Phylum Arthropoda
Arthropoda Includes… Spiders, scorpions, ticks, mites, crustaceans, millipedes, centipedes, insects.
Largest Phylum More than ¾ of all known species Over 900,000 species
Characteristics Exoskeleton—made of at least some chitin Jointed appendages Open circulatory system Complete digestive system Excretory system Dorsal brain and well developed sensory organs
Body Form Head and trunk OR Head, thorax, and abdomen OR Cephalothorax and abdomen
More Characteristics Exoskeleton serves as point of attachment for muscles This allows for a complex muscular system Respiration occurs through one of the following: gills, trachae, spiracles, book lungs, or body surface
Why So Successful? 1. Exoskeleton protects, but does not limit mobility Exoskeleton must, however, be shed 2. Specialized appendages
Why So Successful? 3. Air piped directly to cells 4. Highly developed sensory organs 5. Complex behavior patterns (ants and bees)
Why So Successful? 6. Metamorphosis: uses diverse resources Reduces competition Each stage lives and feeds on different things
Phylum Arthropoda