Chapter 36. Table of Contents. Section 1 Phylum Arthropoda. Section 2 Subphylum Crustacea. Section 3 Subphylum Chelicerata and Myriapoda.

Transcription

1 Arthropods Table of Contents Section 1 Phylum Arthropoda Section 2 Subphylum Crustacea Section 3 Subphylum Chelicerata and Myriapoda

2 Section 1 Phylum Arthropoda Objectives Describe the distinguishing characteristics of arthropods. Explain the process of molting in an arthropod. List the five major subphyla of the phylum Arthropoda.

3 Section 1 Phylum Arthropoda Characteristics of Arthropods The members of the phylum Arthropoda are called arthropods. Arthropods are segmented animals with body segments that bear appendages. Arthropods have an exoskeleton that provides protection and support and contains chitin. Arthropods show a high degree of cephalization. Most have segmented antennae and compound eyes.

4 Section 1 Phylum Arthropoda Segmentation

5 Section 1 Phylum Arthropoda Compound Eye

6 Section 1 Phylum Arthropoda Function of the Compound Eye

7 Section 1 Phylum Arthropoda Characteristics of Arthropods, continued Molting The rigid exoskeleton limits the size to which an arthropod can grow. So, each arthropod periodically sheds its exoskeleton and makes a new one in the process of molting. An anthropod goes through many cycles of molting during its life.

8 Section 1 Phylum Arthropoda Characteristics of Arthropods

9 Section 1 Phylum Arthropoda Characteristics of Arthropods

10 Section 1 Phylum Arthropoda Arthropod Exoskeleton

11 Section 1 Phylum Arthropoda Evolution and Classification Arthropods likely evolved from a common ancestor that lived about 545 million years ago. However, biologists are still uncertain about much of arthropod phylogeny. The similar characteristics of many modern subgroups of arthropods may be the result of convergent evolution.

12 Section 1 Phylum Arthropoda Evolution and Classification, continued Many ancient and extinct arthropods, such as trilobites, had many body segments and one pair of appendages on each segment. Most living arthropod species have some segments that lack appendages and some segments that are fused into a larger structure called a tagma (plural, tagmata).

13 Section 1 Phylum Arthropoda Evolution and Classification, continued Arthropods are usually divided into five subphyla on the basis of differences in development and in the structure of appendages, such as mouthparts. The two major types of mouthparts are: mandibles, which are jawlike chelicerae (singular, chelicera), which are pincerlike The five main subphyla are: Trilobita Crustacea Chelicerata Myriapoda Hexapoda

14 Section 1 Phylum Arthropoda Phylogenetic Diagram of Arthropods

15 Section 1 Phylum Arthropoda Types of Arthropods

16 Section 2 Subphylum Crustacea Objectives Describe the characteristics of crustaceans. Compare aquatic crustaceans with terrestrial crustaceans. Explain the functions of the appendages on a crayfish. Summarize digestion, respiration, circulation, excretion, and neural control in crayfish.

17 Section 2 Subphylum Crustacea Characteristics The subphylum Crustacea contains about 38,000 known species. Crustaceans are so diverse that their single defining characteristic is having two pairs of antennae. Most crustaceans also have: a pair of mandibles a pair of appendages on each body segment some branched appendages 16 to 20 segments and several tagmata

18 Section 2 Subphylum Crustacea Characteristics, continued Some crustaceans respire through their exoskeleton, others respire through gills. Many have a free-swimming larval stage called a nauplius.

19 Section 2 Subphylum Crustacea Anatomy of a Nauplius

20 Section 2 Subphylum Crustacea Diversity of Crustaceans Aquatic Crustaceans Copepods are abundant in marine environments and an important part of the ocean s plankton. In freshwater environments, much of the plankton is composed of water fleas such as Daphnia species. Barnacles are sessile as adults. Free-swimming barnacle larvae attach themselves to marine surfaces and develop a shell that encloses the body. Barnacles use their cirri (singular, cirrus) to sweep food from the water into their mouths.

21 Section 2 Subphylum Crustacea Diversity of Crustaceans, continued Terrestrial Crustaceans Sow bugs and pill bugs are terrestrial isopods. They lack adaptations for conserving water and live only in moist environments. They generally feed on decaying vegetation. Pill bugs roll into a ball when disturbed or threatened.

22 Section 2 Subphylum Crustacea The Crayfish The crayfish is an abundant freshwater crustacean that is structurally similar to lobsters, which are marine crustaceans. Crayfish, lobsters, crabs, and shrimp are decapods, or members of the order Decapoda. Decapoda means 10 feet. Decapods have five pairs of legs that are used for locomotion.

