Natural Selection

Introduction to Natural Selection

  • Natural selection is a key mechanism of evolution, first proposed by Charles Darwin. It suggests the ‘survival of the fittest’ where individuals who are best adapted to their environment are more likely to survive and reproduce.

Mechanism of Natural Selection

  • The process starts with variation within a population. These variations can be due to genetic mutation or sexual reproduction.

  • These variations result in diverse characteristics across individuals. Some traits offer an advantageous adaptation, enabling individuals with that trait to have higher survival rates.

  • These individuals are more likely to reach reproductive age and pass on their advantageous genes to the next generation, known as heritability.

  • Over generations, the number of individuals in the population with the advantageous trait increases. This change in the frequency of a gene in a population over time is evolution.

Result of Natural Selection

  • Natural selection can lead to speciation, where new species form when populations diverge due to different selection pressures.

  • Natural selection can also increase the evolutionary fitness of a population by favouring survival of the individuals best adapted to their environment.

  • Natural selection, however, does not ensure survival. Species that cannot adapt to changing conditions may become extinct.

Influence of Environment

  • Natural selection is heavily influenced by the environment. Environmental factors such as changes in climate, food availability, predation or disease can drive natural selection.

  • Human activity can also influence natural selection, by introducing new selection pressures (e.g. antibiotics leading to resistant bacteria).

Examples of Natural Selection

  • Common examples include Darwin’s finches in the Galapagos Islands, where beak size and shape were selected for based on available food sources.

  • Another example is the peppered moth in Britain during the industrial revolution where darker moths were selected for in polluted areas due to camouflage.

    Misconceptions about Natural Selection

  • Natural selection is often misunderstood. It doesn’t create new genes but selects for existing variations.

  • It doesn’t result in ‘perfect’ organisms as it only acts on existing variations. If there is no beneficial mutation for a certain challenge, selection cannot occur for it.

  • Natural selection does not work towards a ‘goal’. Evolution is a blind and non-directional process.