Download ARTHROPODS HAVE EXOSKELETONS & JOINTS

Arthropods Have Exoskeletons
& Joints
• MOST INVERTEBRATES ARE
ARTHROPODS
– Most common type of invertebrate: arthropod =
invertebrate with segmented body covered by hard
outer skeleton; many pairs of legs; insects, crustaceans
& arachnids are arthropods
• INSECTS ARE SIX-LEGGED ARTHROPODS
• CRUSTACEANS LIVE IN WATER AND ON
LAND
• ARACHNIDS ARE EIGHT-LEGGED
ARTHROPODS
• MILLIPEDES AND CENTIPEDES ARE
ARTHROPODS
Arthropods: exoskeletons
• Exoskeleton made of hard “chitin”, like suit of armor
protecting it & keeping it moist (if on land).
• Joints (where chitin is thin & flexible) allow for
movement; muscles attach around joints for this.
• 3 main body parts: Head, Thorax, & abdomen
• Exoskeleton doesn’t grow, it molts (sheds old one
and grows new one); this is dangerous time because
new one stays soft for awhile.
Insect: 6 legged arthropods
• Arthropods have well-developed nervous & digestive
systems; open circulatory system with blood moving into
body without blood vessels; reproduce sexually; either
male or female parts.
• As adults have 3 body segments, pair of antennae, 6 legs
attached to thorax.
• If on land, have spiracles (openings in exoskeleton to bring
in oxygen).
• Many can blend in to environment, or have wings.
• Many are herbivores with designs for specific plants to eat
(butterfly has tube to reach nectar)
• Some are social insects (bee, termite, ant) living in groups;
work together to get food, maintain nest & care for
offspring; usually just one female (queen) lays eggs.
Insect=most common arthropod
• All insects reproduce sexually; female lays many eggs(often
with protective hard covering to keep from drying out)
• Insects undergo metamorphosis(3 stages of change): Egg
hatches into Larva= spends its time eating; Pupa=second
stage, insect body develops inside of protective casing;
Adult= final stage, insect able to reproduce now
• Some insects skip some of the metamorphic stages
• Many larval stages are common (caterpillar, inchworm);
often larva are very different (mosquito larva live in water &
feed on algae, pupa form on water surface & adult flies off to
feed on blood of animals & lay eggs in water again).
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Crustacean
Arthropods
Most live in water; many used as
food source in important food
webs & by humans.
3 or more pairs of legs & 2 pair
sensory antennae
Most have heart but no blood
vessels like other arthropods
May eat plants/small animals, or
remains of other organisms
(barnacle is filter feeder)
Barnacle larva is free swimming,
then attaches as adult to hard
surface (rock/boat/mollusk shell)
& uses its tentacles to grab food
from surrounding water.
Arachnid- 8 legged arthropod
• Spiders, mites, ticks & scorpions are arachnids.
• Exoskeleton, jointed limbs, segmented bodies
(like all arthropods) but also have 4 pairs of legs
and only 2 body segments; no antennae
• Some are parasites(tics,chigger mites), others are
predators (spiders & scorpions). These get prey
by stinging, biting or injecting venom.
• Most arachnids are spiders. Make strong silk to
form webs to capture food. Spinnerets at rear of
abdomen spins strands of silk into web.
• Some arachnids have spiracles to get oxygen,
while others (some spiders) have “book lungs”
(moist folded pockets within abdomen).
Millipede & Centipede
Arthropods
• Both have long, segmented bodies with many
legs.
• Reproduce sexually, hatch from eggs.
• Millipedes have 2 pair of walking legs on each
body segment; move slowly & eat decaying
leaves & plant matter; may emit foul odor if
disturbed which may harm predators.
• Centipedes move quickly, have 1 pair of legs
per segment, have antennae & jaw-like
mouthparts. Many have pincers on rearmost
segment. Are predators that can paralyze prey.