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Energy can pass through an ecosystem when food is eaten, but some energy is always changed to
heat and not passed on. |
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| Food Chains and Webs |
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Every organism needs energy in order to live. Energy moves to all organisms by processes known
as food chains, energy chains, or food webs. |
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Plants, protists, and other microorganisms are producers. Producers are organisms that make
their own food for energy. Producers get energy to make food from the energy of sunlight or
chemicals in nature. This food can then be used by many other organisms. |
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Consumers are organisms that cannot make their own food. They usually eat other organisms to
get energy to stay alive and grow. All animals are consumers. There are several kinds of consumers.
Herbivores eat only plants. Carnivores, also called predators, eat only other animals, called prey.
Omnivores eat both plants and animals. Decomposers eat waste or dead organisms. |
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When food is eaten, it is not only matter that moves into another animal. The energy in the food
also moves. Arrows in the food chain at the right show how energy can flow through an ecosystem
from a producer to an herbivore, a carnivore, and finally to a decomposer. You can see that the
energy the spotted owl gets from eating the hare came from plants. |
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| Sun plants snowshoe hare spotted owl bacteria |
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On land, almost all kinds of animals’ food can be traced back in some way to plants. In the ocean,
food chains often start with plant-like microorganisms called plankton. Food chains at deepsea vents
start with bacteria. |
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Food chains can be very short, involving only a plant and a decomposer. Chains can also be longer,
involving more than one carnivore. A food chain is not a complete way of describing energy flow in an
ecosystem. This is because consumers usually eat many kinds of other organisms. To see an
ecosystem more fully, you need to look at a food web like the one below. A food web combines
many food chains into one picture. |
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1. |
What is the niche, or role, of a producer? |
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2. |
Draw a diagram showing the sequence of organisms feeding in a food
web. Your diagram may have organisms of your choosing. Describe how your diagram shows
the flow of matter and energy. |
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