BIOL 3454 1nd Edition Lecture 9 Chapter 12I. Multicellylarity a. Advantageous – low surface area to volume ration (individual cells more efficient)II. Sponges are the first multicellular animalsa. Organization is very distinct - cells embedded in an extracellular matrixb. Not recognized as animals or plants until 19th centuryIII. Animals are sisters to choanoflagellate algae – sponges first group of metazoans to branch ofIV. Choanocyte cellsa. Possessed by choanoflagellates and sponges b. Flagellum surrounded by collar of microvillic. Collect particles for filter feeding usually bacteria d. Most organisms with choanocytes are sessile and attach to hard surfacesV. Evidence for metazoan common ancestor being colonial a. Prototype multicellular organism b. Similar cell communication mechanisms exits between choanoflagellates and spongesVI. Evidence against common ancestor of metazoans colonial a. Choanocytes only in adult sponges not in the larval form b. Not seen in other phylogenetic groups lost or suppressed VII. Phylum Porifera a. Latin for porus (pore) and fera (bearing)b. Sponges are amazing filters with few parts c. Range in size from a 2mm across to 2m acrossd. Characteristicsi. Multicellularii. Body with pores that facilitate water movement iii. Aquatic iv. Radial symmetryv. At least 2 cell types with non living extracellular matrixvi. No organs or tue tissues digestion intracellular vii. NS absent or very primitive, limited organismal response to stimuliviii. Asexual reproduction by buds or gemmules sexual reproduction with eggs spermand then free swimming larvae. Sponge structure i. Spicules imbedded in sponging for supportii. Pinacoderm – incurrent pores on cellsiii. Dermal ostia – incurrent pores for the sponge iv. Sponges are suspension feeders – small food particles ingested through phagocytosis for larger particles or pinocytosis for small proteinsf. Anatomyi. SpongocelThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.ii. Ostiaiii. Osculumiv. Non living gelatinous layer (mesohyl) between 2 layers of epithelial tissue *g. Cellular & extracellular sponge components i. Choanocytesii. Mesohyl – gelatinous extracellular matrix *iii. Archaeocytes – ameboid cells that move in the mesohyl1. Scleerocytes – spicules2. Spongocytes – sponging3. Collencytes – collagen4. Lophocytes - collagen iv. Pinacocytes – analogous to epithelial cells closest thing a sponge has tot true tissuesv. Myocyctes – arranged in circular bands around pores, regulate water flow through contraction vi. Pinacocytes – protective contractivevii. Mesohyl – sponging, spicules, archaeocytes viii. Choanocytes – collar cellh. Body forms i. Asconoid ii. Syconoidiii. Leuconoidi. Reproductioni. Asexual – external or internal buds, gemmules (somatic embryogenesis)ii. Sexual – mostly monoecious sponges, cross or self fertilize, parenchymule (free swimming larvae)j. Unusual sponge development i. Calcarea and a few demosongiae ii. Clastula develops then turns outward (puts flagellated cells on the outside)iii. Blastula developsk. Advantages of asexual reproduction i. No dilution of gene pool ii. Clones facored in stanle environments iii. All of population is reproductive iv. Ofspring are most of the time robustl. Disadvantages of asexual reproduction i. Ofspring often do no disperse long distances ii. All the same – not favorable in changing environments iii. Muller rachet – you accumulate negative mutations over time; can lead to a less fit population iv. Most mutations are neutral v. Phenotypic mutations are usually negative m. Monotypic phylum *i. 1 species in entire phylum ii. Family 1 species in entire family n. Advantages of sexual reproduction i. Genetic variations ii. Ofspring dispersalo. Disadvantages of sexual reproduction i. Not all of population can reproduceii. Fragile ofspring iii. Diluted gene pool for all individuals (good for less fit bad for more fit)iv. Most reproductive efort is wasted – have to find a mate most gametes/ofspringdo not survivep. Taxonomy i. Class – calcarea – small calcareous sponges ii. Class – hexactinellida – siliceousiii. Class – demospongiae – 95% of speciesq. Calcarea (calcispongidae)i. Calcium carbonate spicules ii. Any of the 3 sponge forms iii. Typically small & vase shapedr. Hexactinellidai. Glass sponges ii. Deep seaiii. Funnel shapediv. Syncytial cellular structure v. Many nuclei in a single cellvi. Fusion of many cells vii. Cellular replication w/o cytokinesis s. Demospongiae i. Siliceous but not six rayed ii. All leuconoid all shapesiii. Very diverse most species – contain only freshwater spongesVIII. Phylum Placozoa a. Named for greek root plakos (tablet) & zoon (aminal)b. One species – monotypic family & genus c. Monotypic – having only one member d. Scavengers – glide over food, secrete digestive enxymes absorb the productse. Reproduce asexually by budding & fission – eggs produced in captivity i. Mesoderm – most connective tissues, fluids and