Competition is best defined as a process in which the fitness of one species (measured in terms of its ‘r’ the intrinsic rate of increase) is significantly

Competition is best defined as a process in which the fitness of one species (measured in terms of its 'r' the intrinsic rate of increase) is significantly reduced due to the presence of another species. This can occur through various mechanisms such as resource competition, predation, parasitism, and disease.

Step 1: Understand the concept of competition in ecology In ecology, competition is the rivalry between or among living things for territory, resources, goods, mates, etc. It is one of the many interacting biotic factors that affect species distribution and abundance.

Step 2: Understand the concept of 'r' or intrinsic rate of increase The intrinsic rate of increase (r) is a measure of the ability of a species to increase in numbers under ideal conditions. It is calculated as the difference between the birth rate and the death rate of a species.

Step 3: Understand how competition affects 'r' When two species compete for the same resources, the availability of those resources for each species is reduced. This can lead to a decrease in the birth rate and/or an increase in the death rate, which in turn reduces the intrinsic rate of increase (r) of the species.

Step 4: Understand the significance of competition Competition can significantly affect the distribution and abundance of species. It can lead to the extinction of species, or it can drive evolutionary changes that allow species to coexist.

So, competition is best defined as a process in which the fitness of one species (measured in terms of its 'r' the intrinsic rate of increase) is significantly reduced due to the presence of another species.