Lesson 19 Outline list Lesson 21
Fundamentals of Biology
Lesson 20
Arthropods
I. Phyla.
A. Crustacea: lobsters, crabs, shrimp, crayfish.
B. Arachnida: spiders, scorpions, ticks, mites.
C. Insecta.
D. Diplopoda: millipedes.
E. Chilopoda: centipedes.
II. General Characteristics.
A. "Jointed foot".
B. Body segmentation.
C. Exoskeleton of cuticle.
1. Mostly made of chitin.
2. Also contains glycoproteins,
waxes, lipids that seal body fluids in and keep water out.
3. Thin and flexible at joints.
4. Molting during growth.
D. Bundles of muscles attached to inside of cuticle on either
side of joints.
E. Open circulatory system with dorsal heart.
1. Hemocoel: body cavity
2. Filled with a clear hemolymph
fluid that bathes most internal tissues.
F. Ventral nervous system.
G. Separation of sexes.
H. Internal fertilization in terrestrial species; external
fertilization in aquatic species.
I. Regeneration as a means of repair.
III. Crustacea.
A. General Characteristics.
1. Most aquatic; some terrestrial,
some parasitic.
2. Some are filter feeders, using
setae for filters.
3. Cuticle impregnated with CaCO3
– makes it hard.
4. Tiny species prominent in
plankton.
B. Body Structure.
1. Two part division.
a.
Cephalothorax.
i. Two pairs antennae.
ii. Three pairs for feeding.
iii. Appendages for walking: five in the common species.
b. Abdomen.
2. Respiration by gills.
C. Crayfish.
IV. Arachnida.
A. Body Structure.
1. Two part division.
a.
Cephalothorax.
i. No antennae or mandibles.
ii. One pair of chelicerae: contain poisonous fangs.
iii. One pair of pedipalps.
a) Sense and hold food while eating.
b) In male, transfer sperm.
iv. Four pairs of legs.
b. Abdomen.
2. Respiration.
a. Book
lungs.
b. Some have
tracheae.
B. Spiders.
1. All spin silk with spinnerets.
2. Silk is a fine, elastic protein.
3. Silk produced as liquid, but
hardens in air.
4. All are carnivorous.
5. Usually poison their prey.
V. Insecta.
A. Fascinating Facts.
1. 300 million individuals for every
person.
2. 900,000 species.
3. Most terrestrial, some freshwater.
B. Body Structure.
1. Three part division.
a. Head.
i. One pair antennae.
ii. Compound eyes.
iii. Mouth.
b. Thorax.
i. Three pairs legs.
ii. Zero, one, or two pairs wings.
c. Abdomen.
2. Mouth Types.
a. Sponging
(fly).
b. Siphoning
(butterfly).
c. Piercing
(mosquito).
d. Chewing
(grasshopper, most others).
i. Labrum: upper lip.
ii. Mandibles (pair) for chewing.
iii. Maxillae (pair) for feeding.
iv. Maxillary palps for feeding.
v. Labium: lower lip.
vi. Labial palps: fastened to the labium.
3. Wing Types.
a.
Membranous: thin. transparent, with supporting veins (most insects).
b.
Scale-covered: delicate, colored scales (butterfly, moth).
c.
Leather-like: protective (grasshopper).
d. Horny:
protective (beetle).
4. Digestive System.
a. Mouth
b. Salivary
glands.
c. Foregut.
i. Esophagus.
ii. Crop.
iii. Gizzard.
d. Midgut.
i. Stomach.
ii. Gastric ceca provide digestive juices.
iii. Major site of digestion and absorption.
e. Hindgut.
i. Intestine.
ii. Rectum.
iii. Anus.
5. Respiration.
a. Spiracles:
pores that admit air.
b. Tracheae:
finely branched tubes throughout body.
6. Excretory System.
a. Malpighian
tubules: thin ring of tubules encircling junction of stomach and intestine.
b. They
extract nitrogenous wastes from the blood and empty into the intestine for
elimination.
7. Neural System.
a. Sense of
smell usually centered in the antennae.
b. Taste
receptors on the mouthparts.
c. Tactile
hairs over the body enable sense of touch.
d. Compound
eyes.
e. Some have
hearing organs.
8. Reproduction.
a. Male
deposits sperm into the seminal receptacle.
b. Ovipositor
lays the eggs.
c. Eggs are
fertilized as they are laid.
D. Type of development.
1. Egg - Immature - Adult.
a. Immature
is a small version of adult.
b.
Silverfish.
2. Egg - Nymph - Adult.
a. Nymph is
wingless version of adult.
b.
Grasshoppers, crickets, termites, aphids.
3. Egg - Naiad - Adult.
a. Naiad is
aquatic version, with gills.
b. Mayflies,
dragonflies.
4. Egg - Larva - Pupa - Adult (90% of
cases).
a. Larva is
totally different from adult.
b. Pupa is
the immobile stage in which metamorphosis occurs.
c.
Metamorphosis: body structures and organs of the larva are dismantled and
reshaped.
d.
Butterflies, beetles, flies, bees, ants.
E. Major orders.
1. Hymenoptera (bees, wasps, ants).
a.
“Membrane-winged.”
b. Many are
social.
c. Only
stinging insects.
2. Lepidoptera (butterflies, moths).
3. Coleoptera (beetles).
a. Largest
order of insects: 250,000 species.
b.
Exoskeleton of some can support over 1,500 times their own weight.
4. Diptera (flies, mosquitoes,
gnats).
5. Orthoptera (grasshoppers,
cockroaches).
VI. Chilopoda (centipedes).
A. “Thousand-foot.”
B. Carnivore.
C. Flattened body.
D. Many-segmented body with one pair of legs per segment.
E. Amazing speed and agility.
F. Some tropical centipedes can reach 1 ft. and capture worms
and snakes.
VII. Diplopoda (millipedes).
A. “Double-foot.”
B. Herbivore and scavenger.
C. Rounded body.
D. Two pairs of legs per segment.
E. Moves slowly.