Phylum Arthropoda
Arthropods
 Make up about 80% of the known animal
species
 Insects are by far the most common species of
arthropods
 Arthropod means joint-footed
 Range from the deep sea to mountain peaks
 Bilateral symmetry
 Growth requires molting
General Arthropod Characteristics
Arthropods have:
1. Exoskeleton
 - Most prominent characteristic is their outside
skeleton, or exoskeleton.
 - Exoskeleton provides support, protection and
attachment site for muscles. Made of protein and
chitin
 Chitin is a strong, flexible, polysaccharide
 - All arthropods molt, or shed their exoskeletons
periodically. After it molts, it grows before the new
skeleton hardens.
 - Skin glands digest the inner part of the exoskeleton
and other glands secrete the new one.
General Arthropod Characteristics
Arthropods have:
2. Segmented Bodies
 - Have segmented bodies that show various
patterns of segment fusion (tagmosis) to form
integrated unit like the head, abdomen, ...
General Arthropod Characteristics
Arthropods have:
3. Jointed Appendages
 - Have joints between
body sections (includes
legs and antennae)
 - Have jointed
appendages (a structure
such as a leg that grows
out from the main part
of the body)
Arthropod Characteristics
 Cephalization is more prominent than in
annelids (brain and complex sense organs in
the head region)
 Special organs sense touch, vibration, and
chemicals. The eyes of many arthropods are
particularly specialized.
 Open circulatory system. The dorsal heart
pumps blood from the posterior end of the
animal to the anterior end.
 - Blood moves through the hemocoel (major body
cavity)
Phylum Arthropoda –
2 Subphylum
 Subphylum Chelicerates
 Class Arachnida
 Spiders, scorpions, mites, ticks
 Subphylum Mandibulates (4 major classes)
 Class Crustacea
 Crayfish, Crab, Lobster
 Class Chilopoda
 Centipedes
 Class Diplopoda
 Millipedes
 Class Insecta
 Insects, Grasshoppers
Subphyla Chelicera
 Chelicera are pointed appendages (modest
pinchers) used for feeding and manipulating food
(in lieu of chewing mandibles)
 The body of chelicerates has two major parts:
 1. The cephalothorax is a fused section composed of the
head and any body segments that have legs attached.
 2. The abdomen consists of posterior segments that
contain most of the internal organs.
 Lack antennae
 Nearly all have 4 legs
Subphlya Chelicera:
Class Arachnida
Subphyla Mandibulata
Unlike chelicerates, mandibulates have mandibles, or jaws, for chewing food.
All mandibulates have antennae



Three distinct body regions



- segmented sense organs on the head
- head, thorax, abdomen
They have three or more pairs of
walking legs
Subphyla Mandibulata:
1. Class Crustacea
 Crustaceans typically have:
 - two pairs of antennae
 - two or three body sections
 Cephalothorax – head fused with the thorax
 - chewing mouthparts called mandibles.
- 5 or more pairs of legs
• Primarily aquatic, few terrestrial
Ex:
Crustacean
Subphyla Mandibulata:
2. Class Chilopoda
(centipedes) & 3. Class
Diplopoda (millipedes)
Subphyla Mandibulata:
Class Insecta
 Insects typically have:
 The three distinct segments (head, thorax,
abdomen)
 Three pairs of legs attached to the thorax
 Mandibles
 One pair of antennae
 One pair of compound eyes
 Two pairs of wings on the thorax
 Tracheal tubes for respiration
 Tracheal tubes open to the outside through small
holes called spiracles
Class Insecta:
 Grasshopper dissection on Monday!
Homework
 Complete coloring assignment
 Pre-Lab reading for Grasshopper
dissection