MS-LS2-3: Matter Cycles and Energy Flows in Ecosystems
Also called NGSS MS-LS2-3 · Topic: Matter and Energy in Organisms and Ecosystems · Life Science
The Official Wording
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.
NGSS Lead States, 2013 · Read it on nextgenscience.org · checked October 15, 2026
What MS-LS2-3 Means in Plain English
Middle schoolers draw and test a model of an ecosystem that shows two stories at once. Atoms of carbon, water and nutrients go round and round between plants, animals, decomposers, air and soil, while energy from sunlight passes through once and leaves as heat.
Students name the edges of the system they model and track what crosses them, but they do not write chemical equations. It builds on food webs in 5-LS2-1 and how one body uses food (MS-LS1-7), and leads to HS-LS2-4.
MS-LS2-3 I Can Statements
- I can model how matter cycles between living and nonliving parts.
- I can show that energy flows through an ecosystem in one direction.
- I can mark the boundary of a system and what crosses it.
MS-LS2-3 Worked Example
A sealed jar terrarium on a sunny shelf, weighed once a week for a month.
If nothing can get in or out of a sealed jar, can the life inside keep going?
Set It Up: A large glass jar with a lid, soil, moss, a few pill bugs, a damp sponge, a kitchen scale and a thermometer.
- Build the terrarium, close the lid tight and weigh the whole jar.Week 0: 1,642 g
- Set it in bright light that is not direct sun and weigh it each week.1,642 g, 1,642 g, 1,641 g, 1,642 g
- Watch the glass each morning and afternoon.Water beads form, run down, form again
- Note what the pill bugs eat and where dead moss bits go.Bugs chew dead moss, soil gets darker
- Tape a thermometer inside and compare it with the room.Jar a little warmer in light
The moss and pill bugs stayed alive for a month while the mass of the closed jar did not change.
Why it works: Atoms are reused inside the jar as plants, animals and decomposers trade them, but energy has to keep coming in as light and leaves as heat.
Common Mistakes with MS-LS2-3
Saying energy cycles too
“Energy goes from the plant to the bug and back to the plant.”
Try this: Matter cycles but energy does not. Draw energy arrows that enter as light and leave as heat, never looping back.
Forgetting decomposers
A food web that stops at the top predator
Try this: Add fungi, bacteria and small soil animals that break down dead matter, because they return nutrients to the soil and air.
Thinking the jar must get lighter
“The bugs ate the moss, so the mass went down.”
Try this: Eaten matter is not destroyed. It becomes bug, waste, gas or water inside the closed jar, so the total stays the same.
Where MS-LS2-3 Fits
Practice MS-LS2-3
Quick Check
- Where does the energy in a food chain finally go?
- A fallen log slowly disappears. Where did its matter go?
- Why does a sealed terrarium need light but not new food or air?