The Arthropods
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Transcript The Arthropods
Chapter 16
Largest phylum in Kingdom Animalia
Anthropoda means “jointed feet”
Includes lobsters, spiders, scorpions, millipedes, and
insects
Can be harmful or helpful
Harmful: destroy crops, eat other animals’ food, spread
diseases
Helpful: studied by engineers; control the numbers of
harmful arthropods; help plants reproduce; make wax,
honey, medicine, and silk
All arthropods have:
Exoskeleton – their bones are outside of their body
Chitin – allows the bones to be tough and flexible – they bend
without breaking
Arthropods molt – as they grow, their exoskeleton becomes too
small – they outgrow the exoskeleton and throw it away
Jointed appendages – their legs and feet have joints (bend)
Body segmentation – most have 3 parts to their bodies
Head
Thorax (chest)
Abdomen (belly)
Open Circulatory System – they have a heart, but the blood goes
into the body parts after leaving the heart (not veins)
Ventral Nervous System – Ganglia (nerves) are located near the
legs and connected to the brain by one cord
Brain – located in the head
Ganglia – nerves in the legs
Ventral Nerve Cord – big nerve that connects the brain
and the ganglia
Antennae – come out of the head and do taste, smell,
and touch
Compound eyes – insects and crustaceans have these –
able to see all around, not just a few directions
______ OR_________
Simple eyes – able to see very little, usually just light
and dark
Lobsters, crabs, crayfish, shrimp
Kingdom Animalia, Subkingdom Invertebrates, Phylum
Anthropoda, Subphylum Crustacea
Usually live in the water
Carapace – the back plate of a lobster (the front has 6
plates)
Scavengers: they eat anything! They grind their food into
powder using the gastric mill.
They can regenerate (grow new parts)
Reproduce sexually – male gives sperm to the female in the
fall, female lays eggs in the spring that hatch in the
summer
3 classes: Arachnida is the most important class
Arachnids have:
8 legs – 2 of these are pedipalps (legs used for sensing and
mating instead of walking)
2 major segments
Cephalothorax (head-chest)
abdomen
No antennae or mandibles (jaws)
Have chelicerae instead (mouth that looks like fangs)
Respiration by book lungs
Breathe through their stomachs
Usually 4 pair of simple eyes (8 eyes)
Reproduce sexually – females are usually larger than males
Scorpions, mites, and ticks
80% of all animals are insects (bugs)
There are 31 orders under Class Insecta
Structure of Insects:
Three pairs of legs (six legs)
Usually have wings
3 segments to the body
Head
Thorax (chest)
Abdomen
One pair of sensory antennae (2 of them)
M0st insects have 2 pairs (4) wings
Kinds of wings:
Membranous wings: thin, transparent (see through) –
most common kind of wing - like a dragonfly or a bee
Scale-covered wings: butterflies and moths
Continued:
Leatherlike wings: extra set of wings that protects the
wings used to fly – like a cover for wings – grasshoppers
have these
Horny wings: ladybug wings – thick, protect the smaller
wings, cover the back of the bug
Mouth:
Upper lip - labrum
Mandibles - used for chewing
Maxillae – put food into the mouth
Lower lip – labium
Stomach:
Foregut – behind the mouth – this is where salivary glands get
the food wet with spit before going to the gizzard to be
ground up into powder
Midgut – where the stomach is – gastric ceca put more
digestive juices onto the food
Hindgut – place right before the food is excreted (pooped)
Respiration: insects breathe in their abdomens
through tubes called spiracles
Circulation: the insects heart pumps blood into the
abdomen, where it covers the organs – no veins
Excretion: Malpighian tubules are straws that pull
nitrogen out of the insect and put it into the intestines,
where it will become poop
Reproduction: Sexual reproduction
The male puts sperm in the female
The female then lays eggs that will hatch later
Metamorphosis means changing from a baby to an
adult
There are two kinds of metamorphosis:
Incomplete metamorphosis (3 stages)
Grasshoppers, cicadas, and true bugs
Egg
Nymph (teenager – looks like a small adult) – only for insects
that stay on land (cicadas)
OR
Naiad – teenager that doesn’t look like the adult and lives in the
water (grasshoppers)
Adult – the bug
Complete metamorphosis (4 stages)
Most insects – butterflies, flies, beetles, mosquitoes
Eggs
Larva – like a little worm (maggots, grubs, wigglers,
caterpillars) – childhood bug
Pupa – teenager insect – usually inside a case called a cocoon
Adult – the bug