Grade by Grade
B. Life Systems · Biodiversity

What Is Biodiversity?

B2.2 A1.1 A1.5 A2.2About 45 minutes
Learning goals
  • I can explain that biodiversity means the variety of life on Earth.
  • I can describe three kinds of biodiversity: within a species, among species in a community, and among communities and habitats.
  • I can survey and record the living things in a small area like a scientist.

Words to know

biodiversity
The variety of all living things on Earth. It is short for "biological diversity".
species
A group of living things that are alike and can reproduce together to make young that can also reproduce.
population
All the members of one species living in the same area.
community
All the populations of different species living and interacting in the same area.
habitat
The place where an organism lives and gets everything it needs.
ecosystem
A community of living things together with the non-living things around them (air, water, soil, sunlight).
organism
Any single living thing: a plant, an animal, a mushroom, a bacterium.

Count the life around you

Stand in a park in June and look closely. A maple tree. Dandelions. A robin pulling up a worm. Ants on the sidewalk. Moss on a rock. A squirrel scolding you from a branch. Under one log you might find beetles, pill bugs, centipedes and threads of fungus.

All of that variety has a name: biodiversity. In this unit you will find out what biodiversity is, how scientists sort living things, why variety keeps life strong, and what you can do to protect it.

A mossy fallen log with shelf fungi, ferns, dandelions and a mossy rock on a sunny forest floor.
In one small patch of forest you can find mosses, fungi, ferns, wildflowers and trees, and there are animals hiding under the log too. That variety of life is biodiversity. AI-generated image

Remember from Grade 4

In Grade 4 you learned that a habitat gives living things the necessities of life, that a population is all the members of one species in an area, and that a community is all the populations living together. You also built food chains and food webs.

In Grade 6 you use those ideas to understand biodiversity.

What is biodiversity?

Biodiversity is the variety of life on Earth. The word comes from bio (life) and diversity (variety).

Scientists look at biodiversity in three ways:

  1. Diversity within a species. No two members of a species are exactly the same. Black-capped chickadees all look alike at first, but they differ in size, in feather pattern and in hidden traits like how well they resist disease. People differ too: height, hair, eye colour, blood type.
  2. Diversity among species in a community. A healthy pond community has many different species: cattails, duckweed, dragonflies, frogs, snails, fish, turtles, herons and tiny living things you need a microscope to see.
  3. Diversity among communities and habitats. Ontario has many kinds of places to live: forests, wetlands, lakes, rivers, tallgrass prairies, sand dunes, rocky shores and Arctic tundra near Hudson Bay. Each habitat supports its own community.
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Three levels of biodiversity: variety within one species, variety among the species in a community, and variety among communities and the habitats that support them.

Two ways to measure species diversity

When scientists study one place, they often count:

  • Species richness: how many different species live there.
  • Abundance: how many individuals of each species there are.

Two places can have the same number of living things but very different biodiversity. A lawn of only grass has many plants but very few species. A meadow has grasses, wildflowers, insects, spiders and birds: many species.

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A schoolyard survey. If each picture shows one species: 3 trees, 6 flowers, 4 bees, 2 squirrels and 5 birds. That is 20 living things (abundance) and 5 species (richness).
Worked example

Let's compare two places like a scientist

Place A is a mowed lawn. A survey found 200 grass plants, 3 dandelions and 2 ants. Place B is a wild corner of the same park. A survey found 40 grass plants, 12 goldenrod, 9 milkweed, 15 ants, 4 grasshoppers, 2 bumblebees and 1 garter snake. Which place has more biodiversity?

  1. Count the species in A: grass, dandelion, ant = 3 species. (Here we treat "grass" as one species to keep it simple.)
  2. Count the individuals in A: 200 + 3 + 2 = 205.
  3. Count the species in B: grass, goldenrod, milkweed, ant, grasshopper, bumblebee, garter snake = 7 species.
  4. Count the individuals in B: 40 + 12 + 9 + 15 + 4 + 2 + 1 = 83.
  5. Compare: A has more living things, but B has more than twice as many species. Biodiversity is about variety, not just numbers.

Place B has more biodiversity (7 species compared with 3), even though Place A has more individual living things.

Just for fun

Counting species in a mowed lawn: done before your snack is ready. Counting species in a wild meadow: you might need a snack, lunch and a nap!

