Preserving the quality of catchment ares

The layers of earth are based on what two sets of characteristics?

Read the article titled "trans-saharan migration routes to north africa and the eu: historical roots and current trends." why do tens of thousands of sub-saharan africans try to cross the mediterranean each year? how are these refugees commonly portrayed? (site 1)

Which region was the hearth for the largest number of agricultural animals such as pigs sheep and cows