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Written by: Karla Moeller

Illustrated by: Sabine Deviche

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What's a Biome?

Here we see two different biomes—

deserts on the left and grasslands on
the right. But both are land
environments. Images by Bob Protus
and Bkell.

To make sense of complexity, humans often need to

categorize, or group, things. We have food groups,
sexes, eye colors, ages, and movie genres, to name a
few. We categorize all types of things, whether they are
ideas or objects, and whether they are small or large.
One of the largest things that we try to categorize may
be the types of environments found on Earth.

The natural world is more varied than we can imagine,

and one way to try to make this variation easier to
handle is to put different environment types into
groups. We can divide our surroundings many ways—
by how much water there is, by how warm it is, or by
the types of plants or animals we find there.
Depending on what characteristics we choose to
describe an environment, the groupings we end up
selecting may be different.

Usually we group the different natural areas on Earth

into categories based on plant and animal life and how
they are able to survive in that part of the world.
Making groups based on living organisms can be very
complicated. We already know of over 1.7 million
species of organism, and there are likely over 17
million that exist. But again, by grouping organisms
with similar adaptations together, we can see through
some of the complexity and have a chance to better
understand the living Earth.

This biome map shows both land (terrestrial) and water

(aquatic) based habitat types. Click for more detail.

A biome is a type of environment that is defined by the

types of organisms that live there. We can also think of
these as life zones ("bio" means life). Dividing land up
in this way lets us talk about areas that are similar,
even if they’re on different continents. But depending
on whom you talk to, the way we divide up the world
into separate biomes differs.

Biome vs. Biome

Biome categories can be broad or narrow. When we
say forest, you may picture a cool, quiet area with pine
trees, where bears, deer, and rabbits wander around.
Or instead, you might imagine a wet, dark, and noisy
rainforest, where you can see monkeys, parrots, and
big cats.

These are all types of forests, but some people split them
into different forest-type biomes. Click to see more detail.

According to some people, all forest types belong in

one group – the forest biome. But others think that
temperate forests (seasonally cold) with pine trees, are
very different from tropical rainforests, with dense,
leafy canopy and lots of rain. This difference of opinion
means that the number of biomes can range
anywhere from 5 to 20 biomes.

How Different is Different?

Temperate forests get a winter season,

often with snow. Tropical rain forests
are too warm to get snow. Image by
Böhringer.

If we take a closer look at these temperate and rain

forests, we see that they differ quite a bit in the
amount of rain they get and in their temperatures.
Tropical rainforests are warm and don't experience a
winter season. But temperate forests have a defined
winter, with snow and temperatures below zero.

With those cold temperatures, the plants and animals

in temperate rainforests have to have adaptations to
deal with cold weather. Do those groups seem
different enough to you to be in a separate biome?

Don't worry, there is no right or wrong answer. This

method of categorizing is one of convenience, and
sometimes it just depends on why you're dividing the
groups.

Biomes of the World

In order to give you a small taste of the huge diversity
of the types of environments out there, we divide the
world up into only nine biomes. Just remember that
these groups could also be divided into nearly 20
biomes. That means that within each of these biomes
there is a range of temperature and weather
conditions, and we also find some organisms that are
adapted to only part of the biome and others that are
adapted to the full range of conditions within the
boundaries we are defining.

Tropical Rainforest

Tropical rainforest. Image by

WorldWideHappyMedia

You probably picture tropical rainforest as a jungle,

where it stays warm all year. There are too many
animals to count and the huge numbers of trees keep
their leaves year-round. Many of these forests get so
much rain that there isn't even much of a dry season –
more like a rainy season and a rainier season.

Temperate Forest

Temperate forest. Image by Umberto

Salvagnin.

This is the kind of forest where there are four relatively

distinct seasons. Many of the trees shed their leaves in
the fall and become inactive through the cold winter. In
these forests, you find deer, woodpeckers, and bears,
some of which hibernate through the winter.

Desert

A desert with sand dunes. Image by

Jon Sullivan.

Deserts make up the hottest biome, but can also get

cold temperatures in winter. Such temperature swings
make this an extreme environment, where many
animals have to burrow underground to find more
stable temperatures in order to survive. Plants and
animals here must be able to withstand long periods
without water.

Tundra

Tundra in Greenland. Image by Hannes

Grobe.

Tundra is flat and cold with low plants like grass and
moss that only grow during the short summer. A thick
layer of ice lies just below the shallow soil (permafrost)
all year around, and trees cannot penetrate it to anchor
their roots. Many birds visit the tundra in the summer
to nest, but most escape the winter by migrating to
warmer areas. Mice and other small mammals stay
active during the winter in protected tunnels under the
snow.

Taiga (Boreal Forest)

Boreal forest of Alaska. Image by L.B.

Brubaker.

Taiga is the largest land (terrestrial) biome in the

world. It is made up of mainly conical-shaped
evergreen trees with needle-like leaves. These trees
are called conifers because their seeds are clumped
into cones. The taiga has long, cold winters when
most mammals hibernate and birds migrate, or leave
the area because the winters are too cold for them to
stay. Animals like weasels, grouse and rabbits that do
not migrate or hibernate grow dense feathers or fur
and turn white to match the snow.

Grassland

Grasslands. Image by Tony Hisgett

Sometimes called plains or prairie, grasslands are

almost entirely short to tall grasses with no trees. This
land type gets just enough rain to help grasses,
flowers, and herbs grow, but stays dry enough that
fires are frequent and trees cannot survive. Here we
find large mammals that often travel together in huge
herds.

Savanna

Savanna in Tanzania. Image by Nevit

Dilmen.

These tree-studded grasslands receive enough

seasonal rainfall so that trees can grow in open groups
or singly throughout. The animals living here have long
legs for escaping predators and usually are seen in
herds. A combination of fire and grazing animals are
important for maintaining the savannah.

Freshwater

Lakes are usually freshwater, like this

lake in Pakistan. Image by Joonasl.

This water biome is named for the low concentration

of salt found in the water. This includes most ponds,
streams, lakes, and rivers. Because salt is important to
body function, the plants and animals here have many
adaptations that help them save salt.

Marine

Marine environments have salt water,

like this tidepool in Portugal. Image by
Alvesgaspar.

This water biome is the largest biome in the world, as

it includes the five major oceans that cover 70% of the
Earth. Marine water has high levels of salt, so animals
and plants living here have adaptations that help them
get rid of salt or take on water.

Virtual Biomes

Virtually visit some of the biomes

without having to travel.

Take a virtual look inside some of these biomes using

a computer, smart phone, tablet, or Google Goggles.
Our first two virtual biomes are the desert and
rainforest. Compare how the two are different and how
they are the similar. Write up your results in our
biologist notebook.

Additional images from Wikimedia via Adrien Facélina

and Pam Brophy.

View Citation

There are parks in some countries where huge

domes are used to make mini versions of biomes
that visitors can explore.
Explore Biomes:

Tropical Rainforest

Temperate Forest

Desert

Tundra

Taiga

Grassland

Savanna

Freshwater

Marine

Boundless Biomes
Virtual Biomes

Biomes Teacher Guide

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Try our Virtual Biomes

Biome Bits

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Coloring Pages
and Worksheets

 Biome Map Worksheet

 Biome Matching Game Worksheet

All Worksheets

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