Evolutionary Theory and Misconceptions

Outline—Evolutionary Theory & Misconceptions

  • Distinguishing pattern from process components of evolutionary theory

  • Darwin’s greatest contribution to modern science

  • Interpreting evidence for evolutionary theory in the context of its predictions

Early Evidence for Evolutionary Theory

  • Earliest Fossil Discovery:

    • Earliest fossil of a living creature resembles modern cyanobacteria.

    • Fossil sizes span approximately 84 μm to 112 μm.

Transition from Cyanobacteria to Modern Life

  • Question Posed:

    • How did we go from a cyanobacterium to everything alive on earth today?

    • Possible explanations:

    • A. Spontaneous generation

    • B. Evolution

    • C. Orcas did it

Definition of Evolution and Evolutionary Theory

  • Evolution:

    • Change in allele frequencies of a population over time.

  • Components of Evolutionary Theory:

    1. Common descent

    2. Natural selection

Common Descent

  • Concept:

    • All of life evolved from a common ancestor.

    • New species arise over long periods of time through “slight successive modifications” of other species.

  • Predictions of Common Descent:

    1. Species are not static but change through time.

    2. Species are related, not independent.

Prediction 1: Species are Not Static

  • Nature of Life:

    • Life on earth is ancient; most species have gone extinct.

    • Law of Succession:

    • Biogeographical pattern where living species in a specific area are closely related to fossils from the same area.

    • Example:

      • Pygmy armadillo (Zaedyus pichiy) related to fossil glyptodonts.

  • Transitional Forms:

    • Transitional forms link fossils across geologic time.

    • Notable examples include:

      • Tiktaalik (~375 mya): Link between fish and tetrapods.

      • Archaeopteryx: Linking dinosaurs and modern birds.

  • Vestigial Traits:

    • Traits that are reduced versions of traits present in other species.

    • Examples include the human coccyx (vestigial tail).

Current Changes in Species

  • Current Observations:

    • Mycobacterium tuberculosis:

    • Change in DNA of the rpoB gene affecting protein shape and drug resistance.

    • Darwin’s Finches:

    • Observable changes in beak shape and size due to environmental pressures.

Prediction 2: Species are Related, Not Independent

  • Geographical Distribution:

    • Similar species tend to share geographical distribution.

    • Example: Darwin's finches.

  • Types of Homology in Evolution:

    1. Genetic Homology:

    • Similarities among organisms of different species due to heritable characters (common ancestry).

    1. Developmental Homology:

    • Similarities during the embryonic stage indicating a related ancestry.

    1. Structural Homology:

    • Similarities in adult form and structure reflecting evolutionary relationships.

  • Molecular Phylogenies:

    • Analysis of genetic material across various species to establish evolutionary relationships.

Examples and Illustration of Molecular Phylogenies

  • Cats and Their Ancestry:

    • Genetic relationships among various species of Felidae are evolutionary trees indicating divergences and common ancestry.

  • Universal Genetic Code:

    • The Central Dogma of Molecular Biology:

    • DNA→RNA→ProteinDNA \rightarrow RNA \rightarrow Protein confirming genomic similarities across species.

Additional Examples of Evolutionary Evidence

  • Vestigial Traits in Different Species:

    • Comparative analysis of vestigial traits across species, such as the tails in modern whales and tailbones in primates, highlight evolutionary changes over time.