1. -The exoskeleton is made up of chitin and
protein.
a. Provides protection
b. Provides points of attachment for the
muscles that move appendages
-The animal must molt (ecdysis) its old
exoskeleton if it outgrows it.
-Well-developed eyes, olfactory receptors,
and antennae for touch and smell (most at
the anterior end = cephalization).
-Open circulatory system: Hemolymph (the
word “blood” is reserved for a closed
circulatory system) is pumped from the heart
into spaces surrounding tissue and organs.

2. -Respiratory by gills, book lungs, and trachea.

3. -The arthropods came from 4 evolutionary lineages:
1. Trilobites (extinct)
2. Chelicerates (horseshoe crab,
scorpions, ticks, and spiders)
3. Uniramians (centipedes,
millipedes, and insects)
4. Crustaceans (crabs, lobsters,
shrimp, barnacles)

4. Scientists now want to separate these lineages
into different phylums:
Phylum Trilobita, Phylum Chelicerata,
Phylum Uniramia, Phylum Crustacea

5. -Some major classes in phylum arthropods:
Arachnids: Ex. Spiders, scorpions, ticks, mites
Body with 1 or 2 main parts, six pairs of
appendages (Chelicerae, pedipalps, and
4 pairs of walking legs); mostly terrestrial.

6. -Diplopods: Ex. Millipedes
Body with distinct head bearing antennae
and chewing mouthparts, segmented body
with two pairs of walking legs per segment;
terrestrial and herbivorous.

7. -Chilopods: Ex. Centipedes
Body with distinct head bearing large
antennae and 3 pairs of mouthparts;
appendages of first body segment
modified as poison claws; body segments
bear 1 pair of walking legs each;
terrestrial; carnivorous.

9. -Insecta: Ex. Insects
Body divided into head, thorax, and
abdomen; antennae present; mouthparts
modified for chewing, sucking, or lapping;
usually with two pairs of wings and three
pairs of legs; mostly terresterial.

10. -Entomology: study of insects
-Flight is one of the great successes of insects.
 Dragonflies were among the first insects
to fly.

11. -Insects have a complete digestive system.
-Open circulatory system (hemolymph)
-Metabolic wastes removed from the
hemolymph via the excretory organs called
Malpighian tubules.
-Gas exchange via the the trachael system
open to the outside through
spiracles (pores).

12. -Nervous system consists of a pair of ventral
nerve cords that meet in the head, to form the
cerebral ganglion (brain).

13. Many insects undergo metamorphosis.
 Incomplete metamorphosis
(Ex. Immature grasshoppers are small
and molt until finally reaching adult size.)
 Complete metamorphosis
(Ex. Maggot  Fly
Grub  Dragonfly
Catepillar 
Butterfly/Moth)

14. -Reproduce sexually with separate male and
female individuals.
The sexes recognize each other by advertising
with bright colors (butterflies), sound
(crickets), or odors (moths).
Fertilization is internal.
-Crustaceans: Ex. Crabs, lobsters, and shrimp.
Two pairs of antennae, three or more pairs
of appendages. Walking legs in the thorax,
and abdomen. Appendages can be
regenerated if lost.