Date. 1 St primary producer obtain energy from grass, algae (plants) the Sun

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1 Name Energy Textbook pages Iow n Date Ecosystems Sectioii 2i Summary Before You Read In this section, you will explore food chains and food webs, as well as food pyramids. What are the main differences between a chain and a web? Record your ideas below. Mark the Text In Your Own Words Define the bold terms in this summary in your own words. Reading Check 1 What are the different steps in a food chain called? How does energy flow in an ecosystem? Energy flow is the transfer of energy from one organism to another in an ecosystem. Every organism interacts with its ecosystem in two ways: 1. the organism obtains food energy from the ecosystem 2. the organism contributes energy to the ecosystem How are energy flow and feeding relationships in ecosystems modelled? Ecologists use three models to illustrate energy flow and feeding relationships in an ecosystem: 1. Food chains: Food chains show the flow of energy from plant to animal and from animal to animal. Plants are called producers because they produce food in the form of carbohydrates during photosynthesis. Consumers eat plants and other organisms. Each step in a food chain is called a trophic level. Trophic Type of Organism Energy Source Example 1 St primary producer obtain energy from grass, algae (plants) the Sun 25d primary consumer obtain energy from grasshoppers, krill primary producers (herbivores) 3rd secondary obtain energy from frogs, crabs consumer primary consumers (carnivores) 4th tertiary consumer obtain energy from hawks, sea otters secondary (top carnivores) consumers 14 MHR Section 2.1 Energy Flow in Ecosystems 2008 McGraw-HUI Ryerson Limited

2 Name Date Section 2.1 Summary 2. Food webs: Many animals are part of more than one food chain in an ecosystem because they eat or are eaten by several organisms. Interconnected food chains are illustrated in a model called a food web. Animals that eat plants and other animals are called omnivores. 3. Food pyramids: A food pyramid (or ecological pyramid) is a model that shows the loss of energy from one trophic level to another. When one organism consumes another, the energy stored in the food organism is transferred to the consumer. However, not all of this energy is incorporated into the consumer s tissues. Between 80 and 90 percent of it is used for chemical reactions and is lost as heat. This means ecosystems can support fewer organisms at higher trophic levels, as less energy reaches these levels. continued DReading Check 1. What does a food pyramid demonstrate? lii[iiiii great horned long-tailed weasel jackrabbit -. grasses Food pyramid How do dead organisms contribute to energy flow? Decomposition describes the breakdown of organic wastes and dead organisms. Energy is released in decomposition. When living organisms carry out decomposition, it is called biodegradation. Detrivores, such as small insects, earthworms, bacteria, and fungi, obtain energy and nutrients by eating dead plants and animals, as well as animal waste. Decomposers, such as bacteria and fungi, change wastes and dead organisms into nutrients that can once again be used by plants and animals. Detrivores and decomposers feed at every trophic level McGraw-Hit Ryerson Limited Section 2.1 Energy Flow in Ecosystems MHR 15

3 (C0 Like other organisms, your body relies on nutrients to stay healthy. Based on your current understanding, create a definition of what you think a nutrient is. Write your definition in the lines below. processes: 2. the nitrogen cycle Mark the Text 1. the carbon cycle Reading Check Before You Read Textbook pages Check for Understanding sure to reread any parts you do not understand. Highlight any sentences that help you improve your understanding. 1. Name the three main nutrient cycles. Summary Nutrient Cycles in cosystems 22 Sectioi Nutrient cycles describe the flow of nutrients in and out of as living organisms and the atmosphere. Nutrients can also are stored for short periods of time in short-term stores, such Earth s biosphere. Nutrients spend different amounts of time Name Date As you read this section, be 2008 McGraw-Hill Ryerson Limited Section 2.2 Nuirent Cvces ir Ecosvsternc MHR 2 and animals obtain energy by converting carbohydrates and oxygen (On) into carbon dioxide and water. 2. Cellular respiration: During cellular respiration, plants 2) into chemical energy. Carbon is an essential component of cells and life-sustaining chemical reactions. Carbon is cycled through living and decaying organisms, the atmosphere, bodies of water, and converts solar energy and atmospheric carbon dioxide gas 1. Photosynthesis: Photosynthesis is a chemical reaction that soil and rock. Carbon moves between stores via six main How does the carbon cycle work? 3. the phosphorus cycle and other life processes. They are constantly recycled within in stores within the atmosphere, oceans, and land. Nutrients be incorporated into longer-term stores, such as Earth s crust. balanced. There are three main cycles that move nutrients stores as a result of biotic and abiotic processes. Without Nutrients are chemicals required for plant and animal growth How are nutrients cycled in the biosphere? human interference, nutrient cycles are almost perfectly through terrestrial and aquatic ecosystems:

4 How do human activities affect the carbon cyc e? Human activities, such as fossil fuel combustion and land clearance, quickly introduce carbon into the atmosphere from longer-term stores. These actions increase the levels of carbon dioxide, a greenhouse gas that contributes to global climate change. 6. Forest fires 32-) in their shells, which eventually form sedimentary (CC oceans. Marine organisms store carbon-rich carbonate rock. 3. Decomposition: Decomposers release carbon dioxide into 4. Ocean processes: Dissolved carbon dioxide is stored in 5. Volcanic eruptions organic matter in soil. the atmosphere through the decomposition of carbon-rich Name Date

