Transcript Arthropods

June 2, 2016
Classification
Kingdom: Animalia
 Phylum: Arthropoda
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Basic Characteristics
Estimated that there are over 10 million species
 2/3 of all animals on earth are arthropods
 Found all over the world
 Examples: Insects, crustaceans, spiders
(Arachnids), horseshoe crabs, centipedes,
millipedes, trilobites*
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Basic Characteristics
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Range of sizes: 0.3 mm (spider mite)– 4
meters in size (Japanese spider crab)
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Typical arthropod: segmented, coelomate,
bilateral symmetry, exoskeleton &
appendages
Arthropod Systems
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Body Cavity
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Digestive
 Coelomate
 Mouth, stomach, intestine,
Muscular-Skeletal
anus and digestive glands
 Mouth parts have jaws
called mandibles: holding,
chewing, sucking, or biting
 Exoskeleton with
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appendages (leg,
antennae)
Exoskeleton made of
protein and chitin
Muscles attached to the
exoskeleton
First organisms to evolve
joints
Molting to get a bigger
exoskeleton
Arthropod Systems

Nervous
 Movement, sound &
chemicals detected by
antennae; communicate with
pheromones (chemical odor
signals)
 Simple eyes (3-8): detect
light
 Compound eyes (1 pair):
many lenses, complex image
in color
 Ventral nerve cord, anterior
brain, several ganglia
(control body segment in
which they are located)

Circulatory
 One or more hearts
 Open circulatory system
Arthropod Systems

Respiration
1. Gills: aquatic arthropods
2. Tracheal tubes: most land
arthropods, air passages
that carry air throughout
the body powered by
muscle activity. Air in and
out through spiracles
(openings in thorax and
abdomen)
3. Book lungs: spiders and
relatives
4. Diffusion through body wall
Arthropod Systems

Reproduction

Excretory
 Sexually: internal on land,
 Malpighian tubules in
external in water (most 2
sexes)
 Asexually: bees & wasps
○ Parthenogenesis: new
individual develops
from unfertilized egg
abdomen
 Empty into the intestine
Arthropod Systems
Symmetry
 Bilateral
 Appearance
 Segmented into head, thorax, (or
cephalothorax) and abdomen
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June 2, 2016
Class Insecta
Ex: grasshoppers, butterflies, beetles, ants, etc
 1,000,000 described species
 3 body regions: head, thorax, abdomen
 6 legs attached to the thorax (which has 3
segments)
 Adults have 1 or 2 pairs of wings attached to
thorax (some have none)
 2 antennae
 Lateral compound eyes
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Class Arachnida
Ex: spiders, scorpions, ticks, mites, etc.
 65,000 described species
 2 body regions: cephalothroax and abdomen
 8 legs
 No antennae
 Mouth parts are chelicerae (modified
appendages)

 In spiders, these are fangs
Class Crustacea (Subphylum)
Ex: crabs, shrimps, lobster, barnacles, etc.
 44,000 describe species
 2 body regions
 2 pairs of antennae
 5 or more pairs of legs
 Primarily aquatic, few terrestrial
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Class Chilopoda
Ex: centipedes
 2,800 describe world species
 Well-defined head
 1st pair of legs modified for delivering
venom
 Flattened top to bottom
 1 pair of legs per segment
 1 pair of antennae
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Class Diplopoda
Ex: millipedes
 2 pairs of legs per segment
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 First 4 segments have 1 pair of legs
1 pair of antennae
 Well-defined head
 Usually cylindrical
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