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Chapter 33 Invertebrates PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: Life Without a Backbone • Invertebrates are animals that lack a backbone • They account for 95% of known animal species Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eumetazoa Ancestral colonial choanoflagellate Chordata Echinodermata Other bilaterians (including Nematoda, Arthropoda, Mollusca, and Annelida) Cnidaria Porifera LE 33-2 Deuterostomia Bilateria LE 33-3a A sponge A jelly 0.5 mm 250 µm A placozoan (LM) A kinorhynch (LM) A marine flatworm A rotifer (LM) Ectoprocts Phoronids LE 33-3b A brachiopod A ribbon worm 5 mm An acanthocephalan An octopus A ctenophore, or comb jelly A marine annelid 50 µm A loriciferan (LM) A priapulan LE 33-3c A roundworm A scorpion (an arachid) 100 µm 100 µm A cycliophoran (colorized SEM) Tardigrades (colorized SEM) An onychophoran An acorn worm A sea urchin A tunicate Concept 33.1: Sponges are sessile and have a porous body and choanocytes • Sponges, phylum Porifera, live in both fresh and marine waters • Sponges lack true tissues and organs Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Sponges are suspension feeders, capturing food particles suspended in the water that passes through their body Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-4 Food particles in mucus Choanocyte Flagellum Choanocytes Collar Osculum Azure vase sponge (Callyspongia plicifera) Spongocoel Phagocytosis of food particles Amoebocyte Porocytes Spicules Epidermis Water flow Amoebocyte Mesohyl • Choanocytes, flagellated collar cells, generate a water current through the sponge and ingest suspended food • Most sponges are hermaphrodites: Each individual functions as both male and female Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 33.2: Cnidarians have radial symmetry, a gastrovascular cavity, and cnidocytes • All animals except sponges belong to the clade Eumetazoa, animals with true tissues • Phylum Cnidaria is one of the oldest groups in this clade Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Cnidarians have diversified into a wide range of both sessile and floating forms including jellies, corals, and hydras • They exhibit a relatively simple diploblastic, radial body plan Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • The basic body plan of a cnidarian is a sac with a central digestive compartment, the gastrovascular cavity • A single opening functions as mouth and anus • There are two variations on the body plan: the sessile polyp and floating medusa Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-5 Mouth/anus Polyp Tentacle Medusa Gastrovascular cavity Gastrodermis Body stalk Mesoglea Epidermis Tentacle Mouth/anus • Cnidarians are carnivores that use tentacles to capture prey • The tentacles are armed with cnidocytes, unique cells that function in defense and capture of prey Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-6 Prey Tentacle “Trigger” Nematocyst Coiled thread Discharge of thread Cnidocyte • Phylum Cnidaria is divided into four major classes: – Hydrozoa – Scyphozoa – Cubozoa – Anthozoa Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-7 Scyphozoans (jellies) Hydrozoans Cubozoan (sea wasp) Anthozoan (sea anemone) Hydrozoans •Most hydrozoans alternate between polyp and medusa forms Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-8–3 Reproductive polyp Feeding polyp Medusa bud MEIOSIS Gonad Medusa Egg SEXUAL REPRODUCTION Sperm ASEXUAL REPRODUCTION (BUDDING) Portion of a colony of polyps FERTILIZATION Zygote Developing polyp Mature polyp Planula (larva) 1 mm Key Haploid (n) Diploid (2n) Scyphozoans •In the class Scyphozoa, jellies (medusae) are the prevalent form of the life cycle Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cubozoans • In the class Cubozoa, which includes box jellies and sea wasps, the medusa is boxshaped and has complex eyes Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Anthozoans •Class Anthozoa includes the corals and sea anemones, which occur only as polyps Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 33.3: Most animals have bilateral symmetry • The vast majority of animal species belong to the clade Bilateria, which consists of animals with bilateral symmetry and triploblastic development Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Flatworms • Members of phylum Platyhelminthes live in marine, freshwater, and damp terrestrial habitats • They are flattened dorsoventrally and have a gastrovascular cavity • Although flatworms undergo triploblastic