Food Chains
reflect
Have you ever seen a picture that shows a little fish about to be eaten by a big fish? Sometimes
the big fish has an even bigger fish behind it. This is a simple food chain. A food chain is the path
of food energy from one organism to another in an ecosystem. (An organism is any living thing.)
Organisms get
energy from the
food they eat.
Before the little fish
gets eaten, it eats
a plant for its energy. Food chains are the way
energy is moved from one organism to the
next. But where does the energy in the food
chain start? How does energy move through
the food chain?
energy: what is
needed to do work
or cause change
What is eating what in this simplified
food chain?
Where does the e
­ nergy from a food chain start?
Plants get their energy from the Sun. Plants use
the light from the Sun to
make their own food. This
Sun: the star at the
food gives plants energy
center of the Solar
to grow and survive.
System that supplies
Plants also store food to
heat and light to Earth
use for energy later.
Most of the energy on Earth comes from the Sun.
So, the Sun is at the top of most food chains.
The Sun gives energy to these
corn plants.
The organisms that get their energy directly from the
Sun are called producers. A producer uses sunlight
to make its own food. The organisms that get their
energy by eating producers are called consumers.
We will study consumers in the next section.
How does energy flow through a food chain?
Consumers may eat producers (plants) or other
consumers (other animals). Consumers are called
predators when they eat other animals. The
organisms eaten by predators are called prey.
The eagle is a predator. The fish
is the eagle’s prey.
When an animal eats a plant, it gets the energy
stored in the plant. The animal can use this energy
to move and to stay healthy. One animal may also
eat another animal. The predator gets the energy
stored inside of the prey animal. The predator can
then use this energy to move and stay healthy.
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91
Food Chains
The diagram above is an example of a food chain. The energy comes from the Sun. Plants
use the energy to produce plant seeds. A mouse eats the plant seeds. Then, a snake eats
the mouse. Finally, an eagle eats the snake.
Notice that the arrows point from the Sun to the eagle. In other words, the arrows show the
direction in which the energy flows. Sometimes, people draw food chains with the arrows
pointing in the wrong direction. Because the eagle eats the snake, you may think it makes
sense for the arrow to point from the eagle to the snake. It is important to remember that
the flow of energy always goes from the Sun to producers to consumers.
what do you think?
Is the organism shown in this picture a producer or a
consumer? How do you know?
try now
In this activity, you will locate consumers and producers
where you live.
1.Begin by thinking about the living things in your
classroom or home. Do you have any plants or
pets? Identify each living thing that you see. Decide
whether it is a consumer or a producer.
2.Next, take a walk outside. Identify the living things
that you see. Decide whether each is a consumer
or a producer. Be safe. Do not touch any plants you’re unsure of or approach any
animals.
3.Don’t forget to think about yourself. You are a living animal in a food chain. Are you a
consumer or a producer?
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Food Chains
What happens to a food chain in an ecosystem if an organism is removed?
Ecosystems may have many different producers and consumers. An ecosystem may
contain many food chains. A balanced ecosystem has enough producers to support all the
consumers. Some ecosystems contain lots of biodiversity. In other words, they contain
many different kinds of living things. If one organism dies out, other organisms may take its
place in a food chain.
In other ecosystems, however, food chains might be affected much more. If that organism
dies and no other species fill that role, you can imagine how many other organisms will be
affected! Whatever the organism eats might grow more quickly, and whatever predators eat
the organism will have trouble finding food. Can you think of what else might happen?
Let’s think about frogs in a pond. In a pond ecosystem, frogs are consumers of many
different organisms. They eat snails and small insects that get their energy from green
algae. Green algae are the producers in the pond food chain. Large animals like herons eat
the frogs.
Many ponds contain only one kind of frog. If a disease kills off all the frogs, the heron and
other large consumers lose a large part of their food source. They may die off as a result
or have to find a new food source. On the other hand, fewer frogs mean fewer predators
eating insects and snails. More insects and snails may survive. If this happens, they may
eat too much of the pond’s algae. As a result, the food chain may become affected or
broken in several places.
Without bees in an ecosystem, flowers won’t be pollinated. Insects such as this
caterpillar will have fewer plants to eat.
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93
Food Chains
Looking to the Future: Bee Colony Collapse Disorder
Bees are part of the ecosystems in which they live. When they move from flower to flower
they pick up pollen on their bodies. The bees then move the pollen to the next flowers they
land on. By doing this, they help the flowers make fruits and seeds. Without the bees to
move the pollen the plants could not reproduce.
Scientists do not know why, but colonies of bees have been disappearing. This was first
observed in 2006 in North America. Since then, it has been happening all over the world.
This problem is called Colony Collapse Disorder (CCD). Because of CCD, many fruits and
other crops have been ruined.
Scientists aren’t sure what is causing CCD. They have several
hypotheses:
•Poison that is sprayed on crops kills bees.
hypothesis: a
possible answer to a
scientific question
•Insects such as mites harm the bees.
•A virus harms the bees.
•Humans have damaged the habitats where bees live.
Scientists also think that CCD could be from all of these things. They watch bee colonies
carefully and record what they see. They test dead bees to find out what caused them to
die. They are also working to improve the health of living bees.
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Food Chains
What do you know?
Food chains are made up of producers and consumers. Identify whether each of the
following is a producer or a consumer.
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95
Food Chains
connecting with your child
The Food Chain in Store for You
To help students learn more about food
chains and to make the connection to their
everyday lives, take them with you to your
local grocery store.
As you walk the aisles with them, point
out different foods and discuss where
that food comes from. From their studies
in the classroom, they should be able to
identify whether each food is a producer or
a consumer. Then, encourage students to
take it a step further and describe a possible
food chain for the item.
For example, point out a fruit or vegetable.
They should identify this as a producer.
When they think about a possible food
chain, they should explain the plant gets
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energy from the Sun; students might also
describe a small animal that eats the plant
and perhaps a larger animal that eats the
small animal.
Here are some questions to discuss with
your child:
•Is everything in the produce aisle of the
grocery store a producer?
•Are there any consumers in the grocery
store?
•Consider some packaged food, such as
bread or cereal, and ask students to look
at the ingredients to determine the source
of the food. This may take a little more
prompting; for example, students may not
realize that flour comes from wheat.
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