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True or False Bryophytes (mosses, liverworts) and pterophytes (quillworts, horsetails, ferns etc) which retain some dependence on water for sexual reproduction, have not done nearly as well in the aquatic environment as their more terrestrially adapted descendents, the flowering plants. In isogamous algae the gamete designated as the + or – mating types are functionally indistinguishable. Organisms that have meiosis at some point in their life cycle produce gametes that are all individually unique. The overall similarity of the Charophycean life cycle to that of plants is one of the reasons that we consider them the likely ancestors of plants. Diatom cells never have flagellae. Phylum Porifera (from the Greek poros "pore" and Latin ferre "to bear") •Sessile, mostly marine, filter-feeders, > 5000 marine spp but only a few freshwater •Pump water through their bodies to filter out particles of bacteria and algae and other organic matter •simplest multicellular animals—lack tissues (eg muscles, nerves, internal organs) •body has 2 layers of cells separated by a gelatinous mesohyl •Simple skeleton made of spicules inside the mesohyl. •believed to have originated from choanoflagellataes—a unicellular protist •Size a few cm to 2m •Reproduce sexually—gametes produced by the choanocytes or amoebocytes eggs retained inside the mesohyl and motile sperm washed out by water currents—zygote develops into small flagellated larvae that disperse and settle •Also reproduce asexually by gemmules—small packs of tissue in a protective capsule A comparison of unicellar and multicellular choanoflagellates to the body wall of a sponge epidermis Spicules (skeletal elements) Amoebocytes (undifferentiated cells) http://universe-review.ca/I10-82-choano.jpg Mesohyl (separates collar cells from epidermis) Anatomy of a sponge—showing the pattern of water circulation Water enters through tiny ostia (pores), collects in the spongocoel (body cavity) and leaves through the osculum To obtain enough food to grow 100 g, a sponge must filter 1000 kg of water From Campbell and Reece: Biology, Ch. 33, p 648 Development of a sponge from a flagellated larva Sponges have amazing regenerative ability They can completely regenerate themselves if broken apart In this experiment the sponge is strained through cheesecloth to break the cells apart (1,) Cells begin to reaggregate (2-3) Over a period a week it flattens out and reattaches itself to the substrate (4-5), gradually reorganizing itself into an adult sponge (6) http://www.eeob.iastate.edu/faculty/DrewesC/htdocs/spongeREAGG.jpg A freshwater sponge gemmulating --they usually do this in the fall http://psteinmann.net/bilder_spongilla/gemmulae.jpg http://rydberg.biology.colostate.edu/Dissections/CPspongillagemmules.htm http://biology.about.com/library/weekly/aa090700a.htm Spongilla lacustris—the most common freshwater sponge—generally green in shallow water (contain intracellular Chlorella) Often found attached to sticks and rocks, but may grow directly on sand or even mud http://cichlidpark.agava.ru/Images/plan2.jpg http://botany.upol.cz/images/galerie/photos/spong.jpg In softwater lakes where macrophytes don’t do well Spongilla can grow several feet tall, and essentially take over the macrophyte niche in the lake http://images.google.ca/imgres?imgurl=http://www.water-vision.de/Video-Dateien/Bilder/V00061_1.jpg&imgrefurl=http://www.water-vision.de/VideoDateien/vdeu_schwaemme.htm&h=300&w=400&sz=41&hl=en&start=35&tbnid=I8myP7i0xpzs_M:&tbnh=90&tbnw=120&prev=/images%3Fq%3Dspongilla A good closeup of Spongilla growing on a rock near shore, where you can see the oscula very clearly, the ostia are microscopic http://shop.uwphoto.no/500/rsv066cd036.jpg Spongilla growing in deep water or under rocks are generally a pale brown colour—no Chlorella Freshwater sponge spicules (made of silica) http://www.acadweb.wwu.edu/courses/envr429-rm/Robin/images/envr429/77_spongilla_spicules_4 http://images.google.ca/imgres?imgurl=http://www.superiortrips.com/images/stickelback.jpeg&imgrefurl=http://www.superiortrips.com/life_on_a_shipwreck_pag e3.htm&h=480&w=720&sz=41&hl=en&start=15&tbnid=vwbOUlXr9EvT9M:&tbnh=93&tbnw=140&prev=/images%3Fq%3Dfreshwater%2Bsponge%26svnum%3 D10%26hl%3Den%26lr%3D%26sa%3DG