12.3 · Reading an Ohio Food Web

From Ohio 5th Grade Science Power Workbook · Chapter 12 · Lesson 12.3.

Big idea: A food web is read one arrow at a time. Follow the arrows to find what an organism eats, what eats it, and where its energy came from.

Learning goals: Find what an organism eats and what eats it

Find the producers at the base of a web

Explain where the decomposers fit

Three questions to ask of any box

Pick one organism in the web. Ask three things.

What does it eat? Follow the arrows that point into it backwards.

What eats it? Follow the arrows that point out of it.

Where did its energy start? Keep going backwards until you reach a producer, and then the sun.

The base, and the boxes not drawn

The producers sit at the bottom of the web. No arrow points into them from another organism. Their energy came from the sun.

Decomposers are usually left out of the drawing to keep it clear. They are still there. When any organism in the web dies, the decomposers break it down.

Worked examples

Question: Use the woodland web. What does the fox eat, what eats the squirrel, and where did the hawk's energy start?

Steps: Arrows into the fox come from insects, rabbit and squirrel. Those are its foods.

Arrows out of the squirrel go to the hawk and the fox. Those eat it.

Trace the hawk backwards. Hawk, rabbit, grass, sun. Or hawk, squirrel, oak leaves, sun. Every path ends at a producer and then the sun.

Answer: The fox eats insects, rabbits and squirrels. Hawks and foxes eat squirrels. The hawk's energy started at the sun, through the grass or the oak.

Common mistakes

Big does not mean it eats the small

It feels natural that the biggest thing in a web eats the smaller things.

Look at the arrows instead. A deer is much bigger than an oak leaf, and it eats leaves. But a deer is also bigger than a fox, and the fox does not eat the deer. Tiny insects eat the leaves of a huge oak. Size does not decide who eats whom.

Check your thinking: Never guess an arrow from size. If there is no arrow between two boxes, the web does not show one eating the other.

Ohio connection

Reading a web at an Ohio pond

At an Ohio pond, algae and water plants sit at the base. Snails and water insects eat them. Small fish eat the insects and snails. Larger fish and a wading bird eat the small fish.

A web of that pond shows all of it at once, and every arrow points at an eater.

Think: From the description above, name one pond organism that would have two arrows pointing into it, and say what the two arrows mean.

Remember

In, out, back

In: what it eats. Out: what eats it. Back: keep going against the arrows until you hit a producer. Three moves answer almost every web question.

Practice tip

Remember: The web is the evidence. Use only what is drawn.

Tip: If two boxes have no arrow between them, the correct answer is that the web does not show one eating the other. Do not add arrows from what you think you know.

Written practice

Use the woodland web shown in P12.3.1. Trace one complete path of energy from the sun to the hawk. Name every organism on the path in order.

Sample response: The sun's energy is used by the grass to make food. The rabbit eats the grass. The hawk eats the rabbit. So the path is sun, grass, rabbit, hawk.

Scoring guide: 1 point: gives a path that follows the arrows, such as sun, grass, rabbit, hawk, or sun, oak leaves, squirrel, hawk.

1 point: starts at the sun and a producer, not at an animal.

Every correct path begins with the sun and a producer and follows the arrowheads.