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Classification
Kingdom Animalia
Members of the animal kingdom share these basic characteristics:
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mulitcellular (bodies made up of more than one cell)
eukaryotic (each cell contains a nucleus and membrane-enclosed organelles)
cell membranes without cell walls
heterotrophs (do not make their own food but consume other organisms)
The following phyla include some of the most common animals.
Phylum: Porifera
example: sponges
characteristics: aquatic, asymmetrical animals lacking distinct tissues and organs;
sessile body consists of two layers supported by a stiff skeleton; reproduce sexually or
asexually.
Phylum: Cnidaria
(formerly Coelenterata)
examples: corals, sea anemones, jellyfishes, hydras
characteristics: radial symmetry, central mouth surrounded by tentacles, nematocysts;
reproduces sexually or asexually.
Phylum: Ctenophora
examples: comb jellies, sea walnuts
characteristics: gelatinous marine animals with eight bands of cilia; often
bioluminescent; reproduce asexually
Phylum: Platyhelminthes
examples: flatworms (tapeworms, flukes, planarians)
characteristics: three cell layers; digestive cavity having one opening; no circulatory or
respiratory systems; reproduce sexually or asexually.
Phylum Nematoda
examples: roundworms (ascaris, hookworms)
characteristics: mostly parasitic; tubular body, bilateral symmetry; digestive tract with
two openings; reproduce sexually
Phylum: Bryozoa
examples: moss animals
characteristics: microscopic, aquatic organisms; form branching colonies; feed with
ciliated tentacles in U-shaped row.
Phylum: Mollusca
examples: clams, octopuses, snails
characteristics: soft-bodied, true coelom, muscular foot, visceral mass and mantle;
most aquatic; many have shells; reproduce sexually.
Phylum: Annelida
examples: segmented worms (leeches, earthworms)
characteristics: true coelom; longitudinal and circular muscles; fairly complex
circulatory, digestive, respiratory, and nervous systems; reproduce sexually.
Phylum: Arthropoda
examples: horseshoe crabs, lobsters, insects
characteristics: segmented body; paired, jointed appendages; exoskeleton; open
circulatory system; complex nervous system with brain and two ventral nerve cords;
reproduce sexually.
The spiny lobster exhibits arthropod characteristics of an exoskeleton and paired,
jointed appendages.
Phylum: Echinodermata
examples: sea stars, sea cucumbers, sea urchins
characteristics: radial symmetry; calcium endoskeleton; open circulatory system;
complex nervous system with brain and two ventral nerve cords; reproduce sexually.
Phylum: Chordata
examples: fishes, amphibians, reptiles, birds, mammals, tunicates, lancelets
characteristics: has a notochord, throat slits, and tail at some stage of development;
reproduces sexually.
People are in the phylum Chordata. But we're not the only ones. Chordates are divided
into the following classes:
Class: Cephalaspidomorphi
example: lampreys
characteristics: circular mouth has sucking disc, no jaw, no paired fins, one
nostril.
Class: Myxini
example: hagfishes
characteristics: circular mouth has barbles, no jaw, no paired fins, one nostril,
no eyes.
Class: Chondrichthyes
examples: sharks, skates, rays, chimaeras
characteristics: skeleton made of cartilage, jaws, paried fins, paired nostrils,
scales, two-chambered heart.
Class: Osteichthyes
example: bony fishes
characteristics: skeleton made of bone, jaws, fins, most with scales, twochambered heart.
Class: Amphibia
examples: frogs, toads, salamanders
characteristics: begin life in the water, gills replaced by lungs in the adult form,
lay eggs, three-chambered heart.
Class: Reptilia
examples: snakes, lizards, turtles, crocodiles
characteristics: thick, scaly or platelike skin; ectothermic (cold-blooded);
embryo develops in the shell (young born live or hatch from egg); fourchambered heart.
Class: Aves
examples: all birds including penguins, flamingos, eagles, parrots, and ducks
characteristics: outer covering of feathers, endothermic (warm-blooded), have
front limbs modified as wings, lay eggs, four-chambered heart.
Class: Mammalia
examples: humans, whales, horses, bears
characteristics: breathe air, have hair at some stage of development, give live
birth, mammary glands, endothermic (warm-blooded), four-chambered heart.