Density dependence
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| - | '''Intraspecific competition''' is an interaction in [[population ecology]], whereby members of the same [[species]] compete for limited resources. This leads to a reduction in [[Fitness (biology)|fitness]] for both individuals. By contrast, [[interspecific competition]] occurs when members of different species compete for a shared resource. Members of the same species have very similar resources requirements whereas different species have a [[Ecological niche|smaller contested resource overlap]], resulting in intraspecific competition generally being a stronger force than interspecific competition. | + | In [[population ecology]], '''density-dependent''' processes occur when [[population growth rate]]s are regulated by the density of a [[population]]. |
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| - | Individuals can compete for [[Resource (biology)|food, water, space, light, mates or any other resource which is required for survival]] or reproduction. The resource must be limited for competition to occur; if every member of the species can obtain a sufficient amount of every resource then individuals do not compete and the population grows exponentially. [[Exponential growth]] is very rare in nature because resources are finite and so not every individual in a population can survive, leading to intraspecific competition for the scarce resources. | + | |
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| - | When resources are limited, an increase in population size reduces the quantity of resources available for each individual, reducing the per capita fitness in the population. As a result, the growth rate of a population slows as intraspecific competition becomes more intense, making it a [[Density dependence#Negative density-dependence|negatively density dependent]] process. The falling population growth rate as population increases can be modelled effectively with the [[Logistic function#In ecology: modeling population growth|logistic growth model]]. The rate of change of population density eventually falls to zero, the point ecologists have termed the [[carrying capacity]] (''K''). The carrying capacity of a population is the maximum number of individuals that can live in a population stably; numbers larger than this will suffer a negative population growth until eventually reaching the carrying capacity, whereas populations smaller than the carrying capacity will grow until they reach it. | + | |
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| - | Intraspecific competition doesn't just involve direct interactions between members of the same species (such as male deer locking horns when competing for mates) but can also include [[Competition (biology)#By mechanism|indirect interactions]] where an individual depletes a shared resource (such as a grizzly bear catching a salmon that can then no longer be eaten by bears at different points along a river). | + | |
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| - | The way in which resources are partitioned by organisms also varies and can be split into [[Scramble competition|scramble]] and contest competition. Scramble competition involves a relatively even distribution of resources among a population as all individuals exploit a common resource pool. In contrast, contest competition is the uneven distribution of resources and occurs when [[Dominance hierarchy|hierarchies]] in a population influence the amount of resource each individual receives. Organisms in the most prized [[Territory (animal)|territories]] or at the top of the hierarchies obtain a sufficient quantity of the resources, whereas individuals without a territory don’t obtain any of the resource. | + | |
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| - | ==See also== | + | |
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| - | *[[Competition (biology)]] | + | |
| - | *[[Interspecific competition]] | + | |
| - | *[[Logistic function#In ecology: modeling population growth|Logistic model]] | + | |
| - | *[[Population ecology]] | + | |
| - | *[[Sexual dimorphism]] | + | |
| - | *[[Sexual selection]] | + | |
| - | *[[War]] – extreme result of intraspecific competition in [[humans]] | + | |
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In population ecology, density-dependent processes occur when population growth rates are regulated by the density of a population.
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