Chapter 16 The Arthropods
Feb 14, 2016
Chapter 16
The Arthropods
Phylum Arthropoda
Largest phylum in Kingdom AnimaliaAnthropoda means “jointed feet”Includes lobsters, spiders, scorpions, milli-
pedes, and insectsCan be harmful or helpfulHarmful: destroy crops, eat other animals’
food, spread diseasesHelpful: studied by engineers; control the
numbers of harmful arthropods; help plants reproduce; make wax, honey, medicine, and silk
Phylum Arthropoda
All arthropods have:Exoskeleton – their bones are outside of their body
Chitin – allows the bones to be tough and flexible – they bend with-out 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
Phylum Arthropoda
Nervous System Anatomy
Brain – located in the headGanglia – nerves in the legsVentral Nerve Cord – big nerve that connects the
brain and the gangliaAntennae – come out of the head and do taste, smell,
and touchCompound 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
Nervous System Anatomy
Subphylum Crustacea
Lobsters, crabs, crayfish, shrimpKingdom Animalia, Subkingdom Invertebrates, Phy-
lum Anthropoda, Subphylum CrustaceaUsually live in the waterCarapace – 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
Subphylum Crustacea
Subphylum Chelicerata
3 classes: Arachnida is the most important classArachnids have:
8 legs – 2 of these are pedipalps (legs used for sensing and mating instead of walking)
2 major segmentsCephalothorax (head-chest)abdomen
No antennae or mandibles (jaws)Have chelicerae instead (mouth that looks like fangs)
Respiration by book lungsBreathe through their stomachs
Usually 4 pair of simple eyes (8 eyes)Reproduce sexually – females are usually larger than
males
Subphylum Chelicerata
Scorpions, mites, and ticks
Other Arachnids
Class Insecta
80% of all animals are insects (bugs)There are 31 orders under Class InsectaStructure of Insects:
Three pairs of legs (six legs)Usually have wings3 segments to the body
HeadThorax (chest)Abdomen
One pair of sensory antennae (2 of them)
Class Insecta
M0st insects have 2 pairs (4) wingsKinds 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
Wings of Insects
Continued:Leatherlike wings: extra set of wings that pro-
tects 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
Wings of Insects
Mouth: Upper lip - labrumMandibles - used for chewingMaxillae – put food into the mouthLower 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)
Digestion (eating) of Insects
Respiration: insects breathe in their ab-domens 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 reproductionThe male puts sperm in the femaleThe female then lays eggs that will hatch later
Respiration, Circulation, Excretion and Reproduction
Metamorphosis means changing from a baby to an adult
There are two kinds of metamorphosis:Incomplete metamorphosis (3 stages)
Grasshoppers, cicadas, and true bugsEggNymph (teenager – looks like a small adult) – only for
insects that stay on land (cicadas)ORNaiad – teenager that doesn’t look like the adult and
lives in the water (grasshoppers)Adult – the bug
Metamorphosis in Insects
Incomplete Metamorphosis
Complete metamorphosis (4 stages)Most insects – butterflies, flies, beetles, mosquitoesEggsLarva – like a little worm (maggots, grubs, wig-
glers, caterpillars) – childhood bugPupa – teenager insect – usually inside a case
called a cocoonAdult – the bug
Metamorphosis
Complete Metamorphosis