Final answer:
Arthropods are the most successful phylum of animals on Earth with segmentation, jointed appendages, and chitinous exoskeleton. They have various respiratory adaptations and may undergo multiple larval stages.
Step-by-step explanation:
Arthropods represent the most successful phylum of animals on Earth, in terms of number of species as well as the number of individuals. They are characterized by a segmented body and jointed appendages. In the basic body plan, a pair of appendages is present per body segment. Within the phylum, classification is based on mouthparts, number of appendages, and modifications of appendages. Arthropods bear a chitinous exoskeleton. Gills, tracheae, and book lungs facilitate respiration. Embryonic development may include multiple larval stages.