Final answer:
Selection, or 'survival of the fittest,' refers to the reproductive success of individuals with traits that allow them to survive environmental changes, leading to evolutionary change. Traits that aid survival and reproduction, and are thus passed to future generations, are called adaptations, and they result in increased fitness.
Step-by-step explanation:
Selection, often referred to as "survival of the fittest," is a process that involves the more prolific reproduction of individuals with favorable traits that help them survive environmental changes. This concept is crucial in understanding how these advantageous traits can lead to evolutionary change. Some heritable traits provide certain individuals an advantage over others in surviving and reproducing, which means these individuals will likely have more offspring. Over time, if the environment undergoes significant and lasting change, individuals with these favorable traits, due to genetic variability, are more likely to survive, reproduce, and pass on their genes to future generations—this describes the process of natural selection.
These heritable favorable traits are known as adaptations. An adaptation is essentially a trait that enhances the fitness of an organism in its environment. For example, the variations in the beak sizes of finches leading to different feeding adaptations, or the webbed feet in aquatic birds that facilitate swimming. Ultimately, individuals who are most adapted to their environment have a higher chance of survival and passing on these favorable traits to their progeny.