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Chapter 33

Chapter 33. Invertebrates. Overview: Life Without a Backbone. Invertebrates are animals that lack a backbone They account for 95% of known animal species. Fig. 33-2. Calcarea and Silicea. ANCESTRAL PROTIST. Cnidaria. Lophotrochozoa. Common ancestor of all animals. Eumetazoa.

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Chapter 33

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  1. Chapter 33 Invertebrates

  2. Overview: Life Without a Backbone • Invertebrates are animals that lack a backbone • They account for 95% of known animal species

  3. Fig. 33-2 Calcarea andSilicea ANCESTRAL PROTIST Cnidaria Lophotrochozoa Common ancestor of all animals Eumetazoa Ecdysozoa Bilateria Deuterostomia

  4. A sea urchin A marine flatworm A jelly A sponge A ctenophore, or comb jelly

  5. A rotifer Acoel flatworms Ectoprocts 1.5 mm A marine annelid A brachiopod An octopus

  6. A priapulan A ribbon worm A scorpion (an arachnid) A roundworm An onychophoran

  7. Phyla Calcerea and Silcea (Porifera) • Sponges are sedentary animals • They live in both fresh and marine waters • Sponges lack true tissues and organs • Most sponges are hermaphrodites: Each individual functions as both male and female

  8. Sponges are suspension feeders, capturing food particles suspended in the water that pass through their body • Choanocytes, flagellated collar cells, generate a water current through the sponge and ingest suspended food • Water is drawn through pores into a cavity called the spongocoel, and out through an opening called the osculum • Sponges consist of a noncellular mesophyl layer between two cell layers

  9. Fig. 33-4 Flagellum Choanocyte Choanocyte Osculum Spongocoel Phagocytosis of food particles Amoebocyte Pore Epidermis Water flow Amoebocytes Mesohyl

  10. Clade Eumetazoa (true tissues): Phylum Cnidarians • Wide range of both sessile and motile forms including jellies, corals, and hydras • They exhibit a relatively simple diploblastic, radial body plan • The basic body plan of a cnidarian is a sac with a central digestive compartment, the gastrovascular cavity

  11. Fig. 33-5 Mouth/anus Tentacle Polyp Medusa Gastrovascular cavity Gastrodermis Mesoglea Body stalk Epidermis Tentacle Mouth/anus •A single opening functions as mouth and anus •There are two variations on the body plan: the sessile polyp and motile medusa

  12. 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 • Nematocysts are specialized organelles within cnidocytes that eject a stinging thread

  13. Fig. 33-6 Tentacle Thread Nematocyst “Trigger” Thread discharges Thread (coiled) Cnidocyte

  14. Table 33-1

  15. Fig. 33-7 (c) Sea wasp (class Cubozoa) (d) Sea anemone (class Anthozoa) (b) Jellies (class Scyphozoa) (a) Colonial polyps (class Hydrozoa)

  16. Hydrozoans: - Alternate between polyp and medusa forms Scyphozoans: - Jellies (medusae) are the prevalent form of the life cycle Classes of Phylum Cnidaria Video: Hydra Budding Video: Jellyfish Medusae separating from polyp Video: Jellyfish Medusae Cubozoans: Video: Jellyfish tentacles • Includes box jellies and sea wasps • The medusa is box-shaped and has complex eyes • - Cubozoans often have highly toxic cnidocytes Anthozoans: • Includes the corals and sea anemones • Occur only as polyps Video: Sea anemone Video: Box Jelly sting

  17. Clade Lophotrochozoans have the widest range of animal body forms • Includes the flatworms, rotifers, ectoprocts, brachiopods, molluscs, and annelids

  18. Phylum Platyhelminthes • Flatworms live in marine, freshwater, and damp terrestrial habitats (mostly parasitic) • They are tribloblastic acoelomates • They are flattened dorsoventrally and have a gastrovascular cavity (one opening) • No organs for gas exchange or circulation

  19. Flatworms are divided into four classes: 1. Turbellaria (mostly free-living flatworms called planarians; hermaphrodites) 2. Monogenea (are fish parasites) 3. Trematoda (trematodes, or flukes are parasites) 4. Cestoda (tapeworms, parasites in intestine of vertebrates) Video: Tapeworm

  20. Table 33-2

  21. Phylum Rotifera • Rotifers 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 - Rotifers have an alimentary canal (not a gastrovascular cavity), a digestive tube with a separate mouth and anus that lies within a fluid-filled pseudocoelom - Parthogenesis: females producing more females with out the help of males Video: Rotifer

  22. Phylum Mollusca • Includes snails and slugs, oysters and clams, and octopuses and squids • Most are marine, though some inhabit fresh water and some are terrestrial • Soft-bodied animals, but most are protected by a hard shell

  23. All molluscs have a similar body plan with three main parts: • Muscular foot • Visceral mass • Mantle • Many molluscs also have a water-filled mantle cavity, and feed using a rasplike radula • Most molluscs have separate sexes with gonads located in the visceral mass • Many snails are hermaphrodites.

