Enduring Understanding 2D

Growth and dynamic homeostasis of a biological system are influenced by changes in the system’s environment.

All biological systems, from cells to ecosystems, are influenced by complex biotic and abiotic interactions. The availability of resources influences activities in cells and organisms; examples include responses to cell density, biofilm(s) formation, temperature responses, and responses to nutrient and water availability. The availability of resources affects a population’s stability in size and its genetic composition; examples include birth rates versus death rates from bacteria to mammals and global distribution of food for humans.

Homeostatic mechanisms reflect both continuity due to common ancestry and change due to evolution in different environments. Supporting evidence includes a sampling of homeostatic control systems that are conserved across biological domains. Organisms have evolved various mechanisms for obtaining nutrients and getting rid of wastes, including gas exchange, osmoregulation and nitrogenous waste production. Disturbances to dynamic homeostasis effect biological processes, and plants and animals have evolved a variety of defenses against infections and other disruptions to homeostasis including immune responses. At the ecosystem level, disruptions impact the balance of the ecosystem and the interactions between specific organisms therein.