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Arthropods
Chapter 36-37
36.1 Phylum Arthropoda
• Largest animal phylum
• insects, spiders,
shrimp, and centipedes
Characteristics
• “jointed legs”
• Have body segments w/
appendages
• high degree of cephalization
(antennae and compound eyes
Body regions• head, thorax, and abdomen
• 2 or 3 can be fused together
Skeletal Structure
• Have an exoskeleton
• Made of protein &
carbohydrate = chitin
• Sheds exoskeleton
as it grows =
molting
Steps of Molting
1) Animal splits old
tight exoskeleton
2) Crawls out
3) Puffs up w/ air or
water
4) Secretes new
exoskeleton
(very vulnerable)
• Body Cavity & digestive
system possess mouth &
anus
• Nervous system is similar
to annelids, but w/ larger
brains
36.2 Subphylum Crustacea
• Crabs, crayfish, lobsters, shrimp,
barnacles, water fleas, & pill bugs
• Cephalothorax & abdomen
• 5 pairs of walking legs
(1st pair = chelipeds)
Shrimp in
the wild…
Pill bug
B
A
R
N
A
C
L
E
• Jaws (mandibles) are used
for crushing food
• Force water over gills or
respire thru exoskeleton
• 1 or 2 antennae
• 5 pairs of swimmerets help in
locomotion & reproduction
• Regenerate lost appendages
Telson & uropods:
paddle-like tail
• Open circulatory
system
Green gland:
excretory organ
36.3 Subphylum Chelicerata &
Myriapoda
Subphylum Chelicerata
• spiders, scorpions, mites, sea
spiders, horseshoe crabs
• lack antennae
• have six pairs of appendages
Class Arachnida
• spiders, scorpions, mites, ticks
–cephalothorax
•1 pr of chelicerae
•1 pr of pedipalps
•4 prs of walking legs
–abdomen
• 8 simple eyes, chelicerae (fangs)
• spinnerets produce silk threads
• respire thru spiracles that
connect to book lungs
(tracheae)
• Malpighian tubules excrete
wastes while conserving water
Spiders
• Poisonous bite paralyzes prey
• Digestive enzymes then
liquefy organs, which are
drunk later
2 dangerous U.S. species:
Black Widow
• Red hour glass design on
abdomen
• Only females’ bite are dangerous,
extremely poisonous
• Related species: Australian
Brown Widow & Japanese Red
Widow
Brown Recluse
• Southern Spider/ house spider
• Bite causes massive cell
destruction
• Related species are developing
potent venom
Day 3 after a brown
recluse bite…
Day 9 or 10
after brown
recluse bite…
Scorpions
• have large, pincerlike pedipalps
• have stinger on the last segment
of abdomen
Mites, Ticks, & Chiggers
• Has fused
cephalothorax
and abdomen
• Many are
parasitic,
some spread
diseases
• Can cause Lyme disease
(deer tick)
& Rocky Mountain
Spotted Fever
(wood or dog tick)
Subphylum Myriapoda
• Centipedes &
millipedes
Class Diplopoda
• Millipedes
• rounded bodies
• 2 pairs of legs
per segment
• Slow moving
herbivore
• Can expel
cyanide gas
Class Chilopoda
• Centipedes
• have flattened
bodies
• 1 pair legs per
segment
• Carnivorous &
have venomous
claws
• Quick moving
37.1 Class Insecta
–Head: mandibles, 1 pair of
antennae
–Thorax: 3 pairs of jointed legs,
1-2 pairs of wings
–Abdomen: 9-11 segments, no
wings or legs in adults
Comparison of Crustaceans & Insects
Circulatory, Respiratory, &
Excretory
• open circulatory system
• Gas exchange occurs by air-filled
tracheae
• Malpighian tubules remove
cellular wastes while conserving
water
Nervous System
• brain and ventral nerve cord
• sensory structures:
–simple &
compound eyes
–sensory hairs
–sound-sensing tympanum
Insect Development
• They go thru metamorphosis
1) Incomplete metamorphosis:
nymph hatches from egg and
resembles adult
– no wings
– nymph molts several times to
become adult
• Grasshoppers, crickets &
lice
• 3 stages: egg, nymph,
adult
2) Complete metamorphosis:
wormlike larva (caterpillar)
hatches from egg
–molts several times before
becoming a pupa
–pupa molts to produce adult
(does not look like larva or pupa)
• Most insects
(butterflies, beetles, ants,
bees, moths & flies)
• 4 stages: Egg, Larva, Pupa
(resting), & Adult
Entomology: study of
insects and other land
arthropods
Entomologists:
scientists who study
insects
Insect
Diversity
The Success of Insects
• live in almost everywhere
–ability to fly
–exoskeleton
–small size
–short life span
–jointed appendages
37.2 Insect Behavior
Communication
-Pheromones
-Sounds
-Flashes of light
Honey Bee Behavior
Worker bees: females that do not
produce young
Queen bee: only reproductive
female
Drones: males that
develop from
unfertilized eggs
Dancing Bees
2 Types:
–round dance: food is nearby
–waggle dance: direction of food
and the distance from hive
Echinoderms &
Invertebrate Chordates
Chapter 38
38.1 Phylum Echinodermata
• “ spiny-skinned”
–Sessile or motile
–pentaradial symmetry
–endoskeleton
–water-vascular system
–tube feet
Pentaradial Symmetry
Structure
Endoskeleton of calcium
carbonate plates (ossicles)
supports and protects the
body
(1st animals w/ endoskeleton)
Water Vascular System
• Network of
water filled
canals
• Tube feet act
like suction
cups for
moving &
feeding
Parts:
Madreporite- opening on top
Ring canal- center circle
Radial canals- go from ring canal
into each arm/ray
Ampulla- like “bulb” of an
eyedropper
Tube feet- apply suction to a surface
• Push their stomach inside out thru
its mouth when it feeds
• NO circulatory, excretory, or
respiratory organ systems
• Nervous system- nerve ring and
radial nerve that runs along each
arm
Reproduction & Development
• Most have separate sexes
• Each arm has ovaries or testes
• External
fertilization
• Can regenerate
Class Crinoidea
• sea lilies and feather stars
Class Ophiuroidea
• “snake-tail”
• largest echinoderm class
• basket stars and brittle stars
Class Echinoidea
• “spinelike”
• sand dollars and sea urchins
Class Holothuroidea
• “water polyp”
• Sea cucumbers
Class Asteroidea
• “starlike”
• Sea stars (starfish)
38.2 Invert. Chordates
Phylum Chordata (3 Subphyla)
–Cephalochordata
–Urochordata
–Vertebrata (vertebrates)
Subphylum Cephalochordata
• lancelets
• Retain notochord, dorsal nerve cord,
pharyngeal pouches, and postanal tail
thruout life
• feed by filtering water thru slits in
pharynx
Subphylum Urochordata
• tunicates or sea
squirts
• Most are sessile
as adults
• barrel-shaped filter
feeders
• hermaphrodites