Final answer:
Darwin's postulate 3, which relates to finches, states that more offspring are produced than can survive, causing competition for resources and resulting in only some finches surviving to reproduce. This principle is always in effect, not just during environmental changes, and leads to the adaptive evolution of species.
Step-by-step explanation:
When discussing Darwin's postulate 3 and its relation to finches, it focuses on the natural selection principle that more offspring are produced than can survive, leading to competition for limited resources. In the case of Darwin's finches, these birds are a perfect example of this postulate in action. Due to the variation in beak sizes and shapes, which are adapted to the availability of different-sized seeds, there is evidence of differential survival and reproduction. These differences in beak anatomy affect which finches are more likely to survive and reproduce based on the food sources available to them. The correct answer to the question is (A) Yes, always. Finches, like many other organisms, consistently produce more offspring than can survive to maturity, and as a result, only some finches survive to reproduce.
It is important to note that these evolutionary processes that Darwin and Wallace proposed operate constantly, not just during environmental changes. Hence, variations that increase an individual's fitness in its environment will potentially be passed down to the offspring, leading to adaptive evolution over generations.