Common Group Name Arthropods Phylum Arthropoda Subphyla Crustaceans

Common Group Name: Arthropods

Phylum: Arthropoda Subphyla: • Crustaceans Examples: crabs, shrimp, lobster, crayfish, barnacles • Chelicerata (spiders) Examples: horseshoe crabs and spiders • Uniramia (insects) Examples: insects

Body Plan • Body plan includes segmentation, exoskeleton, and jointed appendages. • The number of segments and jointed appendages vary in species • Exoskeleton is an outer covering made of chitin and can be leathery, hard, or waxy.

Feeding • Herbivores, carnivores, omnivores, bloodsuckers, parasites, detrivores, and filter feeders. • First group to show advanced mouthparts: • Pincers, fangs, and jaws

Respiration § Most terrestrial arthropods breathe through branching tracheal tubes. § Air enters and leaves through spiracles. § Spiders breathe using book lungslayers of respiratory tissues. § Aquatic arthropods breathe using featherlike gills or book gills.

Circulation • Arthropods have an open circulatory system. • Blood Flow: Heart- arteries-tissuesleaves the blood vessels-sinuses and cavities-collects back in large sinus near heart-re-enters heart

Excretion • Terrestrial- use malpighian tubes- saclike organs that extract wastes from blood and add them to feces to move through the gut. • Aquatic- use diffusion

Response • All arthropods have a brain. • Brain sends out instruction signals to muscles. • Two main nerves connect the brain to the ventral nerve cord. • Ganglia extend from nerve cord to coordinate the movement of legs and wings. • Sophisticated sense organs: eyes and taste receptors.

Movement • Arthropods use well-developed groups of muscles. • Muscles are made up of muscle cells that contracted when stimulated by nerves. • Muscles pull on the exoskeleton. • Extension and flexion occur.

Reproduction n Terrestrial- sexual, internal fertilization: male place sperm in female or male places sperm into packet picked up by female. n Aquatic- internal or external fertilization

Reproduction in Insects • Usually involves metamorphosis- the process of changing shape and form. • Incomplete Metamorphosis- immature forms (nymphs) lack functional adult structures but look like mini-adults; similar appearance throughout life. • Complete Metamorphosis- insects undergo dramatic physical changes. Larva (different from parent) develops into pupa (looks different from larva) then completely remodels again to become adult.

INCOMPLETE

Other Information • When they outgrow their exoskeleton, arthropods undergo molting- the shedding of the exoskeleton and production of a new larger one. • Molting is controlled by the endrocrine system which releases hormones.

Arthropod Subphyla

Body Plan Crustaceans: • 2 antennae • 2 or three segments (cephalothorax, abdomen), • Mandible- mouthpart for biting • 1 st pair of legs called chelipeds with large claws • 4 pair of walking legs • swimmerets- flipper appendages

Body Plan Chelicerates: • Mouthpart has chelicerae with fangs • 2 body segments • 4 pairs of walking legs • pedipalps- to catch prey • spiders have no jaw and must liquefy their food.

Body Plan Insects: • Jaws • 1 pair of antennae • 3 parts: head-thorax-abdomen • 3 pairs of legs • Most insects are adapted for flight

Feeding in Insects • Three pairs of appendages for mouthparts including two mandibles • Saliva present to help digest food.

• • Response in Insects Compound eyes present Taste and smell chemical receptors They can detect movement Ears present

Movement in Insects • Legs with spines and hooks for grasping and defense • Many can fly and usually have two pairs of wings.