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Animals - Regulating body fluids

Terms in this set (27)

Hypertonic, isotonic & hypotonic, meanings?
Hypertonic - water moves out (low water concentration in the solution)
Hypotonic - water moves in (high water concentration in the solution)
Isotonic - equal inside & out
Why do we regulate body water & solutes?
To achieve homeostasis - ensure the environment is constant
What influences the osmotic concentration of cells?
- Water concentration
- Ions
- Organic solutes (eg. glucose, aacids)
Aquatic animals can be...?
- Osmoconformer (osmostic concentration of internal environment = external environment)
- Osmoregulator (osmotic concentration of internal environment doesn't = external environment)
Achieving a balance involves?
- Water & solutes being exchanged continuoulsy between an animal and its environment (food & fluid intake, excretion and elimination of wastes)
How do terrestrial animals lose water?
- Excretion and elimination of wastes
- Evaporation of water from body surface (sweat) and from breathing
Aquatic animals gain or lose water by?
- Excretion and elimination of wastes
- Osmosis
Features of Osmoconformers?
- They are isotonic to seawater
- Most marine animals are osmoconformers
- Usually cannot tolerate a large change in body salinity, and therefore live in environments where salinity doesn't change much (organisms are called stenohaline)
Features of Osmoregulators?
- Body fluid is different to external environment
- Most marine vertebrates as well as freshwater & terrestrial animals
- Can tolerate a wide range of salinities (euryhaline)
How do marine fish osmoregulate?
Drinks lots of sea water, concentrates its urine, actively excretes salts (gill pumps)
Problem with marine vertebrates?
Not enough water and too much salt, therefore losing water to a salty environment.
Solutions for marine vertebrates water loss?
- Produce small amounts of concentrated urine
- Actively excrete ions (across gills, by kidneys, or salt glands)
Freshwater osmoregulators problem?
Too much water, too few solutes
Solutions for freshwater osmoregulators water loss?
- Don't drink water
- Produce lots of dilute urine
- Have organs that retain salts (eg. kidneys, gills)
Salmon can live in both...?
Ocean & freshwater
Salmon example of migration?
Eggs hatch far upstream (freshwater), they migrate to the ocean, spend 1-8 years maturing in the ocean and eventually return to the same river to breed.
What must animals do/have to acclimatise to new environments?
- Kidney function must alter and Na+/Cl- gill pumps must reverse their direction
- Salmon need several days/weeks in brackish water at river mouth to acclimatise
Problem with terrestrial animals?
- Must osmoregulate
- Generally a few ion concentration problems
- Not enough water in environment (especially desert animals)
- Lost water by evaporation
Solution to terrestrial animal's problem?
- Must drink and/or get water from food
- Keep respiratory surfaces inside
- Some absorb water through skin
- Insulate skin with hair
- Minimise water loss during excretion of waste
Adaptations for desert animals? (eg. throny devils)
- Specialised skin texture to capture dew & rainwater
- Scales are surrounded by tiny interconnected channels that attract water
- Water is then funnelled to the mouth
How do animals excrete nitrogenous wastes?
- Fish excrete ammonia
- Terrestrial animals convert NH3 to a less-toxic form (soluble urea - mammals, invertebrates, insoluble uric acid - reptiles, birds, guanine - spiders, scorpions)
Why are kidneys important for fluid regulation?
Filtering our urine - principal excretory organs of vertebrates
Features of the kidneys?
- Each kidney is composed of nephrons (excretory tubules)
Draw/know features of a nephron
!
Four functions of a nephron in the kidney?
Filtration: all blood plasma except blood cells & large proteins enters tubule
Reabsorption: ions, glucose, aacids, vitamins re-enter blood
Secretion: some ions secreted from blood to tubule
Osmosis: osmodilution & osmoconcerntation
In the kidney's nephrons, what is the primary structure for osmoregulation?
The loop of Henle (Countercurrent multiplication)
Loop of Henle's length is dependant on...?
How concentrated the animal's urine needs to be (eg. desert animals have a very long one - due to the fact that their urine needs to be
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