Materials & Prep
- Project or draw the class food-web cards below: Sun, grass, clover, aphid, grasshopper, ladybug, spider, robin, frog, snake, hawk, mushroom.
- Prepare one half-sheet Food-Web Evidence Organizer per pair with boxes: My claim; Arrow evidence; Energy explanation.
- On the board, draw a large Sun and leave space for a food web. Post: arrow means “energy moves to.”
Schoolyard Prediction
DisplayShow two observations from last week’s bug survey: “Aphids were found on plants” and “a spider was found near insects in the garden.” Ask students to silently sketch arrows showing who eats whom among plant, aphid, and spider. This uses their survey observations and prior knowledge of what animals eat, not food-web notation.
Turn and talkAsk, “If a spider eats an aphid, what does the spider get from the aphid besides something in its stomach?” Listen for “energy” or “fuel to move and live.”
ConfrontReveal the class’s likely arrow conflict. Say, “Eating moves from spider to aphid, but today our arrows show something different: the energy the spider receives. Energy came from the aphid to the spider, so the arrow points aphid to spider.” Have students revise their sketch in a different color. This makes the direction difference visible rather than merely correcting it.
Modeling Energy Arrows
IntroduceDefine a food web as connected food chains that show feeding relationships. Define an energy arrow as an arrow pointing from the organism that provides energy to the organism that receives it. Post the frame: “Energy moves from to because eats .”
ExplainPlants capture energy from sunlight and use it to make their own food. Animals get energy by eating plants or other animals. The Sun is the original source of energy for most food webs.
Worked exampleBuild this chain on the board: Sun → grass → grasshopper → frog → snake → hawk.
Think aloud“I start at the Sun because grass needs sunlight to make food. I draw Sun to grass. The grasshopper eats grass, so energy stored in grass moves to the grasshopper. I draw grass to grasshopper. The frog eats the grasshopper, so the next arrow is grasshopper to frog. I do not point from frog back to grasshopper just because the frog is the eater. That would show energy traveling backward.” Trace the arrows while stating the full pathway aloud.
Analogy“Think of energy like a snack being passed along a line. The person holding the snack passes it to the person who receives it. Our arrow points toward the receiver, not back toward the giver.”
Check for understandingDisplay clover, aphid, ladybug. Students hold up one finger for each arrow direction they would draw, then orally complete: “Energy moves from to because eats .” Expected arrows: clover → aphid → ladybug. Quickly ask one student to explain why ladybug → aphid is incorrect.
Guided Web Building
DisplayAdd these schoolyard relationships to the board: aphids eat clover; grasshoppers eat grass; ladybugs eat aphids; spiders eat aphids and grasshoppers; robins eat spiders and grasshoppers; frogs eat grasshoppers; snakes eat frogs and robins; hawks eat snakes and robins.
Have studentsWith a partner, first say each relationship as “ eats .” Then convert it using the arrow frame: “Energy moves from to .” Invite pairs to direct the teacher where to place each arrow as the class builds one web.
ClarifyA food web is not one straight line. One organism can provide energy to more than one consumer. For example, energy from a grasshopper can move to a spider, robin, or frog if each eats grasshoppers.
Look forObserve whether students reverse arrows after saying “eats.” Prompt students who do: “Who has the energy first? Who receives it next?”
Collaborative Evidence Investigation
StudentsIn pairs, use the completed class web and the Food-Web Evidence Organizer to answer three investigation cards.
- Trace two different energy pathways that begin with sunlight and end with a hawk.
- A student says, “The hawk gives energy to the snake because the hawk eats the snake.” Do you agree? Make a claim and use arrows from the web as evidence.
- Predict what may happen to the energy available to robins if grasshoppers become scarce. Explain using at least one pathway.
ScaffoldGive each pair the three-step checklist: 1. Find what is eaten. 2. Point the arrow toward the eater, the energy receiver. 3. Use the sentence frame, “My claim is . I know because energy moves from to when eats .” Partners may trace one pathway with a finger before writing. Provide a partially completed model for Card 1: Sun → grass → grasshopper → → .
CirculateAsk pairs to distinguish observation from inference. “The web shows an arrow from grasshopper to robin” is evidence. “Robins might have less energy available if fewer grasshoppers exist” is an inference supported by that evidence.
ExtensionAsk ready pairs to explain why a change in grasshopper numbers could affect both frogs and robins, then identify which shared arrow supports their reasoning.
Share and Revise
DiscussSelect one pair that traced Sun → grass → grasshopper → frog → snake → hawk and another that traced Sun → grass → grasshopper → robin → snake → hawk. Have each pair read one claim-evidence-reasoning response.
EmphasizeEnergy can travel through several connected pathways in a web. Arrows show the direction energy moves, from food to eater.
Closing Check
Exit ticketProvide this new mini-web: Sun, berry plant, caterpillar, bird, fox. State: caterpillars eat berry plants; birds eat caterpillars; foxes eat birds. Students draw the energy arrows and write: “Energy moves through this food web from to to to because .”
ExpectedSun → berry plant → caterpillar → bird → fox. Use responses to identify students who still treat arrows as the direction of eating and regroup them for a brief arrow-direction reteach next lesson.