Exposure to ultraviolet (UV) radiation is a major risk factor for most skin cancers. Sunlight is the main source of UV rays. Tanning lamps and beds are also sources of UV rays. People who get a lot of UV exposure from these sources are at greater risk for skin cancer.V rays damage the DNA of skin cells. Skin cancers start when this damage affects the DNA of genes that control skin cell growth. There are 3 main types of UV rays: 1  UVA rays age skin cells and can damage their DNA.
Northern Africa. The Sahara is the largest desert in the world and occupies approximately 10 percent of the African Continent. The ecoregion includes the hyper-arid central portion of the Sahara where rainfall is minimal and sporadic. Although species richness and endemism are low, some highly adapted species do survive with notable adaptations.
Savanna Biome. The Savanna Biome is the largest Biome in southern Africa, occupying 46% of its area, and over one-third the area of South Africa.It is well developed over the lowveld and Kalahari region of South Africa and is also the dominant vegetation in Botswana, Namibia and Zimbabwe.rbanization is not a problem, perhaps because the hot, moist climate and diseases (sleeping sickness, malaria) hindered urban development. Conservation of savanna is good in principle, mainly due to the presence of the Kruger and Kalahari Gemsbok National Parks within the biome.