Who makes the food?

The idea

Autotrophs, including green plants and some bacteria, use simple inorganic food (carbon dioxide and water); heterotrophs, including animals and fungi, use complex substances broken down by enzymes, and depend directly or indirectly on autotrophs.

Nobody feeds the grass

A field of grass has no farmer feeding it. Nobody hands it food. Yet it grows green and tall.

Where does the grass get its food?

• It makes its own food from simple things like carbon dioxide and water
• It takes ready-made food from the soil
• Dead leaves and rotting animals feed it

Sort seven living things

Tap an organism in the tray, then tap its box. A wrong box bounces back and tells you why. When all seven are sorted, press Remove all autotrophs and watch.

Makers and dependents

Autotrophs (green plants and some bacteria) use simple food material: carbon dioxide and water. Heterotrophs (animals and fungi) use complex substances, broken down by enzymes, and depend directly or indirectly on autotrophs.

A mushroom looks like a plant, but it is a fungus. It breaks food down outside its body and then absorbs it.

• Autotrophs | Heterotrophs
• Green plants, some bacteria | Animals, fungi
• Use simple food material: carbon dioxide and water | Use complex substances, broken down by enzymes
• Make their own food | Depend directly or indirectly on autotrophs

Notes

Autotrophs, including green plants and some bacteria, use simple inorganic food (carbon dioxide and water); heterotrophs, including animals and fungi, use complex substances broken down by enzymes, and depend directly or indirectly on autotrophs.

Check yourself

Which pair are both autotrophs?

A tiger never eats grass. Why does it still depend on autotrophs?

Which sentence is correct?

Suppose every autotroph on Earth disappeared. What would happen to heterotrophs?

• Grass and a mushroom. A mushroom is a fungus. Fungi are heterotrophs.
• A deer and a mango tree. A deer is an animal, so it is a heterotroph.
• Grass and a blue-green bacterium — correct. Yes! Autotrophs include green plants and some bacteria.
• It eats deer, and deer eat grass — correct. Yes! The tiger depends on autotrophs indirectly, through the deer.
• It does not depend on them at all. Every heterotroph depends on autotrophs, directly or indirectly.
• It makes food from carbon dioxide and water. Only autotrophs do that. A tiger takes in complex food.
• All bacteria are autotrophs. Only some bacteria are. Many are not.
• Fungi are heterotrophs — correct. Yes! Fungi, like mushrooms, break down food and absorb it.
• Animals make food from carbon dioxide and water. Animals are heterotrophs. They take in complex food.
• Animals that eat other animals would be fine. Those animals eat animals that eat plants. Their food would run out too.
• Fungi would be fine, since they break down food outside the body. Fungi still need complex food that autotrophs made. They would run out too.
• They would lose their food, sooner or later — correct. Yes! They depend on autotrophs, directly or indirectly.