Arthropods

ARTHROPODS Chapter 31

ARTHROPODS ◗ Invertebrates

with bilateral symmetry, coelom, exoskeleton, jointed appendages, and segmented bodies

Advantages of jointed appendages ◗ Allows

more powerful movements ◗ variety of uses: sensing, feeding, mating

Advantage/disadvantge of exoskeleton Made of chitin ◗ protects, supports, attaches muscles ◗ must molt to grow ◗ gets heavier as it gets larger; largest arthropods in water due to bouyancy ◗

Organization of segmented bodies ◗ Fused

segments into 3 regions: head, thorax, abdomen - Uniramians ◗ Fused segments into 2 regions: cephalothorax, abdomen Crustaceans, arachnids ◗ Many segments - diplopods

Respiration Spiracles (holes) attached to branching tracheal tubes Uniramians ◗ book lungs/gills - Arachnids ◗ gills - Crustaceans ◗

Irritability Ventral nerve cord, primitive brain ◗ Antennae ◗ compound, simple eyes ◗ detect chemicals, sounds, movement, pheromones (social) ◗

Circulation ◗ Dorsal

blood vessel

◗ heart ◗ open

circulation

Digestion Complete ◗ mandibles (jaws for chewing) ◗ Sucking mouthparts ◗ varied mouthparts = varied foods = less competition = success ◗

Excretion ◗ Malpighian

tubules -

terrestrial ◗ Green gland - aquatic

Reproduction ◗ Separate

sexes ◗ parthenogenesis ◗ Metamorphosis • Complete - 4 stages - egg, larva, pupa, adult • Incomplete - 3 stages - egg, nymph, adult

Evolution ◗ From

annelids (segmentation) ◗ Trilobytes - extinct

Importance ◗ Pollinators ◗ parasites ◗ product

producers (honey, wax, reseach, silk)

Arachnida (chelicerates) ◗ Spiders,

ticks, scorpions, horse-shoe crab ◗ 2 body regions, 8 legs ◗ chelicerae - pincers, fangs ◗ pedipalps - food handling ◗ spinnerets - not all spin webs

Crustaceans ◗ Crabs,

shrimp, lobsters, barnacles ◗ Gills, mandibles, 2 pr. Antennae, compound eyes, 5 prs. walking legs,

Uniramians ◗ Insects ◗3

body segments, 6 legs ◗ metamorphosis