection:

  • Higher fitness translates to more offspring.

  • Accumulation of favorable traits leads to population change over time.

Important Notes

• Natural selection acts on individuals, but populations evolve over generations.

• Evolution lacks a predetermined goal; adaptations depend on environmental context.