Laboratory 2 ? Animal Diversity II I. Germ Layers A. Ectoderm 1. outer germ layer; gives rise to stem & nervous system B. Mesoderm 1. middle germ layer; gives rise to connective tissue, muscle, bone, blood vessels, kidneys, & other structures C. Endoderm 1. inner germ layer; gives rise to lining of respiratory & digestive tracts II. Body Cavity - space between gut tube (lined with endoderm) & body wall (with its outer covering of ectoderm) A. Acoelomate 1. body plan in which there is no body cavity 2. ex, flatworm (liver fluke) B. Pseudocoelomate 1. Body plan in which body cavity is lined by mesoderm on one side & by ectoderm on the other 2. ex. Phylum Rotifera & Nematoda C. Coelomate 1. body plan in which body cavity is completely lined with mesoderm 2. ex. vertebrates III. Blastospore A. Opening into body cavity of an early embryo that eventually becomes either the mouth (in protostomes) or the anus (in deuterostomes) of the organism IV. Organisms & Evolutionary Trends A. True tissues & 3 distinct germ layers B. Body cavity (pseudocoelom or true coelom) C. Digestive tract & 1 way digestive system D. Circulatory system & closed system E. Cephalization = anterior concentration of sensory organs V. Adaptations for Parasitism A. Adhesive structures (suckers & hooks) 1. facilitate attachment to a host B. Sensory organs 1. important in free-living organisms that must negotiate complex environments 2. reduced in many parasites that spend much of life cycle attached to host C. Feeding modifications 1. reduction of digestive tract & direct absorption of food through body wall in endoparasites that can rely on host to perform digestive functions D. Increased reproductive capabilities (proglottids) 1. necessitated by low probability with which a multiple-host life cycle can successfully be completed E. Either asexual reproduction or hermaphroditism 1. often employed due to low probability of encountering mate when attached to host VI. Acoelomates A. Phylum Platyhelminthes 1. many members of group are dorsoventrally (from top to bottom) flattened 2. bilaterally symmetrical, with 3 germ layers 3. lack body cavity or coelom 4. have advanced nervous, digestive, muscular, excretory, & reproductive systems 5. lack specialized organs for gas exchange & circulation 6. Class Turbellaria a. Planarians, group of free-living freshwater flatworms b. pharynx (on ventral surface) can protrude & retract c. eyespots help organism distinguish light from dark d. region of parenchymal cells of mesodermal origin between ectoderm & endoderm 7. Class Cestoda a. ex. tapeworms Eyespot Auricle Testes Gastrovascular Cavity Pharyngeal Pouch Pharynx Mouth Ciliated epidermis epidermis Gastrovascular cavity Pharyngeal cavity Pharynx Gastrovascular cavity Proglottids Budding zone (immature proglottids) Scolex Neck Suckers Rostellum with hooks b. head (scolex) has suckers & several rows of hooks c. highly adapted to parasitic lifestyle i. most organ systems are degenerate, while reproductive system is highly developed d. proglottids i. segments posterior to scolex that contain male & female reproductive organs ii. fertilization may take place within each proglottid iii. interfertile ? as each proglottid moves posteriorly, fertilized eggs are maturing iv. proglottids furthest from scolex contain more than masses of eggs - segments break loose & are released in feces of host e. life cycle of tapeworm often involves intermediate host 8. Class Trematoda a. all trematodes (flukes) are parasitic b. 2 suckers, 1 located at anterior end, & 1 about ? length of body posterior to first c. many are self-fertilizing hermaphrodites, containing both ovaries & testes VII. Protostome Pseudocoelomates A. Phylum Rotifera 1. multicellular organisms with well-developed tissues & organs 2. bilaterally symmetrical pseudocoelomates with 1-way digestive tract 3. lack specialized organs for gas exchange & circulation 4 ?wheel animals? ? crown of cilia surrounds mouth 5. has thickened trunk region with narrow foot at base, with pointed spurs Yolk glands Reproductive organs Spur Foot Trunk Corona 6. corona, crown of cilia at anterior end, used