The adult fly that emerges from the sponge Spongilla generally harbour the larvae of Sisyra (Class Insecta, Order Neuroptera) as an internal predator/ parasite. http://www.nanfa.org/akiweb/794.JPG http://home.hccnet.nl/d.van.vliet/foto_02/zoetwaterspons.jpg Ephydatia muelleri. Photo:Henry M. Reiswig http://www.ittiofauna.org/webmuseum/invertebrati/microinvertebrati/images/ephydatia-500.jpg http://www.canadianbiodiversity.mcgill.ca/english/species/sponges/spongepages/eph_mue.htm Phylum Cnidaria (from the Greek word "cnidos," which means stinging nettle) •Very diverse phylum containing well known marine species (>10,000 marine spp) such as sea anemones, hydras, a wide variety of jellyfish, and all of the corals •all carnivores and capture prey with tentacles that contain nematocysts •body plan is simple—a radially symmetrical sac with a central cavity, the gastrovascular cavity with a single opening serving as both mouth and anus •two variations, the sessile polyp and the motile medusa •two tissue layers in the body, gastrodermis and epidermis, separated by mesogloea •Reproduction can be sexual, usually gonads developing either on the medusa or the polyp—many species have both polyp and medusa in their life cycle •Asexual reproduction occurs by “budding” From Campbell and Reece: Biology Chapter 33 A cnidocyte of a hydra—contains a stinging capsule (nematocyst) containing an inverted thread which everts under pressure when triggered by touch or chemical stimuli. The spiny thread shoots out from the nematocyst and injects poison into the prey. Other types of nematocysts have different types of threads, some entangle prey and some just stick to prey that bump into the tenctacles A tentacle of Chlorohydra, showing nematocytes and also, many chlorella living inside the animal http://images.google.ca/imgres?imgurl=http://micrographia.com/specbiol/cnidari/hydrozo/hydr0100/hydvir04.jpg&imgrefurl= http://micrographia.com/specbiol/cnidari/hydrozo/hydr0100/hydvir04.htm&h=296&w=480&sz=32&hl=en&start=4&tbnid=ug cZYiBlt4U3hM:&tbnh=80&tbnw=129&prev=/images%3Fq%3Dhydra%2Bnematocysts%26svnum%3D10%26hl%3Den%26l r%3D%26sa%3DG A tentacle squashed under the comound microscope shown many nematocysts http://www.ville-ge.ch/musinfo/mhng/hydrozoa/intro/nematocysts.jpg http://images.google.ca/imgres?imgurl=http://www.visualsunlimited.com/images/water marked/319/319205.jpg&imgrefurl=http://www.visualsunlimited.com/browse/vu319/vu3 19205.html&h=235&w=350&sz=11&hl=en&start=7&tbnid=WSRmOdEIs6JelM:&tbnh=7 7&tbnw=116&prev=/images%3Fq%3Dhydra%2Bnematocysts%26svnum%3D10%26hl %3Den%26lr%3D%26sa%3DG From Campbell and Reece: Biology Chapter 33 Medusa is more or less an upside down polyp that swims around POLYP Polyp and medusa are variations on the same body plan—a radially symmetrical sac (gastrovascular cavity) with a single opening (mouth/anus) surrounded by tentactles. The polyp has its aboral end attached to the substrate, and feeds passively on prey that “bump” into the tentacles. MEDUSA The medusa swims freely by jet propulsion—expelling water out the opening, with its aboral end upwards The generalized life cycle of a hydrazoan alternating between the polyp and medusa stage http://www.biol.andrews.edu/fb/spring/chap.%2033/3306%202.jpg Hydra and Chlorohydra are the most common freshwater genera—no medusal stage Sexual and asexual reproduction in Hydra A hydra “budding” off new polyps asexually http://www.eeob.iastate.edu/faculty/DrewesC/htdocs/hydra-mature.jpg http://z.about.com/d/biology/1/0/P/2/hydrabud.gif Chlorohydra showing the green colour they get from harbouring Chlorella as symbionts Chlorohydra budding http://www.microscope-microscope.org/gallery/hydra-187h.jpg Hydras feed mainly on Cladocera, which often bump into their tentacles—this one has captured and swallowed a Daphia http://www.worth1000.com/entries/34500/34986vopr_w.jpg Craspedacusta sowerbyi—the freshwater jellyfish http://images.google.ca/imgres?imgurl=http://jellieszone.com/images/craspedacusta.jpg&imgrefurl=ht tp://jellieszone.com/craspedacusta.htm&h=216&w=288&sz=22&hl=en&start=3&tbnid=cLKqaQBnwcg YdM:&tbnh=86&tbnw=115&prev=/images%3Fq%3DCraspedacusta%26svnum%3D10%26hl%3Den %26lr%3D%26sa%3DG http://www.niwascience.co.nz/pubs/wa/10-2/alien1_large.jpg The life cycle of