Exam 6 chapter 33 Flashcards

Question

Coelomate Invertebrates

Answer 1

The Mollusks • 93,000+ describes species (second only to the arthropods) • occupy every habitat on Earth • includes snails, slugs, clams, scallops, octopus, cuttlefish, oysters, mussels, squid, chambered nautilus, etc. ## Footnote Mollusks are extremely diverse and important to humans. • size ranges from a few millimeters to that of the giant squid which can grow to 15 meters long and 250 kg • mollusks evolved in the ocean; some slugs and snails are adapted to life on land or in freshwater • economic importance includes: food, mother-of-pearl for jewelry • mollusks can do damage to boats, docks, pilings, and wood exposed to the sea; zebra mussels are invading freshwater ecosystems • some slugs and snails damage flowers, vegetables, and other crops • some snails are intermediate hosts to larval stages of parasites such as flukes

Answer 2

• size ranges from a few millimeters to that of the giant squid which can grow to 15 meters long and 250 kg • mollusks evolved in the ocean; some slugs and snails are adapted to life on land or in freshwater • economic importance includes: food, mother-of-pearl for jewelry • mollusks can do damage to boats, docks, pilings, and wood exposed to the sea; zebra mussels are invading freshwater ecosystems • some slugs and snails damage flowers, vegetables, and other crops • some snails are intermediate hosts to larval stages of parasites such as flukes

Answer 3

• bilateral symmetry ## Footnote • mantle = thick epidermal sheet surrounding the mantle cavity; secretes calcium carbonate shell (for those mollusks that have a shell) • foot = primary means of locomotion (except for octopus, chambered nautilus, and squid); can also be used for attachment, capturing food, digging • head may be well-developed or not ° Internal Organs • coelom is very reduced in size • visceral mass contains digestive, excretory, and reproductive organs • ctenidia = gills (in aquatic mollusks) have much surface area for gas exchange; gills of bivalves also filter out food ° Shells • secreted by mantle; protects against predators and adverse environmental conditions • some mollusks have reduced, internalized, or no shell at all (squids, octopus, and cuttlefish; and slugs) • shell has two layers of calcium carbonate; inner layer is pearlescent (mother-of-pearl or nacre); pearls form when a grain of sand or other irritant lodges between inner shell layer and mantle – layers of nacre reduce the irritation ° Feeding and Prey Capture • radula = rasplike structure with rows of chitinous teeth used to scrape food off surfaces • some radular structures are modified for drilling; others work like a harpoon along with a venom gland • bivalves are only mollusks without a radula ° Removal of Wastes • nephridium = removes nitrogenous waste; works somewhat like a kidney • wastes dumped into mantle cavity • sugars, salts, water, other materials are reabsorbed by nephridial walls and returned to animal’s body to maintain osmotic balance ° Circulatory Sysytem • hemocoel = made of several sinuses and vessel network in gills (All mollusks except for cephalopods have an open circulatory system.) • hemolymph = equivalent of blood • heart – most mollusks have three- chambered heart ° Reproduction • most mollusks have separate sexes • a few bivalves and many freshwater and terrestrial gastropods are hermaphroditic • some oysters can change sex • marine mollusks have external fertilization • most gastropods have internal fertilization • trochophore larva is free-swimming • veliger larva is 2nd free-swimming stage

Answer 4

° Class Polyplacophora: Chitons • marine only • 8 overlapping dorsal plates • body is not segmented • most are grazing herbivores living in shallow marine habitats ## Footnote ° Class Gastropoda: Snails and Slugs • primarily marine (40,000 species) • there are freshwater species also • the only terrestrial mollusks are gastropods a) most gastropods have single shell, but some have lost their shell b) most gastropods creep on their foot, but in some, the foot is modified for swimming c) head has pair of tentacles used for chemo- or mechanoreception; eyes are located at base of tentacles; some have second set of tentacles with eyes on end of tentacles d) unique feature of gastropods is torsion – twisting of body during larval growth so mantle cavity and anus are moved to front of body e) gastropods are predators f) mantle cavity serves as a lung in terrestrial gastropods ° Class Bivalvia: Clams, Mussels, Cockles • most of 10,000 species are marine • some are freshwater species a) no radula; no head b) wedge-shaped foot for digging c) have two shells (valves) d) inhalant siphon is where water enters bringing food and oxygen e) exhalant siphon is where water exits f) see additional anatomy on p. 679, Fig. 33.20 ° Class Cephalopoda: Octopuses, Squids, Nautiluses • more than 600 species • marine only • very active predators a) only mollusks with closed circulatory system b) foot evolved into arms with suction cups, adhesive devices, and hooks for capturing prey c) strong beak-like jaws; radula; salivary glands d) largest relative brain size among invertebrates e) highly developed nervous system f) complex behavior patterns and highly intelligent g) cephalopod eyes similar to vertebrate eyes, but evolved separately h) no external shell, except for chambered nautiluses; cuttlefish and squids have internal shell; octopuses have no shell i) move by jet propulsion when water that entered mantle is forced out through siphon j) ink sac – used as defense k) chromatophores in skin allow cephalopod to change colors for camouflage or communication l) cephalopods have direct development; that is, no larval stage

