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Name____________________________ Period___________

Chapter 56: Conservation Biology and Global Change

In the overview at the beginning of the chapter, the author sets the stage for this final chapter of the book. Lets begin by defining conservation biology. Conservation biology integrates ecology, physiology, molecular biology, genetics, and evolutionary biology to conserve biological diversity at all levels. Concept 56.1 Human activities threaten Earths biodiversity 1. Ecologists organize biodiversity on three levels. In the table below, explain the impact of

decreasing diversity in each division. Before answering this question, read to page 1241, where the topic changes to threats to biodiversity.

Level of Biodiversity Impact

Genetic diversity

If one population becomes extinct, then a species may have lost some of the genetic diversity that makes microevolution possible. This erosion of genetic diversity in turn reduces the adaptive potential of the species.

Species diversity

As more species are lost to extinction, species diversity decreases. Many species that are threatened could potentially provide food, fibers, and medicines for human use, making biodiversity a crucial human resource. Additionally, Each loss of a species means the loss of unique genes, some of which may code for enormously useful proteins.

Ecosystem diversity

There is growing evidence that the functioning of ecosystems, and hence their capacity to perform services, is linked to biodiversity. As human activities reduce biodiversity, we are reducing the capacity of the planets ecosystems to perform processes critical to our own survival.

2. Explain the difference between endangered species and threatened species. An endangered species is one that is in danger of extinction throughout all or a significant portion of its range. A threatened species is one that is considered likely to become endangered in the near future. 3. Use this table to organize your thoughts on how the following three threats affect biodiversity. Threat to Biodiversity How It Reduces Biodiversity Habitat loss

When no alternative habitat is available or a species is unable to move, habitat loss may mean extinction. The IUCN implicates destruction of physical habitat for 73% of the species that have become extinct, endangered, vulnerable, or rare in the last few hundred years.

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Introduced species

Free from the predators, parasites, and pathogens that limit their population in their native habitats, such transplanted species may spread rapidly through a new region, often disrupting their new community by preying on native organisms or outcompeting them for resources. Introduced species contribute to approximately 40% of extinctions recorded since 1750.

Overexploitation

Overharvesting endangers species in restricted habitats or with slow reproductive rates, thus decreasing biodiversity.

4. List five introduced species that present a serious threat to their new communities. Explain the

damage done by each introduced species. Include two introduced species that are a threat in your own region of the country. Indicate these with an asterisk (*).

Introduced Species Damage

1. Brown tree snake Since its introduction, 12 species of birds and 6 species of lizards that the snakes ate have become extinct on Guam, which had no native snakes.

2. Kudzu Has taken over large areas of landscape in the southern United States. Climbs to the top of very tall trees, and blankets them and eventually may kill them. Aggressive competitor for light and water.

3. European starling Quickly spread across North America, where its population exceeds 100 million, displacing many native songbirds

4. Chestnut blight Destroyed the American chestnut, which was the dominant tree species of the temperate forests of the eastern United States

5. Multiflora rose, privet, Asian honeysuckle, Bradford pear

These are some of the aggressive species that are crowding out native plants in the eastern United States. They outcompete for resources, and provide poor-quality food for species depending on the native plants. The student should be encouraged to give locally important introduced species.

Concept 56.2 Population conservation focuses on population size, genetic diversity, and critical habitat 5. What do conservation biologists who adopt the small-population approach study? Conservation biologists who adopt the small-population approach study the processes that cause extinctions once population sizes have been severely reduced.

