The Animal Kingdom ? Protostomes.docx

The Animal Kingdom ? Protostomes Importance of the Coelom True Coelom Fluid-filled body cavity completely lined by mesoderm Lies between the digestive tube and the outer body wall Tube-Within-a-Tube Body Plan Body wall is the outer tube Inner tube is digestive tube Has a mouth at one end and anus at the other Can serve as a hydrostatic skeleton Contracting muscles push against a tube of fluid Advantages Provided space where internal organs could develop Fluid-filled coelom protects internal organs Provides space for gonads to develop Some animals?fluid helps transport materials Lophotrochozoa ? nemerteans, mollusks, annelids, Lophophorate phyla, rotifers, and platyhelminths Phylum Platyhelminthes Characteristics of Flatworms Simplest bilaterally symmetrical triploblastic Outer epidermis derived from ectoderm Inner epidermis derived from endoderm Middle tissue layer develops from mesoderm Acoelomates No body cavity Thought to be a basal group 18S ribosomal RNA indicate that phylum Platyhelminthes is not a monophyletic group Remaining flatworms appear more closely related with Coelomates body plan became simplified through evolution Exhibit Cephalizaiton Evolution of head with a concentration of sense organs at the anterior end Systems Digestive system is gastrovascular cavity Only one opening, a mouth Simple Nervous System Ganglia: wo masses of nervous tissue that makes the brain Ganglia connect to two nerve cords that extend the length of the body Called ?ladder-type nervous system? Classes Turbellaria (planarians) Mainly free living marine Covered by ciliated epidermis Carnivorous Trematoda and Monogenea (flukes) Parasites with a wide range of vertebrate and invertebrate hosts Adults have suckers for attachment May require intermediate hosts Cestoda (tapeworms) Parasites of vertebrates Complex life cycle (one or two intermediate hosts)r hooks for attachment Produces eggs within proglottids No nervous or digestive system Tubellarians: Free Living Flatworms Characteristics of Tubellarians Muscular pharynx that takes in food Simple brain, eye spots, and other sensory organs in the head Protonephridia Structures that function in Osmoregulation Waste disposal Reproductive Organs Planarians Have crossed eyes and flapping ?ear? called auricles Serve as organs of chemoreception (locating food) Capable of learning Not stored in ganglia, but throughout nervous system Carnivorous Trap small animals in a mucous secretion Digestive System Consists of one opening (mouth) Tube like muscular pharynx Branched gastrovascular cavity that distributes food Excretion Protonephridia are blind tubules that end in flame bulbs, collecting cells equipped with cilia Reproduction - Both Asexual Individual constricts the middle and divides into two Each regenerates its missing parts Sexual Hermaphrodites Equipped with male and female organs Flukes Parasitize Other Animals (Trematoda and Monogenea) Have structures such as hooks and suckers Extremely prolific reproductive organs Types of flukes Blood flukes Parasitic in humans and widespread in tropical areas Liver flukes Common in Asia and areas where humans use own feces for fertilizing crops Both go through complicated life cycles involving several different forms Alternation of sexual and asexual stages and parasitism on one or more intermediate hosts Tapeworms Inhabit The Intestine of Vertebrates Characteristics of Tapeworms Parasites in the intestines Have scolex Enables parasite to attach to intestine Body of Tapeworm Consists of a long segmeneted chain of proglottids Each proglottid is an entire reproductive machine, with both male and female parts Proglottids furthest from the head contain the ripest eggs No mouth or digestive system Must absorb already digested food Phylum Nemertea (characterized by proboscis) : Ribbon worms or proboscis worms Characteristics of Nemertea Proboscis A long hollow muscular tube that can be rapidly everted from the anterior end of the body Used to capture prey Some species proboscis are sharp, sticky, or/and secrete toxic fluid Rhynchocoel A chamber surrounding the Probiscis that is a true coelomic space Have no heart Blood circulated by contractions of muscular blood vessels and body movement Acoelomate, but system of blood vessels may be homologous to coelom Classified with the lophotrochozoans Phlym Mollusca: Clams, Oysters, Snails, Slugs, Octopods, and Squids Characteristics of Mollusca Soft body, usually covered by a dorsal shell (CaCO3) Broad, flat, muscular foot, located ventrally Body organs concentrated as a visceral mass (above the foot) Mantle Thin sheet of tissue that covers the visceral mass and contains glands that secrete a shell Generally overhangs the visceral mass, forming a mantle cavity that contains gills and other structures Radula Belt of teeth in the mouth region Used to scrape food or drill a hole in a shell Coelom Reduced to small compartments around certain organs Hemocoel ? Not a Coelom Main body cavity that contains blood Two Open Ended Mouth and anus Open Circulatory System Blood (Hemolymph) bathes the tissues directly Heart pumps blood into a single blood vessel Blood flows into a network of large spaces called sinuses brings blood into direct contact with tissues From sinuses, blood goes to gills and recharged with oxygen Overview HeartAortaSmaller Blood VesselsBlood Sinuses (hemocoel)Blood vessels to gillsHeart First Stage of Larval