  24. Table 33-3

  25. Class Gastropoda • Snails and slugs • The most distinctive characteristic of gastropods is torsion, which causes the animal’s anus and mantle to end up above its head Class Polyplacophora • Chitins • Oval-shaped marine animals encased in an armor of eight dorsal plates

  26. Class Cephalopoda Class Bivalvia • Squids and octopuses • Carnivores with • beak-like jaws surrounded • by tentacles of their modified foot • Cephalopods have a closed circulatory system, well-developed sense organs, and a complex brain - Clams, oysters, mussels, and scallops - Shell is divided into two halves - The mantle cavity contains gills that are used for feeding as well as gas exchange (suspension feeders) Squid

  27. Phylum Annelida • Annelids have bodies composed of a series of fused rings • Segmented worms and are coelomates • Closed circulatory system • Sea, frseshwater habitats, and damp soil

  28. Polychaetes Oligochaetes • Paddle-like parapodia that work as gills and aid in locomotion • Sparse chaetae, bristles made of chitin • Earthworms • Earthworms are hermaphrodites but cross-fertilize • Alimentary canal Hirudinea Blood-sucking parasites, such as leeches

  29. Clade Ecdysozoans • Covered by a tough coat called a cuticle • The cuticle is shed or molted through a process called ecdysis • The two largest phyla are nematodes and arthropods

  30. PhylumNematoda • Roundworms are found in most aquatic habitats, in the soil, in moist tissues of plants, and in body fluids and tissues of animals • They have an alimentary canal, but lack a circulatory system • pseudocoelomate • Non segmented • Tough coat = cuticle

  31. Phylum Arthropoda • Coelomates • Body plan consists of a segmented body, hard exoskeleton, and jointed appendages • The body of an arthropod is completely covered by the cuticle, an exoskeleton made of layers of protein and the polysaccharide chitin • When an arthropod grows, it molts its exoskeleton • Arthropods have an open circulatory system • A variety of organs specialized for gas exchange have evolved in arthropods • Aquatic and terrestrial

  32. Table 33-5

  33. Sub Phyla Cheliceriforms - Clawlike feeding appendages called chelicerae - Include spiders, scorpions, ticks, and mites - Have an abdomen and a cephalothorax, which has six pairs of appendages Sub Phyla Myriapods - Millipedes and centipedes - Are terrestrial, and have jaw-like mandibles - Millipedes (each segment has two pairs of legs) - Centipedes are carnivores (one pair of legs per segment)

  34. Sub Phyla Hexapoda • Insects • Complex organ systems • Evolution of flight • Some insects are beneficial as pollinators, while others are harmful as carriers of diseases, or pests of crops • Insects are classified into more than 30 orders

  35. In incomplete metamorphosis, the young, called nymphs, resemble adults but are smaller and go through a series of molts until they reach full size • - Insects with complete metamorphosis have larval stages known by such names as maggot, grub, or caterpillar Adult Larva (caterpillar) Pupa Later-stage pupa Emerging adult

  36. Sub Phyla Crustaceans • Marine and freshwater environments • Branched appendages that are extensively specialized for feeding and locomotion • Isopods include terrestrial, freshwater, and marine species • Pill bugs are a well known group of terrestrial isopods • Decapods are all relatively large crustaceans and include lobsters, crabs, crayfish, and shrimp Ghost crab Krill Barnacles

  37. Clade deuterostomes • Phylum Echinodermata (sea stars) and phylum Chordata (vertebrates) • Shared characteristics define deuterostomes (Chordates and Echinoderms) • Radial cleavage • Formation of the mouth at the end of the embryo opposite the blastopore

  38. Phylum Echinodermata • Slow-moving or sessile marine animals • Have a unique water vascular system, a network of hydraulic canals branching into tube feet that function in locomotion, feeding, and gas exchange • Males and females are usually separate, and sexual reproduction is external • Central disk has nerve ring and nerve cords Video: Biology of Echinoderm

  39. Table 33-6

  40. Fig. 33-40 (a) A sea star (class Asteroidea) (b) A brittle star (class Ophiuroidea) (c) A sea urchin (class Echinoidea) (d) A feather star (class Crinoidea) (f) A sea daisy (class Concentricycloidea) (e) A sea cucumber (class Holothuroidea)

  41. Class Ophiuroidea Class Asteroidea • - Brittle stars • Have a distinct central disk and long, flexible arms, which they use for movement • Tube feet lack suckers - Sea stars 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 • Sea stars can regrow lost arms • Turn stomach inside out Class Crinoidea Class Echinoidea • - Sea lilies live attached to the substrate by a stalk • Feather stars can crawl using long, flexible arms • Mouth directed upward - Sea urchins and sand dollars have no arms but have five rows of tube feet Class Holothuroidea Class Concentricycloidea • Sea cucumbers lack spines, and do not look like other echinoderms • 5 rows of tube feet - Sea daisies; only three species are known

  42. Fig. 33-UN6

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