Grade by Grade
B. Life Systems · Habitats and Communities

Herbivores, Carnivores and Omnivores

B2.5 A2.1 A1.1 A1.5About 35 minutes
Learning goals
  • I can explain that scientists sort animals by what they eat (their diet).
  • I can sort animals into herbivores, carnivores and omnivores.
  • I can use clues like teeth to infer what an animal eats.
  • I can follow and write a simple program that sorts animals by diet.

Words to know

diet
The kinds of food an animal usually eats.
herbivore
An animal that eats only (or almost only) plants.
carnivore
An animal that eats only (or almost only) other animals.
omnivore
An animal that eats both plants and animals.
canine teeth
Long, pointed teeth used for gripping and tearing.
molars
Wide teeth at the back of the mouth used for grinding.

What's for dinner?

A moose wades into a lake and munches on water plants. A lynx crouches in the snow, ready to pounce on a snowshoe hare. A black bear eats blueberries in the morning and catches a fish in the afternoon.

Three animals, three very different diets. Scientists use an animal's diet to put it into a group.

A bull moose with large antlers stands in a lake with water plants hanging from its mouth.
A moose is a herbivore: it eats only plants, like these water plants it pulled from the lake. AI-generated image

Three diet groups

  • Herbivores eat plants: leaves, grass, twigs, bark, seeds, fruits. Examples: white-tailed deer, moose, beaver, snowshoe hare, grasshopper, monarch caterpillar.
  • Carnivores eat other animals. Examples: grey wolf, lynx, great horned owl, garter snake, great blue heron, spider.
  • Omnivores eat both plants and animals. Examples: black bear, raccoon, striped skunk, red fox, chipmunk, blue jay, American robin.

A handy memory trick: herbivores eat herbs (plants), carnivores eat meat (carne means meat in Spanish and Italian), omni means all.

What about people?

Humans can eat both plants and animals, so scientists group humans as omnivores. Some people choose not to eat meat (vegetarians), for reasons like health, beliefs or caring for animals. They are still able to digest both kinds of food.

herbivore:flat grinderscarnivore:sharp, pointedomnivore:some of eachTeeth give clues about diet (simple drawings)
Simple drawings of teeth. Flat teeth grind plants. Pointed teeth grip and tear meat. Omnivores have some of each.

Clues in an animal's body

You can often infer (make a smart guess) about an animal's diet from its body:

  • Teeth: herbivores have wide, flat molars for grinding plants. Carnivores have long, pointed canine teeth for gripping prey. Omnivores have both.
  • Beaks: a hawk's hooked beak tears meat; a cardinal's thick beak cracks seeds.
  • Claws and talons: sharp talons help an owl grab prey.
  • Eyes: many hunters (like owls and cats) have eyes facing forward to judge distance. Many plant-eaters (like deer and rabbits) have eyes on the sides of their heads to watch for danger all around.
Worked example

Let's sort some Ontario animals

Sort these animals: moose, lynx, raccoon, beaver, garter snake, black bear.

  1. Moose: eats twigs, leaves and water plants: herbivore.
  2. Lynx: hunts snowshoe hares and other animals: carnivore.
  3. Raccoon: eats fruit, nuts, insects, frogs, crayfish and garbage: omnivore.
  4. Beaver: eats bark, twigs and water plants: herbivore.
  5. Garter snake: eats worms, frogs, slugs and small fish: carnivore.
  6. Black bear: eats berries, nuts, plants, insects and fish: omnivore.

Herbivores: moose, beaver. Carnivores: lynx, garter snake. Omnivores: raccoon, black bear.

Eats plantsHERBIVORESmoosebeaverEats animalsCARNIVORESlynxgarter snakeBoth!OMNIVORESraccoonblack bear
A Venn diagram of diets. Animals in the overlap eat both plants and animals, so they are omnivores.

Let's code it!

