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Chemistry Companion Document
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Unit 7 - Matter and Energy in Ecosystems
Biology Unit 7 Content Statements and Expectations
HS SCIENCE COMPANION DOCUMENT
Matter and Energy in Ecosystems
Energy transformations from the Sun to organisms provide energy for all life forms to exist.
Matter transfer in ecosystems between living and non-living organisms provides the materials necessary for all life.
Matter and energy are conserved in ecosystems, although their transformations are not efficient.
B2: Organization and Development of Living Systems
B2.1 Transformation of Matter and Energy in Cells
B2.5 Living Organism Composition
B3.1 Photosynthesis and Respiration
B3.3 Element Recombination
(Content Statement Clarification)
B2.1A - Explain how cells transform energy (ultimately obtained from the sun) from one form to another through the processes of photosynthesis and respiration. Identify the reactants and products in the general reaction of photosynthesis.
Clarification: Explanation is limited to one way flow of energy from the Sun to organisms and energy transformations that occur in the processes of photosynthesis and respiration. Reactants and products may be identified either by chemical formula or name.
B2.1B - Compare and contrast the transformations of matter and energy during photosynthesis and respiration.
B2.5C - Describe how energy is transferred and transformed from the Sun to energy-rich molecules during photosynthesis.
Clarification: Energy-rich molecules are limited to simple carbohydrates produced during photosynthesis.
B3.1A - Describe how organisms acquire energy directly or indirectly from sunlight.
B3.1B - Illustrate and describe the energy conversions that occur during photosynthesis and respiration.
Clarification: Illustrations may include flowcharts, graphic displays or pictures.
B3.1C - Recognize the equations for photosynthesis and respiration and identify the reactants and products for both.
Clarification: The equations may be either words or formulas.
C6H12O6 (glucose/sugar) + 6 O2 (oxygen) 6 CO2 (carbon dioxide) + 6 H2O (water). Also located in Unit 3- Cell Energetics
B3.1D - Explain how living organisms gain and use mass through the processes of photosynthesis and respiration.
B3.1e - Write the chemical equation for photosynthesis and cellular respiration and explain in words what they mean.
Clarification: The general form of the equations will be organized with the reactants on the left side of the equation and the products on the right, but they may consist of names of the participants and their chemical formulas. See also Clarification for B3.1C above.
B3.2A - Identify how energy is stored in an ecosystem.
Clarification: Identification is limited to discussion of chemical bonds as stored energy structures.
B3.2B - Describe energy transfer through an ecosystem, accounting for energy lost to the environment as heat.
Clarification: Descriptions are limited to non-numerical accounting of inefficiencies of energy transformations.
B3.2C - Draw the flow of energy through an ecosystem. Predict changes in the food web when one or more organisms are removed.
Clarification: Drawings will not include numerical data, but emphasize inefficient conversions as energy moves through the trophic levels. Predictions may include changes in populations of organisms at various trophic levels as energy available to them changes.
B3.3A - Use a food web to identify and distinguish producers, consumers, and decomposers and explain the transfer of energy through trophic levels.
B3.3b - Describe environmental processes (e.g., the carbon and nitrogen cycles) and their role in processing matter crucial for sustaining life.
Clarification: Descriptions are limited to names of participants in the carbon and nitrogen cycles and how they are used by and cycled through organisms.
abiotic components of ecosystems
breakdown of food molecules
cellular energy conversion
chemical organization of organisms
energy requirements of living systems
flow of energy
flow of matter
organic compound synthesis
recombination of chemical elements
release of energy
transforming matter and/or energy
transporting matter and/or energy
Real World Context:
Life is comprised of many complex cellular processes that occur in all organisms, including plants and animals. These processes include: the transport of materials, energy capture and release, protein building and waste disposal.
