Final answer:
Mass extinctions can be positive for certain species as they create opportunities for new species to evolve and fill vacant ecological niches.
Step-by-step explanation:
Mass extinctions can be positive for certain species because they create opportunities for new species to evolve and fill the ecological niches left vacant by the extinct species. Following each mass extinction, there is an evolutionary burst as new species develop. For example, after the mass extinction event 65 million years ago, mammals thrived and became our ancestors, benefiting from the ecological niches left by the extinct species.