BIO203_CellPhysiol

BIO203_CellPhysiol - Many taxonomic lineages have...

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1 J.T. Bonner, Integrative Biol . 1: 27-36, 1998 Many taxonomic lineages have independently evolved multicellularity, and multicellularity is not limited to eukaryotes MULTICELLULAR ORGANISMS Why go multicellular? Larger size isolation from outside world, and protection of genes for the next generation Cell differentiation division of labor Evolution of multicellularity? Accidental first step: mutation prevents daughter cell separation Then selection for size: in the size continuum of a unicellular world, there is always room at the “large” end representing an unfilled niche Bonner, 1998 Bonner, 1998 Examples of green algae Volvox daughter colonies individual cells Pediastrum Bonner, 1998 Example of bacterium cyanobacterium heterocysts (nitrogen fixation) [filamentous cyanobacteria date from 3.5 BYA]
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2 Bonner, 1998 Example of a multicellular protist Dictyostelium (cellular slime mold) feed as individual amoebae when food is scarce, aggregate to form fruiting body and spores Selective Pressures for Multicellularity • Aquatic organisms (where multicellularity results from failure to separate) – adherence to substrate – prevent being eaten – faster movement • Terrestrial organisms (where multicellularity results from aggregation) – more effective spore/germ cell dispersal – better feeding Animal Phylogeny Based on Morphology sister taxon to animals s im p le c o m x (paraphyletic) Freeman, Biological Science , Figure 31-10 Animal Phylogeny Based on Molecular Evidence sister taxon to animals shed exoskeleton (paraphyletic) Freeman, Biological Science , Figure 31-13
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3 The Complexities of Metazoan (and Multicellular) Life Large size long diffusion distances vascular system for bulk transport Subdivision of organismal functions tissues and organs Multiple compartments/spaces: unicellular organism multicellular organism intraorganellar spaces intraorganellar spaces intracellular space intracellular space “interior” extracellular spaces interstitial space intravascular space exterior/extracellular space exterior space ) Major physiological challenge: integration and coordination of functional activities across the organism for optimal fitness in the real environment ) Student challenge : Identify, compare and contrast the intraorganismal tissues and organs and compartments in an animal and a plant. Barriers and Barrier Function
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This note was uploaded on 09/16/2011 for the course BIO 203 taught by Professor Loretz during the Fall '09 term at SUNY Buffalo.

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BIO203_CellPhysiol - Many taxonomic lineages have...

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