Final answer:
Adaptations are heritable traits that enhance an organism's ability to survive and reproduce in its environment, brought about through the process of natural selection or 'survival of the fittest'.
Step-by-step explanation:
The inherited characteristics of an organism that enhance its survival and reproduction in a particular environment are known as adaptations. An adaptation is essentially a heritable trait that aids an organism's survival and reproduction by improving the organism's 'fit' to its environment. This process is a result of evolution by natural selection, where traits that provide an advantage in survival and reproduction become more common in a population over time. For instance, the webbed feet of a platypus are an adaptation for swimming, the thick fur of a snow leopard is an adaptation for living in the cold, and the cheetah's rapid speed is an adaptation for catching prey.
Natural selection, often described as 'survival of the fittest', plays a critical role in this by favoring the reproduction of individuals with beneficial traits that enable them to survive shifts in the environment, thus leading to evolutionary change.