What are the different types and rates of extinction?

Extinction can be categorized into several types, including background extinction, which occurs at a relatively constant rate due to normal evolutionary processes, and mass extinction, where a significant percentage of species dies out in a relatively short geological period, often due to catastrophic events. The rates of extinction vary widely; background extinction rates are estimated at about 1 species per million per year, while mass extinctions can result in the loss of 75% or more of species within a few million years. Current biodiversity assessments suggest that human activities are accelerating extinction rates, potentially leading to a sixth mass extinction, with estimates suggesting rates up to 1,000 times higher than the background rate.