MS-LS2-2: Predicting How Organisms Interact
Also called NGSS MS-LS2-2 · Topic: Interdependent Relationships in Ecosystems · Life Science
The Official Wording
Construct an explanation that predicts patterns of interactions among organisms across multiple ecosystems.
Clarification statement: Emphasis is on predicting consistent patterns of interactions in different ecosystems in terms of the relationships among and between organisms and abiotic components of ecosystems. Examples of types of interactions could include competitive, predatory, and mutually beneficial.
NGSS Lead States, 2013 · Read it on nextgenscience.org · checked October 15, 2026
What MS-LS2-2 Means in Plain English
Middle schoolers notice that the same few kinds of relationships show up in every ecosystem. Organisms compete for the same food or space, predators eat prey, and some partners help each other. Students use these patterns to explain and predict interactions in places they have never studied.
The focus is on the type of interaction and its effect on each partner, including links to nonliving factors like water and shelter. It builds on 3-LS2-1 about animal groups and leads to how ecosystems respond to change (MS-LS2-4).
MS-LS2-2 I Can Statements
- I can tell competition, predation and mutualism apart.
- I can find the same kinds of interactions in different ecosystems.
- I can predict how two organisms in a new place will interact.
MS-LS2-2 Worked Example
A card sort that compares a coral reef, a desert and a savanna, then tests a prediction.
Do the same kinds of interactions show up in very different ecosystems?
Set It Up: A set of pair cards from three ecosystems, a three-column sorting mat and a sheet of mystery pairs.
- Read each pair card and ask who gains and who loses.+/+, +/−, or −/−
- Sort the reef cards: clownfish and anemone, shark and parrotfish.Mutualism, predation
- Sort the desert cards: yucca and yucca moth, roadrunner and lizard.Mutualism, predation
- Sort the savanna cards: lions and hyenas over a kill, lion and zebra.Competition, predation
- Predict the type for the mystery pairs, then check with the teacher's key.Most predictions match
Every ecosystem had the same three kinds of interactions, even though the organisms were completely different.
Why it works: Wherever living things share limited resources, the same relationships arise, so the type of interaction can be predicted from who gains and who loses.
Common Mistakes with MS-LS2-2
Calling every pair predation
“Lions and hyenas are predator and prey.”
Try this: Ask who eats whom. Lions and hyenas want the same prey, so they compete, even if they sometimes fight or kill each other.
Thinking mutualism is friendship
“The clownfish is nice to the anemone.”
Try this: Mutualism means both partners gain something they need, like food or shelter. It is a benefit, not a choice to be kind.
Learning examples, not patterns
Memorizing a list of reef pairs only
Try this: Name the pattern behind each pair, then use it to predict a pair from an ecosystem you have not studied yet.
Where MS-LS2-2 Fits
Practice MS-LS2-2
Quick Check
- Bees collect nectar and carry pollen between flowers. What kind of interaction is this?
- Two kinds of birds eat the same seeds in a forest. What do you predict?
- Why can you predict interactions in an ecosystem you have never seen?