Answer 5

a) nemertean body plan resembles that of a flatworm b) some cephalization with two lateral nerve cords c) complete gut with both mouth and anus d) rhynchocoel = fluid-filled sac that serves as hydraulic power source for proboscis e) gonochoric f) sexual reproduction; but some can reproduce asexually by fragmentation but many fragments die and don’t form a new animal

Answer 6

* segmented worms * advantage of segmentation = development and function of individual segments or groups of segments can differ ## Footnote ° The annelid body has ringlike segments a) brain or cerebral ganglion and sensory organs at anterior b) many species have eyes c) head and tail develop first and then segments form between them d) segments divided by septa e) each segment has pair of excretory organs, a ganglion, and locomotory structure (marine annelid segments also have reproductive organs) f) closed circulatory system g) ventral nerve cord connects ganglia in each segment with one another and the brain ° Annelids move by contracting circular and longitudinal muscles against the hydrostatic skeleton ° Chaetae (setae) = bristles that help anchor annelid in substrate so they don’t slip when they move

Answer 7

• marine worms • parapodia = fleshy, paddle-like lateral projections used for swimming, burrowing, or crawling • parapodia also have important role in gas exchange; in some species, they are modified into gill-like structures • predatory polychaetes have powerful jaws • sedentary tube worms have feathery tentacles for filter feeding as well as gas exchange • most polychaetes are gonochoric and fertilization is external • Palolo worms – gamete-filled terminal parts considered a delicacy by some South Pacific natives • fertilization  spiral cleavage  ciliated mobile trochophore larvae growth to adult

Answer 8

° The merge was because both groups have a clitellum – a thickened band on body that secretes mucus to hold worms together during copulation and to form a cocoon for fertilized eggs to develop. ## Footnote ° Earthworm characteristics • head is not well-developed • no parapodia • few chaetae & project directly from body wall • eat their way through soil • no eyes, but do have light-, chemo-, and touch-sensitive cells • hermaphroditic • cross-fertilization • eggs develop into young worms similar to adults ° Leech characteristics • most are freshwater; few are marine; some live in tropical terrestrial areas • dorsoventrally flattened • hermaphroditic • cross-fertilization • clitellum only develops during mating season • suckers at both ends of body • coelom reduced and not segmented • no chaetae (except for one species) • eat detritus or devour small animals • some suck blood – secrete anesthetics and hirudin (anticoagulant) • Hirudo medicinalis = medicinal leech

