Interspecific competition occurs when there is a limiting resource that both species require. Lions and
hyenas occupy the same ecological niche and compete for the same prey.
tation competition occurs when one species more efficiently utilizes a limiting resource than another species
does. Some common examples of exploitation competition include lion and cheetah populations competing for
gazelles at the same time, or two species of shrubs competing for soil nutrients and water. Interspecific competition, particularly exploitation competition, can alter the
composition of the community and can temporarily or
sometimes permanently impact the availability of the
limiting resource.
Parasitism
At least half of the species on our planet are symbionts, or organisms that live in conjunction with another
organism. The majority of these relationships are parasitic, where the parasite consumes the tissues or robs the
resources of the host organism. In some cases, the parasite is a pathogen, causing disease in the host species.
There are many common examples of parasites impacting a human host such as head and body lice, tapeworms,
scabies, and ticks. Parasitic species that live on the surface
of their host are called ectoparasites. Many fungal and
insect ectoparasites attack crop and horticultural species,
causing significant amounts of damage. Athlete’s foot,
mites, fleas, and ticks are commonly found living on the
surface tissues of animals.
Endoparasites are parasitic species that live inside
their host organism and feed on the host organism or
rob the host of nutrients. Many human bacterial diseases are the result of parasites, including tuberculosis,
which is cause by the species Mycobacterium tuberculosis, and the bubonic plague, caused by the bacterium
Yersinia pestis. Endoparasites are relatively protected
from the external environment by their host species
and are provided with a constant source of food (usually the host’s tissue), but they are at constant risk
from attack by the host organism’s immune system.
Both types of parasitism and any accompanying disease
can greatly impact the ecological function of a species.
Parasites can serve as population regulation controls, removing the weakest members in a population, and can
weaken the defenses of an organism such that it loses a
competitive advantage or can make an organism, population, or species more vulnerable to predation or additional disease.
Amensalism
A relationship between organisms of two different
species in which one is unaffected and the other is negatively impacted by the association is called amensalism.
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