Difference between background and mass extinction?

Background extinction refers to the normal extinction rate. These are species that go extinct simply because not all life can be sustained on Earth and some species simply cannot survive. Mass extinction is a widespread event that wipes out the majority (over 50%) of living plants and animals.

Background mean the normal extinction rate. While mass extinction is a wide spread event which proceeds to wipeout over 50% of living plants and animals.

the trilobite is used as an index fossil for various geologic time periods as specific types of the trilobites were present in different geological time periods. they are a group of marine arthropods belonging to the class of trilobita.

explanation:

earthquakes in florida are rare because the state is not located near any tectonic plates. in fact, florida is tied for first place as having the fewest earthquakes of any state. much of florida is limestone and seafloor materials that is not conducive to earthquakes.

explanation: