What process describes the gradual evolution of species through the selection of adaptive traits by nature?

The process that describes the gradual evolution of species through the selection of adaptive traits by nature is known as natural selection. This mechanism is a fundamental concept of evolutionary biology, first introduced by Charles Darwin. Natural selection operates on the premise that individuals within a species exhibit variations in their traits. Those individuals with traits that confer a survival advantage in their environment are more likely to survive and reproduce. Over time, these adaptive traits become more common in the population, leading to gradual changes in the species.

Natural selection is distinct from artificial selection, where humans actively choose which traits are desirable and breed organisms accordingly. Similarly, the term "deliberate selection" implies a conscious choice in the selection process rather than the unconscious, environmental influences that guide natural selection. "Naturally occurring selection" could suggest a non-human influence but does not encapsulate the specific biological process underlying the adaptation and evolution of species as effectively as natural selection does. Thus, natural selection is the most accurate term for describing the process of evolution driven by ecological factors and the inherent variations among individuals.