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Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, have myocytes and are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development.
The Animal Kingdom is one of four kingdoms in the Eukarya Domain. The Animal Kingdom, in turn, is divided into almost 40 phyla. Each of the top nine animal phyla has at least 10,000 species. One basic way to divide animals is between invertebrates and vertebrates. - Invertebrates are animals that lack a vertebral column, or backbone. All animal phyla except Phylum Chordata consist only of invertebrates. Even Phylum Chordata includes some invertebrate taxa. Invertebrates make up about 95 percent of all animal species. - Vertebrates are animals that have a backbone. All of them are placed in Phylum Chordata. Modern vertebrates include fish, amphibians, reptiles, birds, and mammals. Only about 5 percent of animal species are vertebrates.
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