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?
_______________________________________________________________
_______________________________________________________________
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Holt Environmental science
10
How Ecosystems work
Name ______________________________ Class ___________________ Date __________________
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
11
How Ecosystems work
TEACHER RESOURCE PAGE
14.
15
16.
17.
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.”
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.
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.
Lichens break up the rock and begin the
process of turning it into soil that can
support plant life.
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.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
a
a
a
b
carbohydrates
photosynthesis
3
1
5
2
4
b
a
c
SECTION: THE CYCLING OF
MATERIALS
1.
2.
3.
4.
5.
6.
7.
8.
9.
fossil fuels
carbon dioxide
vehicles
six billion metric tons
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.
b
c
burning of fossil fuels, natural burning of
wood, and forest fires
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
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Holt Environmental science
86
How Ecosystems work