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Phylum
Arthropoda
Our
most diverse phylum with more than 1,000,000 insect species alone!
Have
hard exoskeleton made of chitin.
Breathe
with gills, lungs or trachae (air tubes).
Contains
four classes: Trilobita,
Chelicerata,
Crustaceae
and Uniramia.
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Class
Chelicerata
Horseshoe
crabs, spiders, scorpions and ticks.
Named
for their chelicera, the first pair of appendages.
Some
poisonous species: scorpions can sting with their modified last abdominal
segment. spiders can bite.
Many
members, such as the horseshoe crabs, have remained relatively unchanged for
millions of years.
Scorpions
were the first arthropods on land.
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Class
Uniramia
Centipedes,
millipedes and insects.
Named
for their unbranched appendages.
Centipedes
vs. Millipedes:
Centipedes
have only one pair of legs per segment, millipedes have two.
Centipedes
are predators and have poisonous bites; Millipedes are scavengers and
detritivores and may exude a noxious substance from glands along their body.
Insects
were the first animals to fly and remain the dominant animal group in most
habitats.
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Class
Crustacea
Lobsters,
shrimp, crayfish and isopods (pillbugs).
Most
are aquatic. Crustaceans are the most dominant marine arthropod group.
Often
add calcium carbonate to their exoskeleton for an extra-hard shell.
Together,
insects and crustaceans make up about 80% of the named animal species.
Many
species are important to humans (e.g., for food). Barnacles encrusting
ship hulls can slow a ship by as much as 40%.
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