Answer:
Savanna and Sahara
Explanation:
Savanna
Savannas, or grasslands, cover almost half of Africa, more than 13 million square kilometers (5 million square miles). These grasslands make up most of central Africa, beginning south of the Sahara and the Sahel and ending north of the continents southern tip.
Among Africas many savanna regions, the Serengeti (or Serengeti Plains) is the most well-known. The Serengeti is a vast, undulating plain that stretches 30,000 square kilometers (11,583 square miles) from Kenya's Maasai-Mara game reserve to Tanzania's Serengeti National Park.
The Serengeti is home to one of the continents highest concentrations of large mammal species, including lions, hyenas, zebras, giraffes, and elephants. Each year, more than 1 million wildebeest travel in a circular migration, following seasonal rains, across the Serengeti Plains. Their grazing and trampling of grass allows new grasses to grow, while their waste helps fertilize the soil.
The Sahara is the worlds largest hot desert, covering 8.5 million square kilometers (3.3 million square miles), about the size of the South American country of Brazil. Defining Africa's northern bulge, the Sahara makes up 25 percent of the continent.
The Sahara has a number of distinct physical features, including ergs, regs, hamadas, and oases. Ergs, which cover 20 percent of the Sahara, are sand dunes that stretch for hundreds of kilometers at heights of more than 300 meters (1,000 feet). Ergs cover most of Algeria and Libya and parts of Mali and Nigeria. Ergs can contain large quantities of salt, which is sold for industrial and food use.
Regs are plains of sand and gravel that make up 70 percent of the Sahara. The gravel can be black, red, or white. Regs are the remains of prehistoric seabeds and riverbeds, but are now nearly waterless.
Hamadas are elevated plateaus of rock and stone that reach heights of 3,353 meters (11,000 feet). They include the Atlas Mountains, which stretch from southwestern Morocco to northeastern Tunisia; the Tibesti Mountains of southern Libya and northern Chad; and the Ahaggar Mountains in southern Algeria.
Sahara
An oasis is a hub of water in the desert, often in the form of springs, wells, or irrigation systems. About 75 percent of the Saharas population lives in oases, which make up only 2,071 square kilometers (800 square miles) of the deserts vast area.
The Saharas animal and plant communities have adapted to the regions extremely dry conditions. The kidneys of the jerboa, a type of rodent, produce highly concentrated urine that minimizes water loss. A dromedary camel conserves water by changing its body temperature so it doesn't sweat as the day gets hotter. The scorpion limits its activities to night, burrowing into the cooler sands beneath the surface during the day. The scorpion, a predator, also absorbs water from the flesh of its prey.
Saharan plants survive thanks to root systems that plunge as far as 24 meters (80 feet) underground. In parts of the Sahara, plants cannot take root at all. In the southern Libyan Desert, for instance, no greenery exists for more than 195 kilometers (120 miles).