Biodiversity is not just animals

Plants, fungi, bacteria and other tiny organisms count too. Some of the most important biodiversity is in the soil, where you can't see it without a microscope.

Technology connection

Some free apps use computer code to compare a photo with a large collection of identified photos and suggest what species it might be. When people share their sightings in citizen science apps, scientists can map where species live and how that changes over time. But apps can be wrong, so treat a suggestion as a guess to check with a field guide or an expert. Also, a grown-up should help decide which apps to use and what location information to share.

Hands-on activity

Mini-bioblitz: survey a square metre

A bioblitz is when people try to find and record as many species as possible in one place.

You need: 4 metres of string, 4 sticks or pegs, a metre stick or measuring tape, a notebook, a pencil and a magnifying glass if you have one.

  1. With a grown-up, choose a spot outside (a lawn, a garden bed, the edge of a park). Measure a 1 m by 1 m square and mark it with sticks and string.
  2. Spend 15 minutes looking carefully: on top of the ground, under leaves, on plant stems.
  3. Make a table: Species (or description), Sketch, How many. If you don't know a name, describe it ("tiny brown beetle with long antennae").
  4. Count your species richness (number of different kinds) and abundance (total number of living things).
  5. If you can, repeat in a second spot (for example, a lawn and a garden bed) and compare.

Safety: a grown-up should be with you. Don't touch plants you can't identify (poison ivy grows in many Ontario parks). Look at animals without picking them up, and put back any log or stone gently, the way you found it. Wash your hands afterward. In tall grass or woods, check for ticks when you come inside.

What to look for: a neat table, honest counts, descriptions or sketches for unknown organisms, and a sentence comparing the two spots.

Your turn

1

What does the word biodiversity mean?

2

Name the three levels of biodiversity.

3

What is the difference between a population and a community?

4

Two dogs of the same breed have different coat colours. Which level of biodiversity does that show?

5

A pond has frogs, cattails, snails, minnows and dragonflies. Which level of biodiversity does that show?

6

Ontario has forests, wetlands, prairies and tundra. Which level of biodiversity does that show?

7

What is species richness?

More practice: warm-up

1

True or false: fungi and bacteria are part of biodiversity.

2

What does bio mean?

3

Is a mushroom an organism?

4

Name two habitats found in Ontario.

5

A survey finds 3 robins, 2 crows and 5 sparrows. How many species? How many birds?

More practice: on your own

1

Place C has 50 living things of 2 species. Place D has 30 living things of 9 species. Which has more biodiversity? Explain.

2

Explain the difference between a community and an ecosystem.

3

Why might a farm field of only corn have lower species diversity than a hedgerow beside it?

4

Give an example of diversity within the human species.

5

Why is it useful to sketch or describe an organism you can't name?

Challenge

1

Two students survey the same park. One finds 12 species, the other finds 5. Give two reasons their results might differ, and one way to make the surveys fairer.

2

Why do scientists say biodiversity includes three levels, not just "the number of species"? Give an example of something that would be missed by counting species only.

3

A wetland is drained and turned into a field of grass. Describe how this changes biodiversity at all three levels.

Check your understanding

Quiz

1.

Biodiversity means...

2.

All the members of one species living in the same area make up a...

3.

Which example shows diversity within a species?

4.

Place X has 8 species. Place Y has 3 species. Both have 60 living things. Which has higher species richness?

5.

Which of these is part of an ecosystem but not part of a community?

6.

A grown-up should be with you on a bioblitz partly because...

For parents and teachers

Big idea: biodiversity is the variety of life, and scientists look at it at three levels: within a species, among species in a community, and among communities and habitats.

How to help at home:

  • Do the mini-bioblitz together. Count everything, including tiny insects, mosses and fungi. Comparing a mowed lawn with a garden or wild corner shows the idea clearly.
  • On walks, ask: "Which level of biodiversity are we seeing?" (Different-looking dogs of one breed = within a species; a pond full of creatures = among species; a trip that crosses forest and wetland = among habitats.)
  • If you have a phone, free identification apps and field guides from the library can help name species. Treat app suggestions as guesses to check.

Safety: stay with your child outdoors, learn to recognize poison ivy ("leaves of three"), and do a tick check after time in tall grass or woods.

Common difficulties:

  • Thinking biodiversity means "lots of animals". It means variety, and it includes plants, fungi and microorganisms.
  • Mixing up population (one species) and community (many species).