Final answer:
An impact can cause a mass extinction by throwing debris into the atmosphere, reducing sunlight and photosynthesis, and leading to environmental catastrophes like global fires and acid rain, resulting in widespread species extinction.
Step-by-step explanation:
An impact can lead to a mass extinction by causing global catastrophic environmental changes that disrupt the ecological balance and food chains. The most notable is the Cretaceous-Paleogene extinction event approximately 65 million years ago when a massive asteroid impact resulted in the demise of the dinosaurs and many other life forms. This event is characterized by a thick layer of iridium-rich sediment worldwide—evidence of an extraterrestrial object's collision with Earth.
The asteroid impact created a series of global environmental disturbances, including fires, acid rain, and a significant reduction in sunlight reaching the Earth's surface due to debris thrown into the atmosphere. The blockage of sunlight led to a dramatic decrease in photosynthesis, causing a collapse of food chains. Over time, these severe conditions made survival for many species impossible, leading to their extinction.
This event and others like it have played a critical role in shaping the evolution of life on our planet. They stress the importance of random global catastrophes, in addition to natural selection, in determining the survival of species. Larger impacts like these have the power to influence evolutionary paths by causing mass extinctions and enabling the rise of other life forms to dominate in the aftermath.