SY

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.