Phylum facts for kids

Kids Encyclopedia Facts

In biology, a phylum is a major group used to classify living things. It's like a big folder where scientists put organisms that share a basic body plan or are closely related through evolution. A phylum is a step in the classification system, coming after kingdom and before class.

For example, the animal kingdom, Animalia, has about 31 phyla. The plant kingdom, Plantae, has about 14 phyla, and the fungus kingdom, Fungi, has around 8 phyla. Scientists are always learning more about how these groups are related, especially through studying their evolutionary history.

What is a Phylum?
- Grouping by Shared Ancestry
- Grouping by Body Plan
Animal Phyla
Plant Phyla
Fungi Phyla
Protista Phyla
Bacteria Phyla
Archaea Phyla
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What is a Phylum?

The word "phylum" was created in 1866 by a scientist named Ernst Haeckel. It comes from a Greek word, phylon, which means "race" or "stock." Haeckel thought of a phylum as a group of all species that have slowly developed from one common original form. Think of it like a family tree where all the branches from a certain ancestor are part of the same phylum.

In simple terms, phyla are groups of organisms that have a similar general body design. For example, all animals in the Chordata phylum (like us!) have a backbone or a similar rod-like structure at some point in their lives.

Grouping by Shared Ancestry

One way to define a phylum is by how closely organisms are related through their evolutionary history. The main idea is that all organisms in a phylum should be more closely related to each other than to any other group.

However, this can be tricky! As scientists get more information, especially from studying DNA, they learn more about these relationships. This means phyla can sometimes be combined or split apart.

For instance, the "bearded worms" were once thought to be their own phylum. But later, DNA studies showed they were actually a type of annelid worm. So, they were moved into the Annelida phylum. On the other hand, a phylum called Mesozoa was split into two new phyla when scientists found out their members were not as closely related as once thought.

Because of these changes, some biologists think we should just group organisms into "clades" (groups with a common ancestor) without giving them formal ranks like "phylum."

Grouping by Body Plan

Another way to define a phylum is based on its "body plan." This idea was suggested by paleontologists (scientists who study fossils) Graham Budd and Sören Jensen. It's especially helpful for classifying extinct organisms, which are harder to study.

By this definition, a phylum is identified by a set of features that all its living members share. This approach makes it easier to classify fossils, as you can see which phylum they most resemble based on their body features. However, it relies on deciding which groups should be considered phyla, which can be a bit subjective.

Animal Phyla

The animal kingdom has many different phyla. The exact number can vary depending on how scientists count them, especially since some species haven't been discovered yet! For example, there are about 25,000 to 27,000 known types of nematodes (roundworms), but some guess there could be millions more.

Here are some of the main animal phyla:

