equilibrium

Examples of equilibrium in the following topics:

• Varying Rates of Speciation

  • Two patterns are currently observed in the rates of speciation: gradual speciation and punctuated equilibrium.
  • In terms of how quickly speciation occurs, two patterns are currently observed: the gradual speciation model and the punctuated equilibrium model.
  • This early change model is called punctuated equilibrium, because it begins with a punctuated or periodic change and then remains in balance afterward.
  • While punctuated equilibrium suggests a faster tempo, it does not necessarily exclude gradualism .
  • In (b) punctuated equilibrium, species diverge quickly and then remain unchanged for long periods of time.

• Balance and Determining Equilibrium

  • With hair cells in the inner ear that sense linear and rotational motion, the vestibular system determines equilibrium and balance states.
  • Along with audition, the inner ear is responsible for encoding information about equilibrium, or the sense of balance.

• Ecological Succession

  • Communities with a stable structure are said to be at equilibrium.
  • Following a disturbance, the community may or may not return to the equilibrium state.
  • Over time, the area will reach an equilibrium state with a set of organisms quite different from the pioneer species.
  • Eventually, over 150 years, the forest will reach its equilibrium point where species composition is no longer changing and resembles the community before the fire.
  • This equilibrium state is referred to as the climax community, which will remain stable until the next disturbance.

• Ecosystem Dynamics

  • Equilibrium is the steady state of an ecosystem where all organisms are in balance with their environment and with each other.
  • Resistance is the ability of an ecosystem to remain at equilibrium despite disturbances.
  • Resilience is the speed at which an ecosystem recovers to equilibrium after being disturbed.
  • In these cases, external human influences can lead to the complete destruction or irreversible altering of the ecosystem equilibrium.
  • In this example, the forests became less and less resilient over time until the fundamental system equilibrium had changed.

• Regulatory Mechanisms for Cellular Respiration

  • Reactions that are catalyzed by only one enzyme can go to equilibrium, stalling the reaction.
  • In contrast, if two different enzymes (each specific for a given direction) are necessary for a reversible reaction, the opportunity to control the rate of the reaction increases and equilibrium is not reached.

• Hardy-Weinberg Principle of Equilibrium

  • When populations are in the Hardy-Weinberg equilibrium, the allelic frequency is stable from generation to generation and the distribution of alleles can be determined.If the allelic frequency measured in the field differs from the predicted value, scientists can make inferences about what evolutionary forces are at play.

• Nerve Impulse Transmission within a Neuron: Resting Potential

  • The resting membrane potential is at equilibrium since it relies on the constant expenditure of energy for its maintenance.
  • As potassium is also the ion with the most-negative equilibrium potential, usually the resting potential can be no more negative than the potassium equilibrium potential.
  • If the membrane were equally permeable to all ions, each type of ion would flow across the membrane and the system would reach equilibrium.

• Free Energy

  • In a living cell, chemical reactions are constantly moving towards equilibrium, but never reach it.
  • A living cell is an open system: materials pass in and out, the cell recycles the products of certain chemical reactions into other reactions, and chemical equilibrium is never reached.
  • In this way, living organisms are in a constant energy-requiring, uphill battle against equilibrium and entropy.
  • An important concept in the study of metabolism and energy is that of chemical equilibrium.

• Homeostatic Process

  • Homeostasis, in a general sense, refers to stability, balance, or equilibrium.
  • The ultimate goal of homeostasis is the maintenance of equilibrium around the set point.

• Modeling Ecosystem Dynamics

  • These models predict how ecosystems recover from disturbances, returning to a state of equilibrium.
  • As most ecosystems are subject to periodic disturbances and are often in a state of change, they are usually either moving toward or away from multiple equilibrium states.