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BIOLOGY FOR CLASS IX Class IX INVERTEBRATA Content Invertebrates Phylum Protozoa Phylum Porifera Phylum Coelenterata Phylum Platyhelminthes Phylum Nematoda Phylum Annelida Phylum Arthropoda Phylum Mullusca Phylum Echinodermata Invertebrates are animals that do not have a backbone. Invertebrates are cold-blooded; their body temperature depends on the temperature of their environment. Some major groups of invertebrates include: Protozoans - Very primitive, simple animals like amoebas, jellyfish, corals, tapeworms, insects, arachnids, crustaceans, mollusks, echinoderms, etc 1. 2. 3. 4. 5. Phylum Protozoa Heterotrophic or autotrophic Most motile Eukaryotes Unicellular Movement 1. Flagellates(chlamydomonas) 2. Ciliates(paramecium) 3. Pseudopodia (Amoeba) Protozoans hunt, digest and store food. Most are heterotrophs. They feed on other animals to obtain the nutrients they need to live. Waste materials in protozoan are removed from the cell by diffusion through the cell. They are transported out of the cell by food vacuoles that come in contact with the surface. This is known as exocytosis. Respiration takes place when oxygen diffuses into the cell, where the food molecules become oxidized. The energy produced and the organic molecules are used for maintenance and building of the cell. Waste products ,carbon dioxide and water diffuse out of the cell. Binary fission, asexual reproduction by a separation of the body into two new bodies. In the process of binary fission, an organism duplicates its genetic material, or deoxyribonucleic acid (DNA), and then divides into two parts (cytokinesis), with each new organism receiving one copy of DNA. In protists, binary fission is often differentiated into types, such as transverse or longitudinal, depending on the axis of cell separation. Asexual reproduction of protozoans occurs when the cell divides in half by binary fission. Some which are parasites multiply within the host. Phylum Porifera - Sponges • Mostly marine, but include some freshwater inhabitants; usually found attached to the substratum in shallow or deep water. • They are sessile; permanently attached to the substrate • Obtain their food by filter feeding General Morphology • The internal cavity is called the atrium or spongocoel • Water is drawn into it through a series of incurrent pores or dermal ostia present in the body wall into a central cavity and then flows out of the sponge through a large opening at the top called the osculum The Skeleton In the mesohyl is the skeleton composed of tiny pointed structures made of silica or calcium carbonate called spicules. These structures act as an internal scaffolding, but also function in protection Among some sponges the skeleton consist of spongin fibers made of collagenous material; found in many of the commercial sponges Types of Sponges (Canal Systems) A. Asconoid Sponges • Simple vaselike structure • This stucture puts limitations on size; (increase in volume without a corresponding increase in the surface area of the choanocytes) Sponge Reproduction • Most are hermaphroditic or monoecious. • Sperm leaves a sponge via the osculum, and enters a sponge by the currents generated from the choanocytes. Fertilized eggs develop into ciliated free-swimming larvae called parenchymula larvae • Sponges can reproduce asexually by fragmentation • Many of the freshwater sponges can produce asexual bodies called gemmules, aggregations of cells that are enclosed in hard outer covering containing spicules Sponge Taxonomy Class Calcarea (Calcispongidae) • Only sponges that possess spicules composed of calcium carbonate. • Spicules are straight or have 3-4 rays, and do not have hollow axial canals. • Today, their diversity is greatest in the tropics, predominantly in shallow waters Class Hexactinellida (Hyalospongiae) • Glass sponges; characterized by siliceous spicules consisting of six rays intersecting at right angles • Widely viewed as an early branch within the Porifera Class Demospongiae • Greater than 90 percent of the 5,000 known living sponge species are demosponges. • Demosponge skeletons are composed of spongin fibers and/or siliceous spicules • Siliceous spicules with one to four rays not at right angles, All members express the leuconoid body form Yellow sponge growing on a wall on a Caribbean reef. The “simplest” of the complex animals . . . Sea Anemone Jellyfish Hydras Sea Coral Over 10,000 living species Both marine and freshwater Hydras in FW Corals, jellyfish, and anemones in marine Radial symmetry Tissue level of organization Two general body forms exhibited POLYP MEDUSA Polyp Form Medusa Form Sessile Cylindrical body Ring of tentacles on oral surface Flattened, mouth-down version of polyp Free-swimming Show the same internal structure Basic body plan of ALL cnidarians Sac with a central digestive compartment (GVC) Single opening serving as both mouth and anus Ring of tentacles on oral surface All cnidarians are carnivores Tentacles capture and push food into mouth Tentacles are armed with stinging cells Cnidoblasts / cnidocytes Contain stinging capsules called nematocysts The tentacle is stimulated Nematocyst is discharged Pressure on “trigger” Thread uncoils Entangles prey Some species