development, they are acoelomates Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Flatworms are divided into four classes: – Turbellaria (mostly free-living flatworms) – Monogenea (monogeneans) – Trematoda (trematodes, or flukes) – Cestoda (tapworms) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Turbellarians • Turbellarians are nearly all free-living and mostly marine • The best-known turbellarians are commonly called planarians Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Planarians have light-sensitive eyespots and centralized nerve nets • The planarian nervous system is more complex and centralized than the nerve nets of cnidarians Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-10 Pharynx Gastrovascular cavity Eyespots Ganglia Ventral nerve cords Monogeneans and Trematodes • Monogeneans and trematodes live as parasites in or on other animals • They parasitize a wide range of hosts • Trematodes that parasitize humans spend part of their lives in snail hosts Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-11 Mature flukes live in the blood vessels of the human intestine Male Female 1 mm Larvae penetrate skin and blood vessels of humans. Blood flukes reproduce sexually in the human host. Fertilized eggs exit host in feces. Eggs develop in water into ciliated larvae. Larvae infect snails. Asexual reproduction within snail results in another type of motile larva. Snail host •Most monogeneans are parasites of fish Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Tapeworms •Tapeworms are also parasitic and lack a digestive system Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-12 Proglottids with reproductive structures 200 µm Scolex Hooks Sucker Rotifers • Rotifers, phylum Rotifera, are tiny animals that inhabit fresh water, the ocean, and damp soil • Rotifers are smaller than many protists but are truly multicellular and have specialized organ systems Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-13 0.1 mm • Rotifers have an alimentary canal: a digestive tube with a separate mouth and anus that lies within a fluid-filled pseudocoelom • Rotifers reproduce by parthenogenesis, in which females produce offspring from unfertilized eggs Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lophophorates: Ectoprocts, Phoronids, and Brachiopods • Lophophorates have a lophophore, a horseshoe-shaped, suspension-feeding organ with ciliated tentacles Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings •Ectoprocts are colonial animals that superficially resemble plants Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-14 Lophophore Lophophore Ectoprocts Phoronids Brachiopods •Phoronids are tubedwelling marine worms ranging from 1 mm to 50 cm in length Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Brachiopods superficially resemble clams and other hinge-shelled molluscs, but the two halves of the shell are dorsal and ventral rather than lateral, as in clams Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nemerteans •Members of phylum Nemertea are commonly called proboscis worms or ribbon worms Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • The nemerteans’ unique proboscis is used for defense and prey capture and is extended by a fluid-filled sac • Nemerteans also have a closed circulatory system, in which the blood is contained in vessels distinct from fluid in the body cavity Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 33.4: Molluscs have a muscular foot, a visceral mass, and a mantle • Phylum Mollusca includes snails and slugs, oysters and clams, and octopuses and squids • Most molluscs are marine, though some inhabit fresh water and some are terrestrial • Molluscs are soft-bodied animals, but most are protected by a hard shell Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • All molluscs have a similar body plan with three main parts: – Muscular foot – Visceral mass – Mantle Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-16 Visceral mass Coelom Heart Intestine Nephridium Gonads Mantle Stomach Mantle Shell cavity Radula Anus Gill Foot Nerve cords Esophagus Mouth Radula Mouth • Most molluscs have separate sexes with gonads located in the visceral mass • The life cycle of many molluscs includes a ciliated larval stage called a trochophore Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • There are four major classes of molluscs: – Polyplacophora (chitons) – Gastropoda (snails and slugs) – Bivalvia (clams, oysters, and other bivalves) – Cephalopoda (squids, octopuses, cuttlefish, and chambered