In 1735, Carl von Linne, also known as Linneaus, a Swedish botanist, developed a system of organizing and classifying every living thing on earth. This system is still used today. Von Linne’s original system only had two kingdoms. With the invention of microscopes, scientists discovered new forms of life that they couldn’t see before, expanding the Linneaus system into six kingdoms.
Forms of life are classified by how many cells they have, whether the cells are simple or complex, and how they eat. A species is a specific type of animal, such as humans, bears or lions. Closely related life forms are grouped into families. Families are grouped into orders, then classes, phyla and kingdoms.
- Bacteria: Microscopic, single-celled organisms that thrive in wet places, but can grow anywhere. Most bacteria, such as those in yogurt, are helpful, but some can cause illness. Some bacteria can be viewed without a microscope. 36,000 known species.
- Archaea: Like bacteria, archaea are microscopic, simple-celled organisms. Unlike bacteria, they can survive in very hostile environments, including acid and boiling water.
- Fungi: Fungi grow on land, often in damp places. They may be microscopic or huge. A honey fungus in Oregon covers more than 3.5 miles of forest land. Fungi feed on dead plants and other organic matter. The most common type of fungi is mushrooms. Yeasts are also fungi. 100,000 known species.
- Protist: Protists always live in the water. Most are single-celled organisms, but some are multicellular. Some protists use sunlight to make food, while others are more like animals. Protists range in size from microscopic to 150 feet. Seaweed and phytoplankton are both types of protists. 115,000 known species.
- Plant: Plants almost always use the energy of the sun to make food. Plants include ferns, mosses, grasses, flowers, fruiting plants and trees. They range in size from ¼ inch to 280 feet or more. They can live on both the land and water. 310,000 known species.
- Animal: Animals are the most complex of any living thing. They cannot make food from sunlight, but must eat other living things. Animals may live on land or water. Most have ways to get around, including legs, fins or wings. Invertebrates don’t have backbones and include worms, snails, insects, jellyfish, clams, crabs and sea urchins. Vertebrates are animals with backbones and internal skeletons. This group includes mammals, fish, reptiles, amphibians and birds. 1,367,555 known species.
- Botanist: plant scientist
- Hostile: unfriendly, harsh
- Invertebrate: an animal without a backbone
Visit Scholastic to see a video about the kingdoms of life.
Question: How are viruses classified?
Answer: Viruses don’t fall into any of the kingdoms. They are lifeless until they enter a host’s body.