Early in Earth history, the Sun was less luminous, which should have caused Earth to be much colder and all water to

be frozen. Yet all evidence points to the presence of liquid water on Earth. Give two explanations that could resolve the
“faint young sun paradox.” What will be an ideal response?


1. There was a strong greenhouse effect from carbon dioxide, methane and water vapor in
Earth’s atmosphere that trapped solar radiation, thus keeping the Earth warmer.
2. Earth had a low albedo, and reflected less light back to space. In other words, it absorbed
more light, which kept temperatures high enough that water could not freeze.

Environmental & Atmospheric Sciences

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Primary air pollutants ____, whereas secondary pollutants _____

A) enter the atmosphere directly; form by chemical actions involving other pollutants B) form through a series of chemical reactions; occur naturally C) occur naturally; are synthetic D) enter the atmosphere directly; enter the atmosphere through human intervention

Environmental & Atmospheric Sciences

Where there is rapid decomposition of plant matter, we expect to find soils that have

A) a very thin O horizon. B) a tremendous capacity to hold water. C) a particularly thick C horizon. D) high fertility and a very thick B horizon.

Environmental & Atmospheric Sciences

Which of the following is a major contributor to the decline in pollinator populations?

A) Use of genetically modified crops B) Use of domesticated bees for pollinating fruit crops C) Use of insecticides in agricultural areas D) Collisions with vehicles

Environmental & Atmospheric Sciences

Which of the following is true?

A) Antibiotics are effective treatments for viral diseases. B) All viral diseases can be cured. C) Most viral diseases cannot be cured. D) No viral diseases can be cured.

Environmental & Atmospheric Sciences