About Classification - An Overview

To help understand living things, scientists break them down into groups by their traits. This is called, biological classification. Presently, there are 8 levels of groups:

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

The 3 Domains are the highest level of classification to date. They include all known living things on Earth:

Archaea, Eubacteria, Eukaryota

The Eubacteria Domain is made up of bacteria, single-celled living things, also called microorganisms. They have no cell nucleus or organelles. They are prokaryotes. Bacteria is found everywhere on Earth from the soil to inside our bodies. They cause many human illnesses, but are also vital to life on Earth. The study of microorganisms is called microbiology.

The Archaea Domain also has single-celled microorganisms (prokaryotes), however, archeons can survive extreme conditions, like scalding hotsprings and very salty areas. A relatively recent discovery, they are still being studied and updated.

The Eukaryota Domain has more complex organisms with cells that have a nucleus and organelles. They are eukaryotes. This domain is, at present, broken down into 4 Kingdoms:

Protista, Fungi, Plantae, Animalia

The Protista Kingdom is a diverse group, including plant-like algae, animal-like protozoans and fungi-like slime molds. 

The Fungi Kingdom has mushrooms, yeasts, and molds. Important detrivores, they break down dead organisms and recycle nutrients back into the environment. They cause problems when they invade an organism as a fungal infection, like athlete’s foot, but are extremely important to humans, as the source of penicillin, which kills bacteria, and yeast, which drives fermentation and rising bread.

The Plant Kingdom includes trees, shrubs, flowers, grasses, ferns, and mosses. Essential to all life on Earth, plants make their own food, using sunlight through the process of photosynthesis, which feeds all animal life, including us. Plants also absorb carbon dioxide and give off life-giving oxygen.

The Animalia Kingdom includes 9 groups or Phyla (plural of phylum): Annelida (Segmented Worms), Nematoda (Round Worms), Platyhelminthes (Flat Worms), Arthropoda (Insects, Spiders, Scorpions, Lobsters, Crabs, Centipedes, etc.), Porifera (Sponges), Cnidaria (Coral, Jellyfish, Anemones, etc.), Echinodermata (Starfish, Sea Urchins, Sand Dollars, etc.), Mollusca (Snails, Slugs, Clams, Mussels, Squid, Octopuses, etc.), Chordata (Mammals, Birds, Reptiles, Fish, Amphibians, Shark, Rays, etc.)