Students who demonstrate understanding can: Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem.
Clarification statement: Emphasis is on describing the conservation of matter and flow of energy into and out of various ecosystems, and on defining the boundaries of the system.
Assessment boundary: Assessment does not include the use of chemical reactions to describe the processes.
Official wording from the Next Generation Science Standards (NGSS Lead States, 2013). NGSS is a registered trademark of WestEd. Neither WestEd nor the lead states and partners that developed the NGSS were involved in the production of this page, and they do not endorse it. View on nextgenscience.org
Think of an ecosystem as a place where atoms are endlessly reused but energy only passes through. Producers such as grass and algae capture light energy and build food from carbon dioxide, water and minerals. Consumers eat producers or other consumers. Decomposers, such as fungi and bacteria, break down dead organisms and wastes, returning carbon dioxide and nutrients to the air, water and soil, where producers can take them up again. That loop is the cycling of matter.
Energy behaves differently. It enters as sunlight, is stored in food, and at each step along a food chain much of it is released as heat during life processes. Only about a tenth of the energy at one level typically ends up stored in the next, which is why food chains rarely have more than four or five links and why there are far fewer hawks than mice.
Students develop models, such as food web diagrams with labeled arrows or energy pyramids, and they define the boundaries of the system they are modeling, for example a pond or a forest floor, so they can say what enters and leaves it.
Without decomposers, dead material would pile up and nutrients would stay locked inside it. Decomposers are the link that lets matter cycle back to producers.
In science diagrams the arrow points in the direction matter and energy move, from the organism eaten to the eater, which is the opposite of how many students first draw it.
Energy is not destroyed. At each level much of it is transferred to the surroundings as heat, which producers cannot capture and reuse.
Atoms cycle between living and nonliving parts again and again, but energy flows one way, from sunlight through organisms to heat.
In a meadow, grass stores 10,000 units of energy. Using the rough rule that about 10 percent passes to the next level, estimate the energy available to grasshoppers, to mice that eat grasshoppers, and to snakes that eat mice.
Answer: About 1,000 units reach grasshoppers, 100 reach mice and only 10 reach snakes, so each level holds much less energy and can support fewer organisms.
Sealed bottle ecosystems or compost columns let students observe decomposition and argue about what crosses the system boundary. Ask them to draw two diagrams of the same ecosystem: one tracing a carbon atom around a loop, the other tracing energy in a line that ends in heat.
The standard excludes chemical equations, so keep the model at the level of organisms, arrows and labels such as carbon dioxide, nutrients and heat.
Original questions written for this standard. Choose an option or type your answer, then press Check. Every question has a worked explanation.
Answer: C) Decomposers
Decomposers such as fungi and bacteria break down dead material and release nutrients.
Answer: B) Grass to rabbit to fox
Arrows show the direction matter and energy move: from the food to the organism that eats it.
Answer: heat (also accepted: heat energy, thermal energy)
At each level much energy is released as heat, which leaves the ecosystem.
Answer: D) Less energy is available at higher levels of the food chain
Only a small fraction of energy passes from one level to the next, so fewer organisms can be supported at the top.
Answer: C) Matter cycles; energy flows one way
Atoms are reused, but energy enters as light and leaves as heat.
Answer: 500 (also accepted: 500 units)
10 percent of 5,000 is 500 units.
Develop a model to describe the movement of matter among plants, animals, decomposers, and the environment.
Use mathematical representations to support claims for the cycling of matter and flow of energy among organisms in an ecosystem.
Develop a model to illustrate the role of photosynthesis and cellular respiration in the cycling of carbon among the biosphere, atmosphere, hydrosphere, and geosphere.
A full lesson with slides, activities and an exit ticket on matter cycles and energy flows in ecosystems, pitched to grades 6-8 and editable in PowerPoint or Google Slides.
Make a lesson βA printable, differentiated worksheet on MS-LS2-3 with an answer key, ready in about a minute.
Make a worksheet βTurn matter cycles and energy flows in ecosystems into a quiz students answer online that marks itself, with a class summary for you.
Build a test βFood webs with labeled arrows, energy pyramids and cycle diagrams that show matter moving between living and nonliving parts of an ecosystem.
No. The assessment boundary excludes using chemical reactions to describe the processes.