Concept:Natural selection is the process by which organisms best adapted to their environment tend to survive and pass on their traits.
The idea is famously summarised by the phrase “survival of the fittest”.
Explanation:The term “survival of the fittest” was introduced by Herbert Spencer and is closely associated with Darwin’s theory of natural selection.
It means that only those individuals which are best suited to their surroundings are more likely to survive and reproduce successfully.
Adaptive radiation refers to the rapid evolution of many species from a common ancestor, so it does not directly name natural selection.
Population variability describes the presence of differences within a species, which provides the raw material for selection but is not the defining term.
Differential reproduction is a part of how natural selection operates, but it is not the phrase generally used to describe natural selection itself.
Therefore, among the given choices, the term most directly linked to natural selection is “survival of the fittest”.
Answer:D. Survival of the fittest