A food chain shows how organisms obtain energy and nutrients by consuming other organisms. Food chains begin with autotrophs, like plants, that produce their own food. Herbivores then eat the plants, and carnivores eat the herbivores or other carnivores. This continues with increasing trophic levels until reaching top predators with no natural predators. At each level some energy is lost, with decreasing amounts of energy being passed to higher levels.

1. FOOD CHAIN

2. What is a Food Chain?
A food chain shows
how each living thing
gets food, and how
nutrients and energy
are passed from
creature to creature.
Food chains begin
with plant-life, and
end with animal-life.
Some animals eat
plants, some animals
eat other animals.

3. • A food chain starts with the primary energy
source, usually the sun. The next link in the
chain is an organism that makes its own food
from the primary energy source -- an example is
photosynthetic plants that make their own food
from sunlight (using a process called
photosynthesis) and chemosynthetic bacteria
that make their food energy from chemicals in
hydrothermal vents. These are called autotrophs
or primary producers.

4. • Next come organisms that eat the autotrophs;
these organisms are called herbivores or
primary consumers. The next link in the chain is
animals that eat herbivores - these are called
secondary consumers. In turn, these animals are
eaten by larger predators which are called
tertiary consumers. The tertiary consumers are
are eaten by quaternary consumers. Each food
chain end with a top predator, and animal with
no natural enemies. The arrows in a food chain
show the flow of energy, from the sun or
hydrothermal vent to a top predator.

5. • The arrows in a food chain show the flow
of energy, from the sun or hydrothermal
vent to a top predator. As the energy flows
from organism to organism, energy is lost at
each step. There are different trophic levels of
an organism in a food chain. Trophic Level of
an organism is the position it holds in a food
chain.

6. Another Example of a Food Chain
This figure
shows the
energy loss in
each step in a
food chain.

7. Food Chain in an Ocean

8. Trophic Levels in a Food Chain
• Primary producers (organisms that make their
own food from sunlight and/or chemical energy
from deep sea vents) are the base of every food
chain - these organisms are called autotrophs.
• Primary consumers are animals that eat
primary producers; they are also called
herbivores (plant-eaters).
• Secondary consumers eat primary consumers.
They are carnivores (meat-eaters) and
omnivores (animals that eat both animals and
plants).

9. • Tertiary consumers eat secondary
consumers.
• Quaternary consumers eat tertiary
consumers.
• Food chains "end" with top predators,
animals that have little or no natural enemies.
• The last links in the chain are the
decomposers. If you die, they eat you. If you
produce waste, they eat that. If you lose a
leaf, they eat it. Whenever something that

10. was alive dies, the decomposers get it.
Decomposers break down nutrients in the
dead "stuff" and return it to the soil. The
producers can then use the nutrients and
elements once it's in the soil. The
decomposers complete the system,
returning essential molecules to the
producers. Producers use those nutrients
and the food chain carries on.

12. Example of a Food Chain