Lamarck's Theory and Origin of Life Debate

Lamarck's Theory of Inheritance of Acquired Characteristics

• Proposed in 1809
• Focused on the fossil record
• Postulated "inheritance of acquired characteristics"
• New needs: Environmental changes (light, temperature, food) drive organisms to exert themselves, creating new needs and behaviors.
• Use and disuse of organs: Regular use of certain organs strengthens them while unused ones weaken.
• Inheritance: Favorable traits acquired during an organism's life are passed to offspring. This helps them adapt to changed conditions.
• Speciation: Gradual accumulation of acquired traits over generations leads to new species.

Activity 4.5 Debating the Origin of Life

• Students divided into groups based on creationists, spontaneous generationists, eternalists, cosmozoans, and abiogenesists.
• Each group prepares a case for their theory.
• Groups debate their theory, presenting their reasoning for 5 minutes.
• Opponents ask questions for 5 minutes.
• Other class members vote on who presented their case best (not on personal views).

Lamarck's Ideas of Use and Disuse

• Use and disuse: Structures used frequently develop, while unused structures diminish.
• Giraffes example: Giraffes stretched their necks to reach higher leaves, which caused their necks to grow longer. These longer necks were passed on to their offspring.

Inheritance of Acquired Traits

• Lamarck believed changes acquired during an organism's life could be passed down.
• This is now disproven by genetics research.
• Importance: The theory was a significant attempt to explain biological evolution. Explained the existence of vestigial organs.

Activity 4.6

• Students to research evidence supporting and criticizing Lamarck's theory.
• Group presentations

Darwinism (Theory of Natural Selection)

• Proposed by Charles Darwin (1809-1882).
• Darwin's voyage on the HMS Beagle. Observation of species on the Galapagos Islands was crucial to developing this theory.
• Influenced by essay "On the Tendency of varieties on Depart Indefinitely from the original type" by Alfred Russell Wallace.
• Geometric increase: Populations produce more offspring than can survive. Competition exists.
• Struggle for survival: Organisms compete for limited resources.
• Variation: Individuals in a population have variations that might make them better or worse adapted to the environment.
• Natural selection: Those with beneficial traits are more likely to survive and reproduce, passing on these traits.
• Gradual Origin of Species: Adaptations over long time frames lead to the creation of new species.
• Neo-Darwinism: Modern understanding of evolutionary change, integrating genetics into the theory of natural selection.

Darwin's Theory of Finches on the Galapagos Islands

• Darwin studied finches on different Galapagos Islands.
• Found similarities and differences among them.
• Concluded that ancestral finches adapted to different islands and evolved into different species based on food sources/environment (e.g., insectivorous, seed-eating).