Natural Selection

  • Natural selection is a key concept invented by Charles Darwin. It is a principal mechanism of evolutionary change.

  • The process starts with the genetic variation that occurs in all living organisms. This variation can result from alterations in DNA, or be influenced by environmental factors.

  • Not every individual within a population has the same traits. Some of these genetic differences make individuals more likely to survive and reproduce in their specific environment.

  • The individuals with the most advantageous traits are more likely to survive and have offspring. This is sometimes called ‘survival of the fittest’.

  • These individuals pass these advantageous characteristics to their offspring via their genes, ensuring these traits become more common in the next generation.

  • Over time, this process can lead to new species being formed, a process known as speciation.

  • Natural selection can be stabilising, directional, or disruptive. Stabilising selection favours average traits. Directional selection favours traits that are not average. Disruptive selection favours traits at the extreme ends of the range.

  • Forces that can cause natural selection include disease, changes in climate and changes in food availability.

  • If an environmental change favours certain traits, those with these traits are better adapted to the new conditions, which leads to evolution through natural selection.

  • While natural selection may not always bring about perfection, it generally leads to adaptation that is beneficial for the organism’s survival and reproduction.

  • However, natural selection can be slow to bring about these changes, particularly in organisms with long lifespans and low reproduction rates.

  • Developing resistance to antibiotics is an example of natural selection in bacteria. Bacteria with a mutation that makes them resistant survive while the others die off, and then the resistant bacteria multiply.

  • Natural selection is a non-random process. Traits that are beneficial for survival and reproduction are “selected for”, and traits that are harmful are “selected against”.