Insecta Class Characteristics Quiz

Subphylum Hexapoda

• Body with distinct head, thorax, and abdomen • Pair of antennae • Mouthparts modified for different food habits • Head formed from six fused segments • Thorax composed of three segments • Abdomen with variable number of segments (usually 11) • Typically six somites • Thorax with two pairs of wings and three pairs of jointed legs • Separate sexes

Phylum Echinodermata

• Endoskeleton of plates or ossicles • Water-vascular system • Radial or biradial symmetry • No head or brain, but with radial nerves • Endoskeleton of dermal calcareous ossicles • Locomotion by tube feet projecting from the ambulacral groove • Digestive system usually complete • Excretory organs absent • Sexes separate

Class Asteroidea: Sea Stars

• Pentaradial symmetry • Found along shorelines, on muddy and sandy bottoms, and among coral reefs

Class Ophiuroidea: Brittle Stars

• Largest group in terms of number of species • Possess five arms that are slender and sharply set off from their central discs • Five movable plates surround the mouth, serving as jaws • No anus

Class Echinoidea: Sea Urchins

• Compact body enclosed in an endoskeletal test • Lack arms

Class Holothuroidea: Sea Cucumbers

• Greatly elongated compared to other Echinoderms • Cephalization is absent • Tube feet are typically used for movement in species that crawl over the surface of the sea bottom • Hydrostatic skeleton

Phylum Cnidaria

• Characteristic stinging cells (cnidocytes) containing stingers (nematocyst) • Two basic types of individuals: polyps and medusae • Some are polymorphic (2 body plans during life cycle) • Exoskeleton or endoskeleton of chitinous, calcareous, or protein components in some

Phylum Platyhelminthes (Flatworms)

• Acoelomate (no body cavity) with organ-system level of organization • Simplest animals with bilateral symmetry • Triploblastic (three germ layers) • Cephalization • Nervous system with a pair of anterior ganglia with longitudinal nerve cords • Simple sense organs

Phylum Porifera (Sponges)

• Simplest multicellular invertebrates • Body is an assemblage of cells embedded in a gelatinous matrix and supported by needle-like spicules and protein • Sessile (adult) or motile (larva) animals • Depend on water currents to bring them food and oxygen and to carry away their body waste • Types of cells and extracellular matrix consisting of a collagen-like gel with suspended cells that perform various functions • Types of canal system • Most sponges are monoecious/hermaphroditic (have both male and female sex cells in one individual) • Capable of sexual and asexual reproduction • Oocyte retained; sperm ejected