Evolution by natural selection — KCSE Biology

Evolution by natural selection is supported by various lines of evidence. Two significant pieces of evidence are the fossil record and comparative anatomy.

1. Fossil Record: Fossils provide a chronological account of the history of life on Earth. They show how species have changed over time. For example, the transition from fish to amphibians is well-documented by fossils such as Tiktaalik, which exhibits features of both groups.

2. Comparative Anatomy: This involves studying the similarities and differences in the structures of different organisms. For instance, the forelimbs of mammals (like humans, whales, and bats) exhibit similar bone structures, indicating a common ancestor. These homologous structures suggest that these species evolved from a shared lineage.

In summary, the fossil record and comparative anatomy are crucial in providing evidence for evolution, demonstrating how species adapt and change over time.

Evolution by natural selection is a fundamental concept in biology that explains how species evolve over time. Key components include:

• Variation: Individuals within a species exhibit differences in traits.
• Inheritance: Traits are passed from parents to offspring.
• Survival of the fittest: Individuals with advantageous traits are more likely to survive and reproduce.
• Time: Over generations, these advantageous traits become more common in the population.

Example: In a population of beetles, some are green and others are brown. If birds prefer to eat green beetles, the brown beetles are more likely to survive and reproduce. Over time, the population will have more brown beetles than green ones, illustrating natural selection.

Natural selection is not a random process; it is driven by environmental pressures that favor certain traits. This leads to adaptations, which are traits that enhance survival and reproduction in a specific environment.