Sorting Life

Why sort life at all?

Earth is packed with living things - oak trees, jellyfish, bacteria, mushrooms, and you. Scientists have named well over a million kinds of life, and they keep finding more. To make sense of this huge crowd, they sort living things into groups. The science of naming and grouping life is called taxonomy (say it: tax-ON-oh-mee).

Sorting is not just tidying up. When we put living things into groups, we can see how they are related, how they work, and how they came to be over millions of years.

Kingdoms: the big boxes

One of the biggest sorting boxes is called a kingdom. For a long time, students learned about a handful of kingdoms, including:

• Animalia - the animals, like foxes, fish, and insects

• Plantae - the plants, like grass, ferns, and trees

• Fungi - mushrooms, molds, and yeasts

• Protista - tiny, mostly single-celled life, like amoebas

• Two kingdoms of bacteria and other microbes

Notice that fungi get a kingdom all to themselves. They are not a strange kind of plant and not a strange kind of animal. They are their own great branch of life. That is why this course is called The Fifth Kingdom.

Domains: even bigger boxes

Modern scientists added an even larger box above kingdoms, called a domain. There are three domains:

• Bacteria - familiar tiny microbes

• Archaea (say it: ar-KEE-uh) - microbes that often live in extreme places

• Eukarya (say it: yoo-KAIR-ee-uh) - all living things whose cells have a nucleus, a control center that holds the cell's DNA

Plants, animals, and fungi all belong to Eukarya. So do you. Inside that domain, each of these groups still gets its own kingdom.

What clues do scientists use?

How do scientists decide which box a living thing belongs in? They look for clues:

• Cell structure - what the cells are built from and how they are shaped

• How it gets food - does it make its own food or take food in?

• How it reproduces - how it makes more of itself

• DNA - the chemical code inside every cell, which reveals family ties

DNA is a powerful clue. Two living things can look alike on the outside but have very different DNA, or look different yet be close cousins. In the next lessons, we will use these same clues to test the fungi and see exactly why they earned a kingdom of their own.

Safety first: this course is about understanding fungi, not gathering them. Never pick or eat a wild mushroom. Even experts use careful tools and study, and some wild fungi are dangerous. Learning kits use known-safe kinds only.