Lecture on Darwin and Evolution

Introduction to Darwin's Theory of Evolution

• Charles Darwin: English naturalist
• Studied for 30 years before publishing "On the Origin of Species"
• Darwin popularized the concept of natural selection
• Evolutionary ideas predated Darwin, proposed by earlier naturalists and philosophers

The Development of Darwin's Theory

• 1842: Initial manuscript on natural selection published
• 1858: Joint seminar with Alfred Russell Wallace presenting similar ideas
• Darwin expanded the manuscript into a complete book

Observations from the HMS Beagle Voyage

• Darwin was the naturalist on board the HMS Beagle
• Observed variations in species, especially the Galapagos finches
• Noticed adaptations (e.g., beak shapes) based on food sources
• Concept of "descent with modification": organisms better adapted to their environment are more likely to survive and reproduce

Influences on Darwin's Thinking

• Thomas Malthus's essays on population growth
  • Populations grow geometrically; food supply grows arithmetically
  • Leads to competition and limits on population size
  • Only a few individuals survive to reproduce

Concepts of Natural and Artificial Selection

• Natural selection: survival of individuals better suited to the environment
• Artificial selection: human-guided breeding (e.g., pigeons, dogs)

Supporting Evidence for Evolution

• Fossil records show transitional forms
• Earth's age: 4.5 billion years, allowing for extensive natural selection
• Mechanisms of heredity: Mendel's laws of inheritance (studied later)

Comparative Anatomy and Evolution

• Homologous structures: same evolutionary origin, different functions (e.g., vertebrate forelimbs)
• Analogous structures: similar function, different evolutionary origins (e.g., butterfly and bat wings)

Molecular Evidence

• Phylogenetic trees based on genetic data
• Comparison of DNA and proteins helps trace evolutionary history

Quiz Questions

• Question 1: Birds, bees, and bats have different evolutionary histories but all have wings. These wings are examples of:
  • Red: Evolutionary structures
  • Yellow: Analogous structures
  • Green: Homologous structures
  • Blue: Vestigial structures
• Question 2: In a population of snails, individuals with thicker shells survive more. What happens to the mean shell thickness over time?
  • Red: Increase
  • Yellow: Decrease
  • Blue: Remain the same
  • Green: No pattern

Conclusion

• The lecture provided an overview of Darwin's theory of evolution, its development, and the supporting evidence available today. It also covered key concepts such as natural and artificial selection and comparative anatomy.