Bacteria
Marine Animals
Freshwater Animals
Temporary water animals
Protist
- Ex: In Paramecium caudatum the environment is hypotonic to the cell, this means that water will continuously try to enter the P.caudatum. To prevent this and keep homeostasis, the P. caudatum has a vacuole that pumps water out as soon as it gets in by osmosis.
Marine Animals
- Most marine invertebrates are osmoconformers, this means that their osmolarity is the same as the seawater around them.
- Some marine invertebrates and vertebrates are osmoregulators, meaning that they control their internal osmolarity based on the environment. Since the seawater has more solute their the fish’s blood, to prevent dehydration some fish will drink large amounts of water and have specialized kidneys and gills.
Freshwater Animals
- The environment is hypotonic to the animal’s body fluids causing a problem for the species. They will either gain water by osmosis or lose salts by diffusion.
- Many fish solve this problem by barely drinking any water and excreting large amounts of dilute urine.
- Salts lost by diffusion or urine are replenished by eating
Temporary water animals
- Some animals are anhydrobiosis (live without water). They enter a dormant state when they don’t have any water and with water they are active.
- Ex: tardigrades
Protist
- Have a cell wall, so when the cell is placed in a hypotonic solution water will enter and if there comes a point where the cell cannot take anymore water (turgor pressure) the cell becomes turgid.
- If the environment is isotonic(no net diffusion) to the cell, then the cell will become flaccid.
- If the environment is hypertonic to the cell, the cell will shrink and plasmolyze (cell shrinks which causes the plasma membrane to pull away from the wall).