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|
|Platyhelminthes||flatworms, tapeworms, flukes|
|Mollusca||snails, clams, squids|
|Annelida||earthworms, leeches, marine worms|
|Arthropoda||insects, spiders, crustaceans, centipedes|
|Echinodermata||sea stars, sea urchins, sand dollars, sea cucumbers|
|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.
- State how the phylum Chordata differs from other animal phyla.
- Compare and contrast invertebrates and vertebrates.