Answer to Question 1
Desertification is understood as a process that is derived both from natural and human systems. Certain areas received marginal precipitation and are thus inherently prone to desertification. Certain human practicesespecially agriculturalmay augment climatic processes to intensify the negative effects. Such practices include the over-use of land and the over-grazing of land. The areas that are most vulnerable are those on the fringe of desertsthose located between the desert and the semi-arid grasslands.
Answer to Question 2
Answer: Answers will vary, but a correct answer will include three of the following:
(a) addition of water, perhaps by heavy rains, which reduces particle-to-particle cohesion, lubricates, and adds weight to the slope, (b) oversteepening of a slope, (c) removal of vegetation by forest fires or intentional human clearing, which reduces or eliminates the net-like effect of roots holding soils in place, or (d) the land may be shaken by an earthquake. There are also landslides without triggers.
Here are images of live zebrafish that were studied for genetics and head size to give insight into
Human Embryogenesis
Human Body Glands and Hormones
Global Stratification: Income of the World's Nations
Upstream Process - Inoculum Preparation & Expansion
Main body cavities that hold human organs