1. ARTHROPODS Four subphyla
trilobites: ancient seas; extinct
chelicerates: spiders, ticks, mites, scorpions, & horseshoe crabs
crustaceans: crabs, shrimp, & lobster
uniramians: centipedes, millipedes, & all insects
Form and Function: Three most important features:
tough exoskeleton
chitin- makes up the exoskeleton
some hard and brittle, others leathery and flexible
waterproof- restricts water loss
advantages and disadvantages?????
jointed appendages
antennae, claws, walking legs, wings, flippers and others
segmented body plan
some with many-millipede; others with few-crayfish

3. ARTHROPODS Feeding Respiration Internal Transport
Mouth parts designed for different diets
plants, meat, drink blood, flowers, filter feeders
Respiration
Three structures for respiration
gills: aquatic; crayfish, lobster, shrimp
book lungs: aquatic & land; horseshoe crabs, spiders
spiracles- openings connecting the air sacs with the outside air
tracheal tubes: land; insects, some spiders, millipedes;
fig. 28-8; From spiracles long branching tracheal tubes reach into the animals body tissues. The mov’t of body muscles causes the air to move in and out of the spiracles.
Internal Transport
Heart pumps blood through an open circulatory system
contains sinuses- spaces in the tissue in which blood can move

5. ARTHROPODS Excretion Solid wastes leave through the anus
Nitrogen-containing wastes from metabolism varies
terrestrial arthropods use a set of Malpighian tubules
tubes bathed in blood remove the wastes from blood, concentrate them and add them to undigested food, then out the anus
some have excretory glands at the bases of their legs as well
aquatic: diffuses from the body into the surrounding water at unarmored places like the gills.
Others, like the lobster, use a pair of green glands near the base of the antennae.
Response
Brain with a pair of ganglia in the head. A nerve cord runs down the body parts with branching ganglia along the way. Cut off head; still flaps wings

6. ARTHROPODS Response compounds eyes
2000 separate lenses detecting color and mov’t
taste receptors on mouth, legs, and antennae
ear drums detecting sound above the human range; some on legs
These are all key for protection along with venomous stings & bites
Movement
well developed muscles coordinated by a nervous system (fig )
Reproduction
usually internal
spiders and some crustaceans deposit sperm packets, which are picked up by the female.
GROWTH AND DEVELOPMENT IN ARTHROPODS
molting- the shedding of the exoskeleton
The epidermis digests the inner part of the exoskeleton and absorbs much of the chitin. It secretes a new exoskeleton inside the old one.

8. ARTHROPODS Metamorphosis (fig. 28-15) Incomplete has three stages
egg; nymph; adult
Complete has four stages
egg; larva, pupa, adult
larva- caterpillar
pupa- cocoons
insects body is totally rearranged
Controlled by a complicated interaction of hormones
The amount of juvenile hormone keeps the insects at the larval stage and molting for quite a time. As the level decreases it goes into the pupa stage.
Insecticides are used to control the pests because the insecticides affect the balance of the hormones.