Phylum	Meaning	Common name	Key Features	Known Species
Acanthocephala	Thorn head	Thorny-headed worms	Worm with a spiky snout	1,420
Annelida	Little ring	Segmented worms	Many circular body segments	22,000+ living
Agmata	Fragmented	Agmates	Cone-shaped shells made of calcium	5 species, extinct
Archaeocyatha	Ancient cups	Archaeocyathids	Extinct sponge-like reef builders from the Early Cambrian period	3 known classes (Extinct)
Arthropoda	Jointed foot	Arthropods	Segmented bodies, jointed legs, hard outer shell (exoskeleton)	1,250,000+ living; 20,000+ extinct
Brachiopoda	Arm foot	Lampshells	Special feeding organ (lophophore) and a stalk (pedicle)	300–500 living; 12,000+ extinct
Bryozoa (Ectoprocta)	Moss animals	Moss animals, sea mats	Lophophore, no pedicle, tiny hair-like tentacles	6,000 living
Chaetognatha	Longhair jaw	Arrow worms	Spines on head, fins	About 100 living
Chordata	With a cord	Chordates	Hollow nerve cord, notochord (rod-like support), gill slits, tail	About 55,000+
Cnidaria	Stinging nettle	Cnidarians	Stinging cells (nematocysts)	About 16,000
Ctenophora	Comb bearer	Comb jellies	Eight "comb rows" of fused cilia	About 100–150 living
Cycliophora	Wheel carrying	Symbion	Circular mouth with tiny hairs, sac-like body	3+
Echinodermata	Spiny skin	Echinoderms	Five-part radial symmetry, spiny skin	About 7,500 living; about 13,000 extinct
Entoprocta		Goblet worms		About 150
Gastrotricha	Hairy stomach	Gastrotrich worms	Two sticky tubes at the end of the body	About 690
Gnathostomulida	Jaw orifice	Jaw worms	Tiny worms with no body cavity, related to rotifers	About 100
Hemichordata	Half cord	Acorn worms	Stomochord (rod-like structure) in collar, gill slits	About 130 living
Kinorhyncha	Motion snout	Mud dragons	Eleven body segments, each with a top plate	About 150
Loricifera	Armour bearer	Brush heads	Umbrella-like scales at each end	About 122
Micrognathozoa	Tiny jaw animals	None	Body can stretch like an accordion	1
Mollusca	Soft	Mollusks / molluscs	Muscular foot, mantle (tissue that forms a shell)	85,000+ living; 80,000+ extinct
Monoblastozoa		None	Distinct front and back, covered in tiny hairs	1
Nematoda	Thread like	Round worms, thread worms	Round body shape, tough outer layer (cuticle)	25,000
Nematomorpha	Thread form	Horsehair worms, Gordian worms	Long, thin parasitic worms, similar to nematodes	About 320
Nemertea	A sea nymph	Ribbon worms	Unsegmented worms with a proboscis (tube-like organ)	About 1,200
Onychophora	Claw bearer	Velvet worms	Worm-like body with legs ending in claws	About 200 living
Orthonectida		Orthonectid	Tiny, simple, parasitic worms	20
Petalonamae	Shaped like leaves	None	Extinct, leaf-shaped, bottom-dwelling organisms from the Ediacaran period	3 classes, extinct
Phoronida	Zeus's mistress	Horseshoe worms	U-shaped gut	11
Placozoa	Plate animals	Trichoplaxes	Flat body with distinct top and bottom, two layers of ciliated cells	4+
Platyhelminthes	Flat worm	Flatworms	Flattened body, no body cavity. Many are parasites.	About 29,500
Porifera	Pore bearer	Sponges	Body full of holes, simplest animals	10,800 living
Priapulida	Little Priapus	Worms		About 20
Proarticulata	Before articulates	Proarticulates	Extinct, mattress-like organisms with "glide symmetry" from the Ediacaran period	3 classes, extinct
Rhombozoa (Dicyemida)	Lozenge animal	Rhombozoans	Single-celled parasites with a central axis, surrounded by ciliated cells	100+
Rotifera	Wheel bearer	Rotifers	Crown of cilia (tiny hairs) at the front	About 2,000
Saccorhytida	Pocket and wrinkle	None	Tiny (1mm) spherical body with a large mouth, thick but flexible skin, 8 openings around the body. Extinct.	2 species, extinct
Tardigrada	Slow step	Water bears, moss piglets	Microscopic, four-segmented body and head, relatives of arthropods	1,000
Trilobozoa	Three-lobed animal	Trilobozoan	Extinct, mostly disc-shaped organisms with three-part symmetry from the Ediacaran period	18 genera, extinct
Vetulicolia	Ancient dweller	Vetulicolian	Two-part body: large front with a mouth and gill-like openings, segmented back part. Extinct.	15 species, extinct
Xenacoelomorpha	Strange hollow form	Subphylum Acoelomorpha and xenoturbellida	Small, simple animals lacking typical bilateral structures like gut cavities	400+

Plant Phyla

The plant kingdom also has different ways of being defined. All definitions include land plants (embryophytes). Some also include green algae. The table below shows a common way plants are grouped into divisions (which are like phyla for plants).

The way plants are classified can change as scientists learn more. For example, some sources put horsetails and ferns in different divisions, while others put them together.

