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In biology and ecology, a resource is a substance or object in the environment required by an organism for normal growth, maintenance, and reproduction. Resources can be consumed by one organism and, as a result, become unavailable to another organism. [1] [2] [3] For plants key resources are light, nutrients, water, and space to
Natural resources can be a substantial part of a country's wealth; [7] however, a sudden inflow of money caused by a resource extraction boom can create social problems including inflation harming other industries ("Dutch disease") and corruption, leading to inequality and underdevelopment, this is known as the "resource curse".
Earth materials are vital resources that provide the basic components for life, agriculture and industry. [1] [2] [3] Oceanic-continental convergence resulting in subduction and volcanic arcs illustrates one effect of plate tectonics. Cross-cutting relations can be used to determine the relative ages of rock strata and other geological structures.
Most IGCSE subjects offer a choice of tiered examinations: Core or Extended papers (in Cambridge International), and Foundation or Higher papers (in Edexcel). This is designed to make IGCSE suitable for students with varying levels of ability. In some subjects, IGCSE can be taken with or without coursework.
Oceans often act as renewable resources. Sawmill near Fügen, Zillertal, Austria Global vegetation. A renewable resource (also known as a flow resource [note 1] [1]) is a natural resource which will replenish to replace the portion depleted by usage and consumption, either through natural reproduction or other recurring processes in a finite amount of time in a human time scale.
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 negatively density dependent process.
Resource competition can vary from completely symmetric (all individuals receive the same amount of resources, irrespective of their size, known also as scramble competition) to perfectly size symmetric (all individuals exploit the same amount of resource per unit biomass) to absolutely size asymmetric (the largest individuals exploit all the available resource).
where N j is the density of species j, R is the density of the resource, a is the rate at which species j eats the resource, d is species js death rate, and r is the rate at which resources grow when not consumed. It is easy to show that when species j is at equilibrium by itself (i.e., dN j /dt = 0), that the equilibrium resource density, R* j, is