Grade by Grade
B. Life Systems · Habitats and Communities

Communities: Species That Share a Habitat

B2.2 A1.1 A1.5About 35 minutes
Learning goals
  • I can explain the words species, population and community.
  • I can describe a community as a group of interacting species that share a habitat.
  • I can give examples of ways organisms in a community interact.
  • I can find information about a local community and share it.

Words to know

species
One kind of living thing. All robins are one species. All sugar maples are one species.
population
All the members of one species living in the same area, like all the frogs in a pond.
community
All the different populations (species) of plants, animals and other organisms that live together and interact in one habitat.
interact
To act on each other, such as eating, helping, or competing for the same thing.
predator
An animal that hunts and eats other animals.
prey
An animal that is hunted and eaten by a predator.
compete
To try to get the same thing that another organism needs, like food, water, light or space.

A busy pond

Sit quietly beside a pond in June. What do you notice?

Frogs croak from the edge. Dragonflies zip above the water. Ducks paddle by. Cattails sway in the wind, and fish make ripples. A heron stands very still, waiting.

All of these living things share the same habitat. Together they form a community.

A pond with a great blue heron, two mallard ducks, a green frog on a lily pad, a dragonfly and cattails.
Count the species sharing this pond: heron, ducks, frog, dragonfly, cattails and water lilies. Together they make one community. AI-generated image
🐸🐸🐸🐸🦆🦆🐟🐟🐟🐟🐟🦟🦟🦟🦟🦟🦟
Part of a pond community: 4 frogs, 2 ducks, 5 fish and 6 mosquitoes.

Species, population, community

Scientists use three words to talk about living things in a habitat:

  • A species is one kind of living thing, like green frogs, mallard ducks or cattails.
  • A population is all the members of one species in that area. All the green frogs in the pond are one population.
  • A community is all the populations together: the frogs, ducks, fish, mosquitoes, cattails, algae and every other species that lives in the pond.

In the picture above there are 4 species (frogs, ducks, fish and mosquitoes). The 5 fish are one population.

habitat: the pondcommunity: all the species in the pondpopulation: all the green frogsorganism: one green frog
One organism belongs to a population. The population is part of a community. The community lives in a habitat.

Members of a community interact

A community is not just a crowd of living things that happen to be in the same place. They interact: they affect each other every day.

  1. Eating and being eaten. A heron (the predator) eats fish (the prey). Fish eat insects. Insects eat plants.
  2. Competing. Two plants compete for sunlight and water. A frog and a fish may compete for the same insects.
  3. Helping. Bees pollinate flowers while they drink nectar. Birds eat berries and spread the seeds. A tree gives shelter to a bird's nest.
  4. Recycling. Worms, fungi and bacteria break down dead plants and animals, which puts nutrients back into the soil for plants.

Because they interact, a change to one population can affect the whole community.

InteractionWhat happensExample from an Ontario forest
eating (predator and prey)one organism eats anothera red fox catches a mouse
competingtwo organisms need the same thingtwo young maple trees grow toward the same patch of sunlight
helpingboth organisms are better off, or one gets helpa bee gets nectar and pollinates a trillium flower
recyclingdecomposers break down dead thingsmushrooms grow on a fallen log and break it down
Four kinds of interactions in a community.
Worked example

Let's describe a forest community

In a maple forest live sugar maple trees, trilliums, white-tailed deer, chipmunks, blue jays, earthworms and mushrooms. Is this a community? Give three interactions.

  1. Do they share a habitat? Yes, the maple forest.
  2. Are there different species? Yes, at least 7 different kinds.
  3. Interaction 1 (eating): deer eat young maple shoots and other plants.
  4. Interaction 2 (helping): blue jays carry and bury nuts and acorns; some they forget about grow into new trees.
  5. Interaction 3 (recycling): earthworms and mushrooms break down fallen leaves, which gives nutrients back to the maples and trilliums.

Yes, it is a community: many species sharing one habitat and interacting with each other.

Just for fun

Riddle: I'm one green frog. Add all the green frogs in my pond and we're a ___. Add the ducks, fish, cattails and mosquitoes and we're a ___.

Answer: A population, then a community!

Hands-on activity

Community research card

You need: paper, pencil crayons, a library book or a website your grown-up helps you choose.

  1. Choose an Ontario habitat: a marsh, a maple forest, a lake or a city park.
  2. Research 5 species that live there: at least 1 plant, 1 animal that eats plants, 1 animal that eats animals, and 1 decomposer (like a mushroom or worm).
  3. On a large sheet, draw each species. Draw lines between organisms that interact and label each line: eats, competes with, or helps.
  4. Write one sentence: "If ___ disappeared, ___ would be affected because ___."
  5. Present your community card to your family, using the words species, population and community.

Tip: Write down where you found each fact (book title or website name).

Your turn

1

What is a species?

2

What is a population?

3

What is a community?

4

All the white-tailed deer in a provincial park: population or community?

5

Give one example of a predator and its prey in Ontario.

6

Two oak seedlings grow close together. What might they compete for?

7

How do bees and flowers help each other?

More practice: warm-up

1

Is a frog a species, a population or a community?

2

Name 3 species that could be in a pond community.

3

What word means "act on each other"?

4

An owl hunts a mouse. Which one is the prey?

5

Do plants belong to a community?

More practice: on your own

1

In the pond picture there were 4 frogs, 2 ducks, 5 fish and 6 mosquitoes. How many species? How many organisms?

2

A squirrel and a blue jay both eat acorns. What kind of interaction is this? Explain.

3

Why are mushrooms important members of a forest community?

4

Is a group of 50 Canada geese and 20 mallard ducks on a lake one population? Explain.

5

Give an example of an animal that helps a plant spread its seeds.

Challenge

1

Many frogs in a pond get sick and die. Predict two ways this could affect other members of the community.

2

Explain the difference between a population and a community, using a city park as an example.

3

A beaver builds a dam, making a new pond. How does this one species change the whole community?

Check your understanding

Quiz

1.

A population is...

2.

A community is...

3.

A heron eats a fish. The fish is the...

4.

Two maple seedlings grow toward the same sunny gap. This is...

5.

Which is an example of helping?

6.

Why can a change to one population affect a whole community?

For parents and teachers

This lesson builds the vocabulary species, population and community and the idea that members of a community interact (eat, compete, help, recycle).

Common difficulties:

  • Mixing up population (one species) and community (many species). Use a family photo analogy: one family is like a population; the whole neighbourhood is like a community.
  • Forgetting that plants, fungi and tiny organisms are community members too.

At home: Watch a bird feeder or a park for 10 minutes and name the interactions you see (competing for seeds, chasing, eating).