Name________________________________Class____________________Date____________________

Skills Worksheet

Directed Reading

Section: Cycling of MatterRead each question, and write your answer in the space provided.

1. What is the source of the energy that drives the water cycle? Explain.________________________________________________________________________________________________________________________________________________________________________________________________

2. Which of the cycles of matter involves the process of percolation?________________________________________________________________________________________________________________________________________________________________________________________________

3. What are the most important substances that pass through the cycles of matter?________________________________________________________________

Complete each statement by underlining the correct term or phrase in the brackets.

4. The process that returns water to the atmosphere from the surface of lakes and oceans is called [evaporation / transpiration].

5. Water that falls to Earth as rain or snow and seeps into the soilbecomes [surface water / ground water].

6. In the living portion of the water cycle, water is taken up by [condensation / the roots of plants].

7. The process by which water evaporates from the leaves of plants is called [respiration / transpiration].

Read each question, and write your answer in the space provided.

8. How does carbon become part of organic molecules?________________________________________________________________________________________________________________________________________________________________________________________________

Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.

Holt Biology 5 Ecosystems

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Directed Reading continued

9. List three ways carbon atoms return to the nonliving part of the carbon cycle.________________________________________________________________________________________________________________________________________________________________________________________________

Complete each statement by writing the correct term or phrase in the space provided.

10. Organisms need nitrogen to build ______________________.

11. Phosphorus is usually present as ______________________

______________________ in soil and rock.

12. The process of combining nitrogen gas with hydrogen to form ammonia is

called ______________________ ______________________.

13. Nitrogen-fixing bacteria use ______________________ to split molecules of

nitrogen gas and combine the nitrogen atoms with hydrogen.

In the space provided, write the letter of the term or phrase that best completes the statement or answers the question.

______14. All of the following are examples of materials that cycle in ecosystems excepta. energy.b. oxygen.c. water.d. nitrogen.

______15. Which is one way in which carbon dioxide enters the atmosphere?a. percolationb. photosynthesisc. combustiond. evaporation

______16. Bacteria return nitrogen to the soil by which process?a. denitrificationb. assimilationc. nitrificationd. ammonification

Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.

Holt Biology 6 Ecosystems