Africa's grassland, or savanna, ecosystem is an open, grass-covered land with small, interspersed trees. Its diverse species play specific and important roles. Food chains trace the transfer of energy from one organism to another in an ecosystem. They are simple and linear, whereas food webs include all of the interconnected food chains in an ecosystem. Food webs must strike a delicate balance to ensure that no one organism becomes overpopulated within an ecosystem.
Producers, or autotrophs, make up the base of any food web, providing energy, both directly and indirectly, for all organisms within the savanna ecosystem. Producers are often plants that use photosynthesis to produce energy for themselves and for the consumers that eat them. In the African savanna ecosystem, producers include plants such as star grass, lemon grass, acacia trees, red oat grass and jackalberry trees. In many parts of the African savanna, the soil is too thin to support producers other than grasses. In these areas, trees grow on termite mounds instead of soil.
Primary consumers get their energy from the producers of the African savanna. Zebras, antelopes, gazelles, gnus, elephants, giraffes and many species of insects are herbivores, meaning that they eat plants exclusively. These grazers and other plant-eaters make up the second tier of the food chain in African grasslands. Occasionally, primary consumers may be omnivores as well. These organisms, including aardvarks, consume plant life just as herbivores do, but they also sometimes eat meat or insects as well.
Secondary consumers are the omnivores and carnivores, or meat-eaters, that receive their energy by preying on the primary consumers of the African savanna. Africa's big cats -- cheetahs, lions and leopards -- are examples of this group. Other secondary consumers in Africa's savanna include hyenas, wild dogs, humans and snake species.
Secondary consumers aren't the only carnivores that can be found on the African savanna. The grassland is also home to a class of animals known as scavengers. Scavengers receive energy from freshly dead or rotting organisms that have been killed by secondary consumers or that have died from other circumstances. Scavengers of the African savanna include vultures, jackals and hyenas. These animals provide an essential service in reducing animal waste by consuming animal carcasses and recycling their nutrients back into the environment.
Decomposers have the job of breaking down and returning inorganic nutrients into the ecosystem. These organisms, including fungi, termites and bacteria, consume dead matter from plants and animals, as well as waste matter, and release it back into the environment as inorganic nutrients, including carbon dioxide, which is in turn made available to producers. Any remaining energy at this stage goes to the decomposers, and inorganic matter is returned to the nutrient pool.
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