What is the difference between an extinction and a mass extinction?

mass extinction is usually defined as a loss of about three quarters of all species in existence across the entire Earth over a short geological period of time.

Extinction are defined as species that go extinct simply because not all life can be sustained on Earth and some species simply cannot survive.

the reason the two sea urchins don't compete with each other for food, resources, etc. is because the urchins have adapted to the environment but they have also adapted to each other. this is most likely because the genes of the sea urchins.

enhanced global partnerships and exploration capabilities may advance international preparedness for protecting the earth from catastrophic events such as some asteroid strikes, advancing collaborative research on space weather and protecting spacecraft by developing new means for space debris removal.