5 How does the nitrogen cycle work? Nitrogen is an important component of DNA and proteins. Most nitrogen is stored in the atmosphere, where it exists as nitrogen gas (N2). It is also stored in bodies of water, living organisms, and decaying organic matter. Most organisms cannot use atmospheric nitrogen gas. The nitrogen cycle involves four processes, three of which make nitrogen available to plants and animals. 1. Nitrogen fixation: Nitrogen gas is converted into nitrate 3j and ammonium (NH (N0 4j, compounds that are usable by plants. Nitrogen fixation occurs mainly through nitrogen-fixing bacteria, and when lightning strikes in the atmosphere. 2. Nitrification: Ammonium is converted into nitrate and nitrite (N0 2j through the work of nitrifying bacteria. 3. Uptake: Useable forms of nitrogen are taken up by plant roots and incorporated into plant proteins. When herbivores and omnivores eat plants, they incorporate nitrogen into their own tissues. 4. Denitrification: Denitrifying bacteria convert nitrate. back into atmospheric nitrogen. 22 MHR Section 2.2 Nutrient Cyc es jr osvsterns 2008 Mc3raw-HW Rverson Limited

6 How do human activities affect the nitrogen cycle? Fossil fuel combustion and burning organic matter release nitrogen into the atmosphere, where it forms acid rain. cortnued Summary 1. List a human activity that 2008 McGraw-HW Rverson Limited Section 2.2 Nutrient Cycles in Ecosystems MHR 23 Commercial fertilizers and phosphate-containing detergents can cause changes to a phosphorus cycle. Slash-and-burn forest clearance reduces enter waterways and contribute additional phosphate to the flijtflnt cycle. phosphate levels, as phosphate in trees enters soil as ash. It leaches out of the soil and settles on lake and ocean bottoms, unavailable to organisms. cycle 9 How do human activities affect the phosphorus Check through chemical or physical means breaks down rock, releasing phosphate into the soil from longer-term stores. 43-) rock and sediments on the ocean floor. Weathering (P0 Phosphorus carries energy to cells. It is found in phosphate rock. It remains trapped for millions of years until it is Organisms take up phosphorus. When they die, decomposers floors of lakes and oceans, eventually forming sedimentary How does the phosphorus cycle work? return phosphorus to the soil. Excess phosphorus settles on exposed through geologic uplift or mountain building. into the atmosphere or leaches into lakes and streams. High and increased algal growth in aquatic ecosystems, depriving Chemical fertilizers also contain nitrogen, which escapes levels of nitrogen cause eutrophication (too many nutrients) aquatic organisms of sunlight and oxygen. Section Name Date 2.2

7 Name Date ffects of Diooccumulotion on Ecosystems Textbook pages Section 23 Siininry Before You Read Everyday activities, such as driving or heating your home, often pollute ecosystems. In your opinion, which human activity is the most harmful to the environment? Explain. Mark the Text Summarize As you read this section, highlight the main points in each paragraph. Then write a short paragraph summarizing what you have learned. DReading Check 1. What is the difference between bioaccumulation and biomagnification? How can pollutants affect food chains and ecosystems? Human activity creates many harmful pollutants. These build up in the environment when decomposers are unable to break them down. Plants take up these pollutants. The pollutants are then transferred along the food chain until they reach the highest trophic level. Bioaccumulation refers to the gradual build-up of pollutants in living organisms. Biomagnilication refers to the process in which pollutants not only accumulate, but also become more concentrated at each trophic level. Organisms at lower trophic levels may be affected by the pollutant, but primary, secondary, and tertiary consumers will be more affected, because levels will build up in their tissues as they consume contaminated food. An example of this is the PCB concentrations in the orca s food web. When orcas consume food contaminated with PCBs, they store some of the PCBs in their blubber. When salmon (their primary food) is not available, orcas use their blubber for energy. This releases PCBs into their system. Pollutants can build up to toxic levels in organisms at the top of the food chain. They can also affect entire ecosystems when keystone species, species that greatly affect ecosystem health, or the reproductive abilities of species are harmed. What are some human-made compounds that bioac cumulate and biomagnify? PCBs (polychlorinated biphenyls) PCBs were once widely used in industrial products but are now banned in North America. They interfere with normal functioning of the body s immune system and cause problems with reproduction. 30 MHR Secton 2.3 Effects of Bioaccumuation on Ecosystems 2008 McGraw-Hill Ryerson Limited

8 PCBs have a long half-life (time it takes for the amount of a substance to decrease by halt). They stay in the environment for a long time. Aquatic ecosystems are most sensitive to PCBs. Organisms at high trophic levels, like the orca, retain high levels of the pollutant. POPs (persistent organic pollutants) POPs are harmful, carbon-containing compounds that remain in water and soil for many years. DDT (dichioro-diphenyl-trichioroethane) is a toxic POP that was used as a pesticide in the past to control disease carrying mosquitoes. Accumulation is measured in parts per million (ppm). This refers to one particle of a given substance mixed with other particles. DDT is harmful at 5 ppm McGraw-Hill Ryerson Limited Section 2.3 Effects of Bioaccumuation on Ecosystems MHR 31

9 Reading Check 1. Provide an example of how the effects of chemical pollution can be reduced. Heavy metals Once heavy metals enter the biosphere, they do not degrade, and they can not be destroyed. Heavy metals, such as lead (Pb), cadmium (Cd), and mercury (Hg), are toxic at low concentrations; however, small amounts are naturally present in soil. For humans, the most serious source of cadmium poisoning is smoking. Human activities can cause these metals to build up in ecosystems. In the past, use of lead-based insecticides, batteries, and paints, increased lead to harmful levels. Despite reductions, lead still enters ecosystems through improperly disposed electronic waste. How can the effects of chemical pollution be reduced? Some harmful chemical pollutants can be removed from the environment by bioremediation, a process where micro-organisms or plants help clean them up. Reacting contaminants with certain chemicals can also make them less harmful. 32 MHR Section 2.3 Effects of Bioaccumulation on Ecosystems 2008 McGraw-Hill Ryerson Limited