produce toxins Injects toxin into prey, paralyzing it! Cnidocytes cover the length of tentacles Food is forced into the GVC Extracellular digestion begins Enzymes secreted into GVC Intracellular digestion completes process Partially digested food engulfed by endoderm cells First true nerve cells in K. Anamalia Nerve net sends impulses in all directions Cells of epidermis and gastrodermis arranged into contractile fibers Do not have a brain to receive information! Varies among forms Hydras, anemones and corals exist only in polyp form Asexual reproduction (conditions good) Sexual reproduction (conditions unfavorable) Budding in Hydra Budding Zygotes remain dormant until conditions improve Some colonial polyp forms have a medusa phase in their life cycle Specialized reproductive polyps produce tiny medusas by asexual budding Sexual reproduction by medusas produce ciliated larva planula Planula settles and develops into new polyp Medusa and polyp stages Separate sexes produce gametes Fertilization occurs in GVC of female Planula develops and is free-swimming Planula settles, develops into polyp Polyp produces new medusas by budding *Fig. 32-8, PG 690 The cnidarians may be a relatively small group comprising the Animal Kingdom, but they play a major role in any marine habitat. General Characteristics • They exhibit bilateral symmetry: anterior and posterior ends are different; so are the dorsal (top) and ventral (bottom) surfaces • The platyhelminths also exhibit some degree of cephalization Commonly referred to as the 'flatworms' because their bodies are dorsoventrally flattened. • They are acoelomates • This phylum (and all remaining phyla) possess 3 germ layers (=triploblastic) • The mesoderm (third germ layer) gives rise to muscles, various organ systems, and the parenchyma, a form of solid tissue containing cells and fibers Outer Body Covering • The body of some platyhelminthes (e.g., turbellarians) is covered by a ciliated epidermis • Epidermal cells contain rod-shaped structures called rhabdites that when released into the surrounding water, expand and form a protective mucous coat around the animal • The outer body covering of other platyhelminthes (e.g., parasitic forms) is a nonciliated tegument • The tegument is referred to as a syncytial epithelium Organ Systems of the Platyhelminthes Digestive System • Some of the flatworms possess a digestive system, with a mouth, pharynx, and a branching intestine from which the nutrients are absorbed • The intestine, with only one opening, is a blind system Excretory System (osmoregulation) • A network of water collecting tubules adjacent to flame cells or a protonephridia • When cilia beat they move water into the tubules and out the body through pores called nephridiopores Organ Systems of the Platyhelminthes con’t Muscular System • Below the epidermis are layers of circular and longitudinal muscle fibers; used in locomotion Nervous System • Includes: anterior cerebral ganglia, longitudinal nerve cords, and some lateral nerves • Most free living planarians and parasitic larval forms possess a variety of sensory organs (e.g., eye spots, statocysts, rheoreceptors) Reproductive System • Most are capable of some form of asexual reproduction (e.g., many turbellarians reproduce by fission) • Most flatworms are hermaphroditic; however, they often pair with other individuals to exchange gametes Class Turbellaria • Free-living flatworms; mostly marine organisms • Range in size from microscopic (interstitial species between sand grains) to extremely large (two feet) Locomotion • Most move by means of cilia and mucous • Muscle contractions also permit turning, twisting and folding of the body Class Turbellaria con’t Nutrition • Turbellarians are carnivores and prey on other animals or eat dead animal remains. • Planarians have a muscular pharynx that they can insert into their prey and then pump to bring in food fragments • These animals have a highly divided gut to greatly increase the surface area for digestion and absorption Senses • They have well developed sensory structures, including eyespots, mechanoreceptors, and chemoreceptors Class Turbellaria con’t Reproduction • Planarians are capable of asexual reproduction via fission • Also capable of regeneration; exhibit both anterior- posterior and lateral polarity • They are hermaphrodites but usually exhibit cross-fertilization • The penis of some turbellarians is modified as a hollow stylet; sperm tranfer is by hypodermic impregnation, in which the copulating partners stab each other and inject sperm •Over 80000 species •Cylindrical pseudocoeloemates •Have effective hydroskeleton and musculature •Inhabit aquatic areas. Most are parasitic. •Most reproduce sexually. Females can produce ~100,000 eggs a day. •Tricininella spiralis causes trichinosis in humans from under cooked pork •Parasite burrows into muscle tissue forming cysts •Hookworms and pinworms can parasitize digestive systems •Others cause heartworm and elephantiasis Roundworm Hookworm Similar to flat worms Inclide proboscus worms Acoelomate, but have functioning digestive tract Also have a funtioning blood vascular system •Have an anterior prostomium and posterior pygidium; both nonsegmented • Body is divided into a linear series of similar