Name_____________________________
Marine Biology--Mr. Nelson
Water Balance: conserving water in the aquatic environment.
The biological importance of water.
Water is a valuable, life-supporting chemical on earth because it:
1. is a reactant for photosynthesis.
2. is a solvent for many chemical substances needed by living cells.
3. provides the proper medium in which cellular chemical reactions can
take place (i.e. chemical reactions in cells occur in an aqueous solution).
4. acts as a vehicle for rapid diffusion of nutrients.
Conserving water in the aquatic environment
Plants living in water: one could reasonably
assume that plants living in an aquatic environment
should not suffer from water loss problems. However,
in the marine (saltwater) environment, algae tend to
dehydrate.
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(a) Name the process whereby water moves out of the kelp cells to the surrounding sea water.
(b) Compare the water concentration of the kelp cells to the surrounding sea water in the diagram below
by circling “high” or “low”.
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(c) To combat the problem above, marine algae can do the following. Describe how each of these
processes may control water loss from the plant in the marine environment:
(i) secrete a slimy mucous layer.
(ii) increase the concentration of mineral ions in the cell cytoplasm by active
transport.
For marine animals, the osmotic stress takes the form of dehydration.
(i) Show this situation by circling high” or “low” in the diagram below:
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(ii) Here, excessive water loss may be prevented by the following. Describe how each of these
may be used to regulate water loss from animals in the marine
environment:
(a) mucous body secretions and/or scales
(b) active transport of ions out of the cell
(c) varying the concentration and volume of urine
Marine Fish Osmoregulation
Ocean water is a hypertonic environment compared to the inside of cells.
Use a text and the Water Balance: Conserving water in the Aquatic
Environment, to discuss how each of the following helps ocean fish
osmoregulate.
Urine production
Drinking the sea water
Part 2: If marine fish drink the water, how are they getting rid of excess salts?
Scales
Mucous covering the scales