1. Terrestrial Mandibulates: Spiders and Insects
Phylum Arthropoda

2. Characteristics Segmented bodies Jointed appendages Exoskeleton
Specialized for eating, sensing, reproduction, defense and movement
Exoskeleton
Hard covering on the outside of the animal
Limits the growth of the organism (must shed)
Muscles are attached to this layer
Secreted by underlying epidermis
Shed (molted) at intervals

3. Characteristics Bilateral symmetry Muscular system Body cavity Complex
Contains two types of muscles
Body cavity
Coelom is smaller in size  
Most of body cavity consists of hemocoel (sinuses, or spaces, in the tissues)
Filled with blood

4. Characteristics Digestion Circulatory System Complete digestive system
Esophagus, crop, gizzard, midgut, hindgut and anus
Mouthparts modified from appendages and adapted for different methods of feeding
Circulatory System
Open system
Dorsal contractile heart, arteries

5. Characteristics Respiration Obtain oxygen through:
1) body surface (diffusion),
2) gills,
3) tracheal (air tubes) – carry oxygen to muscles
4) book lungs
Spiracles—small openings in the exoskeleton through which air opens

6. Characteristics Water retention—3 structures 1) Malpighian tubules—
excretory structures that remove metabolic wastes from blood and return water to the cells
2) Exoskeleton—
prevents water evaporation
3) Book Lungs—
gas exchange without water loss (also used in respiration)

7. Characteristics Excretory system Paired excretory glands in some
Same as the nephridial system of annelids 
Some with other excretory organs, called Malpighian tubules

8. Characteristics Nervous system
Contains same system of annelid (with dorsal brain connected by a double nerve chain)
Fusion of ganglia in some species  
Well-developed sensory organs
Compounds eyes with many lenses (can see motion and color)

9. Characteristics Reproduction Sexes usually separate,
Paired reproductive organs and ducts;  
Usually internal fertilization;
often go through metamorphosis (change in body form  larva to adult)

10. Classification Phylum Arthropoda (most diverse phylum)
Subgroups of Terrestrial Arthropods:
Subphylum Chelicerata –
Characteristics of all:
six pairs of appendages that include
a pair of chelicerae,
a pair of pedipalps, and
4 pairs of walking legs
No mandibles and no antennae.  
Suck up liquid food from their prey.
Two body segments (abdomen and cephalothorax)

11. Classification Class Merostomata –
Horseshoe crabs are practically unchanged
Have an unsegmented, horseshoe-shaped carapace, and a broad abdomen, which has a long spine like telson.
Book gills are exposed.  
They feed at night on worms and small mollusks and are harmless to humans.
Include horseshoe crabs

12. Classification Class Arachnida – over 50,000 species
Body organization: cephalothorax, abdomen
Examples: Spiders (35,000 species), scorpions, ticks, mites

13. Classification Spiders: Scorpions: Mites and Ticks:
hunt using strong legs and good eyes; weave silk for web (hunt and reproduction); fangs are modified chelicerae (liquefy prey with venom)
Scorpions:
long, segmented abdomen with a stinger;
Mites and Ticks:
mites have one body segment, eat bacteria or skin cells of humans; ticks are mostly parasitic, require blood before molting and can cause Rocky Mtn spotted fever

14. Classification Subphylum Uniramia – Characteristics:
Appendages are unbranched.  
Includes the insects and the myriapods (centipedes and millipedes).
Heads resemble the crustacean head but have only one pair of antennae, instead of two.
Also have a tympanic membrane for sound 
Have mandibles and two pairs of maxillae
Respiration is by body surface and tracheal systems,
Although juveniles, if aquatic, may have gills.

15. Classification Class Chilopoda -
They are active predators with a preference for moist places such as under logs or stones, where they feed on earthworms, insects, etc.  
Each segment (they have between 10 and 70), except the one behind the head and the last two, bears one pair of appendages.
Include: centipedes

16. Classification Class Diplopoda – Include Millipedes
Have cylindrical bodies made up of 25 to 100 segments.
Abdominal segments each have two pairs.
Millipedes are less active than centipedes
Generally herbivorous, living on decayed plant and animal matter

17. Classification Class Insecta –
Most numerous and diverse of all arthropods.
(There are more species of insects than species in all the other classes of animals combined!!)
Have three pairs of legs
Usually have two pairs of wings (although some have one pair of wings, or none)  
Body organization: head, thorax, and abdomen.
The head usually bears a pair of large compound eyes, a pair of antennae, and usually three ocelli.