Notes on Lamarckism

Introduction

• Today’s topic: Lamarckism
• Focus on his theory and its application to evolution
• Importance of understanding for exams

Context of Lamarck's Theory

• Lamarck formulated his theory before genetics was understood
• Genetics not established until after Mendel's work
• Lack of knowledge regarding DNA
  • Offspring resemble parents, but how this occurs was unclear
• Lamarck sought explanations for physical traits and behaviors of organisms

Key Hypothesis: Inheritance of Acquired Characteristics

Definition Breakdown

• Inheritance: Passing on of traits from parents to offspring
• Acquired: Traits gained during an organism's life, not inherited genetically

Main Principles

1. Use and Disuse

   • Organisms respond to changes in their environment
   • Example: If the environment changes (e.g., temperature), organisms adapt
   • Notable point: Organisms cannot will physiological changes (e.g., grow wings)
   • Attributed changes depend on the use of traits (used more = stronger; used less = weaker)

2. Inheritance of Acquired Characteristics

   • Peculiar viewpoint: Physical changes during one's life can be passed on to offspring
   • Example: Dyeing hair does not influence DNA, but Lamarck believed it could

Example: Giraffes' Evolution

• Original state: Short-necked giraffes adapting to reach food
• Response to environmental pressures by stretching necks
• Assumed that longer necks were passed to offspring, progressively leading to longer necks over generations

Application in Exams

• Be prepared to explain different scenarios using Lamarck’s principles
• Example: Loss of legs in lizards evolving into snakes
  • Emphasize disuse of legs leading to gradual disappearance
  • Discuss inheritance of the no/shorter legs in offspring
  • Highlight active response to environmental changes

Terminology Recap

• Lamarckism: Theory that organisms actively adapt and pass those changes to offspring
• Phenotypic Changes: Physical changes that are not genetically inherited
• Use and Disuse Principle: Use leads to stronger traits; disuse leads to weaker traits or disappearance
• Acquired Characteristics: Traits accumulated during life and passed to offspring

Conclusion

• Review of Lamarckism concepts is crucial for understanding evolutionary theories
• Engage with the material actively for better retention