-The exoskeleton is made up of chitin and

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-The exoskeleton is made up of chitin and
protein. a. Provides protection b. Provides
points of attachment for the muscles that
move appendages -The animal must molt (ecdysis)
its old exoskeleton if it outgrows
it. -Well-developed eyes, olfactory receptors,
and antennae for touch and smell (most at the
anterior end cephalization). -Open circulatory
system Hemolymph (the word blood is
reserved for a closed circulatory system) is
pumped from the heart into spaces surrounding
tissue and organs.
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-Respiratory by gills, book lungs, and trachea.
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-The arthropods came from 4 evolutionary
lineages 1. Trilobites (extinct) 2.
Chelicerates (horseshoe crab, scorpions,
ticks, and spiders) 3. Uniramians (centipedes,
millipedes, and insects) 4.
Crustaceans (crabs, lobsters, shrimp,
barnacles)
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• Scientists now want to separate these lineages
• into different phylums
• Phylum Trilobita, Phylum Chelicerata,
• Phylum Uniramia, Phylum Crustacea

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-Some major classes in phylum arthropods
Arachnids Ex. Spiders, scorpions, ticks, mites
Body with 1 or 2 main parts, six pairs of
appendages (Chelicerae, pedipalps, and 4
pairs of walking legs) mostly terrestrial.
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-Diplopods Ex. Millipedes Body with distinct
head bearing antennae and chewing mouthparts,
segmented body with two pairs of walking legs
per segment terrestrial and herbivorous.
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-Chilopods Ex. Centipedes Body with distinct
head bearing large antennae and 3 pairs of
mouthparts appendages of first body segment
modified as poison claws body segments bear 1
pair of walking legs each terrestrial
carnivorous.
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-Insecta Ex. Insects Body divided into head,
thorax, and abdomen antennae present
mouthparts modified for chewing, sucking, or
lapping usually with two pairs of wings and
three pairs of legs mostly terresterial.
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-Entomology study of insects -Flight is one of
the great successes of insects. ? Dragonflies
were among the first insects to fly.
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-Insects have a complete digestive system. -Open
circulatory system (hemolymph) -Metabolic wastes
removed from the hemolymph via the excretory
organs called Malpighian tubules. -Gas exchange
via the the trachael system open to the
outside through spiracles (pores).
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-Nervous system consists of a pair of ventral
nerve cords that meet in the head, to form the
cerebral ganglion (brain).
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Many insects undergo metamorphosis. ?
Incomplete metamorphosis (Ex. Immature
grasshoppers are small and molt until finally
reaching adult size.) ? Complete
metamorphosis (Ex. Maggot ? Fly Grub ?
Dragonfly Catepillar ? Butterfly/Moth)
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-Reproduce sexually with separate male and
female individuals. The sexes recognize each
other by advertising with bright colors
(butterflies), sound (crickets), or odors
(moths). Fertilization is internal.
-Crustaceans Ex. Crabs, lobsters, and
shrimp. Two pairs of antennae, three or more
pairs of appendages. Walking legs in the
thorax, and abdomen. Appendages can be
regenerated if lost.