Stages Trochophore Larva Free swimming, top shaped larva with two bands of cilia around its middle Veliger Larva Developed from Trochophore Larva Has a shell, foot, and mantle Class Chitons Class Polyplacophora (meaning many plates) Shell composed of eight separate but overlapping dorsal plates No eyes or tentacles with head reduced Inhabit rocky intertidal zones Can produce a partial vacuum and helps it adhere to rocky surfaces Class Gastropods (largest group of mollusks) Have well developed head with tentacles Two simple eyes MAY be located on stalks that extend from the head Pulmonate snails Land Snails that do not have gills but a mantle that is highly vascularized and functions as a lung Torsion Twisting of the visceral mass Development of Torsion Bilateral larva develops with one side of the visceral mass growing more rapidly than the other side Digestive tract becomes U shaped and anus lies above the head and gill Torsion is an adaptation to protect its head by being able to draw its head back into the shell first Class Bivalvia (clams, oysters, mussels, scallops) Laterally compressed and completely enclosed by a two part shell that hinges dorsally and opens ventrally Allows for burrowing in the mud Valves of shell are connected by an elastic ligament Some attach permenantly to a substrate, others burrow slowly Consumption Suspension feeders that trap food particles in sea water Incurrent siphon Extension of the mantle to take in water Excurrent Siphon Area where water leaves Water passes over the gillsmucus is secreted by the gills traps food particlesCilia move food to the mouth Cephalopods (squids, octopus, nautilus) Fast Swimming Predatory Animals Characteristics Large head with well developed eyes Have reduced or no shells Characteristic of ONLY nautilus Secretes a mixture of gases similar to air into the other chambers Regulates it?s depth in the ocean Thick muscular mantle with a funnel like siphon Allows it to fill cavity with water and eject water through the siphon Achieves a forceful jet propulsion Can rapidly change colors Ink Sac Produces a thick black liquid that inactivates the chemical receptors of some predators Phylum Annelida (segmented worms) Characteristics of Annelida Bilateral symmetry and tubular body Body is made of series of rings or segments Body wall and internal organs are segmented Segmentation facilitates locomotion In Polychaetes and Earthworms Septa Internally transverse partitions that separate segments Setae Bristle-like structures that provide traction, by alternating contraction of its longitudinal and circular muscles Class Polychaeta Parapodia Pair of paddle shaped appendages For locomotion and gas exchange Bear many stiff setae Well developed head with eyes and antennae Head may also be equipped with tentacles and palps Females and males release their gametes into water at the same time by responding to certain rhythmic variations or cycles in the environment Class Oligochaeta (Earthworms) Lack parapodia Have few bristles per segment Lack a well developed head All are hermaphroditic Has a Cuticle Thin transparent film that is secreted by the epidermis to protect from drying Consumption Food is swallowed through the pharync and passes through the esophagus Esophagus is modified to form a thin walled crop where food is stored and a gizzard In the gizzard, food is ground by sand grains consumed with the meal Rest of digestive system is a long straight intestine Waste exits through the anus Closed Circulatory System Two main blood vessels that extend longitudinally Dorsal Blood Vessel Above the digestive tract Collects blood from vessels in segments Contracts to pump the blood anteriorly Ventral Blood Vessel Carries blood posteriorly Gas exchange takes place through the moist skin Nervous System Consists of a pair of cerebral ganglia (simple brain) Located above the pharynx and a subpharyngeal ganglion below the pharynx Ganglia coordinate muscle contractions of the body wall Lower ganglion, a ventral nerve cord extends beneath the digestive tract to posterior end Reproduction Hermaphroditic Two worms, headed in opposite directions, press their ventral surfaces together Surfaces become glued together by clitellum?s (thick ring of epidermis) secretion Sperm are then exchanged and stored in the seminal receptacles of other worm Clitellum secretes a membranous cocoon and eggs are laid in it Sperm is added as cocoon passes over openings of seminal receptacles Class Lophophorate (Lophotrochozoa) Distinguished by a lophophore, a ring of ciliated tentacles that surrounds the mouth Phylum Brachiopods (lampshells) Body is enclosed between two shells and has a mantle and a mantle cavity Shells are dorsal and ventral, NOT lateral Separates between clams and lampshells Phylum Phoronids Secrete chitinous tubes in which they live Extend lophophores from tubes for feeding Phylum Bryozoans ?moss animals? Form sessile colonies by asexual budding Class Rotifera (crown of cilia) Characteristics of Rotifera Have a crown of cilia on their anterior end Cilia beat rapidly during swimming and feeding giving the appearance of a spinning wheel Have a fixed number of cells after embryonic development Can survive extremes Consumption Muscular organ posterior to the mouth grinds the food Nervous System Has a ?brain? Sense organs, including eye spots Protonephridia with flame cells Remove excess water form the body and maybe waste Ecdysozoa Ecdysozoa