1. Zoology – Arthropod Unit
Chapter 18 Arthropods
Chapter 19 Crustaceans
Chap.20 Terrestrial Arthropods

2. Chapter 18 Objectives
1. Identify characteristics distinguishing phylum Arthropoda
2. Discuss adaptations characteristic of the phylum Arthropoda with regard to
 Body form, morphology & embryonic development
 Feeding and digestion
 Excretion
 Movement/locomotion
 Reproduction
 Sensory/Motor response
 Any special features unique to the phylum
3. Identify derived characteristics that contribute to the phylogeny of phylum Arthropoda

3. Arthropod Diversity

4. Characteristics of Arthropods
Arthro = joint
Poda = foot
Arthropods are named for their jointed appendages
All arthropods have an exoskeleton made of an amino sugar called Chitin

5. Arthropod Appendages
Appendages in arthropods are modified for a number of functions:
Walking legs
Mouth parts
Antennae
Claws
Organs for mating
Holding eggs

6. Modified Appendages

7. Segmentation
Segmentation is an ancestral characteristic that carries over from the Annelids
Note the similarity of the insect caterpillar to polychaete worms

8. Rick Takahashi on Segmentation

9. Fusion of Segments forming Body Regions
These animals have segements in the head and thorax region fused together

10. Segmentation
The millipede below has segments fused in pairs, resulting in 2 pair of legs per “segment”
These animals have little differentiation between body segments

11. Exoskeleton: Advantages
The exoskeleton provides rigid support and strong points for muscle attachment
The exoskeleton also forms a protective shell

12. Exoskeleton: Disadvantages
The exoskeleton prevents drying out, but also prevents respiration through the skin
The exoskeleton provides rigid support, but prevents growth – requiring molting

13. Other Arthropod Characteristics
Striated muscle associated with the exoskeleton, and smooth muscle associated with the gut
Reduced body cavity, filled with blood, forming an open circulatory system
Specialized excretory glands (coxal, antennal or maxillary glands; malpighian tubules)
Specialized respiratory organs (gills, tracheae, book lungs)
Dorsal brain with fused ventral nerve cords

14. Nervous System
Like the annelids, the arthropods have a dorsal brain, fused ventral nerve cords, and paired nerve branches that encircle the pharynx

15. Excretory System
The exoskeleton prevents the use of the skin as an excretory organ. In insects, salts and metabolic wastes are removed by Malpighian Tubules
The malpighian tubules extend into the hemocoel, extract waste materials and funnel them into the digestive tract for removal

16. Respiratory Adaptations
Tracheal system in insects bring air directly to tissues
Book Lungs in Arachnids : a series of flattened tissues to create surfaces for gas exchange
Gills in Crustaceans are extensions of the walking legs

17. Arthropod Phylogeny

18. Arthropod Phylogeny Subphylum Trilobita Subphylum Chelicerata
Extremely common in the early Paleozoic era, trilobites are extinct today
Subphylum Chelicerata
Class Merostomata includes Horseshoe Crabs
Class Pycnogonida includes Sea Spiders
Class Arachnida includes spiders, scorpions, ticks and mites
Subphylum Crustacea
Lobsters, crabs, shrimp, crayfish and others less familiar
Subphylum Uniramia
Myriapods (Centipedes and millipedes) and Insects

19. Trilobites

20. Chelicerates: Arachnids

21. Chelicerates: Scorpions

22. Chelicerates: Ticks and Mites

23. Crustaceans

24. Uniramia: Myriapods Millipedes have 2 pair of legs per segment
Centipedes have 1 pair of legs per segment

25. Uniramia: Insects

26. Chapter 19 Objectives 4. Distinguish Crustaceans from other arthropods
5. Perform a dissection of the crayfish, a representative crustacean.
6. Identify internal and external anatomical features of the crayfish

27. Chapter 20 Objectives
7. Compare and contrast Chilopods, Diplopods, and Insects
8. Discuss adaptations for gas exchange in a terrestrial environment as displayed in the insects
9. Discuss adaptations for excretion of metabolic waste as displayed in the insects
10. Discuss the process of metamorphosis in insects.

28. Chapter 20 Objectives
10. Discuss the process of metamorphosis in insects.
11. Distinguish between complete and incomplete metamorphosis
12. Perform a dissection of the grasshopper, a representative insect
13. Identify internal and external anatomical features of the grasshopper