nautiluses) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chitons • Class Polyplacophora consists of the chitons, oval-shaped marine animals encased in an armor of eight dorsal plates Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gastropods •About threequarters of all living species of molluscs belong to class Gastropoda Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-18 A land snail A sea slug. Nudibranchs, or sea slugs, lost their shell during their evolution. • Most gastropods are marine, but many are freshwater and terrestrial species • Most have a single, spiraled shell • Slugs lack a shell or have a reduced shell • The most distinctive characteristic of gastropods is torsion, which causes the animal’s anus and mantle to end up above its head Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-19 Mantle cavity Anus Mouth Stomach Intestine Bivalves • Molluscs of class Bivalvia include many species of clams, oysters, mussels, and scallops • They have a shell divided into two halves Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings •The mantle cavity of a bivalve contains gills that are used for feeding as well as gas exchange Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-21 Coelom Hinge area Mantle Gut Heart Adductor muscle Shell Anus Mouth Excurrent siphon Palp Water flow Foot Mantle cavity Gill Incurrent siphon Cephalopods • Class Cephalopoda includes squids and octopuses, carnivores with beak-like jaws surrounded by tentacles of their modified foot Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings •Most octopuses creep along the sea floor in search of prey Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-22a Octopuses are considered among the most intelligent invertebrates. •Squids use their siphon to fire a jet of water, which allows them to swim very quickly Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-22b Squids are speedy carnivores with beaklike jaws and welldeveloped eyes. •One small group of shelled cephalopods, the nautiluses, survives today Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-22c Chambered nautiluses are the only living cephalopods with an external shell. Concept 33.5: Annelids are segmented worms • Annelids have bodies composed of a series of fused rings • The phylum Annelida is divided into three classes: – Oligochaeta (earthworms and their relatives) – Polychaeta (polychaetes) – Hirudinea (leeches) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Oligochaetes • Oligochaetes (class Oligochaeta) are named for relatively sparse chaetae, bristles made of chitin • They include the earthworms and a variety of aquatic species • Earthworms eat through soil, extracting nutrients as the soil moves through the alimentary canal Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-23 Cuticle Epidermis Circular muscle Longitudinal muscle Coelom Septum (partition between segments) Metanephridium Anus Dorsal vessel Chaetae Intestine Nerve Ventral vessel cords Nephrostome Clitellum Esophagus Crop Pharynx Giant Australian earthworm Cerebral ganglia Intestine Gizzard Mouth Subpharyngeal ganglion Metanephridium Circulatory system Ventral nerve cords with segmental ganglia Polychaetes •Members of class Polychaetes have paddlelike parapodia that work as gills and aid in locomotion Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-24 Parapodia Leeches •Members of class Hirudinea are bloodsucking parasites, such as leeches Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 33.6: Nematodes are nonsegmented pseudocoelomates covered by a tough cuticle • Nematodes, or roundworms, are found in most aquatic habitats, in the soil, in moist tissues of plants, and in body fluids and tissues of animals • The cylindrical bodies of nematodes (phylum Nematoda) are covered by a tough coat called a cuticle Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-26 25 µm •Some species of nematodes are important parasites of plants and animals Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-27 Encysted juveniles Muscle tissue 50 µm Concept 33.7: Arthropods are segmented coelomates that have an exoskeleton and jointed appendages • Two out of every three known species of animals are arthropods • Members of the phylum Arthropoda are found in nearly all habitats of the biosphere Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings General Characteristics of Arthropods • The diversity and success of arthropods are largely related to their segmentation, hard exoskeleton, and jointed appendages Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings •Early arthropods, such