Division	Meaning	Common name	Key Features	Known Species
Anthocerotophyta	Anthoceros-like plants	Hornworts	Horn-shaped spore-producing parts, no water-carrying system	100-300+
Bryophyta	Bryum-like plants	Mosses	Spore-producing parts that stay attached, no water-carrying system	About 12,000
Charophyta	Chara-like plants	Charophytes		About 1,000
Chlorophyta	Green plants	Chlorophytes		About 7,000
Cycadophyta	Cycas-like plants	Cycads	Seeds, crown of large leaves	About 100-200
Ginkgophyta	Ginkgo-like plants	Ginkgo, maidenhair tree	Seeds not inside a fruit (only one living species)	Only 1 living; 50+ extinct
Glaucophyta	Blue-green plants	Glaucophytes		15
Gnetophyta	Gnetum-like plants	Gnetophytes	Seeds and woody water-carrying system with vessels	About 70
Lycopodiophyta, Lycophyta	Lycopodium-like plants Wolf plants	Clubmosses & spikemosses	Small leaves, water-carrying system	1,290 living
Magnoliophyta	Magnolia-like plants	Flowering plants, angiosperms	Flowers and fruit, water-carrying system with vessels	300,000
Marchantiophyta, Hepatophyta	Marchantia-like plants Liver plants	Liverworts	Spore-producing parts that don't last long, no water-carrying system	About 9,000
Polypodiophyta, Monilophyta	Polypodium-like plants	Ferns	Large leaves, water-carrying system	About 10,560
Picozoa	Extremely small animals	Picozoans, picobiliphytes, biliphytes		1
Pinophyta, Coniferophyta	Pinus-like plants Cone-bearing plant	Conifers	Cones with seeds, wood made of tracheids	629 living
Prasinodermophyta	Prasinoderma-like plants	Picozoans, picobiliphytes, biliphytes		8
Rhodophyta	Rose plants	Red algae	Use special pigments for color	About 7,000

Fungi Phyla

The kingdom Fungi includes many different types of organisms, from mushrooms to molds. Here are some of their main divisions (phyla):

Division	Meaning	Common name	Key Features	Known Species
Ascomycota	Bladder fungus	Ascomycetes, sac fungi	Often have cup-shaped fruiting bodies. Can reproduce without a partner.	30,000
Basidiomycota	Small base fungus	Basidiomycetes, club fungi	Includes bracket fungi, toadstools, smuts, and rusts. Reproduce with a partner.	31,515
Blastocladiomycota	Offshoot branch fungus	Blastoclads		Less than 200
Chytridiomycota	Little cooking pot fungus	Chytrids	Mostly live in water, either feeding on dead matter or as parasites. Have a whip-like tail.	1,000+
Glomeromycota	Ball of yarn fungus	Glomeromycetes, AM fungi	Mostly form special connections with plant roots. Reproduce without a partner but need plant roots.	284
Microsporidia	Small seeds	Microsporans		1,400
Neocallimastigomycota	New beautiful whip fungus	Neocallimastigomycetes	Mostly found in the guts of plant-eating animals.	About 20
Zygomycota	Pair fungus	Zygomycetes	Most feed on dead matter and can reproduce both with and without a partner.	About 1,060

The phylum Microsporidia is usually part of Fungi, but its exact place is still being studied. Also, scientists are thinking about splitting the Zygomycota phylum into several new groups because its members aren't as closely related as once thought.

Protista Phyla

The kingdom Protista is a very diverse group. It includes all eukaryotes (organisms with complex cells) that are not plants, animals, or fungi. Because it's such a mixed group, scientists are still working on the best way to classify them. Many of the phyla listed below are used by different scientific groups.

