Arthropoda
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Arthropods (phylum Arthropoda) are the phylum which includes insects, crustaceans, and all organisms with a hard shell-like segmented body, such as spiders, horseshoe crabs, and centipedes.
Identification
Arthropods have a hard outer shell, or exoskeleton, which is periodically shed and regrown. The body is segmented, usually with 2-3 distinct groupings. Paired and segmented appendages are usually present.
Life Cycle
With the exception of insects, arthropods undergo little to no metamorphosis. Immature arthropods resemble adults. A few crustaceans have a immature form that differs significantly from that of the adult. Some Celicerata have fewer legs in the immature form.
Habitat
Arthropod habitats are very diverse. Arthropods are found in almost every habitat. Feeding is equally varied.
Taxonomy
Formerly, arthropods were divided into only two subphyla, Manibulata and Celicerata. Mandibulate arthropods include crustaceans, hexapods, and Myriapoda.
Number of species
There are 104,000 species found in North America, and 840,000 worldwide.
Subdivisions
There are 4 subphylums in this phylum.