for locomotion & gathering food B. Phylum Nematoda 1. body cavity of nematodes or roundworms is a pseudocoelom 2. most roundworms are slender, cylindrical, & tapered at both ends 3. Typical nematodes a. mouth is terminal & surrounded by 3 lobe-like lips b. posterior end has terminal anus c. spicules, hair-like structures that protrude from anus, used in copulation d. lack specialized structures for gas exchange & circulation i. accomplished via fluid movement in pseudocoelom e. female is longer & stouter than male f. gut tube not clearly as seen in female because of large, coiled oviduct & uterus g. viviparous ? give birth to live young 4. Ascaris Male Female Spicules Mouth Male Ancylostoma Mouth Pharynx Gut Tube Uterus Oviducts Cuticle Cuticle a. common intestinal parasite b. outermost layer of body consists of epidermis & outer cuticle c. muscle layer located inside epidermis 5. Vinegar eel a. free-living nematode frequently found in bottom of barrels in which vinegar is produced b. feed on bacteria & yeast settled to bottom 6. Parasitic nematodes a. pinworms & hookworms parasitize human intestinal tract b. parasitic nematodes are cause of elephantiasis, in which fluid builds up in limbs, resulting in severe swelling c. another parasitic nematode causes trichinosis Longitudinal Muscles Testis Pseudocoelom Intestine Longitudinal Muscles Eggs in Uterus Pseudocoelom Ovary Intestine i. adult nematodes (genus Trichinella) live in intestinal tract ii. females are ovoviviparous, retaining eggs inside body while they develop into larvae iii. larvae are released, bore through intestinal wall, & make way to skeletal muscles, forming cysts enclosed in calcified capsules VIII. Protostome Coelomates A. Phylum Annelida 1. segmented worms 2. major defining characteristic: series of similar segments that make up body 3. bilaterally symmetrical, true coelom, complete 1-way digestive tract with mouth & anus 4. possess high degree of cephalization 5. well-developed closed circulatory system 6. Class Polychaeta a. conspicuous segments with lateral projections (parapodia) b. prominent tentacles on head c. most are marine d. Nereis i. except for head & terminal segments, segments are nearly identical ii. bristle-like setae at end of each parapodium iii. parapodia increase surface area of worm - most polychaetes respire through skin iv. parapodia & setae are sometimes used in locomotion v. setae also anchor worm in place vi. 1st segment bears a pair of jaws on anterior, ventral surface, plua a pair of tentacles, 2 pairs of simple eyes, & a pair of laterally placed conical palps Muscle tissue Cyst Larval worm Parapodia Palp Partially everted pharynx Simple eye Tentacle vii. 2nd segment bears 4 pairs of tentacles viii. tentacles & palps are sensory organs e. Sabella i. fan/peacock worm ii. feathery structures (radioles) on head, used to sweep small food particles out of water iii. construct tube of sand grains & mucus in which they live with only anterior portion & radioles protruding - parapodia reduced to facilitate moving in & out of tube 7. Class Oligochaeta a. conspicuous segmentation b. lack well-defined head c. most are hermaphroditic & are found in fresh water or soil d. internally, segments of earthworm are divided by membranous partitions e. burrow through soil, feeding on decaying leaves & animal debris i. enrich & loosen soil f. clitellum Radioles Pharynx Heart Seminal Receptacle Seminal Vesicle Dorsal Blood Vessel Crop Gizzard Nephridia Intestine Epidermis with Cuticle Circular Muscle Longitudinal Muscle Coelom Dorsal Blood Vessel Ventral Blood Vessel Lumen of Intestine Typhlosole i. swollen girdle which circles body ii. secretes protective cocoon around eggs as they are laid g. setae i. arranged in 2 ventral & 2 lateral longitudinal rows, with 4 pairs of bristles on each segment h. fluid-filled body cavity acts as hydraulic skeleton for muscles to contract against i. coelom is separated into compartments by thin membrane, the septa j. near mouth is conspicuous, thick-walled pharynx, which is connected to body wall by muscle fibers i. used to suck food into mouth k. esophagus extends