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Name Section Date 3.1 How Changes Occur Naturally in Ecosystems Summary Textbook pages 108–121 Before You Read How do you think mature forests, such as the temperate rainforests of coastal British Columbia, change over time? Write your answer on the lines below. ◆ ? Create an Outline Create an outline highlighting the typical changes that occur in an ecosystem undergoing primary succession. ✔ ● Reading Check 1. What is adaptive radiation? How do organisms adapt to change? In natural selection, the best-adapted members of a species survive to reproduce. These individuals may pass favourable characteristics on to their offspring. As abiotic and biotic components of their environment change, adaptive radiation may result. This term describes the change from a common ancestor into a number of different species that “radiate out” to inhabit different niches. For example, 13 species of finches that fill different niches on the Galapagos Islands are thought to have developed from a single species from mainland South America. ● ✔ How do ecosystems change over time? Ecological succession refers to changes that take place over time in the types of organisms that live in an area. There are two types of ecological succession: 1. Primary succession: Primary succession occurs in areas where no soil exists, such as following glaciation or a lava flow. Wind and rain carry spores of lichens to these areas. Lichens obtain nutrients by secreting chemicals that break down rock. As lichens decay, they add organic matter to the developing soil. The first organisms to survive and reproduce in an area are called pioneer species. They are adapted to grow in harsh, nutrient-poor conditions. In time, often over hundreds of years, the weathering of rocks and decay of pioneer species cause soil formation. The abiotic conditions of the ecosystem continue to change as new species of plants and animals colonize the area, each competing for nutrients, moisture, and sunlight. More niches are created and biodiversity increases. 38 MHR • Section 3.1 038_055_BCSci10_U1CH03_098461.in38 38 How Changes Occur Naturally in Ecosystems Pdf 2nd © 2008 McGraw-Hill Ryerson Limited 6/30/08 6:03:11 PM Section Name 3.1 Date Summary continued Eventually, primary succession leads to the development of mature climax communities, such as a boreal forest or grassland. 2. Secondary succession: Small disturbances, such a fire, often occur in ecosystems. Secondary succession— succession that occurs as a result of a disturbance to an area that already has soil and was once the home of living organisms—occurs as a result. It proceeds much faster than primary succession since micro-organisms, insects, ✔ seeds, and nutrients still exist in the soil. ● ✔ ● Reading Check 2. Describe the difference between primary and secondary succession. How do natural events affect ecosystems? Natural events can destroy habitats, reduce biodiversity, and cause regions to undergo succession. Some examples include: • flooding: results in soil erosion, pollution, and disease when toxins or harmful bacteria from untreated sewage enter drinking water • drought: plants and animals die due to lack of water • insect infestations: often result in succession in forests because insects destroy older, weaker trees • tsunamis: huge, rapidly moving ocean waves destroy habitats and salt water carried onto shore changes soil composition © 2008 McGraw-Hill Ryerson Limited 038_055_BCSci10_U1CH03_098461.in39 39 Section 3.1 How Changes Occur Naturally in Ecosystems • MHR Pdf 2nd 39 6/30/08 6:03:13 PM Name Cloze Activity Section 3.1 Date Use with textbook pages 108–117. Change in ecosystems Vocabulary adaptive radiation climax community drought ecological succession flooding insect infestations natural selection pioneer species primary succession secondary succession tsunami Use terms in the vocabulary box to fill in the blanks. Use each term only once. 1. In the process of , living organisms change as the abiotic and biotic components in their environment change. 2. describes the change from a common ancestor into a number of different species that “radiate out” to inhabit different niches. 3. Scientists use the term to refer to changes that take place over time in the types of organisms that live in an area. 4. occurs in an area where no soil exists, such as on bare rock. 5. The lichens and others plants that are the first organisms to survive and reproduce in an area are known as . 6. The process of primary succession leads to the development of a mature community, which is sometimes called a . 7. occurs as the result of a disturbance to an area that already has soil and was once the home of living organisms. 8. can result in soil erosion and soil pollution if toxic chemicals are present in floodwaters. 9. is a huge, rapidly moving ocean wave. 10. 11. 40 can result in crop failures and livestock deaths. , such as the mountain pine beetle in the forests of British Columbia, have a devastating effect on the forest canopy, and bird and mammal habitats. MHR • Section 3.1 038_055_BCSci10_U1CH03_098461.in40 40 How Changes Occur Naturally in Ecosystems Pdf 2nd © 2008 McGraw-Hill Ryerson Limited 6/30/08 6:03:15 PM Name Analyzing Information Section 3.1 1.1 Date Use with textbook pages 111–114. Primary and secondary succession 1. Glacier Retreating As a glacier retreats, the process of primary succession will occur. Describe the various stages that lead to the development of a mature community. 