Biology Regents Practice Exam

Why might two organisms, such as sharks and dolphins, have similar body structures?

1. They evolved in similar environments and specific traits increased their chances of survival

2. They were exposed to the same mutations in different environments

3. They tried to adapt in the same ways regardless of their environments

4. They ate similar foods affecting their growth and development

The correct answer is: They evolved in similar environments and specific traits increased their chances of survival

The similarity in body structures between two organisms like sharks and dolphins can be attributed to the concept of convergent evolution. In this process, different species that occupy similar environments or ecological niches evolve analogous traits that enhance their chances of survival and reproduction. Although sharks are fish and dolphins are mammals, they both live in aquatic environments, which drives similar adaptations such as streamlined bodies, powerful tails, and fins for efficient movement in water. These traits arise not from a shared ancestry but from the adaptive responses to similar challenges posed by their environment, which promotes traits favoring locomotion and hunting strategies suited for a marine lifestyle. The other options do not accurately capture the reason for the structural similarities. The notion of exposure to the same mutations is less relevant because mutations can vary greatly and are dependent on specific environmental factors rather than being universally shared. The idea that they "tried to adapt" is misleading since evolutionary adaptations occur over many generations through natural selection, not through conscious effort by organisms. Lastly, while dietary habits can influence growth and development, they are not the primary drivers of the similar body structures observed in these animals. Instead, it’s the environmental pressures that shape their evolutionary traits leading to the similarity noticed.