Lecture on Evolution and Natural Selection

Introduction to Evolution

• Evolution is a fundamental biological process explaining the diversity of life on Earth.
• There are nearly 9 million different species of animals and plants, excluding microbes.
• Life is believed to have developed on Earth more than 3 billion years ago from simple organisms like single cells.
• Evolution by natural selection is the key process by which these simple life forms developed into the diverse species we see today.

Understanding Natural Selection

• Genetic Variation: Within any population, there is genetic variation. For example, in a population of rabbits:
  • Different alleles for traits such as fur thickness, eyesight, or hearing may exist.
• Environmental Changes: Changes in the environment can affect which traits are advantageous.
  • Rabbits with thicker fur may survive better in colder climates.
  • Rabbits with better eyesight or hearing may avoid predators more effectively.
• Survival and Reproduction: Organisms with advantageous traits are more likely to survive and reproduce, passing these traits to offspring.
  • Over many generations, advantageous traits become more prevalent in the population.

Evolutionary Change

• Definition of Evolution: The change in the inherited characteristics of a population over time through natural selection.
• Example of Speciation:
  • Two populations of the same species may evolve differently if they become isolated or if environmental conditions change.
  • If differences become significant, they may no longer interbreed, leading to the formation of a new species.
  • Example: Pygmy rabbits are so distinct in size that they cannot breed with normal-sized rabbits, indicating speciation.

Further Studies

• For triple biology students, speciation will be explored in more detail in subsequent lessons.
• Additional questions and exercises on evolution by natural selection are available in related resources.

Conclusion

• Evolution and natural selection explain the diversity of life and the adaptive changes in species over time.
• Understanding these processes is crucial for studying biology and the history of life on Earth.