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2.
Identify which of the following gases is most
abundant in Earth’s atmosphere today.
a. argon
c. oxygen
b. nitrogen
d. carbon dioxide
2. Nitrogen is most abundant in Earth’s atmosphere
today.
3. Compare Earth’s early atmosphere with its present atmosphere.
3. Earth’s early atmosphere was composed of many gases that would be
poisonous to us today. As life forms evolved and began to photosynthesize,
oxygen was produced. Once animals adapted to breathing oxygen, they began
to give off carbon dioxide, balancing the production of oxygen.
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4.
Arrange the steps of the oxygen-carbon
dioxide cycle in the correct order:
a.
b.
c.
d.
Animals breathe oxygen
Plants produce oxygen
Plants use carbon dioxide
Animals exhale carbon dioxide
4. The correct order is b, a, d, c.
b.
a.
d.
c.
Plants produce oxygen
Animals breathe oxygen
Animals exhale carbon dioxide
Plants use carbon dioxide
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5. Explain why the
following statement is
incorrect: global warming
could cause oceans to rise,
so the greenhouse effect
must be eliminated
completely.
5. If we were to eliminate
the greenhouse effect
completely, the world’s
climate would become too
cold for humans to survive.
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6. Predict how much colder it is at the top of Mount Everest, which is almost
9km above sea level, than it is at the Indian coastline. Consider only the
difference in altitude. (Hint: the temperature in the troposphere decreases by
6°C/km)
6. The temperature at the
top of Mount Everest is
about 54°C colder.
9km x 6°C/km = 54°C
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7. In 1982, Larry Walters rose to an
altitude of approximately 4900m (just
over 3 miles) on a lawn chair attached
to 45 helium-filled weather balloons.
Give two reasons why Walters’s
efforts were dangerous.
7. Walters’s efforts were dangerous
because the oxygen content of the air
is considerably lower at that altitude
and the temperature is extremely
cold.