BIOL 2004 Study Guide - Final Guide: Seaweed, Isogamy, Phloem
19 Apr 2016
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Attached to some surface: macroscopic, composed of many differentiate cells, several independent evolutionary origins, differences. Gravity is important: not supported by a medium must fight against gravity, rigid structures to allow standing. Gravity not an issue in a buoyant medium. Have to worry about shear forces: current affect anchoring, macroalgae are flexible allows bending with shear forces. Only some macroalgae below 100m: keep photosynthetic material close to the surface, but anchoring in sea bed, have specialized adaptations to absorb long wavelengths of light. Thallus main cell body: basal part usually specialized for anchoring. Attaches to surface of substrate or embeds into it: basic thallus forms. Cells arranged in linear chains: filaments can be branching. Defined number of cells thick, usually only about 1-2 cells thick. Large parts of the thallus have thickness to them. Often see differentiation in cell types in parts of the thallus: usually see differentiation between outter and inner cells, cell walls/extracellular matric.
