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Lecture 11

BIOL 111 Lecture 11-25.doc

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McGill University
Biology (Sci)
BIOL 111
Heather Roffey

BIOL 111Organismal BiologyLECTURE 11INTRODUCTIONS TO ANIMALS SPONGESAnimal Characteristics1eukaryotictrue nucleusDNA is linear as opposed to circularmembranebound organelles eg mitochondria Golgi apparatus endoplasmic reticulumin the domain Eukarya2heterotrophicdifferent feedinguse organic materials as energy and carbon sourcesbring food in by ingestion as opposed to phagocytosis or absorptionfilter feedersaquatic usually sessile organismspredatorskill another animal to eat itherbivoreseat plants or algaeparasitesfeed off of living organismsdetritivoresdirteaters eg earthworm sea cucumber3no cell wallhow do animals support themselves see next section4motile at a some life stage5multicellulardisadvantagesolots of cell divisionoenergetically costlyolonger time to maturityadvantagesomore specializationomore diverse functionsocells can remain small even in large organismsomaterials can diffuse throughout whole cell more quickly6have tissuetissuegroups of structurally similar cells that function togethertissues can functions together as organs to complete more complex tasksnervousconducts impulses eg tissue that makes up the human brain and nervesused for covering and protection eg tissue that lines human digestive epithelialtractconnectiveliving cells in a nonliving matrix blood is connectiveblood cells living flow through plasma nonliving matrixmuscularcontract and lengthen to control movement and supporta given organ may be comprised of some or all of these tissue types eg human stomach contains all four7life cycle is mostly diploidanimals life cycles are much simplerfertilizationtwo haploid cells join to make diploidmeiosisdiploid cell divides to haploidNONE OF THESE CHARACTERISTICS ARE UNIQUE TO ANIMALS1 of 65BIOL 111Organismal BiologyTypes of Structural Support1hydrostatic skeletonfluidfilled cavity acted on by muscleseg earthworms jellyfish2exoskeletonexternal skeletonnonliving covering but produced by livingmade of proteins or calcium carbonate in some aquatic animalsdoes not grow with animalecdysozoansmolting animalsthey must shed their exoskeleton to groweg green dragonfly3endoskeletoninternal supportin vertebrates endoskeleton is made of living tissue ie bonesin some invertebrates endoskeleton is nonliving ie CaCO3Kingdom Animaliahas about 35 major groups phylaabout 17 million species have already been classified but there is an estimate 10 million species97 of animals are invertebratesall animals are monophylogeneticthey all come from one common ancestorcommon ancestor probably a colonial choanoflagellateoindependent cells that live on a stalkowere marineoeach cell has a collar cell and flagellumchoanocollarused flagella to help feedfirst animals were marine and appeared 12 BYA to 700 MYAanimal diversificationooccurred at the Cambrian explosion543488 MYArapid diversificationmost present day phyla and moremany new phyla formedSponges Poriferathere are about 8000 speciesmost sponges are marinesize ranges from 2mm to 2 msponges are sessile as adults but motile as larvaesponge morphology is high variablesponges are filter feeder2 of 65BIOL 111Organismal Biologyothey acquire nutrients and energy by filtering particles from waterSponge Anatomy and Feedingporiferapore bearerostia or incurrent poresabsorb water and food ie phytoplankton cyanobacteria unicellular green algae diatoms etcspongocoelinternal cavityocoelcavityosculum or excurrent poreexpels water and wasteswall of the sponge is made of 4 types of cells embedded in a jelly matrix called mesohyl this is not considered real tissueorganoonly phylum of animals that does no have tissues cells do not work togetherchoanocytes are cells that line the wall of the spongocoel and beat their flagella to create a water current which brings water in through the ostia Flagella then catch nutrientsamoebocytes appear and move like amoeba are motile cells inside the mesohyl which receive the nutrients from the choanocytes and distribute them throughout the organism They also produce eggs and spermepidermal cells make up the external wall of the spongepore cells make up the ostia and osculumspicules are nonliving structures in the mesohyl that provide support and skeleton They can be made of silicon dioxide SiOglass ie glass sponges or calcium carbonate 2CaCOlimestone ie calcareous sponges3some sponge instead of spicules have a more flexible skeleton of spongin which is a protein eg bath spongeswhen choanocytes bring in food the food gets trapped in the collar cells and travel to the main cell body by mucous and engulfed by phagocytosis Then an amoebocyte comes over and takes the food Digestion then occurs intracellularly in the amoebocytesosponges are the only animals that undergo intracellular digestionSponge Reproductionsponges reproduce asexually by fragmentation or buds or sexually by releasing gametes into the waterasexual reproductionofragmentationnot selfinducedif sponge is divided by a wave or predator each segment will become a new organismobuddingclone of parent grows off of parent and then falls offsexual reproductionohermaphroditicdoes not imply self fertilizationsperm and eggs develop inside single cellsbroadcast spermsperm is sent outa sponge filters in different sperm through its ostia its egg is fertilized and develops in the mesohyl3 of 65
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