Chapter 36Section 1

Arthropoda

Characteristics• Lobsters, crabs, crayfish, spiders, &

insects• Arthropods- members of the Phylum

Arthropoda• Segmented animals with appendages-

such as legs & antennae• Arthropod means “jointed foot

Characteristics• Exoskeleton- protection & support

• 3 layers of exoskeleton

• Outer- waxy/protein- prevents water loss and drying out

• Middle- protection layer made of protein & chitin- tough carbohydrate

• Inner-flexible/muscles-movement

Characteristics• Cephalization- brain/sensory

structures located at anterior end• Appendages around mouth to aid

with feeding• Antennae specialized for detecting

chemicals

Characteristics• Open circulatory system

• Compound eyes- eyes made of many individual light detectors with lenses

Molting• Molting- shedding of the

exoskeleton to grow

• Hormones trigger molting

• Arthropods usually hide during this stage because they are vulnerable to predators

Evolution & Classification

• Trilobites- ancient & extinct arthropod

• Tagma- specialized for feeding, locomotion, & reproduction

• Two major mouthparts: mandibles- jaw-like chelicerae- pincer-like

REVIEW!!!• Name three characteristics of

arthropods.

• Why do arthropods molt?

Chapter 36Section 2

Subphylum Crustacea

Characteristics • Two-pairs of antennae

• Mandibles

• Pill bugs, lobster, crayfish

• Nauplius- free-swimming larva stage

Diversity of Crustaceans• Range of sizes, but most are small

• Copepods- no larger than a comma ( , )

• Japanese spider crab- 13 feet

Aquatic Crustaceans• Copepods- marine (plankton)

• Water fleas (Daphnia)- freshwater

• Barnacles- marine- sessile; attach to many different surfaces

–Cirri- appendages that sweep food particles into barnacle’s mouth

Terrestrial Crustaceans• Isopods- pill or potato bug

• Lose water quickly through thin exoskeleton

• Live in moist environments

• Roll into a ball when threatened as a defense

• Feed on decaying vegetation

Crayfish• Freshwater crustacean

• Similar to lobster

• Well-studied because of abundance

• Decapods- crayfish, lobster, crab, & shrimp (10-feet)

External Structure• Body divided into abdomen &

cephalothorax- consists of head & thorax- eight segments & lies behind head

• Carapace- dorsal exoskeleton

• Abdomen- six segments behind cephalothorax

External Structure• Two pairs of antennae- touch &

taste• Antennules- touch, taste, balance• Mandibles- chew food• Maxillae- manipulate food & draw

water over gills• Maxillipeds- manipulate food

External Structure• Cheliped- capture food & pincer

defense• Swimmeret- creating water

current & transferring sperm• Telson & uropods- paddle-like tail• Move in backward movement

called “tail flip”

Digestion• Esophagus stomach teeth-

like structures in stomach grind food to fine paste mixed with enzymes secreted by digestive gland enters intestine for digestion & absorption anus

Respiration• Feather-like gills for respiration

• As crayfish walk, circulate water over gills

Circulation• Open-circulatory system

• Circulatory fluid called hemolymph

• Exchanges carbon dioxide with oxygen in water

• Gills dorsal part of crayfish heart

Excretion• Green glands- excess water,

along with wastes is eliminated

• Waste from green glands leaves through a pore at the base of the antennae

Neural Control• Ganglia

• Controls mandibles, maxillae, & maxillipeds

• Ventral nerve cord runs from the ganglia into the thorax & abdomen

Sensory Organs• Sense vibrations & chemicals by

sensory hairs over entire body

• Compound eye sense light

REVIEW!!!• Name three appendages of the

crayfish and the function of each appendage.

• How do crayfish digest food?

• How do crayfish sense their environment?