Evolutionary Theories: Lamarck's Contribution

Key Figures and Their Theories

Jean-Baptiste Lamarck (1744-1829)

• Believed evolution occurs through natural laws, driven by two forces:
  • One force drives organisms up a ladder of complexity
  • Another force adapts organisms to local environments through use and disuse of characteristics
• Inheritance of Acquired Characteristics:
  • Frequent use of an organ strengthens and enlarges it
  • Disuse weakens it
  • Acquired traits are passed to the next generation
• Example: Giraffes' necks lengthening over generations from reaching high leaves

Thomas Robert Malthus (1766-1834)

• Focused on population growth and resource limitations
• Key idea:
  • Populations grow until resource limits are reached
  • Resource availability influences population size
• Human factor:
  • Struggle for existence based on cost-benefit decisions in sex, work, and children
• Influenced Darwin's application to plants and animals, noting competition for resources within and between species

Sir Charles Lyell (1797-1875)

• Geologist and Uniformitarianism theorist
• Natural processes in the past are the same as those today
• Earth's features formed through small changes over long periods
• Rejected Lamarck's use and disuse theory, suggesting centers of creation instead
• Influenced Darwin by supporting long-term change ideas and encouraging him to publish "On the Origin of Species"

Charles Darwin (1809-1882)

• Traveled on the HMS Beagle, studying geology, fossils, and organisms
• Influenced by Malthus' theory on population growth vs. resource competition
• Theory: Natural Selection
• Favorable traits are preserved, while unfavorable ones are destroyed
• Led to the evolution of new species over time from common ancestors
• Published "On the Origin of Species" (1859), providing a logical explanation for the diversity of life
• Favorable heritable traits become more common in successive generations, while unfavorable traits become less common

Explore the history of evolutionary theories, focusing on Jean-Baptiste Lamarck's ideas on natural laws, inheritance of acquired characteristics, and the role of use and disuse in shaping organisms. Learn about his key theories and their significance in the field of biology.