as trilobites, showed little variation from segment to segment Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • As arthropods evolved, the segments fused, and the appendages became more specialized • The appendages of some living arthropods are modified for many different functions Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-29 Cephalothorax Abdomen Thorax Antennae (sensory reception) Head Swimming appendages (two sets located under abdomen Walking legs Pincer (defense) Mouthparts (feeding) • The body of an arthropod is completely covered by the cuticle, an exoskeleton made of chitin • When an arthropod grow, it molts its exoskeleton in a process called ecdysis Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Arthropods have an open circulatory system in which fluid called hemolymph is circulated into the spaces surrounding the tissues and organs • A variety of organs specialized for gas exchange have evolved in arthropods Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Molecular evidence suggests that living arthropods consist of four major lineages that diverged early in the phylum’s evolution: – Cheliceriforms (sea spiders, horseshoe crabs, scorpions, ticks, mites, and spiders) – Myriapods (centipedes and millipedes) – Hexapods (insects and relatives) – Crustaceans (crabs, lobsters, shrimps, barnacles, and many others) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cheliceriforms • Cheliceriforms, subphylum Cheliceriformes, are named for clawlike feeding appendages called chelicerae • Most marine cheliceriforms are extinct, but some species survive today, including horseshoe crabs Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Most modern cheliceriforms are arachnids, which include spiders, scorpions, ticks, and mites Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-31a Scorpions have pedipalps that are pincers specialized for defense and the capture of food. The tip of the tail bears a poisonous stinger. LE 33-31b 50 µm Dust mites are ubiquitous scavengers in human dwellings but are harmless except to those people who are allergic to them (colorized SEM). LE 33-31c Web-building spiders are generally most active during the daytime. • Arachnids have an abdomen and a cephalothorax, which has six pairs of appendages, the most anterior of which are the chelicerae Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-32 Stomach Intestine Brain Heart Digestive gland Eyes Ovary Poison gland Anus Book lung Gonopore (exit for eggs) Sperm Silk gland receptacle Spinnerets Chelicera Pedipalp Myriapods • Subphylum Myriapoda includes millipedes and centipedes • Millipedes, class Diplopoda, have many legs • Each trunk segment has two pairs of legs Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Centipedes, class Chilopoda, are carnivores with jaw-like mandibles • They have one pair of legs per trunk segment Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Insects • Subphylum Hexapoda, insects and relatives, has more species than all other forms of life combined • They live in almost every terrestrial habitat and in fresh water • The internal anatomy of an insect includes several complex organ systems Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-35 Abdomen Thorax Head Compound eye Antennae Dorsal artery Crop Cerebral ganglion Heart Anus Vagina Malpighian tubules Ovary Tracheal tubes Nerve cords Mouthparts • Flight is one key to the great success of insects • An animal that can fly can escape predators, find food, and disperse to new habitats much faster than organisms that can only crawl Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Many insects undergo metamorphosis during their development • In incomplete metamorphosis, the young, called nymphs, resemble adults but are smaller and go through a series of molts until they reach full size Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Insects with complete metamorphosis have larval stages known by such names as maggot, grub, or caterpillar • The larval stage looks entirely different from the adult stage Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-36 Larva (caterpillar) Pupa Pupa Emerging adult Adult •Insects are classified into about 26 orders Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-37aA ORDER Blattodea APPROXIMATE NUMBER OF SPECIES 4,000 MAIN CHARACTERISTICS Cockroaches have a dorsoventrally flattened body, with legs modified for rapid running. Forewings, when present, are leathery, whereas hind wings are fanlike. Fewer than 40 cockroach species live in houses; the rest exploit