Variation

Understanding Variation

  • Variation refers to the differences between individuals within the same species.
  • Such differences can be due to genetic factors, environmental influences, or a combination of both. This is known as gene-environment interaction.

Genetic Variation

  • Genetic variation arises from differences in the DNA sequences of individuals.
  • Mutations, crossing over during meiosis, and random fertilisation all contribute to genetic diversity.
  • Mutations are random changes in DNA sequences which generate new alleles.
  • During meiosis, homologous chromosomes may exchange pieces of DNA in a process known as crossing over, producing new combinations of genes.
  • Another source of variation comes from the random fusion of gametes during fertilisation. The combination of gametes (and the alleles they carry) is purely by chance.

Environmental Variation

  • Environmental variation is caused by differences in an individual’s environment or lifestyle.
  • This can include factors such as diet, temperature, exposure to sunlight, physical accidents, availability of resources, and other life experiences.
  • It is important to note that environmental variation does not alter the DNA sequence.

Continuous and Discontinuous Variation

  • There are two primary types of variation: continuous and discontinuous.
  • Continuous variation, such as height in humans, displays a range of phenotypes that appear along a spectrum.
  • Discontinuous variation results in distinct categories, and each individual falls into one of these categories, e.g. blood groups in humans.
  • Continuous variation is usually polygenic (controlled by many genes) and often influenced by environment, while discontinuous variation is generally monogenic (controlled by a single gene).

Significance of Variation

  • Variation is essential for natural selection to occur, as it provides the raw material for evolution.
  • It allows the species to adapt to changes in their environment, which is beneficial for the survival of the species.

Remember, understanding variation aids in the understanding of evolution, genetics, and many other areas of biology. Keeping familiar with these details should help enhance your knowledge and boost your confidence in tackling related topics. PLUS, knowing the sources and impacts of variation can assist you in explaining many biological phenomena.