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?