Computers sort things by following if-then rules. Here is a program that asks two questions and gives two kinds of output: a message on the screen and a tally mark added to a chart.

ask "Does it eat plants?" and save the answer as plants
ask "Does it eat animals?" and save the answer as animals
if plants = yes and animals = yes then
say "Omnivore!"
add 1 to the omnivore tally
else if plants = yes then
say "Herbivore!"
add 1 to the herbivore tally
else if animals = yes then
say "Carnivore!"
add 1 to the carnivore tally

A sorting program with two kinds of output: a message and a tally chart.

Worked example

Let's run the program

Run the program for a blue jay, which eats acorns, seeds and insects.

  1. Does it eat plants? Yes (acorns and seeds).
  2. Does it eat animals? Yes (insects).
  3. The first rule checks: plants = yes and animals = yes. True!
  4. The program says "Omnivore!" and adds 1 to the omnivore tally.

The blue jay is an omnivore.

Just for fun

Q: Why did the black bear order berries and a fish for lunch?

A: Because it's an omnivore. Picking just one side of the menu is too hard!

Hands-on activity

Diet detective cards

You need: 12 index cards or paper squares, pencil crayons, a book or a website your grown-up helps you choose.

  1. Choose 12 animals that live in Ontario. On the front of each card, draw the animal.
  2. Research what each animal eats. Write its main foods on the back.
  3. Sort the cards into 3 piles: herbivores, carnivores, omnivores.
  4. "Run" the sorting program above for each card, out loud, with a grown-up acting as the computer. Keep a tally chart of the outputs.
  5. Count your tallies. Which group had the most? Share your chart and one surprising fact you found.

Extension: If you use a block-coding app, build the program with "ask", "if-then-else" and "say" blocks, and make a variable for each tally.

Your turn

1

What is a herbivore? Name two Ontario examples.

2

What is a carnivore? Name two examples.

3

What is an omnivore? Name two examples.

4

A robin eats worms in spring and berries in fall. Which group is it in?

5

An animal has long, pointed canine teeth and forward-facing eyes. What is its diet most likely to be?

6

Which group do humans belong to?

7

In the program, which answers give the output "Herbivore!"?

More practice: warm-up

1

A rabbit eats clover. Herbivore, carnivore or omnivore?

2

A wolf eats deer. Which group?

3

A raccoon eats apples and crayfish. Which group?

4

What does "omni" mean?

5

What are wide, flat back teeth called?

More practice: on your own

1

A monarch caterpillar eats only milkweed leaves. Sort it and explain.

2

A great blue heron stands in a marsh and eats fish and frogs. Sort it and explain.

3

A chipmunk eats seeds, nuts, berries and sometimes insects and bird eggs. Why is it an omnivore?

4

Why do many herbivores, like deer, have eyes on the sides of their heads?

5

Mia runs the program for a lynx. What does she answer to each question, and what is the output?

Challenge

1

A skull has sharp canine teeth at the front and flat molars at the back. What diet group would you infer? Explain.

2

Leo's program only had the rules "if plants = yes then say Herbivore" and "if animals = yes then say Carnivore". What goes wrong when he enters a black bear? How do you fix it?

3

Black bears eat mostly plants (berries, nuts, grasses) but also insects and fish. Why are they still called omnivores and not herbivores?

Check your understanding

Quiz

1.

An animal that eats only plants is a...

2.

Which animal is a carnivore?

3.

Which animal is an omnivore?

4.

Wide, flat molars are best for...

5.

A diet is...

6.

In the sorting program, an animal that eats plants and animals gives the output...

For parents and teachers

This lesson sorts animals by diet (herbivore, carnivore, omnivore) and connects to coding with if-then-else rules.

Common difficulties:

  • Children may call an animal a herbivore because it eats mostly plants. If it regularly eats animals too (like a bear or a robin), it is an omnivore.
  • In the program, the order of the rules matters: check "both" first.

Note on people: Humans are omnivores biologically. Some families are vegetarian or vegan for health, cultural, religious or personal reasons. This is a choice, and it is respected in the lesson.

At home: Play "20 questions" with Ontario animals: ask diet questions to guess the animal.