Chapter 26 The Aquatic Environment.

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review questions

1. The Aquatic Environment.
   1. 71% of the earth’s surface
   2. dissolved salts, gases & organic compounds.
   3. physiologically important
2. Body Fluid
   1. Dissolved inorganic ions (electrolytes)
   2. Water
3. Fig. 26.1 Body fluids account for 60% of the body weight of young adult people
   1. Intracellular
   2. Extracellular: aqueous fluid outside cells. Two compartments:
      1. Interstitial: 1/4 of the body fluid
      2. Blood plasma
4. Fig. 26.2 Body fluids
   1. Blood plasma and interstitial fluids have approximate same ionic composition;
   2. Intracellular is usually different.
   3.  All body fluids approximately isosmotic
   4. These tissues regulate three homeostatic processes
      1. Osmotic regulation
      2. Ionic regulation
      3. Excretion
5. Excretion and osmoregulation
   1. Body fluids are dilute saline solutions.
   2. Reflect origin of life in sea.
   3. Some animals can tolerate greater changes in their fluid concentrations
   4. Osmoregulation and excretion are closely linked
   5. Excretion and osmoregulation usually managed by same organs.
6. Defininions
   1. Isosmotic animals (most marine invertebrates)  
   2. Hyperosmotic animals (most freshwater animals)  
   3. Hyposmotic animals (marine boney fish fish)  
7. Fig 26.3 Osmotic regulation and conformity
   1. Osmoconformers
      1. Advantage: Energy costs low
      2. Disadvantage: Cells cope with variable environment.
   2. Osmoregulators
      1. Advantage: Cells exist in uniform osmotic/ionic environment
      2. Disadvantage: Energy costs  
   3. Few invertebrates are either strict regulators or conformers.
8. More Definitions
   1. Ionoconformer
   2. Ionoregulator
9. Salinities vary in Natural Aquatic Environments
   1. Freshwater
   2. Normal marine (35 ppt = 1000 mOsm)
   3. Brackish (estuaries)
   4. Hypersaline
10. Terrestrial habitats can vary greatly in their temperature and humidity
    1. Figure 26.6 Deserts occur on all continents
11. Sources of Water
    1. Drinking water
       1. What if salty?
    2. Dietary water
       1. water preformed in plant and animal tissue
    3. Metabolic water
       1. C₆H₁₂O₆+ 6O₂ à 6CO₂ + 6 H₂O
12. BIRDS AND MAMMALS
    1. Desert mammals almost never see free water,
    2. water from food, especially carnivores (from prey)
    3. metabolic water (rodents )
13. Box 26.1
    Kangaroo rats
    1. never need to drink
    2. get a lot of water from oxidation water and a little from free water in food
    3. lose a quarter of water to urine (urea), but do produce very concentrated urine
    4. evaporation (mostly from respiratory tract) accounts for almost 75% of water loss
    5. cannot live below about 20% humidity

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