Whole Earth Curriculum WEC

Lesson 02 — What Happens When One Part of a Food Web Changes

Learners predict and model what happens when one part of a food web changes. They remove one organism from a web, trace the ripple in both directions, and practice separating what they predicted (an inference) from what their model shows (evidence).

D06 P3: Intellectual & Cognitive Awareness D06.S2 55 minutes Draft

Objectives

Essential question

What can happen to the rest of a food web when one part changes or disappears?

food webripple effectpredictionevidenceinferencepopulationpredatorprey

Materials

Standard materials

Low-tech / no-cost

Enriched / lab & device

Works in different contexts

Two side-by-side food-web panels. The left panel shows a healthy chain: grass at the bottom, then grasshopper above it, frog above that, and snake at the top, all joined by upward arrows. The right panel shows the same chain with the frog crossed out and labeled 'frog removed.' A big up-arrow next to the grasshopper is labeled 'more grasshoppers' and a big down-arrow next to the snake is labeled 'fewer snakes.' Labels and shapes, not color alone, carry the meaning so it prints clearly in grayscale.
Two side-by-side food-web panels. The left panel shows a healthy chain: grass at the bottom, then grasshopper above it, frog above that, and snake at the top, all joined by upward arrows. The right panel shows the same chain with the frog crossed out and labeled 'frog removed.' A big up-arrow next to the grasshopper is labeled 'more grasshoppers' and a big down-arrow next to the snake is labeled 'fewer snakes.' Labels and shapes, not color alone, carry the meaning so it prints clearly in grayscale.

Lesson 2 — What Happens When One Part of a Food Web Changes

Summary

Learners discover that a food web is connected, so a change in one part ripples through the rest. They remove one organism from a model web, predict what will happen to the other populations, then check the prediction against what the model shows — the same predict → test → observe loop that runs all science.

Objectives

  • Explain how matter and energy move through a food web and what can happen when one part changes. (D06.S2.05.01)

Connection

When the frogs in a pond disappear, something else changes too: the insects they ate become very many, and the birds that ate the frogs go hungry. This is a ripple effect — one change moves through the whole web. It happens in the sea too: when sea otters returned to some kelp forests, the sea urchins they eat were kept in check, and the kelp grew back. One part changed, and everything around it answered.

Materials

  • Change-the-web diagram (before and after)
  • Web cards (from Lesson 1 or rebuilt)
  • Prediction-and-result recording page

Preparation

  • Print or draw the before/after diagram and a recording page for each learner.
  • Have the Lesson 1 web cards ready to rebuild.
  • Prepare one or two “what if” scenarios (remove the frog; remove the grass).

Facilitator note

Written to the learner (“you”). The key distinction this lesson practices is prediction (inference) versus result (evidence): learners write what they think will happen before they move a card, then compare it to what the model actually shows. Insist on the prediction being written first — a correct guess is not the point; the habit of predicting and checking is. Keep the ripple simple for Grade 5: removing a predator lets its prey grow; removing a producer shrinks everything above it. Avoid the word “balance” as if nature were a steady machine — webs shift, and that is normal. The ethics lens (should we care for the living systems we depend on?) is a value we hold, distinct from the evidence of how webs respond (docs/facilitation.md).

Procedure

  1. Gather (5 min). Recall your web from Lesson 1. Ask: what do you think happens if one animal in the web disappears? Say your guess out loud — that is a prediction.
  2. Meet the change (10 min). Look at the before/after diagram. In the first panel, grass feeds the grasshopper, the grasshopper feeds the frog, and the frog feeds the snake. In the second panel, the frog is gone. What changed? The grasshoppers have one fewer eater (their numbers rise), and the snake has lost its food (its numbers fall). That is the ripple.
  3. Predict, then test (20 min). Rebuild your Lesson 1 web. Choose one organism to remove. First, write your prediction on the recording page: which populations will go up, which will go down, and why. Only then remove the card and trace the arrows. Compare: did the model match your prediction?
  4. Separate evidence from inference (10 min). For each change, sort the statements: evidence (what the model actually showed — “the snake has no food”) versus inference (what you reason — “so the snakes will become fewer”). Which is which, and how do you know?
  5. Close (5 min). A food web is a web because every thread is connected. Pull one, and the whole thing moves. Predicting first, then checking, is how scientists learn what those threads do.

Differentiation

  • Support: Remove a single, obvious link (the frog) and provide a fill-in sentence frame: “If the frog disappears, then ___, because ___.”
  • Extension: Remove a producer in a second trial and explain why the ripple is larger; then add one real-world example (a species returning or leaving) and trace it.

Assessment

  • Formative (observation/peer): Can the learner predict a ripple before testing, and name at least one population that rises and one that falls?
  • Self-check: The learner asks, “Did my prediction come from reasoning (an inference), and did I check it against what the model showed (evidence)?”

Home connection

Think of a small change in a place you know — a pond emptied, a field planted, a tree cut down. Predict what might change for the living things there, and tell someone your prediction and your reasoning.

Resources