Density dependent inhibition
Encyclopedia
In population ecology
, density-dependent inhibition describes a situation in which population growth
is curtailed by crowding, predators and competition. In cell biology
, it describes the reduction in cell
division. When a cell population
reaches a certain density, the amount of required growth factor
s and nutrient
s available to each cell becomes insufficient to allow continued cell growth
.
This is also true for other organisms because an increased density means an increase in intraspecific competition
. Greater competition means an individual has a decreased contribution to the next generation i.e. offspring.
Density dependent mortality can be overcompensating, undercompensating or exactly compensating.
Density dependent fecundity
also exists, where the birth rate falls as competition increases.
There also exists density-independent inhibition, where other factors such as weather
or environmental conditions and disturbances may affect a population's carrying capacity
.
An example of a density dependent variable is crowding and competition.
Population ecology
Population ecology is a sub-field of ecology that deals with the dynamics of species populations and how these populations interact with the environment. It is the study of how the population sizes of species living together in groups change over time and space....
, density-dependent inhibition describes a situation in which population growth
Population growth
Population growth is the change in a population over time, and can be quantified as the change in the number of individuals of any species in a population using "per unit time" for measurement....
is curtailed by crowding, predators and competition. In cell biology
Cell biology
Cell biology is a scientific discipline that studies cells – their physiological properties, their structure, the organelles they contain, interactions with their environment, their life cycle, division and death. This is done both on a microscopic and molecular level...
, it describes the reduction in cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
division. When a cell population
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...
reaches a certain density, the amount of required growth factor
Growth factor
A growth factor is a naturally occurring substance capable of stimulating cellular growth, proliferation and cellular differentiation. Usually it is a protein or a steroid hormone. Growth factors are important for regulating a variety of cellular processes....
s and nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...
s available to each cell becomes insufficient to allow continued cell growth
Cell growth
The term cell growth is used in the contexts of cell development and cell division . When used in the context of cell division, it refers to growth of cell populations, where one cell grows and divides to produce two "daughter cells"...
.
This is also true for other organisms because an increased density means an increase in intraspecific competition
Intraspecific competition
Intraspecific competition is a particular form of competition in which members of the same species vie for the same resource in an ecosystem...
. Greater competition means an individual has a decreased contribution to the next generation i.e. offspring.
Density dependent mortality can be overcompensating, undercompensating or exactly compensating.
Density dependent fecundity
Fecundity
Fecundity, derived from the word fecund, generally refers to the ability to reproduce. In demography, fecundity is the potential reproductive capacity of an individual or population. In biology, the definition is more equivalent to fertility, or the actual reproductive rate of an organism or...
also exists, where the birth rate falls as competition increases.
There also exists density-independent inhibition, where other factors such as weather
Weather
Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...
or environmental conditions and disturbances may affect a population's carrying capacity
Carrying capacity
The carrying capacity of a biological species in an environment is the maximum population size of the species that the environment can sustain indefinitely, given the food, habitat, water and other necessities available in the environment...
.
An example of a density dependent variable is crowding and competition.