from pharynx to large thin-walled crop where food is stored l. thick-walled gizzard, where food is ground into bits, is posterior to crop m. brown intestine extends from gizzard to anus n. dorsal vessel runs along dorsal surface of intestine i. visible as dark line under body wall o. ventral vessel on ventral surface of intestine p. hearts are contractile tubes that connect dorsal & ventral vessels between 6th & 11th segments q. blood flows toward anterior end in dorsal vessel, enters hearts which pump it into ventral vessel r. blood flows posteriorly in ventral vessel s. seminal vesicles in 10th & 11th segments store sperm produced by testes until copulation, when they are transferred to another individual t. seminal receptacles of female system, lateral & anterior to seminal vesicles, store sperm from other individuals after copulation u. body wall consists of outer, acellular cuticle, thin epidermic, & 2 muscle layers v. outer layer of muscle is circular & inner is longitudinal w. thin layer of peritoneum separates musclar layers from coelom x. coelom, between body wall & digestive tube, may contain sections of nephridia, dorsal blood vessel above intestine, & ventral nerve cord below ventral vessel y. intestine consists of outer layer of modified visceral peritoneum & inner layer of circular & longitudinal muscle fibers z. typhlosole, folding of dorsal wall of intestine, increases absorptive surface of intestine 8. Class Hirudinea a. marine & freshwater leeches b. dorsoventrally flattened bodies without conspicuous segments Dorsal surface Ventral sucker Ventral surface Oral sucker Posterior Anterior c. characterized by presence of large posterior sucker d. highly specialized predators that feed on blood e. mouth within anterior oral sucker f. have jaws & chitinous teeth for biting g. hermaphroditic, but reproduction is usually by cross-fertilization B. Phylum Mollusca 1. include snails, oysters, clams, octopi, & squids 2. many have a calcareous shell 3. well-developed excretory, digestive, respiratory, & circulatory systems 4. bilaterally symmetrical, true coelomates 5. have three main body regions: a. muscular foot i. sensory & locomotor part of body ii. broad, flat, located ventrally b. visceral mass i. contains most of organ systems c. mantle i. covers visceral mass & secrets shell, if one is present d. radula i. rasping structure covered with chitinous teeth, used in feeding e. closest phylogenetically to annelids i. both have very similar developmental patterns & a similar type of ciliated larva (trochophore larva) ii. mollusks are not segmented 6. Class Bivalvia a. characterized by hinged shell with right & left halves which covers visceral mass b. foot extends out between shells (valve) & is used for locomotion c. lack radula d. includes mussels, clams, oysters e. filter feeders, feeding on microscopic plants & animals (plankton) f. Clams i. 2 shells joined by hinge along dorsal surface ii. growth lines ? concentric lines on shell iii. 2 halves of shell held together by powerful adductor muscles iv. mantle Mantle Gills Adductor muscle Visceral mass Muscular foot - glistening tissue that covers inside of each valve - outer layer secretes shell - thickened at posterior margin of shell to form 2 siphons - water enters clam through incurrent siphon, passes over gills, & exits through excurrent siphon v. muscular foot extends for feeding vi. retractor muscles used to retract foot 7. Class Polyplacophora a. chitons are among most primitive of living mollusks b. 8-part shell is important defining characteristic c. on ventral surface is flat muscular foot, which attaches chiton to rocks d. found along rocky seashores or attached to rocks in shallow water e. if pulled of rocks, chiton curls up, protecting itself with shell 8. Class Gastropoda a. most numerous group of mollusks b. all have coiled shell produced by mantle, which surrounds visceral mass, at least in larvae c. most adults retain shell, which protects against dessication & predators d. snails i. have a slime gland, located in anterior part of foot, which secretes layer of mucus over which snail glides by