lesson 5 human effects on ecosystems -...

Human Effects on Ecosystems

People use offshore oil platforms such as this one to drill for oil under Earth’s surface. Oil can harm the ecosystem. What happens if it spills? How can people clean it up?

Lesson 5

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274ENGAGE

SE.49 Identify and give examples of pollutants found in water, air, and soil (SE-M-A3) SE.50 Describe the consequences of several types of human activities on local ecosystems (e.g., polluting streams, regulating hunting, introducing nonnative species) (SE-M-A4)

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Step

Make a PredictionOil and water do not mix. How could you separate oil from the surface of water? From the surface of a solid? Make a prediction.

Test Your Prediction

Fill a plastic container halfway with water. Float a cork in the water.

Make a Model Using an eyedropper, carefully drip 6–7 drops of oil onto the water’s surface.

Observe Watch the oil, water, and cork for about 30 seconds. Record your observations.

Based on your observations, make a plan to test your prediction. Use only the materials your teacher gives you.

Carry out your plan to clean the oil from the water and cork. Record your results.

Draw Conclusions

Communicate How well were you ableto clean the oil from the water? Fromthe cork? Was your prediction correct?

Infer What can be done to clean up anoil spill in the ocean?

How is your model like the natural world? How is it different? How can a model like yours be useful to scientists?

Research the 1989 oil spill from the Exxon Valdez. Where did the oil spill? How far did it travel? How was it cleaned up? Report your findings.

Explore More

How can you clean up an oil spill?Materials

• plastic container

• water

• cork

• eyedropper

• vegetable oil

• paper towels

• sponge

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275EXPLORE

SI.3 Use a variety of sources to answer questions (SI-M-A1) SI.15 Identify and explain the limitations of models used to represent the natural world (SIM-A5)Also covers SI.22A


What causes polluted soil?The things people do every day affect the

environment. Pollution is the addition of harmful materials to soil, air, or water. As you have learned, the different parts of an ecosystem interact with one another. The addition of harmful materials to one part of the ecosystem can affect the other parts of the ecosystem through these interactions.

Factors that Pollute Soil

Soil is the mixture of rock and bits of once-living parts of plants and animals that covers most of Earth’s landmasses. Soil contains nutrients and microorganisms, both of which are important parts of ecosystems. Microorganisms decompose dead material and return the nutrients to the ecosystem. Plants then use the nutrients for growth.

Soil can become polluted by chemicals, biological materials, or trash. Soil pollution often occurs because waste is not disposed of properly. Chemical pollution of soil can occur when substances such as oil, gas, and other chemicals spill or are not properly disposed of. Underground storage tanks are sometimes used to store harmful chemicals underground. If the tanks are not properly maintained they can leak, resulting in soil pollution.

▶ Essential Question How do human activities affect ecosystems?

▶ Vocabularypollution, p. 276

litter, p. 277

smog, p. 278

ozone, p. 278

pollutant, p. 280

nonnative species, p. 282

▶ Reading Skill Main Idea and Details

Main Idea Details

▶ Technology e-Glossary and e-Review online at www.macmillanmh.com

SE.49, SE.50

These old oil drums can become a source of soil pollution when they begin to rust and leak.

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276EXPLAIN

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Agricultural practices, such as the application of herbicides and pesticides, can cause soil pollution. Farmers apply these chemicals to crops to control weeds and insects, but when they reach the soil, they can negatively change the soil environment.

Litter is trash that is unlawfully disposed of outdoors. Litter is another source of soil pollution. Landfills that are not properly built can allow harmful substances from the trash to leak down into the soil, resulting in pollution.

Consequences of Soil Pollution

All of the sources of soil pollution can change the soil environment and have a negative effect on the ecosystem. When soil is polluted, the harmful substances can leak farther down into the soil and be washed into streams and rivers by the rain.

