​Any part of the physical environment that affects living organisms.

abiotic factor

​The vertical volume of water in the ocean.

water column

​The weight of water pushing down on organisms in deep areas of the oceans.

hydrostatic pressure

An area that provides an organism with its basic needs for survival.

​​habitat

A biological community of interacting organisms and their physical environment.

​​ecosystem

An organism that can tolerate a wide range of temperatures.

​​eurythermal

​An organism that can tolerate a narrow range of temperatures.

​​stenothermal

An organism that can tolerate a wide range of salinities.

​​euryhaline

An organism that can tolerate a narrow range of salinities.

​​stenohaline

The transfer of material from a region of high concentration to regions of lower concentration.

​​diffusion

The movement of water through a membrane to equalize solutions on either side of the membrane.

​​osmosis

​The solute concentration is higher than that inside of the cell, causing a net flow of water out of the cell.

hypertonic

There is no net flow of water into or out of the cell because the solute concentration is the same outside as inside the cell.

isotonic

​The solute concentration is lower than that inside of the cell, causing a net flow of water into the cell.

hypotonic