artropoda
Arthropoda, or arthropods, is the largest phylum of animals, including insects, arachnids, crustaceans, and myriapods, as well as extinct relatives. Members are characterized by a chitinous exoskeleton, a segmented body organized into tagmata, and paired jointed appendages. They have a dorsally located heart and an open circulatory system, a ventral nerve cord, and diverse sensory organs such as compound eyes and antennae. Most arthropods grow by ecdysis, a molting process that replaces the exoskeleton as they increase in size. Respiratory adaptations are diverse, including gills in aquatic forms, book lungs in some arachnids, and a network of tracheae in insects.
Arthropoda is divided into several major subphyla. Trilobitomorpha consists of extinct forms. Chelicerata includes spiders, scorpions,
Ecology and evolution: Arthropods occupy nearly every habitat and play crucial roles as pollinators, scavengers, predators,