habitats ranging from tropical forest floors to caves and deserts. EXAMPLES German cockroach LE 33-37bA ORDER Coleoptera APPROXIMATE NUMBER OF SPECIES 350,000 MAIN CHARACTERISTICS Beetles comprise the most species-rich order of insects. They have two pairs of wings, one of which is thick and leathery, the other membranous. They have an armored exoskeleton and mouthparts adapted for biting and chewing. Beetles undergo complete metamorphosis. EXAMPLES Japanese beetle LE 33-37cA ORDER Dermaptera APPROXIMATE NUMBER OF SPECIES 1,200 MAIN CHARACTERISTICS Earwigs are generally nocturnal scavengers. While some species are wingless, others have two pairs of wings, one of which is thick and leathery, the other membranous. Earwigs have biting mouthparts and large posterior pincers. They undergo incomplete metamorphosis. EXAMPLES Earwig LE 33-37dA ORDER Diptera APPROXIMATE NUMBER OF SPECIES 151,000 MAIN CHARACTERISTICS Dipterans have one pair of wings; the second pair has become modified into balancing organs called halteres. Their head is large and mobile; their mouthparts are adapted for sucking, piercing, or lapping. Dipterans undergo complete metamorphosis. Flies and mosquitoes are among the best-known dipterans, which live as scavengers, predetors, and parasites. EXAMPLES Horsefly LE 33-37eA ORDER Hemiptera APPROXIMATE NUMBER OF SPECIES 85,000 MAIN CHARACTERISTICS Hemipterans are so-called “true bugs,” including bed bugs, assassin bugs, and chinch bugs. (Insects in other orders are sometimes erroneously called bugs.) Hemipterans have two pairs of wings, one pair partly leathery, the other membranous. They have piercing or sucking mouthparts and undergo incomplete metamorphosis. EXAMPLES Leaffooted bug LE 33-37fA ORDER Hymenoptera APPROXIMATE NUMBER OF SPECIES 125,000 MAIN CHARACTERISTICS Ants, bees, and wasps are generally highly social insects. They have two pairs of membranous wings, a mobile head, and chewing or sucking mouthparts. The females of many species have a posterior stinging organ. Hymenopterans undergo complete metamorphosis. EXAMPLES Cicada-killer wasp LE 33-37gA ORDER Isoptera APPROXIMATE NUMBER OF SPECIES 2,000 MAIN CHARACTERISTICS Termites are widespread social insects that produce enormous colonies. It had been estimated that there are 700 kg of termites for every person on Earth! Some termites have two pairs of membranous wings, while others are wingless. They feed on wood with the aid of microbial symbionts carried in specialized chambers in their hindgut. EXAMPLES Termite LE 33-37aB ORDER Lepidoptera APPROXIMATE NUMBER OF SPECIES 120,000 MAIN CHARACTERISTICS Butterflies and moths are among the best-known insects. They have two pairs of wings covered with tiny scales. To feed, they uncoil a long proboscis. Most feed on nectar, but some species feed on other substances, including animal blood or tears. EXAMPLES Swallowtail butterfly LE 33-37bB ORDER Odonata APPROXIMATE NUMBER OF SPECIES 5,000 MAIN CHARACTERISTICS Dragonflies and damselflies have two pairs of large, membranous wings. They have an elongated abdomen, large, compound eyes, and chewing mouthparts. They undergo incomplete metamorphosis and are active predators. EXAMPLES Dragonfly LE 33-37cB ORDER Orthoptera APPROXIMATE NUMBER OF SPECIES 13,000 MAIN CHARACTERISTICS Grasshoppers, crickets, and their relatives are mostly herbivorous. They have large hind legs adapted for jumping, two pairs of wings (one leathery, one membranous), and biting or chewing mouthparts. Males commonly make courtship sounds by rubbing together body parts, such as a ridge of their hind leg. Orthopterans undergo incomplete metamorphosis. EXAMPLES Katydid LE 33-37dB ORDER Phasmida APPROXIMATE NUMBER OF SPECIES 2,600 MAIN CHARACTERISTICS Stick insects and leaf insects are exquisite mimics of plants. The eggs of some species even mimic seeds of the plants on which the insects live. Their body is cylindrical or flattened dorsoventrally. They lack forewings but have fanlike hind wings. Their mouthparts are adapted for biting or chewing. EXAMPLES Stick insect LE 33-37eB ORDER Phthiraptera APPROXIMATE NUMBER OF SPECIES 2,400 MAIN CHARACTERISTICS Commonly called sucking lice, these insects spend their entire life as an ectoparasite feeding on the hair or feathers of a single host. Their legs, equipped with clawlike tarsi, are adapted for clinging to their hosts. They lack wings and have reduced eyes. Sucking lice undergo incomplete metamorphosis. EXAMPLES Human body louse LE 33-37fB ORDER Siphonaptera APPROXIMATE NUMBER OF SPECIES 2,400 MAIN CHARACTERISTICS Fleas are