If you were stranded on an island, what would you do to obtain drinking water?
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Transcript of If you were stranded on an island, what would you do to obtain drinking water?
If you were stranded on an island, what would you do to obtain drinking water?
Salinity & Osmosis
Ms. Springstroh/Marine Biology
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
Seawater
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)
Salinity
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
When water freezes
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
Salinity’s effect on marine organisms
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
Diffusion
Substances move into and out of cells via diffusion
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
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
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
Osmosis
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
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