How is competition best defined in terms of the fitness of a species, measured by its intrinsic rate of increase ('r')?

The fitness of one species is significantly lower in the presence of another superior species.

The correct answer is Option (1) -The fitness of one species is significantly lower in the presence of another superior species.

Competition can be best defined as a process in which the fitness of one species, as measured by its intrinsic rate of increase ('r'), is significantly lower in the presence of another species. This reduction in fitness can occur even when resources such as food and space are abundant.

In interference competition, the presence of one species interferes with or inhibits the feeding efficiency of another species, leading to a decrease in its fitness. This interference can be due to various mechanisms such as aggression, territoriality, or resource monopolization by the superior species. As a result, the fitness of the species experiencing interference is reduced, affecting its ability to survive, reproduce, and increase its population size.

Laboratory experiments conducted by ecologists like Gause and others have demonstrated this competitive dynamic, particularly when resources are limited. In such cases, the competitively superior species, which is better adapted or more efficient in resource acquisition, tends to outcompete and eventually eliminate the other species. This phenomenon is known as competitive exclusion.

However, in natural ecosystems, the evidence for competitive exclusion occurring is not always conclusive. The complexity of natural environments, the presence of multiple interacting factors, and the coexistence of species with diverse adaptations can complicate the competitive dynamics. In some cases, species may exhibit resource partitioning, where they utilize different resources or occupy different niches to coexist without being competitively excluded.

While laboratory experiments provide valuable insights into the principles of competition, studying competition in nature requires considering a broader range of ecological factors and long-term observations. The coexistence of multiple species in nature suggests that competitive exclusion is not always the sole outcome, and factors such as predation, mutualism, and environmental variability also influence species interactions and community dynamics.