Arthropods and Echinoderms Biology I: Chapter 28

ARTHROPODS

Arthropods Phylum Arthropoda Insects, crabs, centipedes, spiders Segmented body Tough exoskeleton made of chitin Jointed appendages

Evolution of Arthropods Fewer body segments Highly specialized appendages for feeding, movement and other functions

- movement strategies

Form and Function in Arthropods Complex organ systems; some only found only in this phylum Tracheal tubes (respiration) Open circulatory system Excrete wastes through saclike tubules

Herbivores, carnivores, omnivores, bloodsuckers, filter feeders, detritivores, and parasites Mouthparts have evolved to allow them to eat anything imaginable Pincers or fangs to sickle-shaped jaws that can cut through the tissues of captured prey Feeding

mosquito centipede butterfly beetle squid spider

Respiration: Terrestrial Arthropods Tracheal tube: one of many branching, air-filled tubes that extend throughout the body Spiracle: small opening located along the side of the body through which air enters and leaves the body Book lung: organ that has layers of respiratory tissue stacked like the pages of a book: used to exchange gases

Respire through feather-like gills (i.e. lobster and crabs) The horseshoe crab respires through organs: book gills

Circulation Open circulatory system Well-developed heart pumps blood through arteries that branch and enter the tissues Blood leaves the blood vessels and moves through sinuses, or cavities The blood recollects in a large sinus surrounding the heart It reenters the heart and is again pumped throughout the body