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

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

Arthropod Diversity

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

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

Modified Appendages

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

Rick Takahashi on Segmentation

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

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

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

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

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

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

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

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

Arthropod Phylogeny

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

Trilobites

Chelicerates: Arachnids

Chelicerates: Scorpions

Chelicerates: Ticks and Mites

Crustaceans

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

Uniramia: Insects

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

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.

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