When even small amounts of pollution stay in the soil they can cause a change in soil chemistry. This can kill or harm the insects and decomposers that live in the soil. If decomposers do not return nutrients to the ecosystem, producers cannot grow. When producers cannot grow, consumers have nothing to eat. Polluted soil will often produce smaller crop yields as well. Soil pollution caused by toxic materials or dangerous biological materials can even pose health risks to humans and other organisms.

I f landfills are not properly constructed they can leak, becoming a source of soil pollution.

What kinds of trash might cause soil pollution?

Clue: Which materials contain chemicals?

Read a Photo

Source of Soil Pollution

Quick Check

Main Idea and Details What

causes soil pollution?

Critical Thinking How can soil

pollution affect the human food

supply?

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277EXPLAIN


How do we use and

pollute air?You cannot see air, and if air is

clean, you cannot smell it or taste it. If air does not move, you cannot feel it or hear it. However, air is all around you.

Earth’s atmosphere holds the gases that living things need to stay alive. These gases are oxygen, carbon dioxide, and nitrogen. Plants take in carbon dioxide to make food. Animals and plants use oxygen to get energy. Some bacteria turn nitrogen into chemicals that plants use to grow.

Sometimes particles of polluting materials build up in the air. These particles are produced when fossil fuels or trash are burned. Dust from plowed fields, construction sites, and mines also can put polluting particles into the air. Chemicals that are produced by factories can cause air pollution.

Some days, you may see a yellow haze in the air over cities. This is a sign of a type of air pollution called smog.

Smog is air pollution that is caused by particles that are produced when fossil fuels are burned. Smog irritates eyes and can make breathing difficult. It is especially dangerous for people who have breathing problems, such as asthma.

Air pollution does not only have consequences near the ground. About 30 km (19 mi) above Earth’s surface, there is a layer of a gas in the atmosphere called ozone (OH•zohn). Ozone is a form of oxygen that protects living things on Earth’s surface from the Sun’s dangerous radiation.

In recent years, chemicals in aerosol cans and air conditioners have escaped into the atmosphere. When these chemicals rise high up into the atmosphere, they set in motion chemical reactions that destroy ozone. When ozone is destroyed, harmful radiation from the Sun reaches Earth’s surface more easily. Evidence suggests that this radiation can increase the chances of getting skin cancer.

▲ Smoke from cars and trucks is a source of air pollution.

▲ Pollution can be seen in the air over many cities.

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278EXPLAIN


Quick Check

Main Idea and Details How is air

pollution produced?

Critical Thinking Discuss how

forest destruction would affect

air pollution.

Dirty Air

Using a plastic knife, smear a thin layer of petroleum jelly on an index card.

Holding the edges of the index card, carefully place the card in a corner of the classroom.

Observe What does the index card look like after one day? After one week?

Infer How does the petroleum jelly help you track air pollution?

Form a Hypothesis Would you expect more air pollution near a road or away from a road? Why?

SI.21

Ash from erupting volcanoes is a source of air pollution.

An ozone hole is a thin area in the layer of gas. Today, the chemicals that destroy ozone are no longer used in aerosol cans. Air conditioners are also made that do not use the chemicals.

In industrial areas, smoke and gases that pour into the air from factories can combine with rain to form acid rain. Acid rain has many harmful consequences. It can kill trees and wear away stone buildings and statues.

Air can also be polluted by events in nature. Gases, dust, and ash from volcanic eruptions can stay in the atmosphere for days, weeks, or months.

NorthernHemisphere (2006)

thicker ozone

thinner ozone

▲ Using special equipment, scientists can track the thickness of the ozone layer.

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279EXPLAIN


What causes

polluted water?Although water that falls from

the sky is not salty, it may have other substances in it that cause it to be unsafe for people to drink. Water that flows over the land may also pick up pollutants. Pollutants are substances that pollute a material such as freshwater. Polluted, or contaminated (kuhn•TAM•uh•nayt•ed), water cannot safely be used by people for drinking, washing, cooking, or swimming.

