Great Migration: Life for Migrants in the City. By the end of 1919, some 1 million blacks had left the South, usually traveling by train, boat or bus; a smaller number had automobiles or even horse-drawn carts.
Genetic variation is increased by meiosis During fertilisation, 1 gamete from each parent combines to form a zygote. Because of recombination and independent assortment in meiosis, each gamete contains a different set of DNA.
Variation resulting from the appearance of mutations is called variation through mutation while that conditioned by subsequent recombination of genes as a result of interbreeding is called variation through recombination.roup variation includes the differences among aggregates of any rankâfrom differences among small groups of individuals within a population to differences among the kingdoms of living nature (animals and plants). In essence, the entire taxonomy of organisms is constructed on the comparative study of group variation.