BIOL 3454 1nd Edition Lecture 9 Chapter 12 I II III IV V VI VII Multicellylarity a Advantageous low surface area to volume ration individual cells more efficient Sponges are the first multicellular animals a Organization is very distinct cells embedded in an extracellular matrix b Not recognized as animals or plants until 19 th century Animals are sisters to choanoflagellate algae sponges first group of metazoans to branch of Choanocyte cells a Possessed by choanoflagellates and sponges b Flagellum surrounded by collar of microvilli c Collect particles for filter feeding usually bacteria d Most organisms with choanocytes are sessile and attach to hard surfaces Evidence for metazoan common ancestor being colonial a Prototype multicellular organism b Similar cell communication mechanisms exits between choanoflagellates and sponges 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 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 across d Characteristics i Multicellular ii Body with pores that facilitate water movement iii Aquatic iv Radial symmetry v At least 2 cell types with non living extracellular matrix vi No organs or tue tissues digestion intracellular vii NS absent or very primitive limited organismal response to stimuli viii Asexual reproduction by buds or gemmules sexual reproduction with eggs sperm and then free swimming larva e Sponge structure i Spicules imbedded in sponging for support ii Pinacoderm incurrent pores on cells iii 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 proteins f Anatomy i Spongocel These 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 g h i j k l m n ii Ostia iii Osculum iv Non living gelatinous layer mesohyl between 2 layers of epithelial tissue Cellular extracellular sponge components i Choanocytes ii Mesohyl gelatinous extracellular matrix iii Archaeocytes ameboid cells that move in the mesohyl 1 Scleerocytes spicules 2 Spongocytes sponging 3 Collencytes collagen 4 Lophocytes collagen iv Pinacocytes analogous to epithelial cells closest thing a sponge has tot true tissues v Myocyctes arranged in circular bands around pores regulate water flow through contraction vi Pinacocytes protective contractive vii Mesohyl sponging spicules archaeocytes viii Choanocytes collar cell Body forms i Asconoid ii Syconoid iii Leuconoid Reproduction i Asexual external or internal buds gemmules somatic embryogenesis ii Sexual mostly monoecious sponges cross or self fertilize parenchymule free swimming larvae Unusual sponge development i Calcarea and a few demosongiae ii Clastula develops then turns outward puts flagellated cells on the outside iii Blastula develops 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 robust 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 Monotypic phylum i 1 species in entire phylum ii Family 1 species in entire family Advantages of sexual reproduction i Genetic variations ii Ofspring dispersal VIII o Disadvantages of sexual reproduction i Not all of population can reproduce ii 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 ofspring do not survive p Taxonomy i Class calcarea small calcareous sponges ii Class hexactinellida siliceous iii Class demospongiae 95 of species q Calcarea calcispongidae i Calcium carbonate spicules ii Any of the 3 sponge forms iii Typically small vase shaped r Hexactinellida i Glass sponges ii Deep sea iii Funnel shaped iv Syncytial cellular structure v Many nuclei in a single cell vi Fusion of many cells vii Cellular replication w o cytokinesis s Demospongiae i Siliceous but not six rayed ii All leuconoid all shapes iii Very diverse most species contain only freshwater sponges 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 products e Reproduce asexually by budding fission eggs produced in captivity i Mesoderm most connective tissues fluids and muscles