If the Early Earth's Atmosphere Contained Little or No O2

question 25

Multiple Choice

If the early Earth's atmosphere contained little or no O2, then where did most of the O2 in our modern atmosphere come from?

• A)the oxidation of metals
• B)photosynthesis
• C)respiration
• D)the breakdown of carbon dioxide
• E)the splitting of water vapor by sunlight

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Definitions:

Cross-sectional Area

The area of a particular section of an object or substance, usually measured perpendicular to a specific axis.

Capillaries

The smallest blood vessels in the body which facilitate the exchange of water, oxygen, carbon dioxide, and many other nutrient and waste chemical substances between blood and the tissues.

Velocity

A physical vector quantity that denotes the rate of change of position of an object with respect to time, including both speed and direction.

Venae Cavae

The two large veins that return deoxygenated blood to the heart; consisting of the superior and inferior vena cava.