Section 1 Phylum Arthropoda Chapter 36 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.

Section 1 Phylum Arthropoda Chapter 36 Segmentation Click below to watch the Visual Concept. Visual Concept

Section 1 Phylum Arthropoda Chapter 36 Compound Eye Click below to watch the Visual Concept. Visual Concept

Section 1 Phylum Arthropoda Chapter 36 Function of the Compound Eye Click below to watch the Visual Concept. Visual Concept

Section 1 Phylum Arthropoda Chapter 36 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.

Section 1 Phylum Arthropoda Chapter 36 Characteristics of Arthropods

Section 1 Phylum Arthropoda Chapter 36 Characteristics of Arthropods Click below to watch the Visual Concept. Visual Concept

Section 1 Phylum Arthropoda Chapter 36 Arthropod Exoskeleton Click below to watch the Visual Concept. Visual Concept

Section 1 Phylum Arthropoda Chapter 36 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.

Section 1 Phylum Arthropoda Chapter 36 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).

Section 1 Phylum Arthropoda Chapter 36 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

Section 1 Phylum Arthropoda Chapter 36 Phylogenetic Diagram of Arthropods

Section 1 Phylum Arthropoda Chapter 36 Types of Arthropods Click below to watch the Visual Concept. Visual Concept

Section 2 Subphylum Crustacea Chapter 36 Objectives • Describethe characteristics of crustaceans. • Compareaquatic crustaceans with terrestrial crustaceans. • Explainthe functions of the appendages on a crayfish. • Summarizedigestion, respiration, circulation, excretion, and neural control in crayfish.

Section 2 Subphylum Crustacea Chapter 36 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

Section 2 Subphylum Crustacea Chapter 36 Characteristics, continued Some crustaceans respire through their exoskeleton, others respire through gills. • Many have a free-swimming larval stage called a nauplius.

Section 2 Subphylum Crustacea Chapter 36 Anatomy of a Nauplius Click below to watch the Visual Concept. Visual Concept

Section 2 Subphylum Crustacea Chapter 36 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.

Section 2 Subphylum Crustacea Chapter 36 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.

Section 2 Subphylum Crustacea Chapter 36 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.

Section 2 Subphylum Crustacea Chapter 36 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

Section 2 Subphylum Crustacea Chapter 36 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

Section 2 Subphylum Crustacea Chapter 36 External Anatomy of a Crayfish

Section 2 Subphylum Crustacea Chapter 36 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.

Section 2 Subphylum Crustacea Chapter 36 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.

Section 2 Subphylum Crustacea Chapter 36 Internal Anatomy of a Crayfish

Section 2 Subphylum Crustacea Chapter 36 Anatomy of a Crayfish Click below to watch the Visual Concept. Visual Concept

Section 2 Subphylum Crustacea Chapter 36 Characteristics of Crustaceans Click below to watch the Visual Concept. Visual Concept

Section 3 Subphyla Chelicerata and Myriapoda Chapter 36 Objectives • Listthe characteristics of arachnids, as represented by a spider. • Explainthe adaptations that spiders have for a predatory life on land. • Identifythe unique characteristics of scorpions, mites, and ticks. • Comparethe characteristics of millipedes and centipedes.

Section 3 Subphyla Chelicerata and Myriapoda Chapter 36 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.

Section 3 Subphyla Chelicerata and Myriapoda Chapter 36 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

Section 3 Subphyla Chelicerata and Myriapoda Chapter 36 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.

Section 3 Subphyla Chelicerata and Myriapoda Chapter 36 Anatomy of a Brown Recluse Spider

Section 3 Subphyla Chelicerata and Myriapoda Chapter 36 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.

Section 3 Subphyla Chelicerata and Myriapoda Chapter 36 Feeding Habits of Spiders Click below to watch the Visual Concept. Visual Concept

Section 3 Subphyla Chelicerata and Myriapoda Chapter 36 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.

Section 3 Subphyla Chelicerata and Myriapoda Chapter 36 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.

Section 3 Subphyla Chelicerata and Myriapoda Chapter 36 Characteristics of Arachnids Click below to watch the Visual Concept. Visual Concept

Section 3 Subphyla Chelicerata and Myriapoda Chapter 36 Types of Arachnids Click below to watch the Visual Concept. Visual Concept

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