Craspedacusta http://sites.estvideo.net/sub.club.stbg/images/bio/craspedacusta.gif Phylum Bryozoa: “moss animals” •Colonial coelomate animals, encased in a hard exoskeleton with openings from which the lophophore—its feeding organ extends. •The lophophore bears a crown of ciliated tentacles, which are hydraulically extended outgrowths of the body wall communicating with the coelomic cavity. •The cilia on the tentacles drive a current of water through the lophophore (filter-feeding) and move a mucous thread filled with food to the centrally located mouth •Freshwater bryozoans have a horseshoeshaped lophophore with a central mouth and an exterior anus. •Reproduce sexually during summer •Form statoblasts--dispersal/resting stage, asexual reproduction during autumn http://bio.classes.ucsc.edu/bio136/bryozoa/bryozoana.gif About 5000 species, mostly marine but some abundant freshwater spp exist. The lophophore of a bryozoan, showing the gut filled with algae A picture of a colonly of Plumatella growing on substrate—aquatic macrophytes are the most common substrate A colony of Plumatella releasing statoblasts http://www.senckenberg.de/images/content/forschung/abteilung/aquazool/mev3/statoblast.jpg Statoblast formation in a bryozoan colonly http://www.flmnh.ufl.edu/malacology/IZ2005/LabNotes/Lab10/Image4.jpg Some of the variation in colony and statoblast morphology seen among freshwater bryozoans Statoblast germinating to release a small polyp, which will branch off more polyps to form a branching colony Some freshwater bryozoan can get very large A colony of Pectinatella magnifica, attached to a stick http://www.magma.ca/~syatabe/water_brains/water_brains.html The freshwater bryozoan Lophopus http://www.micrographia.com/specbiol/bryoz/bryo/loph0100.htm Phylum Platyhelminthes—platy means flat and helminth means worm •the simplest animals that are bilaterally symmetrical and triploblastic •acoelomate—no internal fluid skeleton •mesoderm fills the space between the endoderm (gut lining) and the ectoderm, body wall •well differentiated tissues and organs, eg brain, bilateral nervous system, muscles, excretory organs, reproductive organs •In addition to free living flatworms this phylum also includes tapeworms and flukes Class Turbellaria—means whirlpool (named for the whirling appearance of their cilia) •free living flatworms> 4000 spp mostly marine and benthic, > 200 freshwater spp •<1 mm to > 1cm long •carnivores with an intestine and an extrudable muscular pharynx located in the center of the body—the single opening to the pharynx also serves as the anus •move by coordinated waves of cilia on a secreted mucus trail, though some species can swim by rhythmic muscle contractions. •simultaneous hermaphrodites and lay eggs bundled into cocoons. • young undergo direct development and hatch as juveniles. • Some turbellarians can reproduce asexually by fission. •Regeneration of somatic parts is well documented in Dugesia. Order Tricladida—means three branches •gut has three branches one anterior and two posterior, each with many branched diverticula •Anterior region with tactile auricles and eyespots arranged in a characteristic pattern Order Rhabodocoela—means rod-shaped gut •Straight (unbranched) gut Internal anatomy of Dugesia showing digestive, nervous, and reproductive systems The common freshwater triclad Dugesia tigrina http://animaldiversity.ummz.umich.edu/site/resources/Grzimek_inverts/Turbellaria/v01_id222_con_turanat.jpg/medium.jpg Dugesia with extruded pharynx Flatworm feeding on a mayfly larva Extruded muscular pharynx http://images.google.ca/imgres?imgurl=http://www2.una.edu/microaquarium/images/Flatworms/Planaria_3cm.jpg&imgrefurl=http://w ww2.una.edu/microaquarium/flatworms.htm&h=413&w=298&sz=24&hl=en&start=7&tbnid=PkrURffBKV83kM:&tbnh=125&tbnw=90&p rev=/images%3Fq%3DMesostoma%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DG mating flatworms. Although flatworms are usually simultaneous hermaphrodites they will not self fertilize During copulation worms were observed to move towards each other, touch, then wind themselves around each other. Then they rear up and try to stab each other anywhere, sometimes causing considerable damage to their partner. During that time, spermatozoa are injected into the