The flow of energy into ecosystems is from the Sun to producers through the process of photosynthesis. Producers are able to use this energy to convert carbon dioxide, a gas, and water into energy-rich, highly-condensed carbon compounds, usually carbohydrates. Plants may then use these materials for their own cellular energy needs by the process of cellular respiration. Consumers also obtain usable energy from the biochemical breakdown of carbohydrates and molecules derived from them during respiration. In this way, derived directly or indirectly from a plant source, carbohydrates are foods that, when converted into waste materials, yield usable energy for the organism in the process of cellular respiration. Ultimately, nearly all organisms will be subjected to breakdown by decomposers, who themselves convert mass into waste materials, using the derived energy.
When consumers eat plants or other consumers, they are transferring matter, in the form of flesh, through an ecosystem. Energy is also being transferred as it is stored in the chemical bonds that bind the food molecules together. As this energy is transferred through ecosystems, liberated for organismal use by cellular respiration, conversions are not entirely efficient and heat is lost as a by-product at each step, dissipated into the environment, leaving less
energy available to each successive trophic level.
Organisms may be classified as producers, consumers and decomposers, based on their feeding relationships within their particular food web. These food webs may be from ecosystems that are widely represented in textbooks and of importance to all students, even if they do not live near them.
Changes in relationships and populations of producers and consumers may occur as the result of the loss of one or more types of organisms in the ecosystem. The loss of any group of organisms from an ecosystem changes the flow of energy within that system.
The overall cycling of matter, specifically carbon and nitrogen, through ecosystems as it passes between living systems to abiotic components of ecosystems is very important because it shows the interdependence of organisms with their physical environment, and vice versa.
Human created disturbances in ecosystems or environments, including local and global climate change, uses of tilling and pesticides to favor human crops, human land use, harvesting of fish stocks, pollution, invasive species, and others are common to many ecosystems and represent problems that cause imbalances in the cycling of matter and the transformation of energy through ecosystems.
Instruments, Measurement, and Representations
Chemical equations for overall processes of cellular respiration and photosynthesis
General representations of synthesis and breakdown of large bio-molecules
Diagrams of matter cycling and energy flow in ecosystems
Qualitative descriptions of biodiversity in various ecosystems
Qualitative descriptions of fluctuations in populations due to natural and human generated disturbances
Graphic or geographic representations of size, diversity, key species in ecosystems
Analysis of quantitative data on biodiversity
Representations of specific detailed steps of synthesis and
decomposition (e.g., intermediate steps and molecules, details of dehydration synthesis)
Light Reactions, Calvin cycle, Krebs cycle, glycolysis, or intermediate products in respiration and photosynthesis
Tracking particular atoms or elements (especially carbon)
through the processes of photosynthesis, growth, food webs, and cellular respiration at multiple levels: cellular, organismal, and ecological
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CE: B1.1A, B1.1B, B1.1C, B1.1D, B1.1E, B1.1f, B1.1g, B1.1h, B2.1A
Study photosynthesis using a floating leaf disk assay or fast plants, allowing students to investigate variables of their own choosing. Make predictions about how these variables will affect the rate of photosynthesis or growth rate.
CE: B1.1g, B1.2A, B1.2B, B1.2C, B1.2D, B1.2f, B1.2g, B1.2j, B1.2k
Evaluate the claims of products that promise to increase energy efficiency or promote the use of alternative fuels. Students should work in groups to report their findings to classmates.
CE: B1.1D, B1.1E, B1.1g, B1.1h, B3.3b
Perform a laboratory activity to investigate the effects of nitrogen fertilizers on the growth of algae.
CE: B1.1A, B1.1D, B1.1E, B1.1g, B1.2C, B3.2A, B3.2B, B3.2C, B3.3A
Investigate the effect of an invading species on a local ecosystem. Predict how local food webs are altered as the newcomer changes existing feeding relationships.
CE: B3.1A, B3.3A
Provide, or allow students to draw or collect, common cartoon images and ask them to work in small groups to construct a food web showing the trophic interactions between the members of the web. They should label their images as producers, consumers and decomposers and be sure to include the Sun as the ultimate source of energy to the system.
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