What are some signs that water is polluted? It might smell. It might be cloudy, have a strange color, or have dead fish in it. However, you can’t always tell that water is contaminated by looking at it. It might look clear and still contain chemicals or harmful organisms that could make you sick.

Contamination of Freshwater

Farmers and homeowners use different kinds of chemicals to help their crops and lawns grow. People also use chemicals to kill organisms that are harmful to plants. Some factories and farms produce polluting waste products.

The nutrients and bacteria from animal waste can get washed into lakes and streams when it rains, becoming water pollutants.

Water flowing over polluted ground becomes contaminated. It spreads chemicals and harmful organisms throughout the watershed. It contaminates sources of freshwater like streams and rivers. Water seeping through the ground can carry the chemicals into groundwater.

When a community is built in a watershed, water flows through the community on the way to streams and rivers. As it rushes over streets, it can pick up contaminants such as salt used to melt ice and snow, spilled motor oil, and trash.

Some land-based pollutants are not so obvious, but can still greatly disrupt aquatic ecosystems. Sediment, for example, can get washed into streams when water erodes bare ground. The sediment can smother aquatic animals and block light from reaching algae and aquatic plants—the producers in aquatic food chains. Fertilizer and animal waste from farms can also wash into rivers and streams. Both of these substances have high amounts of nutrients that can lead to algae blooms. When the algae blooms die they use up oxygen dissolved in the water, killing fish.

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280EXPLAIN


Water PollutionProtecting Our Water Resources

The easiest way to deal with water pollution is to prevent it from happening in the first place. Because of this, several laws have been passed by local, state, and federal governments to prevent water pollution. Two of the most important laws passed by the United States government are the 1974 Safe Drinking Water Act and the 1977 Clean Water Act.

The Safe Drinking Water Act sets rules that communities across the United States must follow to keep drinking water safe and clean. The Clean Water Act made it illegal to throw pollutants into surface waters, such as streams, rivers, lakes, and oceans. People or businesses that break this law can be fined.

How can you help ensure your water is safe to use? You can clean up litter from local rivers. You can limit your family’s use of lawn chemicals to help prevent chemical runoff.

Litter can disrupt aquatic Litter can disrupt aquatic ecosystems.ecosystems.

Polluted water from this sewage pipe is pouring into a reservoir.

Nutrients from fertilizer and animal waste runoff can result in algae blooms.

Which form of pollution is most likely due to agricultural practices?

Clue: Read the caption for each photo.

Quick Check

Main Idea and Details What

consequences can water pollution

have on ecosystems and human

health?

Critical Thinking What are some

ways people could prevent water

pollution?

Read a Photo

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281EXPLAIN


How do new organisms

change ecosystems?Humans can change ecosystems by

introducing new species. What are the consequences when a new organism moves into an ecosystem? Nonnative species, also called exotic species, are plant and animal species that have been introduced into an environment that is outside their native range. These organisms can threaten native species.

This is what happened when humans introduced zebra mussels into freshwater ecosystems in the United States. Zebra mussels are native to eastern Europe and Asia. They were accidentally brought to the United States aboard ships coming from Europe and Asia.

In a food web, organisms compete with each other for food and other resources. When a nonnative species such as the zebra mussel is introduced into an ecosystem, it also competes with native species for these resources. Zebra mussels are tough competitors. They can reproduce quickly—a female can produce 30,000 to 100,000 eggs each year. Zebra mussels also have huge appetites and can consume large amounts of food.

Some native species, including other freshwater mussels, cannot compete well with the zebra mussel. As a result, these native species have declined in number since the zebra mussel was introduced into their freshwater ecosystems. Eventually these native organisms may completely disappear and become extinct.

◀ Zebra mussels are about the size of a fingernail, but they can cause big problems. They have been found in the Great Lakes in large numbers.

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282EXPLAIN


Water hyacinths can outcompete native wetland plant species, blocking waterways and prev enting natural interactions.

Nutria are a nonnative species in Louisiana that have damaged coastal wetlands through feeding and burrowing. ▼

▲ English ivy is not native to the United States. In many parts of the country, it can be found overgrowing the landscape.

