Arthropoda
Facts about Arthropods
- Arthropods are invertebrates.
- There are more than one million known arthropod species.
- Arthropods evolved more than 500 million years ago.
- The arthropod species is very diverse. It is the largest phylum. Arthropods also account for 75% of all known organisms, both living and fossilized.
- Arthropods have a hard, sturdy external structure. The structure contains chitin, which provides rigid structural support and prevents extreme drying of the structure (dessication).
- Arthropods are found in a large variety of habitats: the ocean, forests, deserts, grasslands, and freshwater streams or rivers.
- Arthropods have many limbs, jointed appendages, are are symmetrical.
- Most arthropods possess an open circulatory system.
- Arthropods are divided into three groups: Myriapoda (many pairs of legs), Chelicerata (have specialized mouth parts), Crustacea (body is divided into three parts and the organisms are aquatic), and Hexapoda (body is broken up into three sections and organisms have three pairs of legs).