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BIODIVERSITY 8 OVERVIEW Students will look at the three differnt levels where biodiveristy exists and how the interdependence of plants and animals becomes crucial to their survival. BACKGROUND Biological Diversity Biodiversity is the variety and the abundance of species, their genetic diversity, the communities, ecosystems, and landscapes in which these species occur. In addition, biodiversity refers to the ecological structures, functions, and processes at each of these four levels. (Yahner, 1995, p. 125) As was noted in the previous section on “Benefits of Pennsylvania Forests,” more than 3,500 species of plants and animals have been documented in the various habitats throughout Pennsylvania. The forests of the Commonwealth contain more than 90 species of trees and two-thirds of Pennsylvania’s native plants, creating the primary habitat for 120 species of birds and 50 species of mammals. The variety of forest ecosystems within the eastern deciduous forest provides habitat for an incredible variety of plant and animal species — but in many cases that diversity is being negatively affected by human activity. Pennsylvania has lost as many as 156 species of native vascular plants and vertebrates in the past 300 years. An additional 351 species have become endangered or threatened. Moreover, 56 percent of Pennsylvania’s wetlands have been lost since 1780. Currently, habitat destruction and fragmentation, along with degradation from pollution, are the greatest threats to biodiversity. (Penn’s Woods, p.9) Wetlands in Pennsylvania and elsewhere are being lost at an alarming rate. Close to 45 percent of Pennsylvania’s wetlands are forestland wetlands, such as riparian (streamside) forests, temporary ponds and spring seeps. These forested wetlands are particularly important for watershed protection and as wildlife habitat. Section II — Activity 8 There is concern about the maintenance of natural biodiversity worldwide because of the realization that species are being lost today at an unprecedented rate. “An annual rate of extinction of 20,000 to 50,000 species of flora and fauna (assuming a conservative 10 million total species) or 55 to 150 species per day” is predicted by the year 2000 (Yahner, 1995, p. 1280). In Pennsylvania, there are numerous reasons for the loss of species. Some of these reasons include habitat loss and fragmentation, pollution, and competition from exotic species. How much biodiversity is enough? This is a difficult question to answer. The loss of even one species could have damaging effects on an ecosystem and its organisms in ways that are not yet understood. This can be especially true if the species is a key link between other organisms in the ecosystem. Ecologists and foresters have recognized the advantages of a diverse stand of tree for some time. Diverse stands provide habitat for a wider array of plants and animals, and are less likely to be destroyed by an epidemic of disease or insect attack. Plants and animals have a variety of values and benefits, some not yet known or recognized by humans. Not only do many provide major sources of food, but some are also important for the prevention and cure of human illnesses. Maintaining or restoring biodiversity is essential to sustain all the many benefits of the eastern deciduous forest. Wetlands include areas like freshwater and saltwater marshes, wet meadows, swamps, lagoons, bogs and prairie potholes. All wetlands, whether coastal or inland, provide special habitats that serve areas far beyond their boundaries. Wetlands are uniquely important to plants, animals, humans and the total environment. Biodiversity exists at three different levels: ecosystem diversity, species diver- GRADE LEVELS: Grades 6–9 OBJECTIVES: Students will (1) explain the importance of biodiversity, (2) describe the interdependence of living things, and (3) describe how changes to one species can affect another. PENNSYLVANIA PROPOSED ENVIRONMENT & ECOLOGY STANDARDS ADDRESSED: 4.3.7 C. Explain biological diversity. D. Explain biological diversity and the interdependence of living things on earth. 4.3.10 C. Explain biological diversity as an indicator of a healthy environment. D. Analyze the need for a healthy environment. ESTIMATED DURATION: one or two 30 to 60 minute periods MATERIALS NEEDED: copies of student pages. Biodiversity 77 sity, and genetic diversity. Learning about these different levels will help you understand the full importance of biodiversity. Ecosystem diversity: an ecosystem is a community of living organisms in a particular environment and the nonliving things with which it interacts. A desert, for instance, is an ecosystem that includes organisms such as cacti, lizards, and birds and nonliving parts such as sandy soil, rocks, and sunlight. Ecosystem diversity is used to refer to the various large categories of ecosystems called biomes, such as a desert or rain forest, as well as smaller ecosystems, such as riverbank or the north