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.
Your genes have alleles, which are different forms of the same gene. Alleles are like a code for your body that determine hair color and eye color, height, and other genetic features. Genetic variation is the variation in alleles and genes, both within and among populations.Think of a population as a family unit.ene flow is the movement of genetic information between different populations. This method increases genetic variation because introducing new alleles into a population increases the amount of diversity. The more alleles available in a population, the more variation that can occur.