BIO 152 Lecture Notes - Lecture 7: Vascular Tissue, Gastrointestinal Tract, Phloem
16 Apr 2017
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Why is it needed: size and shape. Basic ideas: negative and positive pressure, components. Diffusion: useful for short distances, limit size of active cell, limits size of body without bulk transport. Bulk transport: moving substances through a fluid, works with diffusion in larger bodies. Flatworm (planarian: all cell close to surface. Diffusion of o2, co2: digestive tract branches. Allows for diffusion to all cells in the body. Jellyfish: active cells on inner surface and outer surface, jelly in between is non-cellular and is not metabolically active. Bulk flow relies on pressure to move fluids. Movement across longer distances: fluids flow from higher pressure to lower pressure. Positive pressure: pressure higher in one area pushes fluid away. Negative pressure: pressure lower in one area pulls fluid toward it. Tubes or enclosed spaces: pathway for fluid, allows for pressure differential. Vascular tissue: tubes that carry water and nutrients. Xylem: carries water and minerals from root to lead.
