Final answer:
Intraspecific aggression refers to competition among the same species for resources like mates, while interspecific aggression involves different species competing for shared resources. The former drives natural selection within a species, while the latter can lead to competitive exclusion or increased specialization among species.
Step-by-step explanation:
The main difference between intraspecific aggression and interspecific aggression lies in the species involved and the purpose of such behavior. Intraspecific aggression occurs when members of the same species compete with each other, which could be for resources such as territory, food, or mates. For instance, in scenarios where two male birds of the same species might vie for the attention of a potential mate to propagate their genes. This type of competition is key in driving natural selection and leads to the evolution of specialized adaptations within the species.
On the other hand, interspecific aggression happens among individuals from different species. This form of competition arises when separate species strive for similar resources within the same environment, which may lead to one species outcompeting the other. Such a scenario might be observed in predators of various species that compete for the same prey. This competition can result in a series of ecological dynamics, such as competitive exclusion, decreased reproductive success, or increased specialization amongst the different species involved.