Weathering breaks down and loosens the surface minerals of rock so they can be transported away by agents of erosion such as water, wind and ice. There are two types of weathering: mechanicaland chemical. Mechanical weathering is the disintegration of rock into smaller and smaller fragments.
Crossing over – often, the sister homologous chromosomes of a cell exchange genetic material through recombination of genes.
Independent assortment/random fertilization – there are numerous variety of ways that the chromosomes of the gametes can combine, after meiosis, through fertilization to form a zygote
Mutation – on rare occasion, there is a slight and random change in the genes of a gametic cell caused by environmental factors.
