The animal kingdom includes all kind of living things from sponges to humans to spiders to elephants. Most of them can move on their own, but none of them can make their own food the way that plants can, which means they have to eat things! Like plants, fungi, and protists, animals are eukaryotes, meaning that their cells have a nucleus and other membrane-bound organelles.

Major Phyla (groups)	Description	Masks	Approx. # of species
Annelida	These are worms with segmented bodies, including earthworms and leeches. The sandworms (or "polychaetes") with lots of little legs that you might have seen at the beach are annelids, but millipedes and centipedes aren't— they are arthropods.		15,000
Platyhelminthes	These are the "flatworms." Most of them live in the sea, in fresh water, or in damp soil, but others are parasites, living inside other animals. One you might have heard of is the tapeworm, which lives inside the digestive tracts of humans and other animals. Tapeworms can grow up to 10 metres long inside their hosts!		20,000
Arthropoda	This is the largest phylum of animals, which includes insects, spiders, crabs, lobsters, scorpions, and lots of other creepy-crawlies. Over 80% of known animal species are arthropods!		1,000,000+
Brachiopoda	These creatures, sometimes called the lamp-shells, live underwater and look a bit like clams, although they're not closely related to the molluscs. About 99% of known brachiopod species are extinct, so there are a lot more brachipod fossils around than living ones.		300
Chordata	This phylum is the one that includes humans! Most chordates are vertebrates— things with backbones, from fish to amphibians and reptiles to mammals like us. The phylum's definition actually has to do with having a thing called a notochord down our backs when we're still embryos. That's why there are a couple of invertebrates in here with us, like the "sea squirts," squidgy things that you might find stuck under a dock. They've got notochords too, but no backbone.		60,000
Chaetognatha	Also called the "arrow worms," these ferocious predatory worms live in the sea, stalking their prey with grasping pincers and sometimes even deadly neurotoxin poison. Luckily, they're usually only about three milimetres long.		120
Nematomorpha	These are the "horsehair worms" or "Gordian worms." The adults live in damp areas and are about a metre long, but their young (larvae) are parasites inside arthropods like cockroaches, beetles, and crabs. One species which lives in grasshoppers affects its host's brain so that it hops into water and drowns itself when the worm is ready to leave!		320
Gastrotricha	These little fellows are microscopic and live in both marine and freshwater environments. When they want to stick to something, glands in their body squirt out a kind of natural "glue" which holds them firmly to whatever it is. When they're ready to un-stick, another gland secretes a substance which dissolves the glue and away they go!		100
Ctenophora	Another aquatic phylum, you might mistake a ctenophore, or "comb jelly," for a jellyfish if you saw it floating in the sea. Unlike the cnidarians, though, they don't sting.		100
Mollusca	Most molluscs, like clams, mussels, octopi, and squid, live in the water. There are a couple of types that live on land, though, and you might have seen them in your garden: snails and slugs!		112,000
Hemichordata	This phylum is made up of marine worms, including the "Acorn Worms." They were once thought to have a notochord, and were classed with the Chordates which is why they've got "chordata" in their name.		100
Sipuncula	These are the "peanut worms," which mostly live in shallow marine environments. They live in burrows in sand or rock, and stick their tentacle-surrounded mouths into the water to feed. When threatened, they can retract their mouth and tentacles, so that their shape resembles the shell of a peanut.		300
Bryozoa	These are tiny creatures which live in freshwater and saltwater. Thousands of them living together form colonies, ranging from a few millimetres to several metres across, a bit like the corals of phylum Cnidaria. Most of them are protected by skeletons of calcium carbonate, which grow in all kinds of shapes.		5,000
Nematoda	You might not have heard of nematodes, or "round worms," but they're all over the place! They're found in the water and on land— from the poles to the equator. A lot of them live inside other organisms as parasites. Most are tiny, but one nematode found inside a sperm whale measured 8.5 metres long, though less than a millimetre in diameter!		80,000
Porifera	The porifera, or sponges, are the simplest types of animals. They have no internal organs, muscles, or nerves, and they are completely sessile— they don't move. They live underwater, and the natural sponges we sometimes use in the bath are their skeletons, with the animal's soft parts removed.		5,000
Echinodermata	This phylum includes starfish, sea urchins, and sea cucumbers. All of them live in marine (saltwater) environments.		7,000
Acanthocephala	These are parasitic worms covered in spines which live in the gut of other animals. Gross!		1,500
Rotifera	Rotifers are mostly microscopic; the biggest ones are just barely visible to the naked eye. Their name comes from the Latin for "wheel-bearer," because of the wheel-like tufts which they use to sweep food into their mouths.		2,000
Tardigrada	"Water bears" aren't really bears at all, of course. They look a bit like some kind of alien bear with eight legs and pincers, but you'd need a microscope to see them properly. They're famous for their ability to withstand extreme environments that would kill most living things; they can survive at temperatures as low as -270°C or as high as 151°C, and are found at the top of the Himalayas and in the deepest parts of the ocean.		900
Nemertea	There sure are a lot of different kinds of worms! This phylum includes the "ribbon worms," most of which live on or under the sea floor. They vary in size a lot— they can be as short as three millimetres, or as long as 50 metres, longer than a blue whale!		1,400
Cnidaria	All of these live in the water, and you're probably familiar with them. They include jellyfish, sea anemones, and corals. They all have tentacles with stinging cells called "cnidocytes," but some of them are mild enough that we can't even feel them.		11,000