23 Section 2 Subphylum Crustacea The Crayfish, continued External Structure The crayfish s body is divided into the cephalothorax, which is covered by the carapace and is divided into the head, which has five segments the thorax, which has eight segments the abdomen, which is is divided into six segments

24 Section 2 Subphylum Crustacea The Crayfish, continued External Structure, continued A pair of appendages is attached to each segment of the crayfish. Several pairs have specialized functions. These appendages include: Antennae Antennules Mandibles Maxillae Maxillipeds Chelipeds Walking legs Swimmerets

25 Section 2 Subphylum Crustacea External Anatomy of a Crayfish

26 Section 2 Subphylum Crustacea The Crayfish, continued Digestion Crayfish have a digestive gland that is near the stomach and that secretes enzymes for digestion. Respiration Walking circulates water across the gills. Circulation The circulatory system is open.

27 Section 2 Subphylum Crustacea The Crayfish, continued Excretion Green glands assist in excretion of excess water that enters the body by osmosis. Neural Control The nervous system of the crayfish is typical of arthropods and is similar to that of annelids. Sensory Organs Crayfish sense vibrations and chemicals in the water with thousands of small sensory hairs. Their compound eyes are set on two stalks.

28 Section 2 Subphylum Crustacea Internal Anatomy of a Crayfish

29 Section 2 Subphylum Crustacea Anatomy of a Crayfish

30 Section 2 Subphylum Crustacea Characteristics of Crustaceans

31 Section 3 Subphyla Chelicerata and Myriapoda Objectives List the characteristics of arachnids, as represented by a spider. Explain the adaptations that spiders have for a predatory life on land. Identify the unique characteristics of scorpions, mites, and ticks. Compare the characteristics of millipedes and centipedes.

32 Section 3 Subphyla Chelicerata and Myriapoda Subphylum Chelicerata The subphylum Chelicerata, the chelicerates, includes spiders, scorpions, mites, sea spiders, and horseshoe crabs. Chelicerates lack antennae and typically have six pairs of appendages. The first pair of appendages, the chelicerae, are modified into pincers or fangs.

33 Section 3 Subphyla Chelicerata and Myriapoda Subphylum Chelicerata, continued Class Arachnida Class Arachnida, the arachnids, includes spiders, scorpions, mites, and ticks. The arachnid s body is divided into: a cephalothorax that usually bears six pairs of jointed appendages: one pair of chelicerae one pair of pedipalps four pairs of walking legs an abdomen

34 Section 3 Subphyla Chelicerata and Myriapoda Subphylum Chelicerata, continued Anatomy of a Spider Spiders have eight simple eyes and chelicerae that are modified as fangs. Spiders produce silk threads using spinnerets. Spiders respire through spiracles that connect to book lungs or tracheae. Malpighian tubules function to excrete wastes while conserving water.

35 Section 3 Subphyla Chelicerata and Myriapoda Anatomy of a Brown Recluse Spider

36 Section 3 Subphyla Chelicerata and Myriapoda Spinneret

37 Section 3 Subphyla Chelicerata and Myriapoda Subphylum Chelicerata, continued Life of a Spider Spiders feed on insects and other small animals. Many species are adapted to capture certain prey. Spiders rarely harm humans, but two species in the United States are dangerous: the black widow the brown recluse A male spider is usually smaller than the female. Females lay eggs in a silken case.

38 Section 3 Subphyla Chelicerata and Myriapoda Feeding Habits of Spiders

39 Section 3 Subphyla Chelicerata and Myriapoda Subphylum Chelicerata, continued Scorpions Scorpions have large, pincerlike pedipalps and a stinger on the last segment of the abdomen. Mites and Ticks Mites and ticks have a completely fused cephalothorax and abdomen. Many species are parasitic, and some spread diseases that affect humans.

40 Section 3 Subphyla Chelicerata and Myriapoda Subphylum Myriapoda Members of the subphylum Myriapoda have antennae, mandibles, and unbranched appendages. Class Diplopoda Millipedes have rounded bodies and two pairs of jointed legs on each body segment except the last two segments. Class Chilopoda Centipedes have flattened bodies and one pair of jointed legs on each body segment except the first segment and the last two segments.

41 Section 3 Subphyla Chelicerata and Myriapoda Characteristics of Arachnids

42 Section 3 Subphyla Chelicerata and Myriapoda Types of Arachnids

43 Standardized Test Prep Multiple Choice 1. What do all arthropods have in common? A. spiracles B. antennae C. a cephalothorax D. jointed appendages

44 Standardized Test Prep Multiple Choice, continued 1. What do all arthropods have in common? A. spiracles B. antennae C. a cephalothorax D. jointed appendages

45 Standardized Test Prep Multiple Choice, continued 2. What is the chitin-containing structure that protects and supports the body of an arthropod? F. a tagma G. a chelicera H. an appendage J. an exoskeleton

46 Standardized Test Prep Multiple Choice, continued 2. What is the chitin-containing structure that protects and supports the body of an arthropod? F. a tagma G. a chelicera H. an appendage J. an exoskeleton

47 Standardized Test Prep Multiple Choice, continued 3. Which of the following statements about compound eyes is true? A. Compound eyes have a single lens. B. Compound eyes are located on the abdomen of scorpions. C. Compound eyes are found in all arthropods except crayfish. D. Compound eyes are composed of many individual light detectors.

