Final answer:
The term best describing the independent evolution of similar traits like the swimming forelimbs in penguins and sharks is 'convergent evolution.' This process happens when unrelated species adapt to similar environments and develop analogous structures, which perform similar functions but do not arise from a common ancestral trait.
Step-by-step explanation:
The evolution of species like penguins and sharks, which have forelimbs adapted for swimming despite not sharing a recent common ancestor with such adaptations, is best described by the term convergent evolution. This occurs when unrelated organisms independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. In the case of penguins and sharks, both have developed the ability to swim in water, penguins using their flipper-like wings and sharks using their fins. These analogous structures serve similar functions but are not derived from a common ancestor with such traits.
Another example of convergent evolution can be observed in the similar body shapes and tails of fishes and whales, which despite belonging to different classes of animals (fish are a paraphyletic group of organisms while whales are mammals), have evolved to have a streamlined body suitable for moving through water. Moreover, insects use wings to fly similarly to bats and birds, and although we call them both wings due to their function and superficial similarity, their embryonic origins are different, indicating independent evolutionary paths.