Name Class Date
Skills Worksheet
Active Reading
Section: The Cycling of Materials
Read the passage below and answer the questions that follow.
When we burn fossil fuels, we release carbon into the atmosphere. The carbon returns to the atmosphere as carbon dioxide. Cars, factories, and power plants rely on these fossil fuels to operate. In the year 2000, vehicles were the source of one-third of all carbon dioxide emitted in the United States. All together, about 6 billion metric tons of carbon a year are released into the atmosphere as carbon dioxide. Natural burning of wood or forest fires combined with the burning of fossil fuels make up this 6 billion metric tons. About half of this carbon dioxide remains in the atmosphere, so over a period of years, the amount of carbon dioxide in the atmosphere has steadily increased.
Increased levels of carbon dioxide may contribute to global warming, which is an overall increase in the temperature of the Earth. What happens to the carbon dioxide that is not absorbed by the atmosphere? Scientists estimate that over a billion metric tons of carbon dioxide dissolves into the ocean, which is a carbon sink. Plants probably absorb the remaining carbon dioxide.
IDENTIFYING MAIN IDEAS
One reading skill is the ability to identify the main idea of a passage. The main idea is the main focus or key idea. Frequently a main idea is accompanied by supporting information that offers detailed facts about main ideas.
Read each question and write the answer in the space provided.
1. What do most cars, factories, and power plants rely on to operate?
2. In what form does carbon return to the atmosphere after it is released from the burning of fossil fuels?
3. One-third of the United States’ carbon consumption is used to operate what?
4. How many tons of carbon are released into Earth’s atmosphere every year?
5. Why does the author mention the United States in the fourth sentence?
Active Reading continued
VOCABULARY DEVELOPMENT
In the space provided, write the letter of the term or phrase that best completes each statement or best answers each question.
6. Global warming
a. is carbon dioxide that dissolves into the ocean.
b. is an overall increase in the temperature of Earth.
c. is caused by natural burning of wood and forest fires.
d. makes up half of Earth’s atmosphere.
7. Which of the following statements is true about fossil fuels, carbon, and carbon dioxide?
a. Carbon dioxide returns to the atmosphere as carbon when fossil fuels are burned.
b. Fossil fuels return to the atmosphere as carbon dioxide when carbon is burned.
c. Carbon returns to the atmosphere as carbon dioxide when fossil fuels are burned.
d. none of the above
RECOGNIZING CAUSE AND EFFECT
One reading skill is the ability to recognize cause and effect.
Read each question and write the answer in the space provided.
8. What three things cause carbon to be released into the atmosphere as carbon dioxide?
9. What is one effect of increased levels of carbon dioxide in the atmosphere?
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Environmental science 10 How Ecosystems work
Teacher Resource page
Surfaces left biologically barren (by events,such as a very intense fire) may appear to be “previously unoccupied”; however, the plants which grow in such places are correctly referred to as “secondary succession.”
14. The phosphorus cycle would eventually stop. Without the sun, plants would die, depriving the consumers of their source of food and phosphorus. Without plants to eat, consumers would starve. The carbon cycle would also stop because it is driven by photosynthesis, which could not take place without sunlight. The nitrogen cycle would probably stop as well.Although some nitrogen could continue to move between the soil and the atmosphere without the help of plants (i.e., through processing by bacteria), the ground would eventually freeze without the heat from the sun, and the bacteria would presumably freeze as well.
15 Answers may vary. Sample answer:Leaf lettuce uses photosynthesis toproduce its energy. The lettuce is atthe bottom of the energy pyramidand is the producer. A grasshoppereats the leaf lettuce. The grasshopper is a primary consumer. A bird eats the grasshopper. The bird is the secondary consumer. A house cat eats the bird. The cat is the tertiary consumer.
16. Lichens break up the rock and begin the process of turning it into soil that can support plant life.
17. Clover is part of the carbon cycle because it uses photosynthesis to convert carbon dioxide into carbohydrates. It is part of the nitrogen cycle because it is a legume, which has nitrogen-fixing bacteria in the nodules on the roots of the plant. This bacteria converts atmospheric nitrogen into nitrogen compounds that are useful for other organisms. Clover is part of the phosphorus cycle because it gets the phosphorus that it needs from the soil. Organisms that eat this clover will get the phosphorus they need from the plant.
Active Reading
SECTION: ENERGY FLOW IN ECOSYSTEMS
1. a
2. a
3. a
4. b
5. carbohydrates
6. photosynthesis
7. 3
8. 1
9. 5
10. 2
11. 4
12. b
13. a
14. c
SECTION: THE CYCLING OF MATERIALS
1. fossil fuels
2. carbon dioxide
3. vehicles
4. six billion metric tons
5. Answers may vary. The author wants to point out how much fuel people in the United States use and how much carbon dioxide is emitted because of it. Most people reading this textbook are from the United States, so the author knows this example will be most relevant.
6. b
7. c
8. burning of fossil fuels, natural burning of wood, and forest fires
9. They may contribute to global warming.
SECTION: HOW ECOSYSTEMS CHANGE
1. secondary succession
2. Answers may vary. Pioneer species grow rapidly, then taller plants grow and the pioneer species die. Finally, trees grow and deprive the taller plants of light and water. Eventually, a climax community develops.
3. Accept reasonable responses, which may include secondary succession, climax community, and pioneer species.
4. secondary succession: the sequence of plant growth that occurs when an area of land is allowed to return to its natural state; climax community: the
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Environmental science 10 How Ecosystems work