Nutria are a nonnative species that causes problems in Louisiana. Nutria are small, herbivorous mammals native to South America that were brought to the United States for their fur. Their dense populations and feeding habits cause damage to crop fields and coastal wetlands. These wetlands protect Louisiana from flooding and erosion, and are home to native wildlife.

Water hyacinths are a nonnative plant species that damage coastal wetlands. They can clog waterways and reduce water quality by blocking sunlight and depleting oxygen.

Scientists have tried many methods to remove both of these exotic species from Louisiana. They have not been able to get rid of them completely, but have learned from their attempts and are able to keep these and other nonnative species under control in many areas. Current methods of control include trapping nutria and using herbicides and herbivorous insects to regulate water hyacinths.

Quick Check

Main Idea and Details Why are

nonnative species a problem for

some native plants and animals?

Critical Thinking What are some

ways to prevent the introduction of

nonnative species into an ecosystem?

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283EXPLAIN


How can hunting affect

ecosystems?Though unregulated hunting

can have negative effects on animal populations, regulated hunting can be beneficial to populations and ecosystems. Wildlife management is the process of keeping populations at desired levels for their ecosystem.

Recall that carrying capacity is the maximum population size that an ecosystem can support based on the resources available. Regulated hunting helps to ensure that populations do not reach levels that can be harmful to the ecosystem. When unregulated, some animals, such as nutria and white-tailed deer, can become overpopulated. They may damage their habitat to the point that the carrying capacity is decreased.

Unregulated populations of these animals can consume nearly all of the vegetation in an area and will begin to starve. They can also harm crops and other parts of the ecosystem.

Wildlife managers carefully track the number of organisms in a population and how many are removed by hunting and trapping. They establish regulations to ensure that the number of animals hunted keeps the population in balance.

◀ When unregulated, white-tailed deer can reach dense populations that can be harmful to the ecosystem.

Quick Check

Main Idea and Details How

can hunting be beneficial to

ecosystems?

Critical Thinking What factors

would a wildlife manager consider to

determine how many organisms in a

population can be hunted?

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284EXPLAIN


Think, Talk, and Write Vocabulary Nutria and zebra mussels are examples of .

Main Idea and Details List one way each resource can become polluted: soil, air, water.

Main Idea Details

Critical Thinking Why might an exotic species be harmful in the area where it is introduced, but not in its native area?

Test Prep Which substance is a soil pollutant?

A smogB sedimentC oil D algae

Test Prep Which substance is a gas that protects us from the Sun’s harmful radiation?

A acid rainB smogC ozone D litter

Essential Question How do human activities affect ecosystems?

Visual Summary

Pollution is the addition of harmful materials to soil, air, or water.

Soil, air, and water pollution can be caused by chemicals, sediment, or human and animal waste.

Nonnative species affect ecosystems by competing with native species.

Make a Study GuideMake a folded chart. Use the titles shown. In each box, write the main idea of what you learned.

The End of TreesWrite a science fiction story in which all

the trees on Earth are destroyed by an

event of your choosing. Describe how the

end of trees affects the environment and

all living things on Earth.

Waterborne DiseasesResearch a disease that is caused

by polluted water. Write a report

describing the type of pollution, the

effects of the disease, and ways to

prevent the pollution.

Health LinkWriting Link SI.10

-Review Summaries and quizzes online at www.macmillanmh.com

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285EVALUATE

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Inquiry Skill: Interpret DataEcosystem changes can affect organisms. Scientists

estimate that once there were more than 500,000 bald eagles in the United States. But by the 1960s, there were fewer than 450 nesting pairs. What happened? Scientists discovered particles of an insecticide called DDT in the eagles’ eggshells. The United States outlawed the use of DDT in 1972. Did that help bring eagles back from the edge of extinction? Scientists learned the answer to that question by collecting and interpreting data.