partner. http://www.rzuser.uni-heidelberg.de/~bu6/mate09.jpg A flatworm egg cocoon http://www.ncdc.noaa.gov/paleo/parcs/atlas/beringia/images/fossils46.jpg Turbellarian species differ in regards to the shape of the anterior region, shape of the auricles, placement and size of the eyespots, general body colour and characteristics of the gut diverticula Polycelis felina Planaria gonocephala Dendrocoelium lacteum Polycelis nigra http://images.google.ca/imgres?imgurl=http://www.bioweb.lu/sapro/felina.gif&imgrefurl=http://www.bioweb.lu/sapro/strudel.htm&h=261 &w=161&sz=13&hl=en&start=2&tbnid=2aZ0rcL3vhTS6M:&tbnh=112&tbnw=69&prev=/images%3Fq%3Dpolycelis%26svnum%3D10% 26hl%3Den%26lr%3D%26sa%3DG Order Rhabdocoela, Mesostoma ehrenbergi—an efficient predator on mosquito larvae and zooplankton (copepods and cladocera) in small fishless ponds Mesostoma occasionally harbours endosymbiotic Chlorella Phylum Tardigrada—means slow walker •tiny slow moving animals < 1 mm, found in virtually any type of ecosystem •bodies roughly cylindrical and divided into segments, •four pairs of lobe-like limbs terminating in 4-8 claws or discs •Crawl slowly around on moss or other plant material, sand or mud http://www.museums.org.za/bio/tardigrades/index.htm Common name is “water bear” •Their mouths contain piercing stylets which they use to suck juices from mosses, algae, rotifers or other small animals. •Body cavity (pseudocoel) is present •Over 800 spp known, most with a world wide distribution Tardigrades like the mosses they live on are able to dry up completely and enter a state of suspended animation (cryptobiosis) called a tun. The tun rehydrates quickly and resumes activity within a few minutes after the moss is wetted. Tun formation As the environment dries up, the limbs invaginate, the body contracts and becomes folded. Tun formation is an active process requiring metabolism and synthesis of a protective sugar Trehelose. After the tun is formed further desiccation can take place in 0 % relative humidity and the tardigrade can still survive. Revival typically takes a few hours from natural habitats but depends upon how long the tardigrade has been in the anhydrobiotic condition. While in a state of cryptobiosis tardigrades are able to resist environmental extremes that would be instantly letha to animals if in the active state. In 1842, the French naturalist Doyere first discovered tardigrades were able to withstand being heated for a few minutes to 125 °C, later Rham in 1929 increased this figure to 150°C. Adults have been able to survive being cooled to temperatures of almost absolute zero (-272.8°C) where there is no free molecular vibration and so no metabolism can exist. While in this state the organisms are also greatly resistant to X-Rays of 570,000 Roentgens (only 500 Roentgens would be fatal to a human). Water bears are also resistant to a vacuum (like outer space), some noxious chemicals, boiling alcohol, and pressures six time greater than the bottom of the deepest ocean etc. http://www.museums.org.za/bio/tardigrades/index.htm Ovary containing eggs gut Salivary gland Pharyngeal bulb, muscular Retractable piercing stylets Nerve ganglion on ventral nerve cord Typically tardigrades are dioecious, sexually reproducing with both male and females. Each has a single gonad which lies dorsally to the gut. However, some species are hermaphrodite and the absence of males has been reported in many populations, the females then reproduce asexually by parthenogenesis. Tardigrades express eutely, which means that the number of cells in some organs of the body is fixed from birth, growth occurring by increase in size only and not cell division. They do not have circulatory and respiratory systems and the excretory system may also be minimal. http://biodidac.bio.uottawa.ca/ftp/BIODIDAC/ZOO/TARDIGRA/DIAGCL/TARD002C.GIF Tardigrade eggs http://www.hydro-kosmos.de/mikmak/wmic12.jpg Eggs are laid when the animal moults its skin—the eggs are deposited in the exuvium The widespread distribution of tardigrades may be attributed to the fact that their eggs, and tuns are light enough to be distributed by wind or animals for great distances possibly in the upper atmosphere. http://www.bumblebee.org/invertebrates/images/Tardigra.gif http://zooex.baikal.ru/pictures/izba/tard4.jpg