Arthropods are the largest phyla in the animal world and include insects, spiders, shrimp, centipedes, and other similar animals. Arthropods are commonly found in sea, freshwater, land, and air environments, including various forms of symbiosis and parasites. The word arthropod comes from the Greek ἄρθρον árthron, "segment, book, or segment", and πούς pous (podos), "foot", which when put together means "book-shaped feet" [2]. An arthropod is also known as a booked animal or an animal with a base. The characteristics that distinguish arthropods from other phyla are: segmented bodies, segments usually unite into two or three clear regions, paired segmented limbs (origin of arthropod naming), bilateral symmetry, exoskeleton berkitin. Periodically flowing and renewing as animal growth, alimentary canals such as pipes with the mouth and anus, open circulatory system, only blood vessels that usually form a dorsal structure such as a pipe leading to the alimentar canal with lateral openings in the abdominal region, body cavities; a blood cavity or reduced hemosol and coelom. Their nervous system is like a rope ladder, consisting of an anterior ganglion or brain located above the alimentary canal, a pair of connectors that channel from the brain around the alimentary canal and ganglion nerve cord located below the alimentary canal, excretion usually by the malphigi tubules. Empty tubes entering the alimentary canal and excretory material pass through the anus, respiration with gills or trachea and spiracles, no cilia or nephridia. Arthropods contribute to human food supply, both directly (as food) and indirectly, such as helping pollination. Certain species are known to be dangerous vectors of disease for humans, animals and plants.
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