Transcript Phylum Arthropoda

Phylum Arthropoda
The Arthropods
Arthro = jointed, Pod = foot
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•Largest animal
phylum containing
more than 3x the
number of all
other animal
species
combined.
•More than 750,000 species
identified (in blue).
•Also has the most biomass
of any group.
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Phylum Arthropoda
• General
characteristics:
1.Segmented body
2.Tough exoskeleton
composed of chitin
3.Jointed
appendages.
Main Groups of Arthropods
• Arthropods are classified based on the
number and structure of their body segments
and appendages – particularly their mouth
parts
Subphylum Crustaceans – crabs, shrimp,
lobsters, pill bug, and crayfishes
Subphylum Chelicerates – horseshoe crabs
and arachnids (spiders, ticks, scorpions)
Subphylum Uniramia – insects, millipedes,
and centipedes
Arthropod Digestive System
• Arthropods feed on a variety of things:
herbivores, carnivores, detritivores (detritus =
dead leaves, etc.), filter feeders, and parasites.
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Arthropod Excretion (Urination)
• Malphigian Tubules are used to dispose of
nitrogenous wastes. These thin, tubelike
organs take N2 from blood and add it to feces.
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Arthropod Circulation
• Open Circulation – blood flows from heart to ends of
vessels then out into an open area called a sinus.
Eventually the blood flows back into the vessels
through pores called ostia.
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Arthropod Respiration
• Most terrestrial arthropods breathe through tracheal
tubes that extend throughout the body. Air enters
and leaves the body through openings called
spiracles located along the length of the animal.
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Arthropod Respiration
• Others such as spiders respire using “book lungs”
that have layers of respiratory tissue.
• Aquatic arthropods breathe using gills.
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Arthropod Nervous System
• Arthropods
exhibit
cephalization
having a brain
and central
nerve cord
• How is the
location of the
nerve cord
different than
in humans?
Arthropod Reproductive Organs
• Sexes are separate.
Female
Male
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Arthropod Fertilization
• Aquatic Arthropods reproduce sexually
using both external and internal
fertilization.
• Terrestrial Arthropods reproduce sexually
using internal fertilization.
• Only a few species bear live young. Most
females lay fertilized eggs.
Arthropod Development
• Arthropods undergo a period of molting in
which they shed their exoskeleton and grow a
new one
• Since the animal has no protection at the time
of molting they will often hide themselves
Subphylum Crustaceans
• Have several mouthparts,
three body sections that
may be fused, 5 or more
pairs of legs, and two pairs
of antennae.
• Most are aquatic.
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Subphylum Chelicerates
• Have mouthparts called
chelicarae, two body
sections (cephalothorax
and abdomen), 4-5 pairs of
legs, and lack antennae.
• Most are terrestrial.
• HORSESHOE CRABS have
the body structure more
like a spider with a hard
plated shell like a crab –
they can be as big as a
frying pan!
Subphylum Chelicerates
• SPIDERS: all produce silk, but not all
produce webs.
• MITES & TICKS: small and usually
parasitic. Chiggers, mange, and scabies
mites cause itching painful rashes in
humans and other mammals. Ticks
spread Lyme disease and Rocky
Mountain spotted fever.
• SCORPIANS: have a venomous stinger
than can paralyze and kill prey!
Subphylum Uniramia
• CENTIPEDES: 15 to 170 pairs
of legs – typically one set of
legs per body segment
• Centipedes are carnivorous
and use venomous claws to
catch arthropods,
earthworms, toads, small
snakes, and even mice!
• Centipedes lose moisture
easily so are limited to dark,
damp places.
Subphylum Uniramia
• MILLIPEDES: more legs
than centipedes.
Typically two sets of
legs per body segment
• Feed on dead and
decaying plant material
• Millipedes roll into a
ball when startled
Subphylum Uniramia
INSECTS: These animals have the greatest
impact on the activities of the planet!
Characteristics:
1. Exoskeleton
2. Body is divided into
three parts (head,
thorax, and abdomen)
3. Three pairs of legs
(jointed appendages)
are attached to the
thorax.
Insect Metamorphosis
Morph = shape/form
Metamorphosis – the process of changing
shape or form
Incomplete Metamorphosis:
the young look a lot like the
adult and are called
nymphs – they mature into
adults as they develop
wings and sexual organs.
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Insect Metamorphosis
• Complete
Metamorphosis:
young larvae look
nothing like adult
and even feed in
different ways. The
young molt several
times until finally
molting into a pupa
in which the larva
changes into an
adult.
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