BSC2010-evolution-2-2024 (3)

Evolution Overview Course Name: Evolution by Natural Selection, BSC 2010 Semester: Fall 2024 Peer Tutors Availability of peer-tutoring sessions for additional support in understanding the course material.

Outline of Topics

• What is Evolution?

• Historical Context of Darwin’s Theory

  • Idea of fixed species

  • Confounding evidence

  • Darwin’s observations

• The Theory of Natural Selection

  • Central points of the theory.

  • Progress since Darwin

• Definition of Organic/Biological Evolution

  • Concept: The descent of modern organisms with modification from preexisting life forms.

  • Example Species:

    • Human

    • Gorilla

    • Chimpanzee

    • Gibbon

    • Orangutan

Historical Context of the Theory of Evolution

• Ancient Greeks (2500 years ago):

  • Aristotle: Belief in fixed species.

• Judeo-Christian Views (2000 years ago):

  • Species do not change; each species is divinely created; Earth ~6000 years old.

  • Linnaeus: Considered ideas of evolution absurd.

Confounding Evidence I: Biogeography

• Observations:

  • Similar species often inhabit the same geographic regions.

  • Different species may exhibit similar characteristics despite living in different areas.

  • Specific traits of organisms are often linked to environmental factors (e.g., thick, waxy leaves in desert plants).

Confounding Evidence II: Comparative Morphology

• Study Definition: Examination of similarities and differences in body structures between groups.

• Key Patterns Observed:

  • Similar skeletal structures in different species (e.g., humans and dogs).

  • Presence of vestigial structures in modern organisms.

Homologous Structures

• Illustration: Human arm, dog foreleg, and seal flipper share similar bone structures.

Developmental Homology

• Observation: Both chick and human embryos have gill pouches and tails during early development.

Vestigial Structures

• Examples of Vestigial Structures:

  • Backbone

  • Pelvic girdle in humans where other mammals have tails.

  • Small bones attached to the pelvic girdle (e.g., thighbone).

Confounding Evidence III: Geological Discoveries

• Georges Cuvier's Discoveries:

  • Fossil evidence - deeper layers have simpler fossils compared to shallow layers.

  • Some fossils are similar to known species, while others may appear or disappear between strata.

• James Hutton and Charles Lyell's Contributions:

  • Geology involves gradual changes over time.

Darwin and Wallace

• Charles Darwin's Voyage:

  • Participated in the Voyage of the HMS Beagle (1831-1836).

  • Significant Observations:

    • Observed diverse species, especially in the Galapagos Islands, which contributed to his theory on adaptation.

Theory of Natural Selection

• Life and Work of Charles Darwin (1830-1850s): Ruminated on his theory that was co-published with Alfred Wallace in 1858.

• Significant Publication: Darwin's "The Origin of Species" (1859) introduced natural selection.

Darwin’s Key Facts

• Any species can increase its population size exponentially.

• Observations show population sizes remain stable.

• Limited resources exist.

• Variability within species exists.

• Variability can aid survival and reproduction.

• Inherited traits have implications for survival rates.

Inferences from Darwin’s Facts

• Inference #1: Few offspring survive to reproduce, indicating a struggle for existence.

• Inference #2: Certain traits enhance survival and reproduction likelihood.

• Final Conclusion: Differential reproductive success leads to evolution through natural selection.

Additional Points on Darwin’s Theory

• Natural selection operates on heritable traits only.

• Traits can hold varying benefits based on circumstances.

• Evolution occurs at the population level, not at the level of individuals.

• The diversity of life emerges through evolutionary interactions with the environment.

Darwin’s Later Work

• Published "The Descent of Man and Selection in Relation to Sex" in 1871.