Answer: Even though there are smalll amounts of these gases, they can have a major effect on Earth. For example, increased amounts of carbon dioxide are having a major effect on global warming. :)
-- One feature of Earth is an atmosphere rich in nitrogen and oxygen.
Very unusual.
-- Another feature of Earth is vast quantities of liquid and solid water.
Very unusual.
-- Another feature of Earth is a range of temperatures near the melting point
of water.
Very unusual.
One way in which the study of populations ( human populations - I assume) affects us is that they can help predict the population size in the future and prepare us for it. For example, if we see that the population is decreasing, a country might want to consider supporting child-bearing or immigration to avoid the problem of too many people receiving pensions but not paying taxes.
