1.3+Carrying+Capacity

=Carrying Capacity=



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The carrying capacity is the size of a population that can live indefinitely using the resources available where that population lives. For example, consider an island onto which is dropped a colony of rabbits. As long as there is an adequate supply of food and water, the rabbits will not only survive but they will reproduce and the colony will get larger. The rabbit population can continue to grow as long as food and water are adequate. However, if at some point, there are more rabbits that there is food to feed them, then the rabbit population will start to decline.

This limit is called the carrying capacity. Carrying capacity is not a fixed number; it depends upon factors such as how much each rabbit eats, how fast the food grows, and how well the natural systems of the island can handle the waste produced by the rabbits. Obviously, in a drought year less food would grow and the island would support fewer rabbits. In good years, the island would support more rabbits.

The earth is our island. We have an advantage over the rabbits in that we have developed technology to grow, process, and store food so that we can survive the bad years. We have also developed technologies for handling wastes that we create. However, there is still a carrying capacity that the earth can support. That carrying capacity is a function of the number of people, the amount of resources each person consumes and the ability of the earth to process all the wastes produced. Sustainability is about finding the balance point among population, consumption, and waste assimilation



**Biotic potential** This is the maximum [|reproductive] capacity of a [|population] if resources are unlimited. Full expression of the biotic potential of an organism is restricted by [|environmental resistance], any condition that inhibits the increase in number of the population. It is generally only reached when environmental conditions are very favorable. A species reaching its biotic potential would exhibit exponential [|population growth] and be said to have a high [|fertility], that is, how many offspring are produced per mother. Biotic Potential is a fundamental species characteristic, defined by Chapman (1925) as "the inherent power of organisms to reproduce and survive". In 1931, Chapman redescribed it as: "It is a sort of algebraic sum of the number of young produced at each reproduction, number of reproductions over a period of time, sex ratio of the species, and their general ability to survive under given physical conditions  § Reproductive potential - potential [|natality] : It is the upper limit to biotic potential (in the absence of mortality)  § Survival potential: Because reproductive potential does not account for the number of gametes surviving, survival potential is a necessary component of biotic potential; it is the [|reciprocal] of [|mortality] (in the absence of mortality, biotic potential = reproductive potential) Chapman identified two components:  § nutritive potential - the ability to acquire and utilize food for growth and energy <span style="display: block; line-height: 150%; margin-bottom: 1.2pt; margin-left: 0.25in; text-align: justify; text-indent: -0.25in;"> § <span style="font-family: 'Times New Roman',serif; font-size: 12pt; line-height: 150%;">protective potential - potential ability of the organism to protect itself against the dynamic forces of the environment <span style="display: block; line-height: 150%; margin-bottom: 1.2pt; margin-left: 0.5in; text-align: justify; text-indent: -0.25in;"> § <span style="font-family: 'Times New Roman',serif; font-size: 12pt; line-height: 150%;">assuring successful fertilization (mating) <span style="display: block; line-height: 150%; margin-bottom: 1.2pt; margin-left: 0.5in; text-align: justify; text-indent: -0.25in;"> § <span style="font-family: 'Times New Roman',serif; font-size: 12pt; line-height: 150%;">care of young <span style="display: block; line-height: 150%; margin-bottom: 1.2pt; margin-left: 0.5in; text-align: justify; text-indent: -0.25in;"> § <span style="font-family: 'Times New Roman',serif; font-size: 12pt; line-height: 150%;">Graham Moss = **Environmental Resistance** = The effect of physical and biological factors in preventing a species from reproducing at its maximum rate. <span style="font-family: 'Times New Roman',serif; font-size: 12pt; line-height: 115%;"> [|Factors] in an [|environment] such as predators, [|competition], [|climate] , and [|food] [|availability] , that keep its various [|populations] from reaching their maximum [|growth] potential

=Exponential Growth Curve=



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