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10.2: Animal Classification

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    f-d:57d18af1f0c55ce65850d03c1ccec1b23f48d3c954116bc6e2191701 IMAGE_TINY IMAGE_TINY.1

    Plant or animal?

    Animal. What type? Now that is a good question. This azure vase sponge is an animal, but how is it classified? It is estimated that there are easily over a million species of animals on Earth. How are all these species divided into their various classifications?

    Classification of Animals

    All animals share basic traits. But animals also show a lot of diversity. They range from simple sponges to complex humans.

    Major Animal Phyla

    Members of the animal kingdom are divided into more than 30 phyla. Table below lists the nine phyla with the greatest number of species. Each of the animal phyla listed in the table has at least 10,000 species.

    Phylum Animals It Includes
    f-d:eec5b1b9a4291d86f0fd8de440015c20866aead709c8171b2f4dbd43 IMAGE_TINY IMAGE_TINY.1 Porifera sponges
    f-d:6dbbcad17b672da915aee27ded0dfbdc66776778d5a48a46367edd37 IMAGE_TINY IMAGE_TINY.1 Cnidaria jellyfish, corals
    f-d:4d249d6dc26079db37d8f52f18ad0692d1f77b30bc41862d9fc1d6c0 IMAGE_TINY IMAGE_TINY.1 Platyhelminthes flatworms, tapeworms, flukes
    f-d:dea7e4bb8772a462ed4a6753a171170d638974d8460233a834711577 IMAGE_TINY IMAGE_TINY.1 Nematoda roundworms
    f-d:1e834934c0b549f4dc25406a0e13580b628f6ee852ca947bada90dc9 IMAGE_TINY IMAGE_TINY.1 Mollusca snails, clams, squids
    f-d:f770ca31f13d58bf53b8d841fca6242ce28de3dcfbf208dc145bdfc3 IMAGE_TINY IMAGE_TINY.1 Annelida earthworms, leeches, marine worms
    f-d:b82902ac8072dd86ce358d684b4ca303bec47b3405b259a000af1758 IMAGE_TINY IMAGE_TINY.1 Arthropoda insects, spiders, crustaceans, centipedes
    f-d:f7a7c2b2266e45af5fa0a0bced1facf324ac9e3d5c60a2fa979cc813 IMAGE_TINY IMAGE_TINY.1 Echinodermata sea stars, sea urchins, sand dollars, sea cucumbers
    f-d:97681d5a968411b0abcf91035ca1914c28c8e5be31f42f158d3751b0 IMAGE_TINY IMAGE_TINY.1 Chordata tunicates, lancelets, fish, amphibians, reptiles, birds, mammals

    Invertebrate vs. Vertebrate

    The first eight phyla listed in Table above include only invertebrate animals. Invertebrates are animals that lack a vertebral column, or backbone. The last phylum in the table, the Chordata, also includes many invertebrate species. Tunicates and lancelets are both invertebrates. Altogether, invertebrates make up at least 95 percent of all animal species. The remaining animals are vertebrates. Vertebrates are animals that have a backbone. All vertebrates belong to the phylum Chordata. They include fish, amphibians, reptiles, birds, and mammals.


    • Vertebrates have a backbone, but invertebrates do not.
    • Except for the chordates, all animal phyla consist only of invertebrates.
    • Chordates include both vertebrates and invertebrates.


    1. State how the phylum Chordata differs from other animal phyla.
    2. Compare and contrast invertebrates and vertebrates.

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