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.
Scientists now know that independent assortment of genes occurs  during meiosis in eukaryotes. Meiosis is a form of cell division  that lowers the number of chromosomes in a â¦ parent cell by half to  make four reproductive cells called gametes.