Animals - Phylum Arthropoda

Phylum Arthropoda = Jointed Legs

  • Bilateral symmetry.

  • Segmented body (Thorax, Head, Abdomen).

  • Exoskeleton made of chitin; molting allows growth.

  • Prominent cephalization and ventral nerve cord.

  • Open circulatory system.

Classification

  • Class Arachnida (Scorpions, Spiders, Ticks, Mites).

  • Class Diplopoda (Millipedes).

  • Class Chilopoda (Centipedes).

  • Class Insecta (Moths, Flies, Ants, Bees, Termites, Butterflies) - 90% of phylum.

  • Class Crustacea (Crayfish, Lobsters, Crabs).

Body Plan

  • Exoskeleton for support and structure.

  • Soft; Articulated appendages with joints.

Crayfish Anatomy

  • Cephalothorax and Abdomen.

  • Antennae and compound eyes.

  • Walking legs and swimmerets.

  • Uropods and telson.

Feeding

  • Mandibles and external limbs maneuver food.

  • Complete digestive system (mouth, esophagus, stomach, intestine, anus).

  • Gastric mill (teeth-like chitin surfaces).

Circulation & Respiration

  • Open circulatory system.

  • Gills oxygenate blood.

  • Heart keeps blood moving.

  • Book lung in land arthropods.

Excretion

  • Green gland in head excretes wastes.

Nervous System

  • Highly developed with compound eyes.

  • Antennae are touch-sensitive with statocysts.

  • Touch-sensitive hairs on exoskeleton.

Reproduction

  • External fertilization.

  • Eggs carried by appendages until hatching.

Ecological Roles

  • Pollinators, Predators, Prey, Parasites