Lecture Notes: Evolution and Diversity

Key Themes of Biology

• Flow of Information: Essential for life.
• Interactions within Systems: Critical for life.
• Structure and Function: Key relationship in biology.
• Energy Flow and Matter Cycling: Fundamental processes.
• Evolution: Unifying theme linking unity and diversity.

Historical Perspectives on Evolution

• Early Thinkers:
  • Anaximander: Proposed species change over time.
  • Aristotle: Believed species are fixed.
  • Judeo-Christian Culture: Supported species fixity and a young Earth.
  • Buffon (1700s): Suggested an older Earth through fossil study.

Jean-Baptiste Lamarck

• Influential in 1800s:
  • Theory of Use and Disuse: "Use it or lose it" concept.
  • Inheritance of Acquired Characteristics: Traits acquired in life passed to offspring.
  • Concepts largely debunked, but terms like "wants," "needs," or "learned adaptations" hint at Lamarckian thinking.

Charles Darwin

• Artificial Selection: Observed in domestic animals (e.g., dog breeds, corn, carrots).
• Influences:
  • Charles Lyell: Geological processes and fossil layers suggest an old Earth.
• Voyage of the HMS Beagle:
  • Darwin's exploration of South America and the Galapagos Islands sparked his ideas on evolution.
  • Observed unique adaptations in local species, e.g., Galapagos finches and tortoises.
• Natural Selection:
  • Concept of "survival of the fittest" where fitness refers to reproductive success.
  • Adaptive Radiation: Evolution of many species from a common ancestor in new and diverse environments.
• Publication:
  • Joint paper with Alfred Wallace in 1858.
  • Published "On the Origin of Species" in 1859.

Concepts of Evolution

• Descent with Modification: Modern species evolved from common ancestors, modified over time.
• Natural Selection:
  • Excessive offspring lead to competition.
  • Variability within populations is heritable.
  • Differential reproduction due to beneficial traits.

Modern Understanding

• Phenotypes and Genotypes: Influence on organism's fitness.
• Environmental Influence: Genotypes expressed differently based on environment (e.g., flamingos).

Misconceptions and Clarifications

• Evolution is not driven by an organism’s wants or needs.
• Lamarckian ideas, such as acquired traits being inherited, are not supported by evidence.
• Natural Selection: A mechanism for evolution based on differential survival and reproduction.

Next Steps

• Discussion on how populations evolve through selection pressures in upcoming classes.