wave-like contractions of foot e. slug i. has shell reduced to small, flattened plate, are confined to moist habitats, mostly active at night, & feed on vegetation f. nudibranches i. marine carnivores that live among seaweed & feed on cnidarians ii. backs are covered with projections called cerata iii. many depend on crypsis (hiding) for protection iv. others protected by stinging cells & cerata v. special adaptations to gut prevent nematocysts of cnidarians from being digested, & they are moved to distal tips of cerata, where they are discharged when nudibranches are attacked Dorsal surface Mouth Girdle Foot Cerata 9. Class Cephalopoda a. most highly advanced of mollusks b. all are marine; foot is modifies to form series of tentacles & head c. shell is external for some, but for most, shell is internal or absent d. very prominent & sophisticated eyes, which are similar to those of vertebrates i. eyelid, iris, pupil, lens, cornea, retina ii. specialized features of cephalopod evolved independently - analogous to human eye e. Squids i. mantle covers visceral mass ii. thin internal shell (pen) iii. beak-like jaws in center of tentacles; radula inside jaws iv. carnivorous; use jaws & radula to bite & tear apart prey v. feed mainly on fish & other invertebrates vi. depend largely on swimming speed as defense against predators (no external shell) vii. inc sac produces brown/black fluid secreted when squid is threatened or excited - allows squid to escape viii. funnel-like siphon fits mantle f. Octopus i. lack internal shell ii. less active than squid; spend time hiding in crevices, grabbing fish, snails, & crustaceans g. Shelled cephalopods Fin Mantle Head-foot Eye Arm Tentacle Fin Mantle Head-foot i. chambered nautilus - only living cephalopod with external shell - coiled shell divided into series of transverse internal chambers - only occupies outermost chamber - specialized organ, siphule, extend into all chambers, secreting & absorbing gases, allowing speciment to adjust buoyancy & position in water C. Phylum Onycophora 1. small group of terrestrial true coelomates with distinct head, cylindrical, unsegmented body, & a number of short, unjointed legs 2. found primarily in moist, tropical or southern temperature terrestrial habitats 3. related to arthropods; bilaterally symmetrical 4. Peripatus a. elongate, cylindrical, unsegmented body, covered by thin, flexible, chitinous cuticle similar to that of annelids b. nonjointed conical legs, each ending in a claw c. head consists of 3 segments with 3 pairs of appendages i. 2 short preantennae ii. 2 blunt oral papillae iii. 2 small horny jaws d. open circulatory system, dorsal tubular heart with ostia (openings) & a reduced coelom D. Phylum Arthropoda 1. most numerous of animal phyla 2. found in almost all conceivable habitats, & feed on variety of materials 3. only group of invertebrates fully adapted to terrestrial life 4. characterized by presence of rigid, chitinous body covering (exoskeleton) 5. primitive body plan consisted of number of segments a. each probably bearing 1 pair of jointed appendages Jaws Oral Papillae Preantennae 6. all have open circulatory system, true coelom reduced in size, bilaterally symmetrical 7. Subphylum Trilobitomorpha a. extinct group of primitive marine arthropods b. characterized by distinct head with segmented body, each segment bearing jointed appendages c. head consists of 4 fused segments & bears pair of antennae & compound eyes 8. Subphylum Chelicerata a. relatively simple, mainly terrestrial, lacking antennae & mandibles b. 1st pair of appendages modified to form specialized, fang-like feeding appendages (chelicerae) c. 2 body regions: cephalothorax (fused head & thorax) & abdomen d. Class Merostomata i. group of aquatic arthropods, horseshoe crabs, with compound eyes, gills, & 5 or 6 pairs of appendages in addition to chelicerae ii. 2 body regions: anterior cephalothorax covered by carapace (hard, shell- like outer covering), & posterior abdomen iii. tail spine, at posterior end of abdomen, is used to push animal forward when it burrows & to right animal when overturned iv. 7 pairs of jointed