POP: Lesson - Population Growth and Resource Availability (Topic 3.5) š
ā³ Estimated Reading/Watching Time: 4 - 6 minutes
Explain how resource availability affects population growth.
Population Growth
Population growth curves are graphs of how populations grow. Populations tend to experience characteristic patterns. We will discuss the five most common patterns of population growth in this lesson. Read through the presentation below to learn more about the types of population growth.
When the resources needed by a population for growth are abundant, population growth usually accelerates.
When the resource base of a population shrinks, the increased potential for unequal distribution of resources will ultimately result in increased mortality, decreased fecundity, or both, resulting in population growth declining to, or below, carrying capacity.
Limits on Population Growth
As we've seen, there are different types of population growth. And even in populations that seem to grow without limit (exponential growth), they eventually reach their carrying capacity (K). The factors that limit population growth are called limiting factors, and these limiting factors determine the carrying capacity of the environment.
Environmental resistance refers to the limiting factors that inhibit the growth of a population. For example, too little water for plants or animals is an abiotic factor that would inhibit the growth of a population. An inability to hide from predators would be a biotic factor that would inhibit growth.
When a deer population grows two things can happen:
- predators will increase in abundance because their food source has increased, OR
- the habitat will become crowded, causing disease to become more prevalent in the population and food to grow scarce.
Both of these options are environmental resistance factors for the deer population, causing the deer population numbers to decrease. When some members of the population have died, there will be more resources available for the surviving deer, increasing their biotic potential. If they can keep from growing too quickly, they can maintain a relatively stable population size, where biotic potential and environmental resistance are balanced.
Environmental resistance factors and biotic potential can be likened to a sliding scale. When one is high, the other will be low. It is not often that both environmental resistance and biotic potential are in equilibrium.
When the resources needed by a population for growth are abundant, population growth usually accelerates. When the resource base of a population shrinks, the reduction of resources will ultimately result in increased mortality, decreased fecundity, or both, resulting in population growth declining to, or below, carrying capacity, as seen in our deer example above.
Population growth is limited by environmental factors, especially by the available resources and space.
Resource availability and the total resource base are limited and finite over all scales of time.
You should know that abundant resources will cause a population's growth rate to increase. A reduction in resources will cause the growth rate to decline.
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