side of a mountain. The organisms in an ecosystem depend on each other and on the non-living parts for survival. Species diversity: species diversity is often what is meant when the term biodiversity is used. Species diversity is the remarkable variety of species of living things – plants, animals, fungi, and microorganisms. It is not known how many different species there are on earth. Over 1.4 million have been identified, and millions have yet to be determined. In the 1980’s, scientists estimated there were about 5 million species in total. But as they have done more studies, especially in tropical forests where species diversity is enormous, their estimates have gone up and up — to over 30 million. In fact, some research suggests there may be 30 million species of insects alone. Genetic diversity: each individual organism has thousands of genes that determine its characteristics — its color, height, weight, shape, resistance to disease, and so forth. A common group of genes, called the gene pool, exists for each species. Individual members of a species develop with different genes drawn from the gene pool, which results in genetic diversity. Because of this genetic diversity, organisms can evolve and adapt to changes in their environment, including developing the ability to survive diseases. Wild plants and animals have more varied characteristics — that is, more genetic diversity — than cultivated ones. Individual plants of a cultivated crop, for example, all have the same genes, and none may have the characteristic to fight a particular disease. 78 Biodiversity PROCEDURES 1. Hand out copies of “Student Pages,” briefly lead a class discussion to answer the “pre-activity questions.” ◆ What is biodiversity? (Answer: biodiversity refers to the variety of living things on earth.) ◆ Why is biodiversity important? (Answer: biodiversity helps to ensure the health of the planet by maintaining the balance of living things and providing building blocks of evolution.) Encourage students to give examples of why they think biodiversity is important. 2. Have students read the passage under “Activity A” and discuss how habitat changes can affect biodiversity in positive and negative ways. Use the background information above to help facilitate the discussion. Then have students study the graph that shows species loss during this century and answer the questions. Students should recognize that the rate of extinction has sharply increased in the last decade. The reason for the increase is habitat destruction. Answers to questions: ◆ What do living things need in order to survive? (Answer: responses include clean water, food, clean air, each other.) ◆ How do living things depend on each other? (Answer: responses include providing food sources, protection, balance of predators and prey.) ◆ What is an extreme result of habitat loss? (Answer: students should realize that extinction is the extreme result of habitat loss.) 3. Have students complete “Activity B.” Encourage them to identify the interdependence of living things in the landscape depicted in the activity. Answers to questions: ◆ What features of this habitat can you identify? (Answer: meadow, field, trees, agriculture, plants and wildlife.) ◆ What could happen to the biodiversity in this habitat if a flood wiped out the corn crop? (Answer: there would be fewer mice, which would affect the snake, owl and hawk populations.) Section II — Activity 8 ◆ Mice are an important source of food for owls. How could the owls be affected by the loss of the corn crop? (Answer: they would not have mice to eat.) ◆ How would the owls be affected by the loss of the hawks? (Answer: the owls might have more food to eat because they wouldn’t be competing with hawks.) ◆ What other examples of interdependence can you identify? (Answer: hawks eat snakes, snakes eat mice, mice eat corn; the bird nest in the trees and snags; the snakes and mice nest in the meadow.) ◆ What could you do to increase the biodiversity in this habitat? (Answer: possible answers include plant more trees and shrubs.) ◆ What could happen if this habitat were developed into a shopping mall? (Answer: all of the animals would need to find other places to live.) Section II — Activity 8 4. Activity C: have students share their responses to the questions in “Activity B.” Once students have identified evidence of interdependence on the student sheet, have them brainstorm a list of plants and animals and then make their own connections. EXTENSIONS ■ Think about how you depend on other species of plants and animals. During the next 24 hours, have your students keep track of all the things their families use that are connected to another species. For example, furniture comes from trees, clothing comes from plants and animals, food comes from plants and animals. Have them list their connections on a piece of paper. During the next class you may wish to discuss these connections. ASSESSMENT (See Rubric for Biodiversity in General Information Section) Biodiversity 79