Lesson plan Grade 3 Science
Why the Frogs Left Pebblemoor Marsh: A Grade 3 Claim Lesson
A 55-minute grade 3 lesson where students compare two plans for a drained marsh and make a written claim about which one better helps the animals return.
Objectives
- Students will explain how draining a marsh changed which animals could live there.
- Students will compare two plans against the same goal and the same limit.
- Students will write a claim about one plan and support it with two reasons.
Vocabulary
Key words: marsh, ditch, runoff, cattail, claim, habitat
Teacher overview
A marsh is a shallow place where water sits long enough for plants to take hold, and where cattail roots and the tiny living things in the soil take up much of what washes in from roads and fields. This lesson uses a fictional marsh below the town of Withernay, drained by a ditch dug to dry a neighboring field, and asks students to weigh two repair plans against the same goal and the same limit. A misconception worth naming out loud is the idea that animals simply move somewhere else when their home dries out and are fine; frogs need standing water to lay eggs, so a nearby dry field is not a substitute. The sponge tray gives students something physical to point at when they explain why the ditch pulled the water away.
Procedure
Hook (6 min): Show the class a photograph or a simple drawing of a marsh full of cattails and a second drawing of the same place cracked and dry. Ask what could take the water out of a place like that. Write student ideas on the board and leave them up.
Reading the information cards (12 min): Hand out the two cards. Card A describes Pebblemoor Marsh before and after the ditch was dug, naming the frogs, dragonflies, and cattails, and explaining that runoff from the road used to slow down and drop its dirt in the marsh. Card B describes two plans, a small earth plug in the ditch and a new pond dug in the corner of the field. Read Card A aloud while students follow along, then have partners read Card B to each other and underline the goal and the limit.
Sponge tray model (10 min): Groups set a damp sponge in a tray, sprinkle a spoonful of soil on one end, and pour water slowly over the soil so it runs across the sponge. They observe the water soaking in and the dirt staying behind. Then they tip the tray to make a channel along one edge and pour again, watching the water run past the sponge instead of into it. Ask what the tipped channel stands for in the story.
Handout work (15 min): Distribute the handout. Students answer items 1 through 6 on their own, then draft the claim in item 7. Circulate and push students who write only that one plan is better to name which card sentence supports them.
Closure and formative check (12 min): Hold a two-corner vote. Students stand at the corner matching the plan they chose and take turns giving one reason. Listen for at least two thirds of the speakers citing the spring deadline or the landowner limit rather than personal preference; if fewer do, model one strong claim aloud and have students revise item 7 before turning it in.
Student Handout
Pebblemoor Marsh is a made-up place near the town of Withernay. Read the cards, then answer.
Card A. For many years the marsh held shallow water all spring. Frogs laid eggs in it. Dragonflies hunted over it. Cattails grew thick along its edge. Rain that ran off the road went into the marsh first. The water slowed down there. Dirt from the road settled to the bottom. Cattail roots and tiny living things in the mud took in much of the waste. Clean water then trickled on to Duffield Brook. Last year a farmer dug a ditch beside the marsh to dry a wet field. The ditch pulled the marsh water into the brook. By June the marsh was dry mud. The frogs and the dragonflies were gone. The cattails died back to brown stalks.
Card B. The town has two plans. Plan A puts a small earth plug in the ditch so rain stays in the marsh again. Volunteers can build it in one weekend. Plan B digs a new pond in one corner of the field. A rented machine would take three weeks to dig it. Both plans have the same goal: the marsh must hold water before the frogs lay eggs in early spring. Both plans have the same limit: the farmer will give up only a small corner of the field.
- What changed at Pebblemoor Marsh last year?
- Name two animals that left the marsh after that change.
- The marsh used to clean the runoff from the road. Tell how the plants and the mud did that job.
- Plan A plugs the ditch. Plan B digs a new pond in the field. Which plan puts water back into the marsh itself?
- The goal is a marsh that holds water before the frogs lay eggs in early spring. Which plan meets that goal better? Tell why.
- The farmer will give up only a small corner of the field. Which plan does that limit hurt more?
- Make a claim. Which plan should Withernay pick? Give two reasons from the cards.
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Answer Key
- Answer: A ditch drained it. Accept any answer stating that a ditch dug beside the marsh carried the water away to Duffield Brook and left dry mud by June.
- Answer: Frogs and dragonflies. Card A names both, and an answer naming the cattails as well should be counted correct since they died back at the same time.
- Answer: The water slowed and the dirt settled. Accept any answer that includes slowing the runoff so dirt sinks, or roots and tiny living things in the mud taking in the waste, before the water reached the brook.
- Answer: Plan A. The plug holds rain inside the marsh basin, while the new pond would sit in the field beside it and leave the marsh dry.
- Answer: Plan A. Accept any answer using the timing sentences on Card B, since volunteers can build the plug in one weekend while the rented machine needs three weeks, so only Plan A is certain to be finished before early spring. Also accept the reason that Plan B's pond sits in the field and leaves the marsh itself dry, as in item 4.
- Answer: Plan B. The new pond needs a piece of the field, and the farmer will give up only a small corner, so the limit works against Plan B while the plug sits in the ditch that is already there.
- Answer: Plan A, with two supported reasons. Accept any claim for Plan A backed by two of these: it refills the marsh itself, it can be built in one weekend before egg-laying, it needs almost none of the field, or it brings back the plants and mud that were cleaning the road runoff. A claim for Plan B may earn full credit if the student supports it with card evidence, such as the pond giving the farmer a drier field, and answers what happens to the dry marsh.
Differentiation
Support
Read both cards aloud a second time with students tracking on their own copy, and highlight the goal sentence and the limit sentence in two colors before any writing begins. Let these students answer items 1 through 4 by circling words on the card, and give item 7 as a sentence frame with a word bank of the two plans and four reasons.
Extension
Ask students to write a short letter to the fictional farmer proposing a version of Plan A that also keeps the field drier, then explain which parts of the original goal and limit their new idea still meets. Have them predict what the marsh will look like one spring after the plug is built and what a volunteer should measure to find out whether the plan worked.
ELL supports
Pre-teach "marsh," "ditch," and "runoff" with the sponge tray before the cards are read, using the tipped channel to show water leaving. Post a two-column chart labeled goal and limit and fill it in as a class. Provide the frames "The marsh changed because ___" and "I pick Plan ___ because ___ and ___," and accept a labeled before-and-after drawing for item 1.
Extensions
Set the sponge trays aside for a second session in which groups add a strip of green craft foam as marsh plants and test whether water carrying soil runs clearer with the strip than without it. Have students record what they see and write one sentence connecting the result to the job Pebblemoor Marsh used to do for Duffield Brook.