Biotic Potential And Environmental Resistance 2b431u

BIOTIC POTENTIAL AND ENVIRONMENTAL RESISTANCE Biotic Potential This is the maximum rate at which the population of a given species can increase when there are no limits on its rate of growth. Species vary in their biotic potential or capacity for population growth under ideal conditions. Generally, populations of species with large individuals, such as elephants and blue whales, have a low biotic potential while those of small individuals, such as bacteria and insects, have a high biotic potential. The intrinsic rate of increase (r) is the rate at which the population of a species would grow if it had unlimited resources. Individuals in populations with a high intrinsic rate of growth typically reproduce early in life, have short generation times (the time between successive generations), can reproduce many times, and have many offspring each time they reproduce. Some species have an astounding biotic potential. With no controls on population growth, a species of bacteria that can reproduce every 20 minutes would generate enough offspring to form a layer 0.3 meter (1 foot) deep over the entire earth’s surface in only 36 hours! Fortunately, this is not a realistic scenario. Research reveals that no population can grow indefinitely because of limitations on resources and competition with populations of other species for those resources. In the real world, a rapidly growing population reaches some size limit imposed by one or more limiting factors, such as light, water, space, or nutrients, or by exposure to too many competitors, predators, or infectious diseases. There are always limits to population growth in nature. Environmental Resistance This is all of the limiting factors that act together to limit the growth of a population. Together, biotic potential and environmental resistance determine the carrying capacity (K): the maximum population of a given species that a particular habitat can sustain indefinitely without being degraded. The growth rate of a population decreases as its size nears the carrying capacity of its environment because resources such as food, water, and space begin to dwindle.

Example of Biotic Potential  

Rabbits – an organism with a high biotic potential Doles vs. humans

Example of Environmental Resistance 

Predation by coyotes is an environmental resistance o Factor to rabbit population

Environmental resistance can be classified into two broad categories  Density – independent factors  Density – dependent factors Biotic Potential  Biotic potential refers to unrestrained biological reproduction of offspring if their reproduction is unrestrained. Constraints include:  Scarcity of resources  Competition  Predation  Disease