▶ Learn ItWhen you interpret data, you use information that has

been gathered to answer questions or solve problems. It is much easier to interpret data that have been organized and placed on a table or a graph. Tables and graphs allow you to quickly see similarities and differences in the data.

The table below shows the data gathered about bald eagle eggs. It lists the average number of eggs that hatched in the wild during a 16-year period. It also lists the levels of insecticide found in the eggs during that time.

Bald Eagle–Hatching Data

YearAverage # Hatched

DDT in Eggs parts/million

1966 1.28 42

1967 .75 68

1968 .87 125

1969 .82 119

1970 .50 122

1971 .55 108

1972 .60 82

1973 .70 74

1974 .60 68

1975 .81 59

1976 .90 32

1977 .93 12

1978 .91 13

1979 .98 14

1980 1.02 13

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286EXTEND

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▶ Try ItStudy the table, then interpret data to answer these questions:

In which year did the amount of insecticide in eggshells begin to decline? Why?

Did the amount of insecticide continue in a steady decline?

Do the data give evidence that insecticide in eggs and the numbers of young hatched are related?

▶ Apply It Now use the data from the table to make two line graphs: one to show the average number of eggs that hatched and one to show the insecticide in the eggs. Do your graphs make it easier to interpret data? Why or why not?

Lay one graph carefully on top of the other so the years across the bottom line up. Hold the pages up to the light. How would this help someone understand the relationship between the eagle eggs that hatched and the amount of insecticide in the eggs?

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287EXTEND

SI.19 Communicate ideas in a variety of ways (e.g., symbols, illustrations, graphs, charts, spreadsheets, concept maps, oral and written reports, equations) (SI-M-A7) SI.34 Recognize the importance of communication among scientists about investigations in progress and the work of others (SI-M-B5)Also covers SI.17, SI.22

c

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288

DOK 1

Fill each blank with the best term from the list.

adaptation, p. 250

camouflage, p. 255

ecosystem, p. 224

estuary, p. 269

food chain, p. 224

food web, p. 238

pollution, p. 276

predator, p. 228

prey, p. 228

smog, p. 278

1. All living and nonliving things in an environment make up a(n) .

2. A network of food chains that have some links in common is called a(n)

.

3. An ecosystem where plants and animals are adapted to different salt contents is called a(n) .

4. Animals that are eaten by other animals are called .

5. A characteristic that helps an organism survive in its environment is a(n)

.

6. Some organisms blend in with their environment using .

7. The path that energy and nutrients follow in an ecosystem is a(n) .

8. Air pollution that is caused by particles that are produced when fossil fuels are burned is called .

9. An organism that hunts other organisms for food is called a(n)

.

10. The addition of harmful substances to air, water, and soil is called .

LS.26

LS.25

LS.26

LS.28

LS.29

LS.29

LS.23

SE.49

LS.28

SE.50

Visual Summary

Make a Study Guide Assemble your lesson study guides as shown. Attach the study guides for lessons 4 and 5 to the back. Use this unit study guide to review what you have learned.

Lesson 1 Food chains

show the flow of energy

among living things in an

ecosystem.

Lesson 2 Food webs

are food chains linked

together.

Lesson 3 Organisms

have adaptations that

help them survive in their

environments.

Lesson 4 Earth has

many different types of

major land and water

ecosystems.

Lesson 5 Human

activities, such as pollution

and hunting, can affect

ecosystems.

-Glossary Words and definitions online at www.macmillanmh.com

UNIT 5 Review

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289

DOK 2–3

Louisiana EcosystemsCreate a skit about how organisms interact and survive in a Louisiana ecosystem.

What to Do

1. Working with a group, choose a local ecosystem in which to set your skit.

2. Choose several organisms from your ecosystem that interact.

3. Identify each organism’s adaptations that allow it to survive.

4. Write and perform your skit.LS.26, LS.27, LS.29

Answer each of the following. 18. Infer How do the abiotic characteristics of this pond environment act as limiting factors in this environment?SE.48

-Review Summaries and quizzes online at www.macmillanmh.com

11. Sequence Explain the predator-prey

relationships in the diagram above.