Answer 9

The Arthropods ◊ The most successful of all animals ◊ Two-thirds of all animals are arthropods ## Footnote ◊ Great economic importance a) pollinate crops b) food for humans and other animals c) damage to crops; insects are voracious herbivores d) carriers or spreaders of disease to plants and animals including humans ◊ Four extant classes plus one that is extinct: a) Class Chelicerata (spiders, mites, ticks, horseshoe crabs) b) Class Crustacea (crabs, shrimp, lobsters, barnacles, pill bugs) c) Class Hexapoda (insects) d) Class Myriapoda (centipedes, millipedes) e) Class Trilobita (trilobites) is extinct. ◊ Arthropod Key Features & Organ Systems a) mouthparts – • chelicerae (pincers) in chelicerates • mandibles (biting jaws) in hexapods, crustaceans, and myriapods b) segmentation – • body segments look alike in some arthropods • tagmatization = the fusion of segments into specialized functional groups - tagmata include: head thorax abdomen - in some arthropods, head and thorax are fused to form a cephalothorax c) exoskeleton – • made of chitin and protein; this combination is strong and flexible • provides antagonism for muscles, support for body, protection against physical forces • can protect against water loss • limitations of exoskeleton include: - size (weight gets too great with increased size) - rigidity (arthropods must undergo ecdysis or molting) d) jointed appendages – • may be modified into antennae, various kinds of mouthparts, legs • can bend to extend or retract • joints serve as a fulcrum for appendage movement so leverage is possible e) circulatory system – • open circulatory system • heart pumps blood anteriorly; blood flows toward posterior through spaces between tissues; when heart relaxes, blood returns to posterior region of heart through one-way valves f) nervous system – • double chain of segmented ganglia along ventral surface • three fused ganglia form brain • functions such as eating, moving, and copulating can be carried out even when brain is removed • compound eyes composed of ommatidia (individual visual units) • ocelli = simple eyes present in some arthropods g) respiratory system – • gills – in marine crustaceans • book gills – in horseshoe crabs • outer epithelium or gut for gas exchange – in some tiny arthropods • tracheae – in terrestrial arthropods; tracheae branch into tracheoles; • spiracles = openings in exoskeleton where air enters; they can be closed to prevent water loss • book lungs – in many spiders h) excretory system – • in aquatic arthropods, waste diffuses from blood in gills • Malpighian tubules occur in terrestrial insects, myriapods, and chelicerates. - slender projections from digestive tract - attached at junction of midgut and hindgut - tubules contain fluid, and nitro- genous wastes from blood that bathes tubules are precipitated as uric acid or guanine that are then emptied into hindgut for elimination - water and salts are reabsorbed by hindgut and returned to arthropod’s body - Key adaptation to life on land

Answer 10

◊ Chelicerate characteristics: • two tagmata = anterior prosoma which bears all appendages and opisthosoma which contains reproductive organs • pair of chelicerae (fangs or pincers) • pair of pedipalps - copulatory organs in male spiders - large pincers in scorpions - sensorial in most other chelicerates • four pairs of walking legs ° mostly carnivorous, but mites are mostly herbivorous ## Footnote 1) Order Araneae: Spiders • important as predators of insects • produce silk that is forced out of spinnerets • wolf spiders and tarantulas hunt rather than spin webs • all spiders have poison glands with channels through their chelicerae • poison/venom paralyzes prey • bites of black widow and brown recluse can be fatal to humans and large mammals 2) Order Acari: Mites and Ticks • found in every habitat • predators and parasites of variety of organisms • most mites less than 1 mm long • in mites, cephalothorax and abdomen fused into ovoid body • respiration using tracheae or directly through body surface • ticks are blood-sucking parasites of humans and other animals • some ticks carry disease-causing agents such as Rocky Mountain spotted fever, Lyme disease, and red-water fever (affects cattle, horses, sheep, dogs)

Answer 11

° about 35,000 species of mostly marine organisms, but some such as crayfish live in freshwater; still others are terrestrial (pill bugs) or semiterrestrial (sand fleas and beach fleas) ## Footnote ◊ Crustacean characteristics: • three tagmata = cephalon and thorax (may fuse to form cephalothorax) and abdomen • two pairs of antennae (crustaceans are only arthropods to have this) • three pairs of appendages for chewing and manipulating food • various pairs of legs (located on abdomen and thorax) • crustacean appendages (with possible exception of first pair of antennae) are biramous (“two- branched”) • large crustaceans have feathery gills for respiration • gas exchange in smaller crustaceans occurs directly through thin regions of cuticle or through entire body a) crustacean reproduction • gonochoric (except for barnacles) • characteristic nauplius larva with three pairs of appendages • nauplius is evidence for single common ancestor b) decapod crustaceans = shrimp, lobster, crab, crayfish • five pairs of thoracic appendages • calcium carbonate reinforces exoskeleton • cephalothorax covered by carapace • pincers used for obtaining food • swimmerets on ventral surface of abdomen in lobsters and crayfish • uropods are paired flattened appendages at posterior that form a paddle • telson = tail spine • uropods and telson push water anteriorly, thus propelling animal posteriorly c) sessile crustaceans = barnacles • sessile adults, but nauplius larva is mobile • adults are filter-feeders; sweep legs through water in order to gather small food particles • hermaphroditic condition is thought to be related to their sessile lifestyle • barnacles have longest penis relative to their size; allows sessile animals to cross-fertilize

