Arthropods McGraw Hill Education（节肢动物麦格劳希尔教育）.pdfVIP

46 Arthropods Concept Outline 46.1 The evolution of jointed appendages has made arthropods very successful. Jointed Appendages and an Exoskeleton. Arthropods probably evolved from annelids, and with their jointed appendages and an exoskeleton, have successfully invaded practically every habitat on earth. Classification of Arthropods. Arthropods have been traditionally divided into three groups based on morphological characters. However, recent research suggests a restructuring of arthropod classification is needed. General Characteristics of Arthropods. Arthropods have segmented bodies, a chitinous exoskeleton, and often have compound eyes. They have open circulatory systems. In some groups, a series of tubes carry oxygen to the organs, and unique tubules eliminate waste. 46.2 The chelicerates all have fangs or pincers. Class Arachnida: The Arachnids. Spiders and scorpions FIGURE 46.1 are predators, while most mites are herbivores. An arthropod. One of the major arthropod groups is represented Class Merostomata: Horseshoe Crabs. Among the here by Polistes, the common paper wasp (class Insecta). most ancient of living animals, horseshoe crabs are thought to have evolved from trilobites. Class Pycnogonida: The Sea Spiders. The spiders that are common in marine habitats differ greatly from he evolution of segmentation among annelids marked terrestrial spiders. Tthe first ma