BIOL 3454 1nd EditionExam # 3 Study Guide Lectures: 17-21Lecture 17 10/1I. cnidarians & ctenophoransnatures dart gun- cnidarians have nematocysts - specialized organelles that requirephylum cnidaria- greek knide (nettle)- latin aria (suffix for plural)- cnidocytes (all have) stinging organelle- nematocysts - are a type of cnidocyte fastest animal motion recorded- longest fossil history of any animal - 700my- all aquatic prefer shallow warm water- most are sessile - most slow or slightly swim- many exist in symbiotic relationships- mutualistic commensalistic parasitic- common to name after shipsRelationship- mutualism - both indiv benefit- commensalism - one benefits one has no effect- parasitism - one benefits the other losseseconomic importance- most cnidarians of minimal economic consequence except for corals- reefs provide food and tourism- coral reefs are the most diverse aquatic ecosystem (>50% all marine species, <1% of ocean area)Characteristics - test question about non-living part of cnidarian- cnidocytes present usually nematocysts- aquatic- readially or birdially symmetrical- have polyps & medusae- diploblastic wiht mesoglea- extracellular digestion- simple nerve net- no excretory or respiratory system- no coelomic cavitypolyps vs medusae- cnidarians have two- polyp - sessile hydroid- medusa - jellyfish mobile- seem different but both have a saclike body plan- medusa is just an unattached polyppolyps- reproduce asexually- budding- fussion- pedal laceration- exhibit strong phenotypic plasticity or polymorphism- single genotype can have multiple phenotypes- hydrozoa hydrnths vs gonagiaMedusae- free swimming with bell or umbrella shaped bodies- tetramerous symmetry (body parts in fours)- statocysts for orientation and ocelli for light reception- sense gravity statocysts !!!!!Cnidarian life cycles- polyps an medusae play different roles- lots of variation between taxonomic groups- poly usually sessile, some collections of polyps and medusae- polyps asexual- medusa sexualwhy the variation?- phylogenetic constraint- anthozoans branch off before medusa evolves- true loss of character state- hydrozoans probably lost the medusa- some may have medusa reduction so drastic it appears as loss- all based on nich and evolution; only need 1 way of reproducingBody Wall- outer endodermis inner gastrodermis mesoglea between- no true muscle cells- mesoglea covers body thickest in stalk thinnest in tentacles- gives support through hydrostatic pressure- acts like an elastic skeleton- jelly in the jellyfishCnidocytes- unique cell type to the phylum- several types; adhesive recoiling nematocysts- cnidoblast during development- cnidae (organelle) are discharged cell is resorbed- nematocyst - specialized type of cnidae with chitin like material- covered by operculum- hydrostatic pressure differences- trigger called a cnidocil - modified cilium- 2 ways to make something hard chitin or NaCl- nematocytefeeding & digestion- polyps carnivorous- tentacles capture prey and suck into gastrovascular cavity- digestion is internal but extracellular *****- medusa usually filter feeders but not always- end of mouth or mouth tube called manubrium- corals usually supplement diet with symbiotic algaecoral bleaching- water gets too warm algae evicted from corral polyps- if water cools can return- if water doesnt cool coral dies from starvation- expected to result in the destruction of most coral reefs by 2050nerve net- diverse simple NS- base of epidermis and base of gastrodermis- 2 nets that interconnect- two way transmission- vesicles only on one side of synapse in most animals on both sides in cnidarians no myelin ****- only group animal that have 2 way nerve single- no myelin- neuromuscular system- combination of sensory and nerve cells- still represented in all animals- digestive system in annelids- nerve plexuses in mammals- no centralization although some have rhopalia- cluster of sensory cells precursor to centralizationClass Hydrozoabasic terms (polyp)-base salk one or more zooids-hydrorohiza - base like a root stolon- hyrocauli - stalks cellular part called the coenosarc covering called the perisarc- individual polyps attached to hydrocaulus hydranths or gastrozooids for feeding- thecate (covered) or athecate (naked) polypsobelia life cycle- germ cell - zygote - fertilization - asexual reproduction budding - reproductive polyp - meiosisTubalaria life cycle- actinula emerges - actinula - young polyp - adult polyp - gonophores - larva developing in gonophoreClass Hydrozoabasic terms (medusa)- velum - margin of the bell that projects inward- entocodon - developmental layer from ectoderm unique to hydrozoa. differentiates into musclesHydra sp.- cnidaria that is not a corral- 16 species in N America- live on underside of aquatic leaves- > 3cm- body is a slender stalk with tentacles at one end and a basal disc for attachment- mouth located on top of a conelike structure called a hypostome- catches prey with nematocysts on tentacles- reproduces sexually & asexuallyhydra anatomy- EM Epitheliomuscular cells - for covering & contraction- interstitial cells -- undifferentiated stem cells (everything but EM cells)- gland cells- secrete the adhesive that allows the Hydra to attach found around the foot- cnidocytes- through the whole epidermis- Sensory cells- in the epidermis have synapse on one end and a flagellum on the other- nerve cells- both one way and two wayPhysalia- man o war- pneumaatophore (sail) for floatation- drift with the currents- dactylooids - fishing tentacles- gonozooids or gonophores - sacs containing empty space & ovaries or testesLecture 18 10/3/14I. Class Scyphozoaa. Most of the jellyfish b. No velum, margin of mbrella scalloped with lappets (notches Rhopalia (sensory centers) between the lappetsc. Posses a nerve net d. Lots of nematocysts for prey capturee. Mouth on sumbrellar side f. Manubrium with four frilly oral arms g. 4 gastric ouches each with a hanging gastric filament h. Radial canals from each pouch lead to a ring canal II. Aurelia anatomya.III. Aurelia life cycle a. Sexes separate, fertilization internal ingastric pouch of femaleb. Zygotes develop in seawaterc. Larvae becomes a scyhistoma, a hydralike form that bud to produce clonesd. Strobilation – the process by which Aurelia makes saucerlike buds called ephyrae and becomes a strobilai. Ephyrae get loose and become mature jellyfishii.IV. Cassiopeia – upside down jellyfisha. No tentacles on umbrella margin b. High