Phylum	Meaning	Common name	Key Features	Known Species	Image
Amoebozoa	Amorphous animals	Amoebozoans	Move using "false feet" (pseudopodia)	About 2,400	Amoeba proteus
Apicomplexa	Apical infolds	Apicomplexans, sporozoans	Mostly parasites, have a special structure to invade host cells	Over 6,000	Toxoplasma gondii
Apusozoa	Apusomonas-like animals		Glide using two or three whip-like tails (flagella)	32	Podomonas kaiyoae
Bigyra	Two rings		Have a double helix in their whip-like tail's connection zone		Aplanonet3
Cercozoa	Flagellated animal	Cercozoans	Identified by DNA, don't have very clear physical features		Euglypha sp.
Chromerida	Chromera-like organisms	Chrompodellids, chromerids	Two whip-like tails, chloroplasts with four membranes	8	Vitrella brassicaformis
Choanozoa	Funnel animals	Opisthokont protists	Have thread-like false feet; some have a collar of tiny hairs around a whip-like tail	About 300	Desmarella moniliformis
Ciliophora	Cilia bearers	Ciliates	Have many tiny hairs (cilia) and a "mouth"	About 4,500	Paramecium bursaria
Cryptista	Hidden		Identified by DNA, have flat structures inside their cells	246	Rhodomonas salina
Dinoflagellata	Whirling flagellates	Dinoflagellates	Two whip-like tails, one wraps around the cell, the other points backward	2,957 living; 955 fossil	Dinoflagellate
Endomyxa	Within mucus		Identified by DNA, often parasites inside other eukaryotes		Vampyrella lateritia
Eolouka	Early groove		Two whip-like tails, with a groove on their underside for feeding	23	Stygiella incarcerata
Euglenozoa	True eye animals		Two whip-like tails, one in a special pocket, unique tail structure	2,037 living; 20 fossil	Euglenoid movement
Ochrophyta, Heterokontophyta	Ochre plants	Heterokont algae	Two whip-like tails, chloroplasts with four membranes and chlorophyll a and c	21,052 living; 2,262 fossil	Diatoms
Haptista	Fasten		Thin, microtubule-based feeding arms, complex mineral scales	517 living; 1,205 fossil	Coccolithus pelagicus
Hemimastigophora	Atypical flagellates	Hemimastigotes	Oval or worm-like, two rows of cilia, plates under the membrane	10	Hemimastix amphikineta
Malawimonada	Malawimonas-like organisms	Malawimonads	Small, free-living, two whip-like tails, one or two vanes on the back tail	3	Malawimonasms
Metamonada	Middle monads	Metamonads	Live without oxygen, some have no mitochondria; four whip-like tails per unit		Giardia muris trophozoite
Opisthosporidia	Spores with a tail		Parasites with tough spores and a way to invade host cells		Fibrillanosema spore
Percolozoa	Percolomonas-like animals		Complex life cycle with amoebae, flagellates, and cysts		Naegleria fowleri lifecycle stages
Perkinsozoa	Perkinsus-like animals	Perkinsozoans	Parasitic, two whip-like tails, can form spore-like structures	26	Dinovorax pyriformis
Provora	Devouring protists		Identified by DNA, free-living, eat other eukaryotes, two whip-like tails	7	Ubysseya fretuma
Pseudofungi	False fungi		Identified by DNA, eat by engulfing food, have a spiral structure in their whip-like tail's connection zone	Over 1,200	Phytophthora cactorum
Retaria	Organisms with net-like feet		Feed using net-like or rod-like false feet, often through a skeleton	10,000 living; 50,000 fossil	Foraminifères de Ngapali
Sulcozoa	Groove-bearing animals		Live with oxygen, have 0, 1, 2, or 4 whip-like tails, a stiff outer layer, and a feeding groove	40+	Collodictyon telophase constrict
Telonemia	Telonema-like organisms	Telonemids	Eat by engulfing food, pear-shaped, two whip-like tails, unique internal structure	7	Telonema rivulare

Bacteria Phyla

Bacteria are tiny, single-celled organisms. There are currently 40 recognized bacterial phyla. Here are a few examples:

Acidobacteriota: A diverse group, many of which haven't been grown in labs yet.
Actinomycetota: Includes bacteria with high G+C content in their DNA, like some that cause diseases.
Bacillota: Includes bacteria with low G+C content, like Bacilli (which can form spores) and Clostridia.
Chlamydiota: Often live inside other cells as parasites.
Chlorobiota: Green sulfur bacteria, which use light for energy.
Pseudomonadota: A very well-known phylum, including common bacteria like Escherichia coli (E. coli) and Pseudomonas aeruginosa.
Spirochaetota: Includes bacteria like Borrelia burgdorferi, which causes Lyme disease.

Archaea Phyla

Archaea are also single-celled organisms, similar to bacteria but with different evolutionary histories. Currently, two phyla are officially recognized:

Nitrososphaerota
Thermoproteota: The second most common archaeal phylum.

Other phyla have been suggested but are not yet officially named, such as "Euryarchaeota" (the most common archaeal phylum) and "Nanoarchaeota" (tiny organisms that live with other organisms).