Chapter 28 The Environmental Challenges

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review questions

  1. Animals live in varied environments
    1. Freshwater: Lots of water, but little salt
    2. Seawater: Lots of water, but a lot of salt
    3. Land: Little water or salt
  2. Animals in Freshwater
    1. Hyperosmotic
    2. Gain water by osmosis
    3. Lose ions by diffusion
    4. Shell, cuticles, scales
    5. Gain ions from food
  3. Table 28.1
  4. Fig 28.1 Water-salt relations in a freshwater animal
    1. Gills highly permeable / lots of ion exchange here !
    2. Make large amounts of dilute urine
    1. Fig 28.8a Water-salt relations in freshwater teleost fish
      1. Image from Wikipedia


  5. Fig 28.2 Ion exchanges mediated by active Na+ and Cl- transport in the gill epithelium of freshwater teleost fish
    1. Absorb or actively transport ions into body
    2. Requires ATP
    3. Cl-  exchanged for HCO3
    4. Na+ exchanged for H+
    5. Fish have Cl cells in the gills
  6. Animals in Saltwater
    1. Hyposmotic
    2. Gain ions from water
    3. Water loss
  7. Table 28.3
  8. Intracellular Ionic Regulation in Marine Invertebrates
    1. most are osmoconformers
    2. active ionic regulation
    3. pelagic animals pump out sulfate ions for buoyancy
  9. Hagfish Osmoregulation
    1. Marine and Stenohaline
    2. osmoconformers
    3. ionic regulators
  10. Marine Teleosts
    1. Fig 28.7b Water-salt relations in marine teleost fish
      1. Marine bony fish constantly loose water
      2. Obtain water in food and seawater
      3. Produce scant isosmotic urine
      4. Movement of water and ions in saltwater fish
        1. image from wikipedia


  11. Salt balance in marine teleosts
  12. Fish Gills: Box 28.3
    1. active transport of ions out of the gills.
    2. chloride cells excrete Cl, Na
    3. Direction of transport depends on water salinity
  13. Marine air-breathing vertebrates
  14. Marine Reptiles
  15. Fig 28.9 Avian salt glands
  16. Marine birds
  17. Marine Mammals
    1. Do not have salt glands and do not drink seawater
    2. Obtain water from food and metabolism
    3. Modifications in nasal passages to reduce water loss
  18. Kidneys produce urine hypertonic to sea water
    1. humans cannot drink seawater (lose more water to get rid of excess salt)
    2. whales can (but gain Na)
  19. Fig. 28.10 Water-salt relations in a marine shark
    1. hyposmotic (1/3) but ONLY in regards to salts
    2. slightly hyperosmotic overall because they retain urea in their blood
    3. water enters by osmosis and in food, and is removed in urine.
    4. urea concentration is 100 times higher than that in mammals
  20. Marine Elasmobranchs (sharks and rays) use trimethylamine oxide (TMAO)
  21. Ionic regulation in marine sharks and rays
    1. rectal gland
  22. Definitions
    1. stenohaline
    2. euryhaline
  23. Figure 27.4 Salinity trends in an estuary
  24. Figure 27.5 The responses of a resident osmotic regulator to variations in salinity in an estuary
    1. Brackish water animals are often euryhaline
    2. Most are iso-osmotic
    3. can tolerate considerable dilution.
    4. Active regulators are hyperosmotic to brackish water and better resist environmental fluctuations
  25. Figure 28.11 Types of osmotic regulation
    1. Hyper-isosmotic:
    2. Hyper-hyposmotic:
  26. Catadromic and Anadromic fish
  27. Catadromic and Anadromic fish
  28. Lamprey Osmoregulation
  29. Lamprey osmoregulation, cont.
  30. fresh-water elasmobranchs
  32. Moist-skinned animals: Earthworms
  33. Terrestrial Animals
    1. Surrounded by dry/desiccating environment
    2. Must limit water loss from evaporation
      1. Skin permeability
      2. Respiratory membranes
      3. Kidneys concentrate urine to decrease water
  34. Amphibia
  35. Frogs and other Amphibians
  36. Amphibians
  37. Desert Frogs
  38. Figure 28.22 Arboreal frogs of the genus Phyllomedusa spread protective lipids secreted by integumentary glands over their skin surface
  39. Arthropods: Insects and Arachnids
  42. Water Loss in Insects and Arachnids
  43. Water Loss in Insects and Arachnids
  44. Water Gain in Insects and Arachnids
  45. Water Gain in Insects and Arachnids
  46. Figure 28.18  Within a phylogenetic group, the total rate of evaporative water loss is an allometric function of body size
  47. A Phylogenetic Perspective of Evaporative Water Loss in Birds
  48. The kangaroo rat is a desert mammal that has quite different means of water conservation than humans.
    1. most of its water from carbohydrate metabolism.
    2. minimizes water loss from evaporation by aestivation during the heat of the day.
    3. generates concentrated urine
  49. Figure 28.24 A kangaroo rat water budget



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