Final answer:
Mass extinctions involve a significant loss of species over a short period of geologic time, while regular extinctions occur at a slower rate over a much longer period of time. Regular extinctions occur due to natural selection, while mass extinctions are caused by major environmental catastrophes. The current mass extinction is primarily driven by human activities.
Step-by-step explanation:
Mass extinctions and regular (background) extinctions are both forms of extinction, but they differ in terms of scale and duration. Mass extinctions involve a significant loss of species over a short period of geologic time, while regular extinctions occur at a slower rate over a much longer period of time.
Regular extinctions are part of natural selection and occur when organisms are unable to adapt to changes in their environment. They occur at a rate of about one out of one million species becoming extinct per year.
On the other hand, mass extinctions are caused by major environmental catastrophes and have a much larger impact on life. They have occurred at least five times in Earth's history, with extinctions being caused by events such as asteroid impacts and volcanic activity. The current mass extinction is unique because it is primarily driven by human activities like habitat destruction, introduction of exotic species, and over-harvesting.