Final answer:
The matching of ionic concentration in blood plasma to that of the external environment is known as ionic conformity. It is distinct from ionic regulation, which is the organism’s active control over internal ion concentrations to maintain osmotic balance.
Step-by-step explanation:
The matching of ionic concentration in blood plasma to the ionic concentration of the external environment is known as ionic conformity. This term refers to organisms that do not regulate the ionic concentration of their body fluids, but instead match it to their environment. In contrast, ionic regulation refers to the active management of electrolyte levels within an organism's body fluids, such as blood plasma, interstitial fluid, and intracellular fluid.
Osmoregulation is critical in maintaining osmotic balance, and involves processes that ensure proper hydration, electrolyte levels, and acid-base balance, through the movement of water and ions across semi-permeable membranes, influenced by osmotic pressure. This balance protects cells by ensuring that environmental conditions do not lead to excessive swelling or shrinkage due to water influx or efflux, maintaining isotonic conditions.