Evolution and Natural Selection

• Lamarck's Theory:

  • Use or Disuse: Organisms can alter their physical structures by using or not using parts of their bodies.

  • Inheritance of Acquired Traits: Traits developed during an organism’s lifetime can be passed on to future generations.

  • Darwin's Theory:

  • Key concepts include:

  1. Struggle for Existence:

     • Populations must compete for limited resources like food and living space.

  2. Variation and Adaptation:

     • Variation: Differences in traits among individuals.

     • Adaptation: Heritable characteristics that enhance survival and reproduction.

     • Example of Adaptations:

       • Polar bears have thick white fur for warmth and camouflage, thick fat layers for insulation, and sharp teeth for eating prey.

  3. Survival of the Fittest:

     • Fitness refers to how well an organism can survive and reproduce.

     • High Fitness: More individuals survive and reproduce.

     • Low Fitness: Fewer individuals survive and reproduce.

Mechanisms of Evolution

1. Natural Selection:

   • Organisms with traits better suited for their environment are more likely to survive and reproduce.

   • Example: In a new area with dark rocks, black mice are less visible to predators than tan mice, leading to a higher survival rate for black mice.

Evolutionary Concepts

• Descent with Modification:

  • Living species descend from common ancestors with changes over time, forming a single tree of life that connects all organisms.