2. Results of Forest Fire After a forest fire, not much is left except ash and burnt trees. Describe the sequence of events that will occur during secondary succession. © 2008 McGraw-Hill Ryerson Limited 038_055_BCSci10_U1CH03_098461.in41 41 Section 3.1 How Changes Occur Naturally in Ecosystems • MHR Pdf 2nd 41 6/30/08 6:03:17 PM Name Applying Knowledge Section 3.1 Date Use with textbook pages 115–117. How natural events affect ecosystems For each major event listed below, summarize the effects on their mature communities. Natural event Effects on mature community Fire Flooding Tsunami Drought Insect infestation 42 MHR • Section 3.1 038_055_BCSci10_U1CH03_098461.in42 42 How Changes Occur Naturally in Ecosystems Pdf 2nd © 2008 McGraw-Hill Ryerson Limited 6/30/08 6:03:20 PM Name Assessment Section 3.1 Date Use with textbook pages 108–117. How changes occur naturally in ecosystems Match each Term on the left with the best Descriptor on the right. Each Descriptor may be used only once. Term 1. 2. 3. 4. 5. Descriptor adaptive A. a mature commuradiation nity that continues to climax change over time community B. the development ecological of a number of new succession species from a comnatural selection mon ancestor pioneer species C. organisms, such as lichens and other plants, that are the first to survive and reproduce in an area D. changes that take place over time in the types of organisms that live in an area E. the process in which, over time, the best adapted members of a species will survive and reproduce Circle the letter of the best answer. 6. The process that makes change possible in living things is 7. Each of these finches from the Galapagos Islands has evolved different shapes and sizes of beaks. This is an example of: A. primary succession B. secondary succession C. bioremediation D. adaptive radiation 0 Years 300 Years 8. The diagram above represents which of the following: A. adaptive radiation B. climax community C. ecological succession D. natural succession 9. An example of a pioneer species would be A. moss B. lichen A. ecological succession C. deciduous trees B. primary succession D. coniferous trees C. natural selection D. adaptive radiation © 2008 McGraw-Hill Ryerson Limited 038_055_BCSci10_U1CH03_098461.in43 43 Section 3.1 How Changes Occur Naturally in Ecosystems • MHR Pdf 2nd 43 6/30/08 6:03:22 PM Comprehension Analyzing Information PCBs and the orca Page 36 Primary and secondary succession Page 41 1. PCBs are synthetic chemicals. Their full chemical name is polychlorinated biphenyl. 2. PCBs were used for industrial products, such as heat exchange fluids, paints, plastics, and lubricants for electrical transformers. 3. PCBs stay in the environment for a long time. Aquatic ecosystems and species that feed on aquatic organisms are especially sensitive to the effects of PCBs. PCBs bioaccumulate and biomagnify and also have a long half-life. 4. PCBs become concentrated in the orca’s blubber. 5. When salmon stocks are low, the orca’s blubber is burned for energy. The PCBs are released into the orca’s bloodstream and interfere with its immune system making it more susceptible to disease. 6. Diagram should be similar to Fig. 2.55 on page 95 of the student textbook. The pyramid should include the food chain for orcas and demonstrate the total PCB load that the orca is exposed to. 1. Answer should include the following sequence: • Lichens begin to grow. This begins the process of soil formation. • Plants, such as mosses, begin to grow. • Insects, micro-organisms, and other organisms move in. • Grasses, wildflowers, and shrubs begin to grow. More insects and micro-organisms move in. • Tree seeds are transported by animals. Deciduous trees grow. • Coniferous trees germinate. • Mature community develops. 2. Answer should include the following sequence: • Exposed soil will contain micro-organisms, worms, and insects as well as the seeds of wildflowers, weeds, grasses, and trees. • Other seeds may blow in or be carried in by animals. • Deciduous trees grow. Assessment Effects of bioaccumulation on ecosystems Page 37 • Coniferous trees return. • Mature community may only take decades to establish. 1. F 2. D 3. E 4. B 5. C 6. A 7. C 8. D 9. B 10. C 11. A 12. D Chapter 3 Ecosystems continually change over time. Section 3.1 How Changes Occur Naturally in Ecosystems Applying Knowledge How natural events affect ecosystems Page 42 NATURAL EVENT EFFECTS ON MATURE COMMUNITY Fire • causes secondary succession • results in regrowth Flooding • causes soil erosion • results in soil and water pollution, leading to widespread disease Tsunami • water carries away or destroys plants and animals • disrupts habitats and foods webs • salt from salt water changes composition of soil Drought • destroys habitats • results in the death of plants and animals • leads to crop failures and livestock deaths Insect Infestation • results in losses to forest canopy • disrupts habitats and food webs Cloze Activity Change in ecosystems Page 40 1. natural selection 2. adaptive radiation 3. ecological succession 4. primary succession 5. pioneer species 6. climax community 7. secondary succession 8. flooding 9. tsunami 10. drought 11. insect infestations Assessment How changes occur naturally in ecosystems Page 43 1. B 2. A 3. D 4. E 5. C 6. C 7. D 8. C 9. B © 2008 McGraw-Hill Ryerson Limited Workbook Answers • MHR 5