Lecture on Evolution and Natural Selection

Jul 30, 2024

Lecture on Evolution and Natural Selection

Key Topics Covered

  • Special Creation Thinking vs. Population Thinking
  • Definition of Evolution
  • Natural Selection as an Evolutionary Mechanism
  • Theories and Contributions by Key Figures
  • Evidence Supporting Evolution

Special Creation Thinking vs. Population Thinking

Special Creation Thinking

  • Beliefs: Ancient Perspective
    1. Species do not change.
    2. Species are not related.
    3. Life on Earth is young (~6,000 years old).

Population Thinking

  • Beliefs: Modern Perspective
    1. Species do change.
    2. Species are related.
    3. Life on Earth is old (billions of years).

Definition of Evolution

  • Key Definition (Exam Note):
    • Change in allele frequencies in a population over time.

Natural Selection as an Evolutionary Mechanism

  • One of four evolutionary mechanisms (others not covered in this lecture).
  • Proposed by Charles Darwin and Alfred Russel Wallace.
  • Explains how populations adapt to their environments.
  • Important Concept (Exam Note):
    • Populations evolve, not individuals.

Contributions by Key Figures

Charles Darwin

  • Published On the Origin of Species by Means of Natural Selection (1859).
  • Proposed that evolution by natural selection could explain well-adapted populations.

Alfred Russel Wallace

  • Co-formulated the theory of natural selection along with Darwin.

Plato

  • Greek philosopher.
  • Believed species do not change (typological thinking).

Aristotle

  • Developed the Great Chain of Being (Hierarchy of Species).
  • Believed species do not change but were hierarchically ranked.

Jean-Baptiste Lamarck

  • First to propose that species change over time.
  • Incorrectly believed in evolution as a progressive change up a hierarchy.

Evidence Supporting Evolution

Fossil Record

  • Fossils show that species have changed over time.
  • Relative Age of Fossils: Deeper fossils are older.
  • Absolute Age of Fossils: Can be measured using radioactive decay.

Transitional Features

  • Traits intermediate between ancestral and derived species.

Vestigial Traits

  • Structures that are fully functional in one species but poorly developed in another.
  • Examples: Tiny hip and leg bones in whales and snakes, reduced wings in flightless birds, eye sockets in blind fish.

Homologies

Genetic Homology

  • Similarities in DNA, RNA, or amino acid sequences.

Developmental Homology

  • Similarities in embryo stages.

Structural Homology

  • Similarities in adult morphology.

Case Study: Cetaceans

  • Internal Consistency: Multiple data sources support the same conclusion of shared ancestry.
  • Closest living relatives to whales: Hippos.
  • Evidence: Fossil record, DNA sequences, vestigial bones.

Summary

  • Key Concepts for Exam:
    • Special Creation Thinking vs. Population Thinking.
    • Definition of Evolution.
    • Natural Selection.
    • Contributions from key figures.
    • Evidence supporting evolutionary theory.