This is an interaction in population ecology where members of the same species compete for limited resources. This leads to a decrease in the fitness of both individuals, but the more adapted individual survives and is able to reproduce. In contrast, interspecific competition occurs when members of different species compete for a common resource. Members of the same species have fairly similar resource requirements, while different species have fewer resources in competition, so intraspecific competition is usually a stronger force than interspecific competition. Individuals may compete for food, water, space, light, mates or any other resource needed for survival or reproduction. For competition to occur, the resource must be limited; if each member of a species can get enough of each resource, then individuals will not compete and the population will grow exponentially. Sustained exponential growth is rare in nature because resources are finite and therefore not every individual in the population can survive, leading to intraspecific competition for scarce resources. When resources are limited, an increase in population size reduces the amount of resources available to each individual, thereby reducing the fitness of the population per capita. As a result, the population growth rate slows down as intraspecific competition increases, making this process negatively dependent on density. Environmental resources are limited and not infinite. The environment can only support a certain number of individuals before its resources are completely exhausted. Populations that exceed this limit will suffer negative population growth until they reach throughput, while populations that are smaller than throughput will grow until they reach throughput. Intraspecific competition involves not only direct interactions between individuals of the same species, but can also involve indirect interactions when an individual depletes a common resource. The way in which organisms allocate resources also varies and can be divided into fight and competitive competition. Fighting competition involves a relatively equal distribution of resources among the population, as all individuals use a common pool of resources. In contrast, rivalry is an unequal distribution of resources that occurs when hierarchies in a population affect the amount of resources each individual receives. Organisms in the most valuable territories, or at the top of the hierarchy, receive a sufficient amount of resources, while individuals without territories receive no resources.