Instructions: Given a text passage, come up with an appropriate title for it. The title should accurately represent what the main focus of the passage is. The title of a passage may be present in the first few sentences of the passage and/or be referred to multiple times in the passage. The title should be 1-5 words long.
Input: '' Survival of the fittest '' is a phrase that originated from Darwinian evolutionary theory as a way of describing the mechanism of natural selection . The biological concept of fitness is defined as reproductive success . In Darwinian terms the phrase is best understood as '' Survival of the form that will leave the most copies of itself in successive generations . ''
Output:
Survival of the fittest