Describe the competitive exclusion principle, and explain how competitive exclusion may affect community structure.

Answer and Explanation:

The principle of competitive exclusion says that two different species that share the same niche in the same habitat can not coexist in a stable way. This is because species with identical niches have the same necessities, which means that they will compete for the same resources. If these species have the same requirements, they can not coexist.

When two competing species coexist, this is because one of the species evolved and uses a different resource, occupies a different area or makes use of the resources at different times during the day. The result of these changes is that the species involved use different niches, a process known as niche partitioning or niche differentiation. Niche specialization might produce genotypic separation that provokes that the subpopulations of a species diverge to a completely new species.

Two species can not coexist indefinitely on the bases of the same limited resource. Exclusion occurs when the effective niche of the dominant competitor entirely fills the fundamental niche of the inferior competitor. If there is not any differentiation between them or the habitat makes it impossible to differentiate, the dominant species displaces the weak species, monopolizing the resources. The other weaker species makes use of new resources, migrates or gets extinguished.  

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.