Interactions Among Organisms
● Examples include competition, mutualism, commensalism, and parasitism.
● Competition can be among the members of the same or different species and usually occurs with organisms that share the same niche.
● An ecological niche refers to the role of an organism in its environment including type of food it eats, how it obtains its food and how it interacts with other organisms.
● Two species with identical ecological niches cannot coexist in the same habitat. Competition usually results in a decrease in the population of a species less adapted to compete for a particular resource.
● If the population of one or other of the symbiotic organisms becomes unbalanced, the populations of both organisms will fluctuate in an uncharacteristic manner.
** Symbiotic relationships include parasitism, mutualism, and commensalism.
● Some parasites live within the host, such as tape worms, heartworms, or bacteria. Some parasites feed on the external surface of a host, such as aphids, fleas, or mistletoe.
● The parasite-host populations that have survived have been those where neither has a devastating effect on the other.
● Parasitism that results in the rapid death of the host is devastating to both the parasite and the host populations.
● It is important that the host survive and thrive long enough for the parasite to reproduce and spread
● For example, bacteria, which have the ability to digest wood, live within the digestive tracts of termites; plant roots provide food for fungi that break down nutrients the plant needs.
● For example, barnacles that attach to whales are dispersed to different environments where they can obtain food and reproduce; burdock seeds that attach to organisms and are carried to locations where they can germinate.
Predator- Prey relationships
● Fluctuations in predator–prey populations are predictable. At some point the prey population grows so numerous that they are easy to find. A graph of predator–prey density over time shows how the cycle of fluctuations results in a stable ecosystem. ● As the prey population increases, the predator population increases.
● As the predator population increases, the prey population decreases.