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An "'arthropod'" is an invertebrate animal defined by several morphological and biochemical features. Among these features are: segmented body covered by a hard [[exoskeleton]], periodically molt (a process known as [[ecdysis]]), [[tagmosis]], paired jointed appendages on varying segments, [[hemocoelic]] [[body cavity]] containing the hear, striated (for the most part) muscles, and epithelial tissue (which is usually non-ciliated).

An "'arthropod'" is an invertebrate animal defined by several morphological and biochemical features. Among these features are: segmented body covered by a hard [[exoskeleton]], periodically molt (a process known as [[ecdysis]]), [[tagmosis]], paired jointed appendages on varying segments, [[hemocoelic]] [[body cavity]] containing the hear, striated (for the most part) muscles, and epithelial tissue (which is usually non-ciliated).

Arthropods make up by far the majority of animal species, with more than a million currently described as estimates for as many as 9 million in total<ref>http://www.ucmp.berkeley.edu/arthropoda/arthropoda.html</ref>. Within the phylum Arthropoda are the classes commonly known as [[insect]]s, [[crustacean]]s, [[arachnid]]s ([[spider]]s and [[scorpion]]s), and the [[extinct]]  [[trilobite]]s.

Arthropods make up by far the majority of animal species, with more than a million currently described as estimates for as many as 9 million in total.<ref>http://www.ucmp.berkeley.edu/arthropoda/arthropoda.html</ref> Within the phylum Arthropoda are the classes commonly known as [[insect]]s, [[crustacean]]s, [[arachnid]]s ([[spider]]s and [[scorpion]]s), and the [[extinct]]  [[trilobite]]s.

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