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DSTP Science Review

DSTP Science Review. Biology. What are the characteristics of living things?. Obtain, use and transform energy Respond to their environment Reproduce Are made of individual units called cells. Cells carry out the three processes listed above. HOW BIG DO CELLS GET?

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DSTP Science Review

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  1. DSTP Science Review Biology

  2. What are the characteristics of living things? Obtain, use and transform energy Respond to their environment Reproduce Are made of individual units called cells. Cells carry out the three processes listed above

  3. HOW BIG DO CELLS GET? Cell size is limited by how easily chemicals can get across the cell membrane. Small cells have a high surface area to volume ratio. Chemicals inside the cell are always close to the cell membrane, and can leave quickly. As a cell grows larger, the surface area/volume ratio becomes smaller. It takes longer for chemicals to reach the cell membrane. This means that the interior of the cell will not get nutrients and will build up wastes.

  4. Osmosis: Diffusion of water across a semi-permeable membrane Guess what happens: Case 1: Assume sugar can’t cross the membrane. Concentration of sugar outside cell: 9 % Concentration of sugar inside cell: 5 %

  5. 5% glucose 9 % sugar Since sugar can’t go into the cell, water will flow out of the cell. The cell shrinks.

  6. Case 2: Concentration of sugar outside cell is 3 %Concentration of sugar inside cell is 8 %. 3 % sugar 8 % sugar Since sugar can’t get out of the cell, water will enter the cell. The cell will swell up.

  7. 6 % sugar • Since the two concentrations are the same, • the same amount of water flows in and out. • The cell stays the same size. 6 % sugar

  8. Evidence for Evolution • Fossils record • Comparative Anatomy • Comparative Embryology • Molecular evidence • Plate tectonics and earth’s history • Astronomy • Microbiology • Evolutionary-Developmental Biology (Evo-Devo)

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