appendages attached to cephalothorax v. 1st pair of appendages, chelicerae, are used mainly to capture & break up food vi. Next 4 pairs are walking legs, ending in a small pincer vii. Next pair are grooming legs, ending in leaf-like structures used to clean gills viii. Last pair very small & highly modified ix. unsegmented abdomen bears 6 pairs of appendages - 1st flap related to reproductive system - last 5 plate-like & bear gill lamellae (book gills) e. Class Arachnida Head Thorax Abdomen i. terrestrial arthropods with no gills, simple eyes, & 6 pairs of jointed appendages (4 pairs of walking legs, plus 2 pairs of other appendages, including pair of chelicerae) ii. Spiders - chelicerae & pedipalps used to capture & kill prey - book lungs ? modified book gills - some have trachea - set of spinnerets at posterior end of abdomen, anterior to anus - extrudes silk, produced by glands within abdomen - used to spin webs & wrap prey after capture iii. Mites & ticks - many are ectoparasites (external parasites) - cephalothorax & abdomen are fused & segmentation largely lost - flattened body; difficult to dislodge parasite - chelicerae modified into needle-like piercing organs iv. Scorpions - 1st group of arthropods to become adapted to land - long, slender abdomen ends in stinging apparatus - carnivorous; stinger injects venom to paralyze or kill prey 9. Subphylum Crustacea a. characterized by presence of jaw-like mandibles (chewing mouth parts), 2 pairs of antennae, & biramous (2-branched) appendages b. 2 body regions: cephalothorax & abdomen c. Class Malacostraca i. common aquatic arthropods (lobsters, crayfish, crabs, shrimps) ii. respire mainly by gills iii. Crayfish - cephalothorax covered by carapace - rostrum, anterior extension of cephalothorax, bears compound eyes - appendages on posterior segment of abdomen are modified into fan shaped structures (uropods) that can create a large surface area when spread out - 1st 2 appendages modified to form antennules & antennae - next 6 pairs of appendages form specialized mouthparts - posterior to mouthparts are 5 pairs of walking legs - 1st pair ? large, pincer-like cheliped ? used to grasp food - posterior to walking legs are series of swimmerets, anterior used by adult males for transfer of sperm & posterior used by females to hold eggs & young iv. Barnacles - include free-living & sessile forms - some live commensally on whales, marines, turtles & fish - feathery structures protruding from carapace are thoracic appendages, which sweep food particles in mouth - goose barnacles have large stalk (peduncle) which attaches animal to substrate 10. Subphylum Hexapoda a. largest group of arthropods b. characterized by uniramous (unbranched) appendages, 1 pair of antennae, jaw-like mandibles, 3 pairs of legs c. body consists of head, thorax (to which legs are attached), & abdomen d. Class Insecta i. mainly terrestrial arthropods with distinct head, thorax & abdomen, 1 pair of antennae, 3 pairs of legs, jaws, & up to 2 pairs of wings ii. can survive many kinds of conditions iii. exoskeleton, chitinous covering of body, protects internal organs & prevents dessication iv. has system of tracheal tubes that reach all cells of body, carrying oxygen & removing carbon dioxide v. Grasshopper - head bears pair of compound eyes & 3 simple eyes (ocelli) - anterior segments are heavier & function to protect thinner posterior wings - wings are modifications of cuticle - posterior segments of abdomen modified for reproduction - female has 4 pointed ovipositors at end of abdomen used in egg-laying - spiracles, along lower sides of thorax & abdomen open into tracheal tubes 11. Subphylum Myriapoda a. uniramous appendages, 1 pair of antennae, & jaw-like mandibles b. head & segmented body, with 1 or 2 pairs of legs per segment c. Class Chilopoda i. centipedes have long flattened bodies with many segments, each of which has single pair of legs d. Class Diplopoda i. millipedes have long, relatively cylindrical body with many segments, each bearing 2 pairs of legs Christopher Laboratory 2 ? Animal Diversity II
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