48 Standardized Test Prep Multiple Choice, continued 3. Which of the following statements about compound eyes is true? A. Compound eyes have a single lens. B. Compound eyes are located on the abdomen of scorpions. C. Compound eyes are found in all arthropods except crayfish. D. Compound eyes are composed of many individual light detectors.

49 Standardized Test Prep Multiple Choice, continued 4. What are the major respiratory organs of crayfish? F. gills G. lungs H. tracheae J. book lungs

50 Standardized Test Prep Multiple Choice, continued 4. What are the major respiratory organs of crayfish? F. gills G. lungs H. tracheae J. book lungs

51 Standardized Test Prep Multiple Choice, continued 5. How do mites and ticks differ from spiders? A. Mites and ticks have mandibles. B. Mites and ticks have two pairs of antennae. C. Mites and ticks have a unique respiratory system. D. Mites and ticks have a fused cephalothorax and abdomen.

52 Standardized Test Prep Multiple Choice, continued 5. How do mites and ticks differ from spiders? A. Mites and ticks have mandibles. B. Mites and ticks have two pairs of antennae. C. Mites and ticks have a unique respiratory system. D. Mites and ticks have a fused cephalothorax and abdomen.

53 Standardized Test Prep Multiple Choice, continued The illustration below shows four animals. Use the illustration to answer the question that follows.

54 Standardized Test Prep Multiple Choice, continued 6. Which animal has a chitinous exoskeleton? F. snail G. grasshopper H. hydra J. squid

55 Standardized Test Prep Multiple Choice, continued 6. Which animal has a chitinous exoskeleton? F. snail G. grasshopper H. hydra J. squid

56 Standardized Test Prep Multiple Choice, continued 7. mandible : crayfish :: chelicera : A. pill bug B. scorpion C. barnacle D. millipede

57 Standardized Test Prep Multiple Choice, continued 7. mandible : crayfish :: chelicera : A. pill bug B. scorpion C. barnacle D. millipede

58 Standardized Test Prep Multiple Choice, continued The graph below shows data about molting and two causes of mortality in crabs. Use the graph to answer the questions that follow.

59 Standardized Test Prep Multiple Choice, continued 8. During which months are you most likely to find crabs in molt? F. January through March G. April through June H. July through September J. September through January

60 Standardized Test Prep Multiple Choice, continued 8. During which months are you most likely to find crabs in molt? F. January through March G. April through June H. July through September J. September through January

61 Standardized Test Prep Multiple Choice, continued 9. What is the relationship between molting and mortality? A. Molting increases mortality. B. Molting decreases mortality. C. Molting has no effect on mortality. D. Molting and mortality occur at different times of the year.

62 Standardized Test Prep Multiple Choice, continued 9. What is the relationship between molting and mortality? A. Molting increases mortality. B. Molting decreases mortality. C. Molting has no effect on mortality. D. Molting and mortality occur at different times of the year.

63 Standardized Test Prep Short Response Some arthropods are terrestrial and some are aquatic. Give examples and describe the distinguishing characteristics of each type of arthropod.

64 Standardized Test Prep Short Response, continued Some arthropods are terrestrial and some are aquatic. Give examples and describe the distinguishing characteristics of each type of arthropod. Answer: Spiders and millipedes are terrestrial. The exoskeleton is lighter, respiration is by book lungs or tracheae, and water is conserved. Crayfish and crabs are aquatic, the exoskeleton is heavier, respiration is by gills, and excess water is excreted by green glands.

65 Standardized Test Prep Extended Response Base your answers to parts A & B on the information below. All arthropods undergo many cycles of molting throughout their lifetime. Part A Describe the process of molting in arthropods. Part B Explain how the anatomical structure of an arthropod relates to the function of molting.

66 Standardized Test Prep Extended Response, continued Answer: Part A In between molts, the tissues swell and put pressure on the exoskeleton. Molting is then induced by hormones. Enzymes digest the old exoskeleton and the epidermis synthesizes a new one. The old exoskeleton then loosens, breaks along specific lines, and is shed. Part B: The exoskeleton covers the body and therefore limits growth. Molting provides a means for allowing growth.