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Teaching about energy in biological processes is supported by 6 key concepts:3.1 The Sun is the major source of energy for organisms and the ecosystems of which they are a part. Producers such as plants, algae, and cyanobacteria use the energy from sunlight to make organic matter from carbon dioxide and water. This establishes the beginning of energy flow through almost all food webs. Energy from the Sun fuels life on EarthThe continual input of energy, mostly from sunlight, sustains the process of life. Sunlight allows plants, algae and cyanobacteria to use photosynthesis to convert carbon dioxide and water into organic compounds like carbohydrates. This process is the fundamental source of organic material in the biosphere. There are a few exceptions to this, such as ecosystems living around hydrothermal vents on the ocean floor, which derive their energy from the chemical compounds such as methane and hydrogen sulfide. In either case, the overall productivity of an ecosystem is controlled by the total energy available. Energy flows through all life on EarthDiagram of a food chain for waterbirds of the Chesapeake Bay. Image from US Geological Survey Food webs show how energy moves throughout a system. Plants use energy from the Sun to create organic matter. Plants are then eaten by primary consumers who are in turn eaten by secondary consumers, and so on. In each step, the energy that was originally emitted by the Sun is consumed, but that energy also dissipates with each step. Animals use up 90% of the energy contained in the foods they eat for their normal activities. This leaves just 10% of the original energy available for the next consumer. The efficiency of the food chain decreases as you go upward. (Learn more about the transfer of energy in the food chain.) This points out a critical factor in the distribution of energy in human foods too. Eating producers (plants) at the bottom of the food chain is the most efficient way for humans to acquire energy for living. This has implications for humans as we strive to keep a growing human population adequately nourished. These ideas also introduce the origin of organic matter that later can become fossil fuels. The original source of energy in fossil fuels is sunlight, which fueled photosynthesis. Oil and natural gas come from photosynthetic plankton, which have been preserved in sediments on the ocean floor, heated, and chemically altered into hydrocarbons. Coal comes from plants that have been buried in sediment, compacted, and preserved. These ideas are further explored in Energy Principle 4. (Learn more about where oil comes from.) Helping students understand these ideasCompanion video by the Department of Energy While many students can readily relate to the idea of the terrestrial food web, the marine food web may be less familiar to them. Students may be surprised to learn that about half the Earth's primary productivity of organic material comes from the oceans. Other topics that tie into this theme are:
Bringing these ideas into your classroomA variety of foods, each with its own embodied energy and environmental footprint. Compared to Energy Principles 1 and 2, this principle is more concrete and easier to visualize. We all have direct experiences with different types of foods. Many of these concepts, such as how sunlight drives photosynthesis and food webs, are commonly taught in middle school and high school curricula. Educators can take these opportunities to tie in an energy theme with these topics. A quantitative approach can be used to examine the energy embodied in different types of foods. Here are some examples of activities that do this.
Related teaching materialsTeaching about Food with teaching materials for college students A hands-on way to teach these topics is from the point of view of a meal or a community garden. All of the concepts contained in this principle can be illustrated in a garden that produces food. Teaching materials from the CLEAN collection
Find activities and visuals for teaching this topicSearch by grade level: middle school high school intro college upper college search all grade levels References
How does climate affect the type of biome found in an area?Because climate determines plant growth, it also influences the number and variety of other organisms in a terrestrial biome. Biodiversity generally increases from the poles to the equator. It is also usually greater in more humid climates.
What are some changes that can occur in ecosystems?Some changes that can occur in ecosystems are seasons, tide cycles, population sizes, succession, evolution, landscape changes, and climate changes.
Which of the following is true about the effects of altitude on climate?Which of the following is true about the effects of altitude on climate? Temperature, atmospheric pressure, and humidity decrease with increasing altitude.
Which organisms provide most of the nutrients supply in the ocean?Importance of phytoplankton
Phytoplankton are the foundation of the aquatic food web, the primary producers, feeding everything from microscopic, animal-like zooplankton to multi-ton whales. Small fish and invertebrates also graze on the plant-like organisms, and then those smaller animals are eaten by bigger ones.
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