If you were stranded on an island, what would you do to obtain drinking water?

1. If you were stranded on an island, what would you do to obtain drinking water?

2. Salinity & Osmosis Ms. Springstroh/Marine Biology

3. Seawater • Contains many solutes, or dissolved materials • Can be almost any dissolvable material • Most solutes in sea water are sodium (Na+) and chloride (Cl-) ions (charged particles), which, when bonded together, form salts (ex: NaCl) • Most come from hydrothermal vents • Evaporates leaves behind ions (charged particles, ex. Na+)  ions combine to form salts

4. Salinity • The total amount of salt dissolved in sea water • If 1000 grams of sea water evaporate and 35 grams of salt are left behind, the salinity = 35 ppt(parts per thousand)

5. When water freezes • Ions are left behind in the unfrozen water • Increases the salinity of unfrozen water surrounding the ice • Icebergs are not salty • Water is added back to the ocean via precipitation– rain and snow

6. Salinity’s effect on marine organisms • HUGE effect on marine organisms! • Most marine organisms would die in fresh water • Even small changes in salinity can greatly affect marine organisms. • Luckily, the ocean’s salinity hardly changes. • Organisms living in areas where salinity fluctuates (river mouths) have evolved to cope with changes in salinity

7. Diffusion • Ions (ex. Na+) and other solute molecules move around just like water • Always want to “spread out”– go from areas of high concentration to low concentration until evenly distributed… this is called diffusion • Substances move into and out of cells via diffusion

8. If a fish’s cells contain less sodium than the seawater, sodium will diffuse (move) into the fish’s cells. • Can be a problem if the fish is sensitive to sodium Too much sodium diffuses in = Nemo has a problem

9. How can this problem be solved? • With a barrier!!! • What is that barrier? • The cell membrane! • The cell membrane is selectively permeable • Allows some substances (ex: O2& CO2), but not all substances (ex: Na+, Cl-, NaCl, proteins) to diffuse across the membrane

10. Osmosis • Diffusion of water molecules across a selectively permeable membrane • Water diffuses easily across cell membranes because it has no overall charge, just like the majority of the membrane itself

11. IF: • total concentration of solutes (dissolved substances) inside the cell < outside the cell • (This means the concentration of water inside the cell is greater than outside the cell) • THEN: • Water will move out of the cell • RESULT: • The cell may shrivel

12. IF: • total concentration of solutes (dissolved substances) inside the cell >outside the cell • (This means the concentration of water inside the cell is less than outside the cell) • THEN: • Water will move into the cell • RESULT: • The cell swell and burst