chapters 12 & 13 porifera, cnidaria and ctenophora


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CHAPTERs 12 & 13 PORIFERA, CNIDARIA AND CTENOPHORA. Phylum Porifera (pore-bearer). I . A . Characterisitics : Usually asymmetrical, sometimes radially symmetrical Contain no tissues , organs, or muscles - PowerPoint PPT Presentation




Phylum Porifera (pore-bearer)

I. A. Characterisitics:Usually asymmetrical, sometimes radially symmetricalContain no tissues, organs, or muscles

Filter feeders: water moves in through the pores into the central body cavity and out through the osculum.Phylum porifera supported by a skeletal system consisting of needle-like spicules composed of silicon salts (glass) or calcium carbonate (CaCO3), and/or a soft and pliable skeleton made of organic fibers composed of fibrous collagen or spongin.

Composition of Skeleton is used to classify porifera Contain three cell types: 1. pinacocytes: line the outer surface, may be mildly contractile

2. mesenchyme cells: amoeboid cells that move about in the mesohyl (middle cell layer) specialized for reproductionsecreting skeletal elementstransporting and storing foodform contractile rings around openings (pores)3. choanocytes: (collar cells) cells with flagella that create water currents and the collars the filter food out of the water (phagocytosis).

Maintenance Functions B. Digestion: the break down of food occurs inside food vacuoles/lysosomes (intracellular)Excretion: nitrogenous waste occurs by diffusion

Respiration: O2 and CO2 gas exchange occurs by diffusionEndocrine System: may use chemical messages for communication among cellsReproductionSkeletal: spicules or sponginReproduction *****(know in detail)a. Sexual reproduction:Sponges are monoecious (produce both sex cells in a single individual) but produce eggs and sperm at different times.

Zygote develops into a free-swimming larva that will settle to a substrate after 2 days.

b.Asexual reproduction:the formation of gemmules (resistant capsules that contain masses of amoeba-like mesenchyme cells)gemmules are formed when the sponge dies or is under environmentally stressful conditions.

gemmules are formed in the mesohyl

Asexual reproduction is also regeneration (an internal budding process producing identical clones of the parent).

3 Different types of anatomy C. Morphology of Sponges ****Body formation is based on the pathway of water currents flowing through the sponge

3 canal types:

1. Asconoid sponges: simplest body plan, water moves in ostia (pores) spongocoel out a single osculum2. Syconoid sponges: water moves in ostia incurrent canals radial canals spongocoel out a single osculum

Leuconoid sponges: most complex with a branched canal system, water moves in ostia incurrent canal excurrent canals smaller spongocoel out multiple osculum

Cnidaria Stinging celledA. Characteristics:Radial or biradial symmetryDiploblastic (2 tissue layers), endoderm and ectoderm with gelatinous mesoglea in betweenGastrovascular cavity (GVC)Nervous system: nerve netHave Cnidocytes which contain special organelles called nematocysts for attachment, feeding and defense, often contain toxins.

Maintenance FunctionsDigestion: begins in the gastrovascular cavity (GVC) and is completed in food vacuoles, undigested waste exits out the mouth (intracellular), no anus present

Excretion: GVC also functions in the exchange of nitrogenous waste through diffusion

Respiration: the exchange of gases (O2 & CO2) also functions through diffusion of the GVC

Reproduction: GVC functions to release the gametes (egg and sperm cells)

Skeletal & locomotion: support and movement are aided by a hydrostatic skeleton (the GVC fills with water).

Muscular: contraction of epitheliomuscular cells aid in movement.

C. Reproduction ***Exhibit alternation of generationsEach generation is a different body form

2 different forms:polypasexual and sessile cylindrical body with a mouth at the top surrounded by food-gathering tentacles reproduces by budding (the bud is the offspring of the polyp and becomes the next generation = medusa body plan

Medusa medusadioecious (separate sexes), sexual, and free-swimmingbody shaped like an inverted bowl with the tentacles hanging down around the mouth underneath formed by budding from a polyphas sexual reproduction by releasing egg (female) and sperm (male) into the water

zygote develops into a planula larva (the offspring)Larva plants itself into the ground and will grow to become the next generation of polyp.

D. ClassesHydrozoa: ie) Obelia, Hydra, Portuguese man-of war (phasalia)2. Scyphozoa: (true jellyfish) ie) Aurelia, Stinging nettle

3. Cubozoa: (medusa is cuboidal) ie) Sea wasp4. Anthozoa: ie) sea anemones and stony and soft coral

Ctenophora III. Phylum CtenophoraA. CharacteristicsBiradial symmetryDiploblastic with gelantinous mesogleaMonoeciousGastrovascular cavityNerve net

Adhesive structures called colloblasts that capture prey.Eight rows of ciliary band, called comb rows, for locomotion.Examples: Pleurobranchia, Boroe (Sea Fan and Sea Pin)