Section: How Ecosystems Change

Name______Class______Date______

Skills Worksheet

Active Reading

Section: How Ecosystems Change

Read the passage below and answer the questions that follow.

Another example of secondary succession is old-field succession which occurs when farmland is abandoned. When a farmer stops cultivating a field, grasses and weeds quickly grow and cover the abandoned land. The pioneer grasses and weeds grow rapidly and produce many seeds to cover large areas.

Then, over time, taller plants such as perennial grasses grow in the area. These plants shade the ground, which keeps light from the shorter pioneer plants. The long roots of the taller plants also absorb most of the water in the soil and deprive the pioneer plants of adequate water to survive. The pioneer plants soon die from lack of sunlight and water. As succession continues, the taller plants are deprived of light and water by growing trees. Finally, slower-growing trees such as oaks, hickories, beeches, and maples take over the area and block out the sunlight to the smaller trees. After about a century, the land can return to the climax community that existed before the farmers cleared it to plant crops.

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 type of succession is old-field succession?

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2.Summarize what happens to a field when a farmer stops cultivating it.

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VOCABULARY DEVELOPMENT

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

3.What key terms are used in this passage?

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Active Reading continued

4.Define the terms you identified in the previous question.

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SEQUENCING INFORMATION

One reading skill is the ability to sequence information, or to logically place items or events in the order in which they occur.

Sequence the statements below to show the steps in old-field succession. Write “1” on the line in front of the first step, “2” on the line in front of the second step, and so on.

_____5.Taller plants grow in the area and shade the ground.

_____6.A climax community exists.

_____7.Pioneer grasses and weeds grow and produce many seeds.

_____8.A farmer stops cultivating a field.

_____9.Trees grow and shade the taller plants.

_____ 10. The taller plants die.

_____ 11. The pioneer plants die.

_____ 12. Slower-growing trees shade the smaller trees.

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.

13.What causes pioneer grasses and weeds that have grown in an abandoned field to die?

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14.What happens after a farmer abandons a field and the stages of old-field succession take place?

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Holt Environmental Science1How Ecosystems Work

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Holt Environmental Science1How Ecosystems Work

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Surfaces left biologically barren (byevents, such as a very intense fire) mayappear to be “previously unoccupied”;however, the plants which grow in suchplaces are correctly referred to as “secondary succession.”

14.The phosphorus cycle would eventu-ally stop. Without the sun, plantswould die, depriving the consumersof their source of food and phospho-rus. Without plants to eat, consumerswould starve. The carbon cycle wouldalso stop because it is driven by pho-tosynthesis, which could not takeplace without sunlight. The nitrogencycle would probably stop as well.Although some nitrogen could con-tinue to move between the soil andthe atmosphere without the help ofplants (i.e., through processing bybacteria), the ground would eventu-ally freeze without the heat from thesun, and the bacteria would presum-ably 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 grasshopperis a primary consumer. A bird eatsthe grasshopper. The bird is the sec-ondary consumer. A house cat eatsthe bird. The cat is the tertiary consumer.

16.Lichens break up the rock and beginthe process of turning it into soil thatcan support plant life.

17.Clover is part of the carbon cyclebecause it uses photosynthesis toconvert carbon dioxide into carbohy-drates. It is part of the nitrogen cyclebecause it is a legume, which hasnitrogen-fixing bacteria in the nod-ules on the roots of the plant. Thisbacteria converts atmospheric nitro-gen into nitrogen compounds that reuseful for other organisms. Clover ispart of the phosphorus cycle becauseit gets the phosphorus that it needsfrom the soil. Organisms that eat thisclover will get the phosphorus theyneed 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 OFMATERIALS

1.fossil fuels

2.carbon dioxide

3.vehicles

4.six billion metric tons

5.Answers may vary. The author wantsto point out how much fuel people inthe United States use and how muchcarbon dioxide is emitted because oft. Most people reading this textbookare from the United States, so theauthor knows this example will bemost relevant.

6.b

7.c

8.burning of fossil fuels, natural burningof wood, and forest fires

9.They may contribute to global warming.

SECTION: HOW ECOSYSTEMS CHANGE

1.secondary succession

2.Answers may vary. Pioneer speciesgrow rapidly, then taller plants growand the pioneer species die. Finally,trees grow and deprive the tallerplants of light and water. Eventually, aclimax community develops.

3.Accept reasonable responses, whichmay include secondary succession, cli-max community, and pioneer species.

4.secondary succession: the sequenceof plant growth that occurs when anarea of land is allowed to return to itsnatural state; climax community: the

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final stage of succession, usually consisting of large hardwood trees; pioneer species: the first plants and algae to grow on an abandoned piece of land.

5.3

6.8

7.2

8.1

9.5

10.6

11.4

12.7

13.Taller plants grow and block out thesunlight. They grow larger roots andtake more water from the soil.

14.The field returns to a climax commu-nity similar to the one that existedbefore the farmer cleared the field.

Map Skills

1.developed regions

2.United States; Australia

3.Answers may vary but should mention increased industry, number of automo-biles, polluting technology, etc.

4.Answers may vary but should suggest a possible lack of population.

Quiz

SECTION: ENERGY FLOW IN

ECOSYSTEMS

MatchingMultiple Choice

1.c7.b

2.a8.b

3.d9.c

4.e10.c

5.f

6.a

SECTION: THE CYCLING OF MATERIALS

Matching

1.h5.f

2.c6.e

3.a7.d

4.a8.b

Multiple Choice

9.a

10.a

SECTION: HOW ECOSYSTEMS CHANGE

MatchingMultiple Choice

1.c7.d

2.d8.a

3.e9.b

4.b10.a

5.b

6.f

Chapter Test General

MATCHING

1.c4.f

2.d5.a

3.e6.b

MULTIPLE CHOICE

7.c14.d

8.b15.a

9.d16.b

10.b17.d

11.a18.a

12.a19.a

13.a20.b

Chapter Test Advanced

MULTIPLE CHOICE

1.d

2.c

3.d

4.a

5.a

COMPLETION

6.photosynthesis

7.hydrogen sulfide

8.decomposers

9.cellular respiration

10.legumes

11.fire

12.primary

SHORT ANSWER

13.Accept any reasonable answer. Sample answer: Owls eat mice and mice eat grain. Both owls and mice depend onthe plants that produce grain for theirenergy source. Grain is the producerin this scenario.

14.A pyramid is the perfect shape to rep-resent energy levels. Because the baseis the largest part of the pyramid, it isused to show where the most energy

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