Biomes | ASU - Ask A Biologist

To make sense of complexity, human beings often have to sort, or group things together. We have food groups, sexes, eye color, ages and movie genres, to name a few. This makes it easier for us to talk about the things we encounter. But sometimes, the way a group of things should be divided becomes a bit confusing.

Let's think about dogs, for example. We can describe dogs as a large group of four-legged hairy friends with claws. Or we can divide them into groups by size: large, medium and small dogs. We can also divide them by race, like Labrador, Poodle, or Great Dane. Within a race, they can be further divided by color.

What is a biome?

The same thing can happen when talking about natural environment. The natural world is more varied than we can imagine, and the separation of similar groups can help us better define what we see. This makes it a little easier to try to understand the world around us and look for important patterns.

We can divide our environment in many ways - by how much water there is, by how hot it is or by the types of plants or animals found there. Depending on the characters we choose to describe an environment, the groups we just selected may be different.

We usually group the different natural spaces of the Earth into categories based on plant and animal life and the way they are able to survive in that part of the world. Divide by living organisms is very complicated. We already know more than 1.2 million species of organisms, and there are probably more than 7 million species. But again, by grouping organisms that share similar adaptations, we can see some of the complexity and have the opportunity to better understand the living Earth.

Biome vs. Biome

Categories of Biomes can be broad or narrow. When we say "forest", it is possible to imagine a quiet and cool area of ​​pines, and where bears, grouse and rabbits walk. Or, on the contrary, you can imagine a humid, dark and noisy tropical forest, where you can see monkeys, parrots, and big cats.

According to some people, all types of forests belong to a group - the forest biome. But others think that the temperate forests (cold seasonal) with pine trees are very different from the rainforests, with dense and leafy canopy and lots of rain. This difference of opinion means that the number of biomes can range from 5 to 20 biomes.

How different is different?

If we take a closer look close to these temperate forests and the rain, we see that they differ somewhat in the amount of rain they receive and in their temperatures. The rainforests are warm and do not experience a winter season. But temperate forests have a defined winter, with snow and subzero temperatures.

Biomes | ASU - Ask A Biologist
Do these groups seem to be different enough to be classified in a separate biome? Do not worry, there is no right or wrong answer. The natural world is more varied than we can imagine, and the separation of similar groups can help us better define what we see.

With these low temperatures, plants and animals in temperate forests have to have adaptations to cope with low temperatures. Do these groups seem to be different enough to be classified in a separate biome?

Do not worry, there is no right or wrong answer. This method of categorization is one of convenience, and sometimes it just depends on why you are dividing the groups.

Limits of Biomes

You probably imagine a forest like a rainforest, where it is hot all year round. There are too many animals to count and the large number of trees keep their leaves throughout the year. Many of these forests get so much rain that they have virtually no dry season - rather a rainy season and a rainier season. This is the type of forest where there are four relatively distinct seasons. Many of the trees lose their leaves in the fall and become inactive during the cold winter. In these forests, there are deer, grouse and bears, some of which hibernate during the winter.

Deserts constitute the hottest biome, but can reach very cold temperatures in winter. Such changes in temperature make this an extreme environment, where many animals have to hide underground, where there are more stable temperatures, in order to survive. Plants and animals here should be able to withstand long periods of time without water.

The tundra is flat and cold with low plants such as grass and moss growing only during the short summer. A thick layer of ice lies just below the shallow soil (permafrost) throughout the year, and the trees can not penetrate into it to anchor their roots. Many birds visit the tundra in the summer to nest, but most escape from winter by migrating to warmer areas. Mice and other small mammals remain active during the winter in tunnels protected under snow.


Sometimes called plains or pastures, the prairies are almost entirely short and tall grasses, with no trees. This type of soil takes in enough rainwater to help flowers and herbs grow, but is kept dry enough so that fires are frequent and trees can not survive. Here we find large mammals that often travel together in large herds.

These prairies of spiked trees receive enough seasonal rainfall such that they can grow in open groups or separately along the savanna. Animals that live here have long legs to escape from predators and are usually seen in herds. A combination of fire and grazing animals are important for the maintenance of the savanna.

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

This water biome is the largest biome in the world, as it includes the five large oceans that cover 70% of the land. Sea water has high levels of salt, so the animals and plants that live here have adaptations that help them get rid of excess salt or take it to take water.

Facelina and Pam Brophy.