parts or segments, and each segment is called a metamere • The pattern of repeated segmentation is called metamerism • Each metamere is separated from the next by a transverse septum • Each metamere acts as a hydrostatic skeleton • Each metamere has longitudinal and circular muscles; longitudinal muscle contraction causes segments to shorten; circular muscle contraction causes segments to elongate • Each segment usually bears one or more chitinous bristles called setae; help anchor segments Nervous System • Consists of a brain, which is connected to a pair of ventral longitudinal nerve cords, with a ganglion in each segment (metameric) Circulatory System • Closed circulatory system, in which the blood is always enclosed within blood vessels that run the length of the body and branch to every segment • Several hearts (5 in earthworms) are used to pump blood through the closed circuit Excretory System • Consists of paired (metameric) metanephridia • Excretory tubes with ciliated funnels that remove waste from the coelomic fluid; open to the outside via excretory pores. Note: Not all organ systems are metameric For example, the digestive system extends the length of the organism and is differentiated along its length Reproductive System • Most annelids are hermaphroditic, but they are usually cross fertilizers. • Earthworms and leeches form pairs and reciprocally fertilize one another • Some annelids (e.g. marine sandworms) are dioecious and they release eggs and sperm into the marine environment, where gametes unite to form trochophore larvae Polychaetes: General Characteristics cont. •Prostomium is well equipped with sensory and feeding structures Polychaetes: General Characteristics cont. • Mouth is located just below the prostomium, but in front of the modified segments peristomium • Digestive system includes a muscular pharynx that can be everted through the mouth • Pharynx is equipped with pincer-like jaws • Although many of the smaller polychaetes lack respiratory structures, the larger one do possess gills • Gills are usually modifications of the parapodia Class Polychaeta: Diversity cont. • Chaetopterus is tube dweller; lives in a U-shaped tube • Parapodia are highly modified into 3 fan-like structures that bring water into the tube • The notopodium secretes a mucous bag that traps food from the water flowing through the tube; the bag is periodically passed anteriorly toward the mouth Class Polychaeta: Diversity cont. • Arenicola lives in a J-shaped burrow • It employs peristaltic movements to generate a water flow • Food is filtered out from the front of the burrow Class Oligochaeta cont. • Earthworms feed on vast quantities of soil that contains living and decaying organic material. • Digestive tract of the annelids shows specialization along its length: mouth, pharynx, crop (food storage), gizzard (grinding), calciferous glands (accessory glands that excrete excess calcium from the food) • Remainder of the gut is the intestine - for digestion and absorption • Its surface area is increased because of a dorsal longitudinal fold called the typhlosole Class Hirudinea cont. • Leeches crawl over the surface in a loop like fashion, with the use of 2 suckers. • Body is extended due to circular muscle contraction and the attachment of the anterior sucker to the substrate. • Posterior sucker is subsequently released, and longitudinal muscles contract bringing the posterior part of the body forward. Class Hirudinea con’t • Most leeches are active predators; however, some are the parasitic, bloodsucking forms. • Blood suckers have blade like jaws that they use to penetrate the skin of a host. • Blood is prevented from clotting because they secrete a powerful anticoagulant; anesthetics are also released • A muscular pharynx subsequently pumps blood into the gut. Metamerism- body is segmented. Exoskeleton and metamerism causes molting Exoskeleton- body covered with a hard external skeleton Why an exoskeleton? Why not bones? Exoskeleton good for small things, protects body from damage (rainfall, falling, etc.). Bones better for large things Bilateral Symmetry- body can be divided into two identical halves Jointed Appendages- each segment may have one pair of appendages, such as: legs wings mouthparts Open Circulatory System- blood washes over organs and is not entirely closed by blood vessels. Our system is a closed one Ventral Nerve Cord- one nerve cord, similar to our spinal column Introduction • Includes animals such as squids, snails, oysters, clams and slugs. • Most are marine, but many are freshwater and some live on the land • Despite the diversity of form and function among the molluscs, all members of this group have the same basic body plan. • This is often indicated by presenting a hypothetical ancestral mollusc (HAM) • HAM is hypothetical primitive ancestor that has characteristics that appear among most members of the mollusca A Closer look at HAM The foot - a broad, flat muscular organ that is adapted for locomotion and attachment The visceral mass - contains the internal organs The mantle - a fold of tissue that drapes over the visceral mass; space between the mantle and the visceral mass is called the mantle cavity The Shell • The mantle is responsible for secreting the