Common Group Name: Arthropods

Chelicerata (spiders) 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.

First group to show advanced mouthparts: Pincers, fangs, and jaws 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 lungs- layers of respiratory tissues. Aquatic arthropods breathe using featherlike gills or book gills.

Circulation Arthropods have an open circulatory system. Blood Flow: Heart- arteries-tissues-leaves 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 Terrestrial- sexual, internal fertilization: male place sperm in female or male places sperm into packet picked up by female. 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.

COMPLETE 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 1st 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.