Final answer:
Whales and fish, despite their similar appearances, are distantly related; whales are more genetically similar to horses than to sharks. Birds and butterflies are also distantly related, as they belong to different classes of animals. To determine evolutionary relationships, both morphological features and DNA sequences are considered.
Step-by-step explanation:
When looking for the two organisms that are least alike, or most distantly related evolutionarily, the key is to consider their genetic similarities and common ancestry. Whales and fish may look similar due to convergent evolution, as both have adapted to life in water, but they are not closely related. Whales are mammals and share a more recent common ancestor with other mammals, such as the horse, making a whale and a horse more genetically similar than a whale and a shark, which is a fish.
In contrast, birds and butterflies both have the capability of flight, yet they are distantly related as birds are vertebrates and butterflies are insects. Therefore, when faced with such comparisons, a combination of morphological features and DNA sequences must be analyzed to determine evolutionary relationships.