Water Balance 2/19

Osmoregulation

The regulation of osmotic pressure and water content in an organism to maintain homeostasis.

Evolutionary Adaptation

Occurs over multiple generations; an example is birds evolving insulating down feathers for cold climates.

Physiological/Behavioral Adjustment

Happens within an individual’s lifetime and is reversible; an example is a bird fluffing its feathers to retain heat.

Ectotherms

Organisms that rely on external heat sources, such as reptiles basking in the sun.

Endotherms

Organisms that generate internal heat through metabolism, such as mammals shivering to generate heat.

Countercurrent Heat Exchange

A mechanism found in birds and marine mammals that reduces heat loss and saves energy in cold environments.

Water Potential (Ψ)

Measures the tendency of water to move from one area to another, moving from HIGH Ψ to LOW Ψ.

Osmoconformers

Organisms that match body fluid osmolarity to the environment, such as marine invertebrates.

Osmoregulators

Organisms that maintain constant internal osmolarity despite external changes, like freshwater and terrestrial animals.

Na⁺/K⁺ pump

A mechanism in animal cells that pumps sodium out and potassium in to prevent excessive water intake.

Turgor Pressure

The pressure created by water entering plant cells that helps keep the plant upright.

Plasmolysis

Plants lose turgor pressure when the environment is hypertonic, cells lose water and shrink, Causing them to wilt

Hyperosmotic

A condition referring to freshwater fish, which are constantly gaining water by osmosis.

Hypoosmotic

A condition referring to marine fish, which constantly lose water by osmosis.

Seawater Survival in Marine Birds

Marine birds drink seawater and survive due to specialized salt glands that excrete excess salt.

Water-Saving Adaptations

Adaptations in land animals such as impermeable surfaces and efficient waste systems to minimize water loss.

Hypertonic outside cell

concentrated solutes on outside of cell

Hypotonic outside cell

dilute solutes on outside of cell