Variation in Individuals of the Same Species

Different individuals of the same species can have different characteristics, a phenomenon known as variation.
Variation can be categorised into two types: genetic variation and environmental variation.
Genetic variation originates from the genetic material, DNA. It is caused due to differences in genes and combinations of genes inherited from parents.
Every individual (except identical twins) has a unique combination of genes. This leads to genetic variation.
Environmental variation comes from factors in an individual’s environment. For example, the type of diet or the amount of sunlight can cause differences among individuals.
Sometimes, both genetic and environmental factors contribute to variation. An example could be human health - your genetic makeup may make you more susceptible to certain conditions, but your environment also has a significant impact.
Characteristics that are controlled by genes are called inherited characteristics. Examples include eye colour, blood type, and inherited diseases.
Characteristics controlled by environmental factors are called non-inherited characteristics. These characteristics are not passed from parents to offspring.
Some characteristics, like skin colour or height, are usually a combination of genetic and environmental factors.
Variation within a species is essential for evolution and survival. It provides the variation on which natural selection acts upon.
Sexual reproduction is a major cause of variation as it causes genes from two parents to mix. This results in offspring genetically different from both parents and hence contributes to genetic diversity.
Mutations are random changes to genetic material. They introduce new variety into a population, although not all mutations result in noticeable or beneficial changes.
Variation is fundamental to the process of evolution as it allows for the survival of the fittest, where those best adapted to their environments are more likely to survive and reproduce.
Over time, as the environment changes, those organisms with variations that allow them to adapt to the new environment are more likely to survive and pass on their genes. This process is known as natural selection.