Lecture on Evolution and Galapagos Finches

Introduction to Species Diversity

• Millions of species on Earth
  • Over 300,000 beetles
  • 177,000 butterflies
  • Thousands of mammals, fish, and birds
• Importance in understanding how so many species came to be

Researchers' Focus: The Galapagos Islands

• Remote location offering unique insights into species formation
• Historical significance of Charles Darwin's visit
• Recent studies by biologists Peter and Rosemary Grant

Peter and Rosemary Grant's Research

• Focus on Daphne Major, a smaller island
• Initial plan for a short-term study turned into 40 years of research
• Regular summer visits since 1973
• Primarily studied the Galapagos finches
  • The finches were brought to scientific attention by Darwin
  • 13 species of finches on the Galapagos

Unique Habitats and Finch Adaptations

• Islands differ in size, topography, and height
• Finches adapted to diverse habitats
  • Example species and their specialized beaks:
    • Warbler Finch: fine needlelike beak for insects
    • Woodpecker Finch: robust beak for beetles and termites
    • Cactus Finch: long sharp beak for cactus flowers
    • Ground Finches (large, medium, small): varied beak sizes

Evolutionary Questions and DNA Evidence

• All finches on Galapagos are more related to each other than to any mainland species
• Indicates a single common ancestor
• Key question: How do different species arise from one common ancestor?

Detailed Study on Daphne Major

• Small island size enabled intense monitoring
• Daily routine involved netting and documenting finches
• Key data recorded:
  • Beak size and shape
  • Bird weight
  • Identification tags

Natural Selection Observations

• 1977 drought led to 80% mortality in medium ground finches
  • Larger beaks had survival advantage
  • Natural selection shifted average beak size larger in next generation
• 1983 El Niño event brought heavy rains and opposite effect
  • Small beaks favored due to abundance of small seeds

Role of Songs and Appearance in Species Formation

• Songs as a mate selection factor
  • Different species have distinct songs
• Appearance as another factor
  • Experiments showed males court females with similar size and appearance

Mechanisms of Species Formation in Finches

• Geographic and ecological isolation as key factors
• Adaptation to unique island conditions led to trait changes
• Changes in mating traits led to species separation

Broader Implications for Evolution

• Insights from Galapagos finches apply to general understanding of species diversity
• Diverse environments offer more opportunities for evolutionary changes
• Ongoing significance of Darwin's observations on evolution