Amolecule that can be used as a molecular clock has a neutral mutation rate of one mutation per 5 million years. how many years ago did two species share a common ancestor if the molecules found in these two species differ by a total of eight mutations?

The answer is atmosphere. there are four spheres of the earth: 1. geosphere (from greek word 'geo' = ground), 2. hydrosphere (from greek word 'hydro' = water), 3. biosphere (from greek word 'bio' = life), and 4. atmosphere (from greek word 'atmo' = air). a magnetosphere is a region of space around astronomical objects controlled by the magnetic field of that object. through the process of elimination, since lightning is present in the air, it can be found in the atmosphere.