shell. • The shell is comprised of three layers: • The outside of the shell is covered by an organic layer periostracum • The middle prismatic layer is characterized by densely packed prisms of calcium carbonate laid down in a protein matrix • The inner nacreous layer is composed of calcium carbonate sheets laid down over a thin layer of protein Gills • The gills of HAM are often indicated as one or more pairs of bipectinate gills, flattened filaments attached to a longitudinal axis on either side The Radula • The mouth cavity of HAM possesses a specialized rasping organ called the radula; sits on a cartilaginous structure - odontophore • Particles of food brought into the mouth are bound in mucous secreted by the salivary glands Other Features of HAM • Nervous system consists of a nerve ring and 2 longitudinal nerve cords • Coelom is reduced • Open circulatory system • The excretory organs of the molluscs are metanephridia; inner ends open into the coelom via a ciliated funnel called the nephrostome; wastes leave the body via the nephridiopore Molluscan Larval Stages • Most molluscs produce a free-swimming ciliated larvae called the trochophore larvae • In some molluscs the trochophore develops into the adult, but in other molluscs (e.g., gastropods) there is a second larval stage called the veliger General Characteristics • Adults exhibit pentamerous radial symmetry • Radially symmetry is secondary; larvae are bilaterally symmetrical and undergo metamorphosis to become radially symmetrical adults. Echinoderm larva General Characteristics cont. •Poorly ganglionated; possess few sensory structures • Body wall contains an endoskeleton of calcareous plates - ossicles General Characteristics cont. • Possess a network of canals throughout the body - water vascular system. • The canals are connected to extensions called tube feet (=podia), located on the oral surface • The water vascular system is important for locomotion, feeding, and gas exchange. • Sexes are separate; gametes shed into the water; fertilization is external Class Asteroidea • Typically have 5 arms which merge with a central disc • Mouth is located in the center of oral surface which is directed downward Water Vascular System • On the aboral surface is the opening of the water vascular system the madreporite (=sieve plate) • Water enters the madreporite and goes through the stone canal canal to the ring canal • Water then passes through a radial canal extending into each arm • All along the length of these canals are lateral canals that terminate in a bulb-like structures called ampullae equipped with tube feet • Tube feet line the grooves on the oral surface - ambulacral grooves How the Podia Operate • Ampulla contract and force fluid into the podia causing it to become extended • Suckers at the tips of the podia come into contact with the substrate and adhere to the surface • Then the podia contract, thereby forcing water back into the ampulla, and the body is pulled forward Nutrition • Mouth leads to a 2-part stomach: a large cardiac stomach and a smaller pyloric stomach • The pyloric stomach connects with digestive glands (=pyloric cecae) that runs into each arm • A short intestine extends from from the pyloric stomach to an anus on the aboral surface • Associated with the intestine are rectal cecae that pump the fecal wastes out of the anus Additional Characteristics • The endoskelton is made up of calcareous plates that often penetrate the dermis as spines • Between the spines and plates are projections called papulae, which function in gas exchange and excretion • Other projections on the body wall include tiny jaw-like appendages called pedicellaria Class Echinoidea • Lack arms • Body is enclosed in a shell or test • Body surface is usually covered with moveable spines Sea Urchins • Spherical body • Ambulacral plates bearing tube feet that radiate out toward the aboral surface • Use podia and spines during locomotion • The spines are moveable and articulate with the with the calcareous ossicles • Sea urchins generally feed by scraping algae off of rocks • Accomplished via a complex chewing apparatus called Aristotle's lantern Class Holothuroidea • Lack arms • Oral-aboral axis is greatly extended • Endoskeleton is reduced to a few ossicles scattered over the surface of the animal making them rather soft bodied • Some species crawl along the substrate using podia; others have peristaltic locomotion via muscle contractions Dermal ossicles • At the oral end of the body are a group of tentacles (modified podia) that surround the mouth; used in feeding • Have a muscular cloaca that is partly used in gas exchange • The actual gas exchange structures are branching structures called respiratory trees Class Crinoidea • Most primitive of the echinoderms • Unusual in that the oral surface is directed upward • Aboral surface is attached to the substrate by means of a bendable stalk • The portion of the crinoid body attached to the stalk is called the crown; bears a number of arms • Along the length of the arms are branches called pinnules • The arms and the pinnules have ambulacral grooves with suckerless podia (secrete mucus) • The ambulacral grooves are heavily ciliated and the cilia is used to direct food to the mouth (=filter feeding)