Arthropods

• 80% of all animals are arthropods, 76% of those are insects
• Major Classes of Arthropods

  • Chilipoda (includes the centipedes)
  • Insecta (includes all 6 legged insects)
  • Diplopoda (includes the millipedes)
  • Crustacea (includes barnacles, lobsters, crabs, and shrimp)
  • Chelicerata (includes spiders, mites, and scorpions)
• Shared Characteristics of Arthropods

  • Coelomates (has a body cavity)
  • Bilateral symmetry
  • Jointed appendages (arms and legs)
  • Exoskeleton made of Chitin
  • 3 body regions (head, thorax, abdomen)
  • Open circulatory system
  • Well developed sensory organs (tympanum, compound eyes, antenna)
• Arthropod Digestive System

  • Complete DIGESTIVE systems with mouth, organs, and anus
• Arthropod Nervous System

  • Nervous systems composed of a Dorsal brain
• Arthropod Feeding


  • Herbivores
  • Carnivores
  • Omnivores
  • Bloodsuckers
  • Filter feeders
  • Detritivores
  • Parasites
• Arthropod Mouthparts


  Evolved to eat almost any food, can include pincers or fangs or sickles shaped jaws
• Insect Gas Exchange System

  1. Terrestrial arthropods breathe through a network of branching tracheal tubes

  2. Air leaves and enters body through Spiracles (small openings on along the side of the body)

  3. Book lungs are organs that have layers of respiratory tissues

  4. Aquatic arthropods have featherlike gills like Molluscs
• Open Circulatory System


  • Terrestrial arthropods dispose of nitrogenous waste using Malpighian organs that extract waste from the blood and add them to the feces
  • In aquatic arthropods, Diffusion move cellular wastes from the body into the water
• Arthropod Nervous System


  • Well-developed nervous system
  • All arthropods have a brain that serves as the central switchboard
  • Most arthropods have sophisticated sense organs like eyes and taste receptors
• Arthropod Movement


  • Move using well-developed groups of Muscles that are controlled and coordinated by the nervous system
• Arthropod Reproduction


  • Terrestrial arthropods have Internal sexual fertilization, including females picking up a sperm packet
  • Aquatic arthropods may have external or internal fertilization
• Arthropod Growth and Development

  1. Molting: The exoskeleton does NOT grow as the animal grows, so they go through periods of molting when they outgrow their exoskeleton

  2. Molting is caused by hormones

  3. Arthropods either go through complete or incomplete Metamorphosis
• The difference between open and closed digestive systems is that open digestive systems (incomplete) have a single opening that serves as both the mouth and anus, while closed (complete) digestive systems have two separate openings for the mouth and anus, which is more efficient for nutrient absorption and supports larger, more complex organisms