regfers to the process of ecdysis, or molting, Animals sheds its cuticle Phylum Nematoda (round worms) Physical Characteristics Elongated cylindrical threadlike nematode body Covered with a tough, flexible cuticle Epidermis does not consist of distinct cells Pseudocoelom Serves as a hydrostatic skeleton Exhibit Bilateral symmetry Lack specific circulatory system Evolved to become a simpler organism Sheds its cuticle periodically Types of Nematodas Ascaris Parasite that spends its adult life in the human intestine ingests partly digested food Hookworms Attach to the lining of the intestine and suck blood Pinworms Common in children Trichina Worm Lives inside a variety of animals Humans typically become infected by eating undercooked food Phylum Arthropods (characterized by jointed appendages and exoskeleton of chitin) Adaptations of Arthropods Body is segmented Provides opportunity for specialization of segments Hard Exoskeleton Composed of chitin and proteins Serves as a coat of armor and prevents excessive loss of moisture Supports underlying tissue Molting Process of shedding an old exoskeleton Represents a net metabolic loss and vulnerability to predators Paired, jointed appendages Can be modified for many functions Nervous system Resemebles that of annelids Consists of a brain and ventral nerve cord with ganglia Successive ganglia may fuse Antennae Sense taste and touch Compound eyes Composed of many light sensitive units called ommatidia Have an Open Circulatory System Dorsal, tubular heart pumps hemolymph into a dorsal artery From arteries, hemolymph flows into large spaces that collectively make up the hemocoel Hemolymph re-enters the heart through ostia (openings in the heart) Respiratory System Terrestrial Forms System of internal branching of air tubes called tracheae, or tracheal tubes Book lungs Evolution of Arthropods Onychophora: Velvet Worms Most likely branched early from the arthropod line Have paired appendages but NOT JOINTED Tardigrada Tiny animals have unbranched, clawed legs Trilobites (early arthropods) Inhabited shallow Palezoic seas (500 mya) Filtered mud to obtain food Each segment had a pair of segmented biramous appendages Two jointed branches extending from the base Inner walking leg and outer branch with gills Myriapoda (centipedes and millipedes) Branched appendages called uni-ramous appendages Jaw like mandibles and a single pair of antennae Chilopoda (Centipedes) Able to run rapidly because of long legs Use poison claws located just behind the head on the first trunk segment Diplopoda (millipedes) Have two pairs of legs on body segments Feed on living and dead vegetation Chelicerates (Horseshoe Crabs and Arachnids) Chelicerate body consists of cephalothorax (head and thorax fused) and an abodomen DO NOT HAVE ANTENNAE Have chelicerae Fanglike appendages Have pedipalps Merostomes Almost all are extinct, only horseshoe crab has survived Arachnids (spiders, scorpions, ticks, mites) Carnivorous and prey on insects and arthropods Gas exchange Either tracheal tubes, book lungs or both Book Lung Consists of 15 ? 20 plates that contain blood vessels Air enters through the abdominal slits and circulates between the plates Oxygen diffuses into the blood and carbon dioxide diffuses out Spinnerets Secretes silk and spun into fibers Poison Glands Brow Recluse Spider Violin shaped dorsal stripe Venom destroys the tissues surrounding the bite Subphylum Crustaceans (lobsters, shrimp, crab) Nauplius Larva (Distinctive feature) The first stage after hatching Has only the most anterior three pairs of appendages Have statocysts Sense organs that detect gravity Hard mandibles Used for biting and grinding food Lie on each side of the ventral mouth First and Second Maxillae Used for manipulating and holding food Posterior to mandibles Two large glands located in the head excrete waste and regulate salt balance Use specialized appendages to transfer sperm into the female Lobster Five segments of head and eight segments of thorax are fuxed into a cephalothorax Covered on the top and sides by carapace, shield composed of chitin and calcium saltsFourth segment of thorax has pair of large chelipeds Pinching claws Swimmerets Small paddlelike structures used for swimming and holding eggs Class Insecta Subphylum Hexpoda Cockroaches, mayflies, and cicadas are among the insects that have survived relatively unchanged from Carboniferous period Articulated (jointed), Tracheated (have tracheal tubes) hexapods (six feet) Body Plan 3 Distinct Parts Head Thorax Abdomen Uniramous appendages 3 pairs of legs from the thorax Sometimes two pairs of wings One pair of antennae protrudes from the head Tracheal System Air enters the tracheal tubes through spiracles, tiny openings in the body wall Oxygen passes directly to the internal organs Excretion Accomplished by Malpighian tubules Receive metabolic wastes from the blood, concentrate wastes, and discharge them into the intestine Also conserve water Molting Immature stages between molts are called instars Incomplete Metamorphosis Larva that resembles the adult but lacks functional wings and reproductive structures Complete Metamorphosis Egg Larva Pupa Adult Spends most of life as larva Adaptations that contribute to Success Exoskeleton Protection and prevents water loss Segmentation Allows for mobility and flexibility and specialization Ability to Fly Reproductive Capacity Cryptic Coloration Allows them to blend into the background