Arthropods 5 th Grade

Phylum: Arthropod - “Arthropoda” *4 major groups: 1) Crustaceans 2) Arachnids 3) Centipedes & Millipedes 4) Insects

DEFINING Characteristics that arthropods have: (what makes them unique) Invertebrates –(no backbone) Exoskeletons –(external skeleton) Segmented Bodies Jointed Appendages Most have antenna

Characteristics that arthropods have that they share with other organisms: Bilateral symmetry Open circulatory system One way digestive system (2 openings) Most reproduce sexually

Exoskeleton: hard outer shell or skeleton

Exoskeleton – Advantages and Disadvantages PROS: 1)Protects the body 2)Prevents water from evaporating so the insect does not dry out CONS: 1)Limits movement 2)Have to lose shell and regrow a new one in order to grow

Since their exoskeletons prevent arthropods from moving or growing quickly, what do they use to help them move and grow? *Other body parts help them move: 1)segmented bodies 2)jointed appendages Some undergo a process called “molting” Molting = the process of shedding an outgrown exoskeleton and growing a new one that is larger

Adaptations for Movement Segmented Bodies: Jointed Appendages:

Molting: the process of shedding an outgrown exoskeleton and growing a new one that is larger

Most arthropods have an antenna Antenna: an appendage attached to the head that contains sense organs

ALL arthropods have Bilateral Symmetry

Open Circulatory System Closed Circulatory System ARTHROPODS have an OPEN CIRCULATORY SYSTEM

Look for the one way digestive system (2 openings) and the open circulatory system

Largest Arthropod Groups CharacteristicCrustaceansArachnidsCentipedes and Millipedes Insects Number of Body Sections 2 or 3223 Pairs of Legs5 or more4Many3 Pairs of Antennae 2NONE11

Examples of Crustaceans Crayfish Lobster Shrimp Pill bug

Examples of Arachnids Spiders Mites Scorpions Ticks

Examples of Insects Fly Butterfly Ant Grasshopper

Centipedes and Millipedes