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ARTHROPODS. SUBPHYLA: TRILOBITA, CRUSTACEA, CHELICERATA, AND UNIRAMIA. Phylum Arthropoda “jointed feet”. Characteristics: segmentation Jointed, paire appendages Exoskeleton – chitin Cephalization Compound eyes Coelom Open circulatory system Ventral nerve cord. The Exoskelton.
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ARTHROPODS SUBPHYLA: TRILOBITA, CRUSTACEA, CHELICERATA, AND UNIRAMIA
Phylum Arthropoda “jointed feet” • Characteristics: • segmentation • Jointed, paire appendages • Exoskeleton – chitin • Cephalization • Compound eyes • Coelom • Open circulatory system • Ventral nerve cord
The Exoskelton • The exoskelton is composted of the polysaccharide chitin. An arthropod can not grow without periodically shedding the exoskeleton. This process is called molting or edcysis. During the few days following the replacement of the exoskeleton, the animal is extremely vulnerable and must hide from predators. There is also the problem of desiccation.
Advantages Protection Support Site for muscle attachment Flexible at the joints Disadvantages Heavy Must be molted Advantages & Disadvantages of the Exoskelton
Subphylum Trilobita • All members of this phylum are extinct
Subphylum Crustacea • Only arthopods with 2 pair of appendages on their head that serve as feelers • Most have 16-20 segments which are fused into several tagmata • Most have gills for respiration • Most have a free-swimming larva called a nauplius
Subphylum Chelicerata • Have piercing and sucking mouth parts called chelicerae
Class Arachnida • Include: spiders, scorpions, mites and ticks • Cephalothorax and abdomen • Cephalothorax – 6 pairs of jointed appendages • 1 pair of chelicerae (used to inject venom into prey) • 1 pair of pedipalps (holding food, chewing, & reproduction • 4 pairs of walking legs • 8 simple eyes at anterior end
Abdomen • Spinnerets • Respiration • Book lung • Tracheae and spiracles • Excretory organs • Malpighian tubules • Coxal glands
Mites and Ticks • Most abundant and specialized archnids • Completely fused head and cephalothorax
Subphylum Uniramia • Classes • Insecta • Diplopoda • Millipedes • 2 pair of legs on each body segment • Rounded bodies • Poor vision with a good sense of smell • Feed on plants or decaying plant matter • Secrete a noxious fluid that contains cyanide when threatened
Chilopoda • Flattened bodies with one pair of legs per segment ( except first and last 2 segments) • May have 15 – 175 pairs of legs • The appendages on the first segment are modified into a pair of poison claws • Long antennae and two clusters of simple eyes • Move quickly and feed mostly on earthworms and other insects