12. Critical Thinking How could you demonstrate a population’s carrying capacity using a classroom full of

students?

13. Why are decomposers important to a food web?

A They prey on carnivores.

B They break down plant and animal

matter.

C They are food for producers.

D They produce oxygen.

14. Cause and Effect Explain why nonnative species can cause problems for native species.

15. Problem and Solution What structural and behavioral adaptations do organisms living in a desert have?

16. Make a Model Draw a diagram of a simple food chain for an ecosystem found in Louisiana.

17. Problem and Solution Create and complete a table with Examples of Pollutants, Effect on Ecosystem, and Solution across the top. List Water, Air, and Soil down the left side. Compare your table with your classmates.

LS.28

SE.48

LS.24

SE.50

LS.29

LS.23

SE.49

19. Main Idea and Details Explain the difference between a food chain and a food web.

20. How do organisms interact in different ecosystems?

LS.25

LS.24, LS.25, LS.27, LS.28

DOK 3

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290

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4 Use the food web below to answer questions 4–5.

How could you describe a predator-prey relationship using the diagram above?

A. The mouse and frog have a predator-prey relationship.

B. The frog and grasshopper have a predator-prey relationship.

C. The grass is a predator of the mouse and grasshopper.

D. The grasshopper is prey for the mouse, snake, and frog.

5 Which shows a correct food chain in the food web diagram above?

A. grass mouse snake

B. grasshopper frog snake

C. snake mouse grass

D. frog grasshopper grass

6 Which is most likely a pollutant that can be found in water?

A. sediment

B. smog

C. oxygen

D. ozone

LS.28

LS.23

SE.49

1 A town used pesticides to control mosquitoes in the area. Scientists later observed that the population of one type of bat had decreased. Which is the best conclusion you can draw from this information?

A. People overhunted the bats.

B. This type of bat ate mosquitoes.

C. The bats’ habitat was destroyed.

D. The bats died from disease spread by the mosquitoes.

2 Which organism is missing from the food chain below?

Sun grasshopper mouse snake

A. grass

B. rabbit

C. coyote

D. earthworm

3 Which of these human activities most likely causes pollution?

A. recycling paper

B. fertilizing your lawn

C. properly disposing of trash

D. planting trees

SE.50

LS.23

SE.49

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291

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Question Review Question Review

1 pp. 276–283 7 pp. 268–269

2 pp. 224–225 8 pp. 224–225, 230–231

3 pp. 276–281 9 pp. 268–269

4 pp. 228–229, 238–239 10 pp. 224–225, 268–269

5 pp. 224–225 11 pp. 254–255

6 pp. 280–281 12 pp. 282–283

7 Which ecosystem are organisms that can survive variations in the salt content of water best adapted to live in?

A. ponds and lakes

B. streams and ponds

C. wetlands

D. estuaries

8 How are decomposers and consumers similar?

A. They carry out photosynthesis.

B. They cannot make their own food.

C. They are not part of a food chain.

D. They are producers.

9 How are rivers and streams different from lakes and ponds?

A. They contain freshwater.

B. They are bodies of running water.

C. They are shallow.

D. They are home to algae.

10 Which resource is most likely needed to sustain a population of herbivorous fish living in a freshwater ecosystem?

A. shrimp

B. salt

C. algae

D. sand

LS.27

LS.24

LS.26

SE.48

11 Which bird’s foot is best adapted for swimming?

A. C.

B. D.

12 The zebra mussel was introduced into a lake ecosystem. Within a few years, the zebra mussel population soared, and it showed no sign of declining. Which conclusion can you draw?

A. The mussels will soon become extinct.

B. The mussels are not adapted to freshwater.

C. The mussels play a vital role in the lake’s ecosystem.

D. The mussels have no natural predators in the lake.

LS.29

SE.50

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lesson 5 human effects on ecosystems -...

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