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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
 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.
INCOMPLETE
COMPLETE
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.
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•
•
•
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.