Exploring the Diverse World of Arthropods: Characteristics and Groups

1. Chapter 2 Section 2Arthropods -Arthos means joint Podos means foot or leg -Examples: Crabs, lobsters, centipedes, scorpions, spiders & grasshoppers -Broken into 4 major Groups: Crustaceans, Arachnids, Centipedes/Millipedes & Insects

2. Characteristics of Arthropods • Invertebrates that have an external skeleton, a segmented body, and jointed attachments (appendages). • They have bilateral symmetry, an open circulatory system, a digestive system with 2 openings and most reproduce sexually.

3. Outer Skeleton • Called an exoskeleton, it is waterproof and waxy • Protects and helps prevent evaporation of water • Exoskeleton doesn't grow with the animals’ body so it sheds and grows a new larger one that is soft for a while - molting

4. Segmented Body • Easy to see the segments on the bodies of centipedes, millipedes, in the tails of shrimp and lobsters • An arthropod may have up to three sections – a head, midsection, and a hind section

5. Jointed Appendages • Jointed for flexibility • Appendages tend to be highly specialized tools used for moving, obtaining food, reproducing, and sensing the environment • Examples: legs, wings, antenna, mouthparts

6. Diversity • Over one million identified * Copy the chart on the top of page 49 into your notebooks

7. Chapter 2-Section 2 Crustaceans Notes

8. Crustaceans • Examples: crabs, lobsters, shrimp, crayfish, barnacles, water fleas, krill, and pill bugs • Most live in water • Important food source • Have two main body parts: a head-chest region and an abdomen

9. Body Structure • The head-chest region is covered by a part of the exoskeleton called the carapace • Have a pair of appendages attached to each body segment • The first two pairs of appendages are antennae

10. Body Structure • Behind the antennae are the crayfish’s mandibles, or jaw • Also has a clawlike appendage used for capturing food and for protection • Has four pairs of walking legs • Attached to the abdomen are appendages used for reproduction and swimming

11. Obtaining Oxygen and Food • Some crustaceans, such as the lobster and crayfish see with compound eyes. They can detect movement and changes in light • A crayfish takes in oxygen through gills. They are used to absorb oxygen dissolved in water. They are attached to each walking leg.

12. Crustaceans • If a crustacean loses an appendage, it can regenerate a new one • When a crustacean molts, it partially replaces the lost appendage • After molting several times, the lost appendage is completely replaced.

13. Life Cycle • Most crustaceans begin their lives as microscopic, swimming larvae. • The larvae develops into adults by metamorphosis.

14. Chapter 2 Section 2Arachnids Examples: Spiders, scorpions, ticks & mites

15. Characteristics • Live in dry, warm places • 2 main body parts: head-chest section, and the abdomen • 4 pairs of appendages attached to its head-chest region • Spiders have 8 simple eyes – eyes only sense change in light

16. Use of Appendages • 4 pairs total: • 1st pair is used for feeding • 2nd pair is used to smell/touch and hold food in place • Last 4 legs are used for walking

17. Examples • Scorpions – Predators • Spiders – Predators • Ticks – Parasites • Mites - Parasites