This illustration of the three domains of life is like a family tree. The branches that are very far apart are not very similar. Branches that are near each other indicate closely related groups.
Click on image for full size
Windows to the Universe original image
Classification of Living Things
Scientists have found and described almost two million species on Earth. Plus,
new species are being discovered every day. That's a lot of species! How
do we make sense of it all?
Scientists put similar species into groups so that those millions of species
do not seem so overwhelming. If you know what the groups are like, you can figure
out what different species are like. For instance, let's say that a friend
of yours tells you that he saw an egret last weekend. You have never heard of
an egret before, but if he tells you that an egret is a type of bird, you should
have some idea of what it is like.
Living things are divided into three large groups:
These three groups are called domains. The drawing at the left shows the three
domains of life. The distance between groups indicates how closely related they
are. Groups that are close together, like plants and animals, are much more
closely related than groups that are far apart, like plants and bacteria!
The Eukaryota domain is divided into several groups called kingdoms.
Shop Windows to the Universe Science Store!
"
Science, Evolution, and Creationism", by the National Academies, provides fascinating background on these topics for all, and is particularly useful for the Earth and space science classroom. Check our other
books in our
online store.
You might also be interested in:
Each Eubacteria is a tiny prokaryotic cell. Some can make food from sunlight through photosynthesis. Cyanobacteria, also called blue-green algae, are able to do this. They have been living in the oceans
...more
Members of the Kingdom Protista are an unusual group of organisms that were put together because they don't really seem to belong to any other group. Some protists look or act like plants, others look
...more
Kingdom Plantae has almost 300,000 different kinds of plants. Plants are found all over planet Earth. They can live in fields, in swamps, in oceans and in the desert. They can live where it is hot and
...more
There are many different kinds of plants. Some have big leaves. Some have small leaves. Some even have flowers. All plants make their own food. When sunlight hits the leaves of a plant, photosynthesis
...more
Biomes are large areas of the world where there are similar plants, animals, and other living things. The living things are adapted to the climate. Explore the links below to learn more about different
...more
You may have heard of photosynthesis. That's where a plant uses energy from the Sun's rays to make its own food. The opposite of photosynthesis is called respiration. The difference is that respiration
...more
Scientists are interesting in knowing how many species can fit on the Earth. The number of species is called diversity. If there are a lot of species, then diversity is high. If there are few species,
...more