bloodsucking ectoparasites on birds and mammals. Their body is wingless and laterally compressed. Their legs are modified for clinging to their hosts and for long-distance jumping. They undergo complete metamorphosis. EXAMPLES Flea LE 33-37gB ORDER Thysanura APPROXIMATE NUMBER OF SPECIES 450 MAIN CHARACTERISTICS Silverfish are small, wingless insects with a flattened body and reduced eyes. They live in leaf litter or under bark. They can also infest buildings, where they can become pests. EXAMPLES Silverfish LE 33-37hB ORDER Trichoptera APPROXIMATE NUMBER OF SPECIES 7,100 MAIN CHARACTERISTICS The larvae of caddisflies live in streams, where they make houses from sand grains, wood fragments, or other material held together by silk, Adults have two pairs of hairy wings and chewing or lapping mouthparts. They undergo complete metamorphosis. EXAMPLES Caddisfly Crustaceans • While arachnids and insects thrive on land, crustaceans, for the most part, have remained in marine and freshwater environments • Crustaceans, subphylum Crustacea, typically have branched appendages that are extensively specialized for feeding and locomotion Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Decapods are all relatively large crustaceans and include lobsters, crabs, crayfish, and shrimp Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Planktonic crustaceans include many species of copepods, which are among the most numerous of all animals Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Barnacles are a group of mostly sessile crustaceans • They have a cuticle that is hardened into a shell Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 33.8: Echinoderms and chordates are deuterostomes • Sea stars and other echinoderms, phylum Echinodermata, may seem to have little in common with phylum Chordata, which includes the vertebrates Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Chordates and echinoderms share characteristics of deuterostomes: – Radial cleavage – Development of the coelom from the archenteron – Formation of the mouth at the end of the embryo opposite the blastopore Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Echinoderms • Sea stars and most other echinoderms are slow-moving or sessile marine animals • A thin, bumpy or spiny skin covers an endoskeleton of hard calcareous plates • Unique to echinoderms is a water vascular system, a network of hydraulic canals branching into tube feet that function in locomotion, feeding, and gas exchange Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-39 Spine Anus Stomach Gills Central disk Madreporite Digestive glands Radial nerve Ring canal Gonads Ampulla Radial canal Podium Tube feet • Radial anatomy of many echinoderms evolved from the bilateral symmetry of ancestors • Living echinoderms are divided into six classes: – Asteroidia (sea stars) – Ophiuroidea (brittle stars) – Echinoidea (sea urchins and sand dollars) – Crinoidea (sea lilies and feather stars) – Holothuroidea (sea cucumbers) – Concentricycloidea (sea daisies) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sea Stars • Sea stars, class Asteroidea, have multiple arms radiating from a central disk • The undersurfaces of the arms bear tube feet, each of which can act like a suction disk Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-40a A sea star (class Asteroidea) Brittle Stars •Brittle stars have a distinct central disk and long, flexible arms Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-40b A brittle star (class Ophiuroidea) Sea Urchins and Sand Dollars •Sea urchins and sand dollars have no arms but have five rows of tube feet Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-40c A sea urchin (class Echinoidea) Sea Lilies and Feather Stars • Sea lilies live attached to the substrate by a stalk • Feather stars crawl using long, flexible arms Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-40d A feather star (class Crinoidea) Sea Cucumbers • Sea cucumbers do not look much like other echinoderms • They lack spines, and their endoskeleton is much reduced Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-40e A sea cucumber (class Holothuroidea) Sea Daisies •Sea daisies were discovered in 1986, and only two species are known Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 33-40f A sea daisy (class Concentricycloidea) Chordates • Phylum Chordata consists of two subphyla of invertebrates as well as hagfishes and vertebrates • Chordates share many features of embryonic development with echinoderms Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings