ArthropodsArthropods
(“jointed foot”)(“jointed foot”) ¾ of all animals on planet Earth! ¾ of all animals on planet Earth!
750,000+ species….why so numerous 750,000+ species….why so numerous and successful?and successful?
1: Reproduce fast & in large 1: Reproduce fast & in large numbersnumbers
opportunity for variation is therefore great opportunity for variation is therefore great take advantage of different food take advantage of different food
sources…pass through developmental sources…pass through developmental stages such as ‘larva’ and ‘adult’ in stages such as ‘larva’ and ‘adult’ in metamorphosismetamorphosis
#2: Exoskeleton (outside)#2: Exoskeleton (outside)
Changed the single fortress (shell) to a Changed the single fortress (shell) to a flexible suit of armorflexible suit of armor
Protection; barrier against loss of body Protection; barrier against loss of body fluids; must be recycled and shed fluids; must be recycled and shed (molted!) to make room for growth(molted!) to make room for growth
#3: Segmentation#3: Segmentation
More flexible movementMore flexible movement Creates lots of interior ridges for muscle Creates lots of interior ridges for muscle
attachments, going in different directionsattachments, going in different directions
#4: Striated Muscles#4: Striated Muscles
voluntary and quick contracting (but, they voluntary and quick contracting (but, they get tired quickly….need lots of oxygen to get tired quickly….need lots of oxygen to burn food for quick energy!burn food for quick energy!
#5: Efficient air moving #5: Efficient air moving systemssystems
Gills in water; book lungs for spiders; Gills in water; book lungs for spiders; tracheae (pipes) for insectstracheae (pipes) for insects
#6: jointed appendages#6: jointed appendages
modified for locomotion (legs, wings), modified for locomotion (legs, wings), eating (claws, mouthparts), sensing eating (claws, mouthparts), sensing (antennae)(antennae)
#7: Sense Organs#7: Sense Organs
eyes (simple or compound); hair on legs, eyes (simple or compound); hair on legs, body, antennae; chemical sensesbody, antennae; chemical senses
Arthropod Groups (taxa)
The arthropods are divided into two large groups that exist today:
Chelicerates
and
Mandibulates
Chelicerate Arthropod Characters:
Pincher-like mouthparts - chelicerae - and pedipalps
NO antennae
Two body regions, usually - cephalothorax & abdomen
Four pairs of legs
Horseshoe crabs and arachnids are only living groups
Mandibulate Arthropod Characters:
Mouthparts are mandibles - normally chewing sideways
One or two pairs of antennae
Various body region arrangements - cephalothorax & abdomen / head & trunk / head, thorax & abdomen
Variable leg numbers
Insects, crustaceans & myriapods
Classes of Myriapods(many legged arthropods)
(all have one pair of antennae, a head region, and trunk with many pairs of legs, use trachea)
Diplopoda - millipedes
Chilopoda - centipedes
Myriapods
Millipede (Diplopoda)
Two pair of legs per visible segment, attached under body.
Centipede (Chilopoda)
Pair of fangs under head, one pair legs per visible segment - attached to side of body.
No fangs, no eyes, legs attached to side of body.
[one pair of antennae, head & trunk regions, trunk with many pairs of legs]
Insecta ClassInsecta Class
3 segments 3 segments head, thorax, abdomen head, thorax, abdomen 1 pair of antennae1 pair of antennae Special characteristics:Special characteristics:
WingsWings PheromonesPheromones MetamorphosisMetamorphosis
PhereomonesPhereomones
Chemical signalsChemical signals Used forUsed for
Marking trailsMarking trails Identification of organismsIdentification of organisms Signaling troubleSignaling trouble Signaling sexual readinessSignaling sexual readiness
Metamorphosis Metamorphosis
IncompleteIncomplete Born as a smaller version of the adultBorn as a smaller version of the adult 3 stages3 stages Egg Egg nymph nymph adult adult Nymph molts many times into different Nymph molts many times into different
“stage” of nymph“stage” of nymph
MetamorphosisMetamorphosis
CompleteComplete Born as a complete different version than Born as a complete different version than
adultadult 88% of metamorphosis88% of metamorphosis 4 stages4 stages Egg Egg larva larva pupa pupa adult adult
Classes of Crustacea• mostly marine, fresh water, a few terrestrial• all have two pair of antennae• five or more pairs of legs• segmented abdominal appendages• head & trunk or cephalothorax & abdomen body arrangement• have gills
Sowbugs or pillbugs
Sand fleas
Barnacles
Crabs, lobster, shrimp