Carrying Capacity

Key Questions

• One of ways to understand how many organisms can grow in an ecosystem is to look at the very basics.

You have seen and heard about ecosystems as expressed a pyramid: a large base with layers above that are smaller and smaller.

The base of all ecosystems are the producers or what we call plants such as trees, grass, shrubs, herbs and algae. These use sunlight and carbon dioxide and water to make food for their growth, reproduction and repair.

Of all of the production made by those producers, only 10% is left over for the second level of the pyramid.

The second level eats or consumes that 10% of first level and these are called primary consumers or herbivores (herb eaters).
After using the food from the first level for growth, reproduction and repair, only 10% of that first 10% is available for the next level.

That gives the last level 1% from that first level to grow, reproduce and repair. This third level contains secondary consumers.

Each step up the pyramid, the number that can be supported is reduced by 90%. Fewer herbivores, then even fewer carnivores.
Most ecosystems can only support 4 levels.
Only two can support 5: tropical and temperate rainforests.

The carrying capacity is the overall frequency that habitat can sustain, which is inhibited by the limiting factor

Explanation:

Carrying Capacity is the total frequency of individuals within a community a habitat can sustain.

Limiting Factors are biotic or abiotic factors which limit the carrying capacity.

For example, within a population of foxes, there is enough space and water for 20 individuals. However, the population of rabbits has decreased and now can only sustain 15 individual foxes.

In this circumstance, the limiting factor is the available food (rabbits) for the foxes, and thus the carrying capacity is 15 foxes.

Carrying capacity is the maximum population size of a species that the environment can sustain indefinitely given available resources.

Explanation:

Carrying capacity is the maximum sustainable population of a species the environment can sustain for an indefinite period of time given available resources. This is the point where the population theoretically cannot grow any larger and it is not growing any larger.

For functional purposes, carrying capacity will typically be an upper limit, but certain circumstances can temporarily take a population above this (though the population will decrease sharply thereafter).

Carrying capacity is determined and affected by a number of variables. The total geographic space available to a species determines the population number, but so does the amount of energy available for that species to consume. Interactions with other species, including humans, will also affect carrying capacity.

Carrying capacity can be increased by the amount of food available, the local extinction of a competitor, an increase in species fertility, a decrease in predation, an increase in the amount of habitat available for use, and adaptations to the environment, such as resistance to disease or adaptations that serve to decrease the amount of energy spent on obtaining food.

Carrying capacity can be decreased by disease, an increase in predation, hunting or harvesting by humans, a decrease in available habitat such as habitat destruction by humans, parasites, competition with another species for a resource, or changes in the weather that make the species less suited to the environment.

A similar question was answered here in the calculus section of Socratic.