Why are STEM cells controversial?
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<h3>∴ ║ Living Things Need Energy ║∴</h3>The ability to obtain and use energy is one of the eight characteristics of all living things. Scientists classify organisms based on how they get their energy: autotrophs or heterotrophs. Organisms are divided into three main groups- the producers, the consumers and the decomposers.
Producers get their energy from abiotic factors (non-living sources). Most producers are plants and get their energy directly from the sun using a process called photosynthesis. There are also some bacteria that can make their own food from chemicals using a process call chemosynthesis. Examples of common producers are grasses, trees and flowers. Algae (which are protists, not plants) are the main producers in aquatic ecosystems. Remember we call these autotrophs because they can make their own food.
Consumers cannot make their own food. Instead, they get their energy by eating other organisms. These are also called heterotrophs. There are many types of consumers. Herbivores, such as grasshoppers and prairie dogs, only eat producers. Carnivores eat animals. Coyotes, badgers, and falcons are all carnivores. Organisms that eat both producers and other consumers are known as omnivores. Most humans are omnivores. Scavengers are a special type of omnivore. They eat dead plants and animals. Vultures and many insects are common scavengers.
Decomposers are a very special type of heterotroph because they get energy by breaking down dead or dying organisms. Bacteria and fungi (mushrooms, molds and mildews) are examples of decomposers. Decomposers are important to ecosystems because they return important nutrients such as water, carbon dioxide and nitrogen to the soil. Plants then use these nutrients to grow, creating a cycle of nutrients through the ecosystem.
Each of these organisms depends on the others. Producers get energy from the sun or chemicals and then give some of this energy to consumers. The consumers then give some of their energy to the decomposers. Together, these organisms form a food chain. A food chain is a series of events in which food energy is transferred from one organism to another. All food chains have the basic structure of producer ⇒ primary consumer ⇒ secondary consumer ⇒ tertiary consumer ⇒ decomposer. There are many overlapping food chains in an ecosystem. These overlapping food chains are known as a food web.
As energy passes from level to the level in a food chain within a food web, the amount that each organism receives decreases. For example, in a grassland ecosystem, the grasses get energy needed for life from the sun. Some of this energy is used by the grass to grow and reproduce. When a prairie dog eats the grass, it only gets 10% of the energy the grass originally had. The prairie dog then uses some of the energy from the grass to grow and reproduce. When a coyote eats the prairie dog, it only gets 10% of the energy the prairie dog originally had. This decrease in energy at each level of the food chain can be represented by an energy pyramid.
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