Phenotypic plasticity is the ability of an organism

Organism

In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

 to change its phenotype

Phenotype

A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...

 in response to changes in the environment

Environmental change

Environmental change is defined as a change or disturbance of the environment by natural ecological processes, and is described in the following articles:*Climate change*Environment...

. Such plasticity in some cases expresses as several highly morphologically distinct results; in other cases, a continuous norm of reaction describes the functional interrelationship of a range of environments to a range of phenotypes. The term was originally conceived in the context of development

Morphogenesis

Morphogenesis , is the biological process that causes an organism to develop its shape...

, but is now more broadly applied to include changes that occur during the adult life of an organism, such as behaviour.

Organisms may differ in the degree of phenotypic plasticity they display when exposed to the same environmental change. Hence, phenotypic plasticity can evolve and be adaptive if fitness is increased by changing phenotype.
In general, sustained directional selection

Directional selection

In population genetics, directional selection is a mode of natural selection in which a single phenotype is favored, causing the allele frequency to continuously shift in one direction...

 is predicted to increase plasticity in that same direction.

Some responses will be similar in all organisms, for example in organisms that do not thermoregulate, as temperatures change lipids in the cell membrane must be altered by creating more double bonds (when temperatures decrease) or removing them (when temperatures increase).

Generally phenotypic plasticity is more important for immobile organisms (e.g. plant

Plant

Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s) than mobile organisms (e.g. animal

Animal

Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s). This is because immobile organisms must adapt to their environment or they will die, whereas mobile organisms are able to move away from a detrimental environment. Examples of phenotypic plasticity in plants include the allocation of more resources to the root

Root

In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...

s in soils that contain low concentrations of nutrients

Plant nutrition

'Plant Nutrition is the study of the chemical elements that are necessary for growth. In 1972, E. Epstein defined 2 criteria for an element to be essential for plant growth:# in its absence the plant is unable to complete a normal life cycle or...

 and the alteration of leaf

Leaf

A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

 size and thickness. The transport proteins present in roots are also changed depending on the concentration of the nutrient and the salinity of the soil. Some plants, Mesembryanthemum crystallinum

Mesembryanthemum crystallinum

Mesembryanthemum crystallinum is a prostrate succulent plant that is native to Africa, Western Asia and Europe. The plant is covered with large, glistening bladder cells, reflected in its common names of Common Ice Plant, Crystalline Iceplant or Iceplant.-Uses:Its leaves are edible, as with some...

for example, are able to alter their photosynthetic pathways to use less water when they become water- or salt-stressed. Nevertheless, some mobile organisms also have significant phenotypic plasticity, for example Acyrthosiphon pisum of the [Aphid] family exhibits the ability to interchange between asexual and sexual reproduction, as well as growing wings between generations when plants become too populated.

In epidemiology

Epidemiology

Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...

, there exists a theory that rising incidences of coronary heart disease

Coronary heart disease

Coronary artery disease is the end result of the accumulation of atheromatous plaques within the walls of the coronary arteries that supply the myocardium with oxygen and nutrients. It is sometimes also called coronary heart disease...

 and type II diabetes in human populations undergoing industrialization is due to a mismatch between a metabolic phenotype determined in development and the nutritional environment to which an individual is subsequently exposed. This is known as the 'thrifty phenotype

Thrifty phenotype

The thrifty phenotype hypothesis says that reduced fetal growth is strongly associated with a number of chronic conditions later in life. This increased susceptibility results from adaptations made by the fetus in an environment limited in its supply of nutrients...

' hypothesis.

See also

• Acclimation
• Baldwin effect
  Baldwin effect
  The Baldwin effect, also known as Baldwinian evolution or ontogenic evolution, is a theory of a possible evolutionary processes that was originally put forward in 1896 in a paper, "A New Factor in Evolution," by American psychologist James Mark Baldwin. The paper proposed a mechanism for specific...
  
  
• Developmental biology
  Developmental biology
  Developmental biology is the study of the process by which organisms grow and develop. Modern developmental biology studies the genetic control of cell growth, differentiation and "morphogenesis", which is the process that gives rise to tissues, organs and anatomy.- Related fields of study...
  
  
• Evolutionary physiology
  Evolutionary physiology
  Evolutionary physiology is the study of physiological evolution, which is to say, the manner in which the functional characteristics of individuals in a population of organisms have responded to selection across multiple generations during the history of the population.It is a subdiscipline of both...
  
  
• Beneficial acclimation hypothesis
  Beneficial acclimation hypothesis
  The Beneficial Acclimation Hypothesis is the physiological hypothesis that acclimating to a particular environment provides an organism with advantages in that environment...
  
  
• Allometric engineering
  Allometric engineering
  Allometric engineering is the process of experimentally shifting the scaling relationships of a population. More specifically, the process of experimentally breaking the tight covariance evident among component traits of a complex phenotype by altering the variance of one trait relative to another....
  
  

External links

• Special issue of the Journal of Experimental Biology concerning phenotypic plasticity
• Massimo Pigliucci’s Evolutionary Ecology Lab web page
• Developmental Plasticity and Evolution - review of the book from American Scientist
• Isidro T. Savillo's Impermanence of Sexual Phenotypes from Biologybrowser (Thomson Reuters)