In: Biology
In details, what are the causes of variation between individuals within species?
A pre-requisite for natural selection is that there should be variation among the individuals of the same species or among different species in order to ensure their differential survival. The vairations that cause individuals of the same species to differ from each other can be manifested in the form of the following:
(1) Mutations: A mutation is any change in the genetic composition of an individual that leads to change in their phenotypic characteristics. These are heritable if they occur in the germline.
(2) Meiosis: Meiosis refers to the type of cell division in which the DNA content is reduced to half, i.e., a diploid cell gives rise to two haploid daughter cells. This process occurs only in the germ cells. Hence, whatever changes occur in a cell undergoing meiosis are inherited by the offspring. During meiosis, variations develop via crossing over (prophase-I) and independent assortment (metaphase-I).
(3) Sexual reproduction: It is a type of reproduction which causes genetic material from two distinct individuals of the same species to combine during fertilisation, and creates new gene combinations in offspring.