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ARTHROPODS. Arthropods. (“jointed foot”) ¾ of all animals on planet Earth! 750,000+ species….why so numerous and successful?. 1: Reproduce fast & in large numbers. opportunity for variation is therefore great
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Arthropods • (“jointed foot”) • ¾ of all animals on planet Earth! 750,000+ species….why so numerous and successful?
1: Reproduce fast & in large numbers • opportunity for variation is therefore great • take advantage of different food sources…pass through developmental stages such as ‘larva’ and ‘adult’ in metamorphosis
#2: Exoskeleton (outside) Changed the single fortress (shell) to a flexible suit of armor • Protection; barrier against loss of body fluids; must be recycled and shed (molted!) to make room for growth
#3: Segmentation • More flexible movement • Creates lots of interior ridges for muscle attachments, going in different directions
#4: Striated Muscles • voluntary and quick contracting (but, they get tired quickly….need lots of oxygen to burn food for quick energy!
#5: Efficient air moving systems • Gills in water; book lungs for spiders; tracheae (pipes) for insects
#6: jointed appendages • modified for locomotion (legs, wings), eating (claws, mouthparts), sensing (antennae)
#7: Sense Organs • eyes (simple or compound); hair on legs, body, 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
Orders of Arachnids • Scorpions • Pseudoscorpions • Daddy Long-Legs • Mites & Ticks • Spiders
Pseudoscorpion Tick (a mite) Scorpion Wolf Spider Daddy-long-legs
chelicerae eyes pedipalp
Mite and Tick Body Regions pedipalps & chelicerae cephalothorax abdomen
American dog tick male Blacklegged (deer) tick female
Clover mites Twospotted spider mites Predatory mite
daddy long-legs cephalothorax abdomen
Spider Anatomy pedipalp chelicera (fang) cephalothorax narrow waist abdomen
Abdomen Cephalothorax Chelicera (fang) Pedipalp Jumping Spider
Wolf spider with egg case Spitting spider Orb-weaving spider Tarantula
Black widow with egg case Brown recluse
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 [one pair of antennae, head & trunk regions, trunk with many pairs of legs] 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.
Millipede (Diplopoda) Centipede (Chilopoda) Garden centipede
Insecta Class • 3 segments head, thorax, abdomen • 1 pair of antennae • Special characteristics: • Wings • Pheromones • Metamorphosis
Phereomones • Chemical signals • Used for • Marking trails • Identification of organisms • Signaling trouble • Signaling sexual readiness
Metamorphosis • Incomplete • Born as a smaller version of the adult • 3 stages • Egg nymph adult • Nymph molts many times into different “stage” of nymph
Metamorphosis • Complete • Born as a complete different version than adult • 88% of metamorphosis • 4 stages • Egg larva pupa 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
Crayfish cephalothorax (Decapoda) Sowbug (Isopoda), a terrestrial crustacean