Answer 12

° largest group of animals in terms of number of species and number of individuals ° found in every habitat on land and in fresh water, but few found in sea ## Footnote ◊ External characteristics of insects: • primarily terrestrial • size range is 0.1 mm to 30 cm in length or wingspan • mouthparts modified piercing, sucking, or sopping up liquids • most with compound eyes; some with ocelli • head, thorax, and abdomen • thorax has three segments, each segment with a pair of legs • many insects have one or two pair of wings • wings are saclike outgrowths of body wall ◊ Internal organization of insects: • digestive tract is tube about same length as body in many; but in those insects that feed on juices, digestive system is coiled and may be several times longer that body • digestion occurs in stomach or midgut • Malpighian tubules for excretion • tracheae for gas exchange • spiracles are openings between segments along side of abdomen and thorax where air enters ◊ Sensory receptors of insects: • eyes • sensory setae sensitive to mechanical and chemical stimuli; numerous on antennae and legs • tympanum = thin membrane that acts like eardrum; detects sound waves and vibrations • pheromones are chemicals released by insects for communicating mating signals, trail markers, etc. ◊ Insect life histories: • metamorphosis = change in form • simple metamorphosis = egg  nymph stages  adult • complete metamorphosis = egg  larva  pupa (chrysalis)  final molt into adult or imago

Answer 13

° both have head followed by numerous similar segments ° both are gonochoric ° fertilization is internal ° all lay eggs ## Footnote ◊ Subclass Chilopoda = centipedes • one pair of legs per segment • some centipedes hatch with a final number of legs; others add legs after hatching • those centipedes that do not add legs tend to care for their young; a rather uncommon behavior among invertebrates • carnivorous • poison fangs ◊ Subclass Diplopoda = millipedes • two pairs of legs per segment • herbivorous • roll into flat coil or sphere for defense • glands produce foul-smelling fluid • some produce cyanide gas

Answer 14

◊ General characteristics: • exclusively marine • deuterostome development • endoskeleton of calcium carbonate plates • pentaradial symmetry • water-vascular system aids in movement and feeding • larvae have bilateral symmetry; therefore, echinoderms thought to have evolved from bilaterally symmetrical ancestors • oral surface faces substrate in the asteroids, ophiuroids, and echinoids • oral surface faces away from substrate in the crinoids • holothuroids have horizontal axis and oral surface that faces forward ◊ Endoskeleton: • ossicles = calcium carbonate plates that make up the endoskeleton • depending on the class, ossicles may be more loosely arranged, tightly fit together to form a test (shell), or scattered throughout body * mutable collagenous tissue can change texture from tough and rubbery to fluid in seconds if the animal is disturbed * echinoderms can autotomize (cast off) body parts ◊ Water-vascular system (WVS): • radially organized • madreporite = structure on aboral surface where water enters • WVS extends out into each arm of a sea star; ampulla (bulb) allows tube foot to extend or contract • gas exchange occurs across body surface and the tube feet • holothuroidians also have respiratory trees that branch off the hindgut; water enters and exits through anus ◊ Regeneration and Reproduction • many echinoderms can regenerate body parts - asteroids and ophiuroids autotomize arms - holothuroidians can eviscerate their digestive system • some echinoderms can reproduce asexually by splitting • sexual reproduction is the norm • echinoderms are gonochoric • fertilization is external • larvae are bilateral and each class of echinoderms has a characteristic larva

Answer 15

a) Class Asteroidea: Sea stars • organized in parts of five or multiples of five • predators b) Class Ophiuroidea: Brittle stars • arms are slender and “snake-like” • arms join central disk very abruptly • tube feet for feeding, not locomotion • brittle stars have no anus ## Footnote c) Class Echinoidea: Sea urchins and Sand dollars • no arms • five double rows of tube feet extend through calcareous test (shell) • spines are moveable and have a ball- and-socket joint d) Class Holothuroidea: Sea cucumbers • oriented horizontally to substrate • parts of five • filter feeders • have respiratory trees • if skin is rubbed, can go from rigid to liquid in a couple minutes e) Class Crinoidea: Sea lilies & Feather stars • oral surface faces up, filter feeders

Exam 6 chapter 33 Flashcards

(40 cards)