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Natural Cycles

Water and certain chemicals - such as oxygen, carbon, and
nitrogen - are constantly being exchanged between air, water, soil,
plants, and animals.
Carbon and oxygen make up the gas carbon dioxide. Plants
take in carbon dioxide during photosynthesis. Plants use the
carbon from carbon dioxide to make food during photosynthesis.
This food provides matter and energy to form new plant cells.
During photosynthesis, plants also release oxygen into the
air. Animals breathe in oxygen. Plants also take in oxygen during
respiration. Both animals and plants give off carbon dioxide during
respiration.
Dead plants and animals produce carbon dioxide as they
decay.
Carbon from ancient dead plants is stored as fossil fuel,
such as coal, oil, and gas.

Comprehension Questions

I. Say which of the following statements are false and
which are true. Correct the false statements to make them
true.

1. Water and certain chemicals - such as oxygen, carbon, and
nitrogen - are not constantly being exchanged between air,
water, soil, plants and animals.
2. Plants take in carbon dioxide during photosynthesis.
3. Plants use the carbon from carbon dioxide to make food
during photosynthesis.
4. The food does not provide matter and energy to form new
plant cells.
5. During photosynthesis plants do not release oxygen into
the air.

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