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12.4: The Biodiversity Crisis

Created by: CK-12

Lesson 12.4: True or False

Name___________________ Class______________ Date________

Write true if the statement is true or false if the statement is false.

_____ 1. Biodiversity refers to the variety of life and its processes.

_____ 2. Scientists have identified about 1.9 million species alive today.

_____ 3. Many of the most important prescription drugs come from wild species.

_____ 4. Biodiversity helps ensure that at least some species will survive major environmental changes.

_____ 5. Plants and algae maintain the atmosphere; during photosynthesis, they add carbon dioxide and remove oxygen.

_____ 6. Evidence shows that the fifth mass extinction is occurring now.

_____ 7. It is possible that in 1000 years, we could lose more than half of Earth’s species.

_____ 8. The single biggest cause of extinction today is habitat loss due to forest fires.

_____ 9. Global climate change, largely due to the burning of fossil fuels, threatens the existence of many species.

_____ 10. Exotic species introduced by humans into new habitats have resulted in extinction of native species.

_____ 11. Plants fixing nitrogen and making it available to animals is an important ecological service due to biodiversity.

_____ 12. Most species alive today have yet to be identified.

Lesson 12.4: Critical Reading

Name___________________ Class______________ Date________

Read these passages from the text and answer the questions that follow.

Why Is Biodiversity Important?

Human beings benefit in many ways from biodiversity. Biodiversity has direct economic benefits. It also provides services to entire ecosystems.

Economic Benefits of Biodiversity

The diversity of species provides humans with a wide range of economic benefits:

  • Wild plants and animals maintain a valuable pool of genetic variation. This is important because domestic species are genetically uniform. This puts them at great risk of dying out due to disease.
  • Other organisms provide humans with many different products. Timber, fibers, adhesives, dyes, and rubber are just a few examples.
  • Certain species may warn us of toxins in the environment. When the peregrine falcon nearly went extinct, for example, it warned us of the dangers of DDT.
  • More than half of the most important prescription drugs come from wild species. Only a fraction of species has yet been studied for their medical potential.
  • Other living things provide inspiration for engineering and technology.

Ecosystem Services of Biodiversity

Biodiversity generally increases the productivity and stability of ecosystems. It helps ensure that at least some species will survive environmental change. It also provides many other ecosystem services. For example:

  • Plants and algae maintain the atmosphere. During photosynthesis, they add oxygen and remove carbon dioxide.
  • Plants help prevent soil erosion. They also improve soil quality when they decompose.
  • Microorganisms purify water in rivers and lakes. They also return nutrients to the soil.
  • Bacteria fix nitrogen and make it available to plants. Other bacteria recycle the nitrogen from organic wastes and remains of dead organisms.
  • Insects and birds pollinate flowering plants, including crop plants.
  • Natural predators control insect pests. They reduce the need for expensive pesticides, which may harm people and other living things.

Questions

1. List and describe three examples of the economic benefits of biodiversity.

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2. List and describe four examples of ecosystem services of biodiversity.

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Lesson 12.4: Multiple Choice

Name___________________ Class______________ Date________

Circle the letter of the correct choice.

  1. Biodiversity refers to
    1. the variety of life and its processes.
    2. the variety of life and its processes, including the variety of living organisms.
    3. the variety of life and its processes, including the variety of living organisms, and the genetic differences among them.
    4. the variety of life and its processes, including the variety of living organisms, the genetic differences among them, and the communities and ecosystems in which they occur.
  2. Scientists have identified about ____________ species alive today.
    1. 1.9 billion
    2. 1.9 million
    3. 5 million
    4. 30 million
  3. Economic benefits of biodiversity include
    1. the prevention of soil erosion.
    2. a valuable pool of genetic variation.
    3. the natural pollination of flowering plants.
    4. all of the above.
  4. How have exotic species affected biodiversity?
    1. They have resulted in the extinction of native species.
    2. They have resulted in the over-harvesting of fish, trees, and other organisms.
    3. They have resulted in global climate change.
    4. all of the above
  5. What is the biggest cause of extinction today?
    1. pollution
    2. exotic species
    3. global warming
    4. habitat loss
  6. Biodiversity is beneficial to ecosystems in which of the following ways?
    1. the natural prevention of soil erosion
    2. the natural purification of water in rivers and lakes
    3. the natural control of insect pests
    4. all of the above
  7. Scientists estimate that there may be up to ____________ species alive today.
    1. 30 billion
    2. 30 million
    3. 1.9 million
    4. 1.9 billion
  8. It is likely that Earth could lose half of its species in the next ____________ years.
    1. 50
    2. 100
    3. 500
    4. 1000

Lesson 12.4: Vocabulary I

Name___________________ Class______________ Date________

Match the vocabulary word with the proper definition.

Definitions

_____ 1. the variety of life and its processes

_____ 2. species that may out-compete native species

_____ 3. valuable benefit of biodiversity found in wild plants and animals

_____ 4. mass extinction due to human actions

_____ 5. identified species alive today

_____ 6. beginning of the sixth mass extinction

_____ 7. single biggest cause of extinction today

_____ 8. can result in crowding out other species

Terms

a. 1.9 million

b. biodiversity

c. exotic species

d. genetic variation

e. habitat loss

f. overpopulation

g. Pleistocene

h. sixth mass extinction

Lesson 12.4: Vocabulary II

Name___________________ Class______________ Date________

Fill in the blank with the appropriate term.

1. The single biggest cause of extinction today is ____________ loss.

2. Biodiversity generally increases the productivity and stability of ____________.

3. Scientists have identified about ____________ million species alive today.

4. ____________ mass extinctions are recorded in the fossil record.

5. The sixth mass extinction is due to ____________ actions.

6. ____________ species may carry disease, prey on native species, and disrupt food webs.

7. Over 99 percent of all species that ever lived on Earth have gone ____________.

8. ____________ refers to the number of species in an ecosystem or the biosphere as a whole.

9. Global ____________ change is raising Earth’s air and ocean temperatures.

10. Pollution causes widespread harm to ____________.

Lesson 12.4: Critical Writing

Name___________________ Class______________ Date________

Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.

Define biodiversity. Discuss three reasons why biodiversity is important.

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