Final answer:
A useful feature of an organism shaped by natural selection for its current function is called an adaptation, which is a trait that helps the organism survive and reproduce in its environment.
Step-by-step explanation:
A useful feature of an organism shaped by natural selection for the function it now performs is called an adaptation. An adaptation is a genetically-based trait that has evolved because it helps living things survive and reproduce in a given environment. For instance, the webbed feet of a platypus are an adaptation for swimming just as a snow leopard's thick fur is an adaptation for living in the cold.
Natural selection
is the process that drives organisms to develop adaptations. Organisms with traits that better enable them to adapt to their environment will tend to survive and reproduce in greater numbers. These adaptive traits become more common in the population over time. For example, the variation in finch beaks, which shifted from generation to generation, is a result of natural selection based on food availability and an adaptation to that environment.