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6. Explain what an extinction vortex is, and describe one field study that supports this idea. A small population is vulnerable to inbreeding and genetic drift, which draw the population down an extinction vortex toward smaller and smaller population size until no individuals survive. 7. Why is genetic variation the key issue in the small-population approach? Genetic variation is a key issue with the small-population approach because it enables evolutionary responses to environmental change, such as the appearance of new strains of pathogens. 8. On what type of population does the declining-population model focus? The declining-population model focuses on threatened and endangered populations that show a downward trend, even if the population is far above its minimum viable population. 9. What is the emphasis for study in the declining-population model? The declining-population approach emphasizes the environmental factors that caused a population decline in the first place. If, for instance, an area is deforested, then species that depend on trees will decline in abundance and become locally extinct, whether or not they retain genetic variation. 10. Scientists drilled nest holes for red-cockaded woodpeckers in an attempt to increase their

population levels. How is this action a response to the declining-population model? This is a response to the declining-population model because it focused on what factors were causing the red-cockaded woodpeckers to decline in the first place, the destruction of their habitat and a lack of breeding cavities. Concept 56.3 Landscape and regional conservation help sustain biodiversity 11. Describe how the increase in cowbirds is related to forest fragmentation. Cowbirds need forests, where they can parasite the nests of other birds, and open fields, where

they can forage for insects. Thus, their populations are growing where forests are being cut and fragmented, creating more edge habitat and open land.

12. What are potential positive and negative effects of movement corridors? Movement corridors can promote dispersal and reduce inbreeding in declining populations and are especially important to species that migrate seasonally. However, a corridor can also be harmfulfor example, by allowing the spread of disease. 13. Explain the concept behind a zoned reserve. A zoned reserve is an extensive region that includes areas relatively undisturbed by humans surrounded by areas that have been changed by human activity and are used for economic gain.

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The key challenge to the zoned reserve approach is to develop a social and economic climate in the surrounding lands that is compatible with the long-term viability of the protected core. Concept 56.4 Earth is changing rapidly as a result of human actions This section looks at human impact on ecosystems. 14. How has agriculture affected nitrogen cycling? What are some negative consequences of nutrient enrichment? Agricultural practices have increased the amount of nitrogenous materials in the soil. After it exceeds a critical load, this material eventually leaches into groundwater or runs off into freshwater and marine ecosystems, contaminating water supplies and killing fish. 15. Explain the process of biological magnification. Discuss at least one example. Accumulated toxins become more concentrated in successive trophic levels of a food web. This phenomenon is referred to as biological magnification and it occurs because the biomass at any given trophic level is produced from a much larger biomass ingested from the level below. For example, biological magnification of PCBs has been found in the food web of the Great Lakes, where the concentration of PCBs in herring gull eggs, at the top of the food web, is nearly 5,000 times that in phytoplankton, at the base of the food web. 16. What is meant by the greenhouse effect? What would life on Earth be like without this effect? Much of the solar radiation that strikes the planet is reflected back into space. Although CO2 , water vapor, and other greenhouse gases in the atmosphere are transparent in visible light, they intercept and absorb much of the infrared radiation Earth emits, re-reflecting some of it back toward Earth. This process retains some of the solar heat. Without the greenhouse effect, the average air temperature at Earths surface would be a frigid 18C, and life as we know it would not exist. 17. What is contributing to the great increase in atmospheric carbon dioxide? What are potential effects of this increase? Fossil fuel burning could contribute to the warming of the earth. An increase of only 1.3C would make the world warmer than at any time in the past 100,000 years. A warming trend would also alter the geographic distribution of precipitation, likely making agricultural areas of the central United States much drier, for example. 18. How is atmospheric ozone depleted? What are projected effects of this depletion? The destruction of atmospheric ozone results primarily from the accumulation of

chlorofluorocarbons (CFCs), chemicals once used widely in refrigeration and manufacturing. Decreased ozone levels in the stratosphere increase the intensity of UV rays reaching Earths surface. The consequences of ozone depletion for life on Earth may be severe for plants, animals, and microorganisms. Some scientists expect increases in both lethal and nonlethal forms of skin cancer and in cataracts among humans, as well as unpredictable effects on crops and natural communities.

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Concept 56.5 Sustainable development can improve human lives while conserving biodiversity 19. Explain the concept behind the phrase sustainable development. Sustainable development is the concept of economic development that meets the needs of

people today without limiting the ability of future generations to meet their needs. Test Your Understanding Answers Now you should be ready to test your knowledge. Place your answers here: 1. d 2 .d 3. e 4. a 5. c 6. a