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Section 1: Arthropod Characteristics Arthropods have segmented bodies and tough exoskeletons with jointed appendages. K What I Know W What I Want to Find Out L What I Learned Essential Questions • • • What is the importance of exoskeletons, jointed appendages, and segmentation to arthropods? What are some similarities and differences among the organ systems of arthropods? What are the methods used by arthropods to respond to stimuli? Copyright © McGraw-Hill Education Arthropod Characteristics Vocabulary Review New • • • • • • • • • • • • ganglion Copyright © McGraw-Hill Education thorax abdomen cephalothorax appendage molting mandible tracheal tube book lung spiracle Malpighian tubule pheromone Arthropod Characteristics Arthropod Features • Arthropods are segmented invertebrates with bilateral symmetry, coelomate body cavities, and protostome development. • Arthropods have exoskeletons with jointed appendages. • Between 70-85% of all named animal species are arthropods. Copyright © McGraw-Hill Education Arthropod Characteristics Arthropod Features Segmentation • Segments can be fused into three main body regions: a head, thorax, and abdomen. • The head has mouthparts, eyes, and often antennae. • The thorax is the middle body region to which legs and wings are attached. • The abdomen is the posterior end of the arthropod and bears additional legs, contains digestive structures and the reproductive organs. Copyright © McGraw-Hill Education Arthropod Characteristics Arthropod Features Exoskeleton • • • • Provides a framework for support Protects soft body tissues and slows water loss Provides a place for muscle attachment Made of chitin Copyright © McGraw-Hill Education Arthropod Characteristics Arthropod Features Exoskeleton • Arthropods have paired, jointed appendages, which are structures that extend from an animal’s body. • Adapted for a variety of functions, such as feeding, mating, sensing, walking, and swimming. • Exoskeleton is made of nonliving material and cannot grow, so arthropods must shed their old exoskeletons through molting. Copyright © McGraw-Hill Education Arthropod Characteristics Body Structures of Arthropods Feeding and digestion • Arthropods have diverse feeding habitats and structures. • Many arthropods have a pair of appendages called mandibles that are adapted for biting and chewing. • Arthropods can be herbivores, carnivores, filter feeders, omnivores, or parasites. Copyright © McGraw-Hill Education Arthropod Characteristics Body Structures of Arthropods Respiration • Arthropods obtain oxygen by using one of three structures : • Gills- found in most aquatic arthropods • Tracheal tubes – system of branching tubes that carry oxygen through the body • Book lungs – saclike pockets with highly folded walls, increasing surface area for gas exchange • Both tracheal tubes and book lungs open to the outside through openings called spiracles. Copyright © McGraw-Hill Education Arthropod Characteristics Visualizing Respiratory Structures Animation FPO Add link to animation from page 766 (Figure 6) here. Copyright © McGraw-Hill Education Arthropod Characteristics Body Structures of Arthropods Circulation • Most arthropods do not rely on their circulatory system to carry oxygen • Transports nutrients and removes wastes Excretion • In most arthropods, cellular wastes are removed via Malpighian tubules, which connect to and empty into the gut. • Crustaceans and some other arthropods do not have Malpighian tubules and instead have modified nephridia. Copyright © McGraw-Hill Education Arthropod Characteristics Response to stimuli • Vision: • A compound eye has many facets, which are hexagonal in shape. • Each facet sees part of an image. • The brain combines the images into a mosaic. Copyright © McGraw-Hill Education Arthropod Characteristics Response to stimuli • Hearing: • Many arthropods have a sense organ called a tympanum, which is a flat membrane used for hearing. • Arthropod tympanums can be located on the forelegs, on the abdomen, or on the thorax. Copyright © McGraw-Hill Education Arthropod Characteristics Response to stimuli • Chemicals • Many insects communicate with pheromones – chemicals secreted by many animal species that influence the behavior of other animals of the same species. • Give off signals related to feeding and mating Copyright © McGraw-Hill Education Arthropod Characteristics Movement • The muscles are attached to the inner surface of the exoskeleton on both sides of the joint. • The strength of muscle contraction depends on the rate at which nerve impulses stimulate muscles. Copyright © McGraw-Hill Education Arthropod Characteristics Reproduction • Most arthropods reproduce sexually. • Most arthropods brood or incubate their eggs, but do not care for their offspring once they hatch. Copyright © McGraw-Hill Education Arthropod Characteristics Review Essential Questions • What is the importance of exoskeletons, jointed appendages, and segmentation to arthropods? • What are some similarities and differences among the organ systems of arthropods? • What are the methods used by arthropods to respond to stimuli? Vocabulary • • • • thorax abdomen cephalothorax appendage Copyright © McGraw-Hill Education • molting mandible • tracheal tube • book lung • spiracle • Malpighian tubule • pheromone Arthropod Characteristics
