What Is a Food Chain?
What Is a Food Web?
Exploring Science
Plants That Eat Meat. Down in the swamp there are plants that eat meat. One is
the Venus fly trap. Its outer leaves have “teeth.” A fly crawls onto one of these
leaves. It brushes against a trigger hair on the leaf. In less than a second, the leaf
snaps shut. The “teeth” form a cage around the fly. The plant digests the fly.
The pitcher plant also eats meat. A sweet odor attracts an ant into the plant.
When the ant tries to crawl out, pointed hairs block its way. It falls into a liquid,
where the plant digests it.
Both these plants are green. They are unlike other green plants, which do not
“eat” insects. What makes them different? Plants must take in nitrogen to make
foods. The nitrogen usually comes from nitrates in the soil. Soil in the swamp is
poor in nitrates. So the meat-eating plants get nitrogen from animal proteins. That
is why these plants eat insects.
Links in the Chain
Green plants, and other food makers, use energy from sunlight to produce food.
Food makers are producers.
Organisms that feed on other living things are consumers. Some animals eat
only producers. These are first-level consumers. A rabbit that eats grass is a firstlevel consumer. Animals that eat first-level consumers are second-level consumers. A snake that eats the rabbit is a second-level consumer. A third-level
consumer eats second-level consumers. A hawk that eats the snake is a third-level
consumer.
The grass, rabbit, snake, and hawk are links in a food chain. At the start of any
food chain is a producer. In a drawing of the chain, an arrow joins each organism
to the one that eats it. The arrows show how energy flows along the chain. This
chain is short. Many food chains are very long. An animal that eats other animals is
called a predator (PRED-uh-tur). The animal a predator eats is its prey. In the food
chain above, the hawk is a predator. Its prey is the snake. Which other organisms
in the chain are predators? Which are their prey?
Exploring Science
Fly Eats Toad—Toad Eats Fly. A spadefoot toad is about to start its life on land. In
the mud nearby lives a maggot. This maggot is the larva (LAR-vuh) of a horsefly.
Only the larva’s head and jaws stick out of the mud. When the toad hops close to
the larva, the larva attacks. The larva injects the toad with poison and sucks it dry.
The scientists who watched the fly eat the toad were amazed. They then observed
not one, but hundreds of fly larvae eating toads. One scientist said, “This is
unusual, because everyone knows that toads eat flies.” The scientists collected fly
larvae and spadefoots from the mud. They took them to their laboratory, and
observed the same events. Then they reported their findings.
You Are What You Eat
Producers and consumers are part of food chains. A rabbit eats grass. A snake
eats the rabbit. A hawk eats the snake. Here’s another food chain: A frog eats a
cricket. A fish eats the frog. A hawk eats the fish.
Most organisms are part of more than one food chain. The hawk, for example, eats
the snake. It is part of one food chain. But the hawk also eats a fish. It is then part
of another food chain. Two or more food chains can link to make up a food web. In
a food web, food chains link together.
Consumers that eat only plant foods are herbivores (Hur-buh-vohrs). A deer is a
herbivore. Consumers that eat only meat are carnivores (KAR-nuh-vohrs). A
mountain lion is a carnivore. An omnivore (OM-nuh-vohr) eats both kinds of food.
Which are you—omnivore, herbivore, or carnivore?
In a food chain, herbivores are first-level consumers. Carnivores are at the
second level, or higher. So are omnivores.
Another kind of consumer is the decomposer (dee-kum-POH-zur). Decomposers
break down, or decompose, wastes and dead organisms. Scavengers (SKAV-injurs) are one kind of decomposer. A vulture is a scavenger. It feeds upon dead
animals that it finds. Tiny decay bacteria are another kind of decomposer. So are
fungi (FUN-jy). These are non-green plant-like organisms.
Decomposers of all kinds are important for the food web of a community. They
return nitrogen and other materials to the soil
Fish
Snake
Dragonfly
Grass
Leaf
Name:
Class:
Date:
Questions
1) An organism that makes its own food is called a ________________.
2) An organism that must eat anther organism for food is a _____________.
3) A _________ __________ demonstrates how energy moves from one
organism to another.
4) Animals that hunt other animals are called _____________.
5) Animals that are hunted for food are called ______________.
6) Look at the food chain on page 1. Place each organism next to its place below.
Producer: __________________
First Level Consumer: ________________
Second Level Consumer:______________ Third Level Consumer: ____________
7) When food chains link together to show the interrelationships between chains,
this is called a __________ _______.
8) Which type of consumers are scavengers? _____________________.
9) Where would the sun fit in a food chain or web? Explain your answer.
10) How is a person both a first level consumer and a second level consumer?
Explain your answer.