Arthropods

Phylum: Arthropoda

• Common name = arthropods• Ex. Insects, spiders, crabs, shrimp, centipedes,

lobsters, ticks

Week 6

Monday

Arthropods

• Arthropods have:– Segmented body

• Head• Thorax • Abdomen

– Tough exoskeleton made of chitin– Jointed appendages

Cephalothorax⇛

Evolution of Arthropods

• Led to – Fewer appendages– Few segments– Highly specialized appendages

• Antennae• Pincers• Walking legs• Flippers• Claws

Feeding

• Herbivores, carnivores, omnivores

• Bloodsuckers, filter feeders, detritivores, parasites

• Mouthparts range from pinchers to fangs to sickle-shaped jaws depending on diet

Respiration

• Terrestrial– Breathe thru a network of branching tracheal

tubes– Air enters through spiracles = little openings along

body– Spiders uses book lungs

• Aquatic – Featherlike gills– Horseshoe crabs have book gills

Circulation

• Open circulatory system• Well-developed heart

Excretion

• Terrestrial– Malpighian tubules = saclike organs that extract

wastes from the blood and add them to feces (digestive wastes)

• Aquatic– Diffusion

Response

• Well-developed nervous system

• All have a BRAIN

Movement

• Muscles are attached to exoskeleton

• Pull of muscles against exoskeleton allows arthropods to move

• All have jointed appendages

Reproduction

• Terrestrial– Internal fertilization

• Aquatic – Internal or external fertilization

Growth and Development

• Exoskeletons DO NOT GROW, arthropods must MOLT

• Molting = arthropod sheds entire exoskeleton and makes a new larger one

• Molting arthropods are vulnerable and hide until they are done

Crustaceans

• Primarily aquatic• Crabs, shrimps, lobsters, crawfish, barnacles• 2 pairs of branched antennae• 2 or 3 body segments• Chewing mouthparts = mandibles

Tuesday

Associated Vocabulary

• Cephalothorax = fused body segment consisting of head and thorax

• Abdomen• Carapace = part of exoskeleton that covers the

cephalothorax• Mandible = biting, grinding mouthpart• Chelipeds = claws• Swimmerets = flipper-like appendages for

swimming

Chelicerates

• 2 body segments• Most have 4 pairs of walking legs• Horseshoe crabs, spiders, ticks, scorpions

From Prentice Hall Biology, 2006

Eyelash mites

Demodex folliculorum

Brown Recluse

Black Widow

Associated Vocabulary

• Chelicerae = mouthparts with fangs for stabbing and paralyzing prey

• Pedipalps =mouthparts for grabbing prey• Book lungs• Book gills• Spinnerets = organs in spiders that contain silk

glands for spinning webs

Uniramians

• Contains more species than all other animal groups combined!

• Jaws• 1 pair of antennae• Unbranched appendages• Insects, centipedes, millipedes

Centipedes and Millipedes

• Millipedes– Highly segmented body– 2 pairs of legs per segment– Live under rocks and decaying logs– Roll up or secrete toxins for defense

• Centipedes– 1 pair of legs per segment– Carnivorous and venomous– Live under rocks or in soil in humid areas

Insects

• 3 body segments = head, thorax, abdomen• 3 pairs of legs• 1 pair of antennae• 1 pair of compound eyes• 2 pairs of wings

Wednesday

Insects are the largest class of

animals!

Response to Stimuli

• Compound eyes with many lenses detect tiny movements and color changes

• Chemical receptors on mouthparts, legs and antennae (taste/smell)

• Well-developed ears (grasshoppers have ears on their legs!)

Adaptations for Feeding

• 3 pairs of appendages used as mouthparts– Mandibles to saw/grind (ex. ant)– Tube-like mouthpart to suck nectar (ex. moth)– Sponge-like mouthpart to lap up food (e. fly)

• Digestive enzymes in saliva – Bee saliva changes nectar from flowers into honey

Movement and Flight

• 3 pairs of legs– Walking, jumping, capturing/holding prey– Many species have spines or hooks on legs

• 2 pairs of wings made of chitin

• Evolution of flight allowed insects to disperse long distances and colonize many habitats

Metamorphosis

• Process of changing shape and form

– Complete metamorphosis• Egg-larva-pupa-adult• Larva looks nothing like adult

– Incomplete metamorphosis• Egg-nymph-adult• Nymphs look like adults

Advantage = larva and adults don’t compete for resources

Insects and Humans

• Beneficial– Honey– Wax– Pollination – Silk– Food

• Harmful– Damage wood– Damage clothes– Stings– Crop damage– Disease

Insect Communication

• Audio– Crickets

• Visual– Fireflies

• Chemical– Bees – Pheromones

Insect Societies

• Society = a group of closely related animals of the same species that work together for the benefit of the whole group– Bees– Ants– Termites

• Castes = groups of individuals that perform specific functions