Skim coating weak concrete is only a temporary fix. Another option is to lay a thicker overlay and slow-dry the new surface. To slow-dry, cover the driveway with moist, breathable material. Keep the material wet to provide additional moisture for the concrete to absorb.
The two main sources of genetic variation are gene shuffling and  mutations. A mutation is a process wherein the structure of a gene  is altered.Edit. Share to: Blobbert. 37,033 Contributions. Answered.In Genetic Engineering.he 4 types of genetic variation are 1) mutation-is the mutation of a gene. this is really rare, most mutations are in the recessive trait so they are hidden by a dominant t â¦ rait. Most mutations have no effect but some can be harmful and very few have positive effects.
A source of new variability is necessary for continued evolution to occur. Sources of genetic diversity External. Much of variation in populations, species, is retained due to changes in the environment (adaptive traits are only good in some environments, and not in others).or any evolutionary change to occur there must be some genetic variation in the population; the greater the amount of variability, the greater the possibilities for change. Natural selection decreases variability in populations: in a uniform environment, better adapted types should completely replace unfit types.