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Backyard Explorer 3 to 5 / Week 05 / Friday
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Week 05 · Plants: Built From Air and Water

Friday

Make the argument
// Where the stuff of a plant really comes from
⏱ about 15 min

Friday: Make the Argument

Rocket stands on a crate in the workshop. "I claim that plants are built mostly from air and water!"

Raven holds up the field notebook. "A claim needs evidence," she says. "What have we got?"

Nova projects three cyan cards in the air: the willow, the celery, the leaf.

"Each one is a clue," she says. "Put them together."

Rocket hops down. "Then we have a case," he says. "Let me write it out."

Claim, evidence, reasoning

Scientists do not just say what they think. They back it up.

A claim is what you think is true.

Evidence is the facts and observations that support the claim.

Reasoning explains how the evidence supports the claim.

This week your claim is: plants grow mostly from air and water.

EvidenceWhat it shows
The willow grew heavy but the soil barely changed.The plant was not built from soil.
Colored water climbed the celery stem.Roots and stems bring water into the plant.
Leaves have tiny holes that let air in.Plants take in carbon dioxide from the air.
Plants in a dark closet grow weak and pale.Light is needed to power the work.
CLAIM OR EVIDENCE?
  • Read the question.
  • Tap your answer.
The soil weighed almost the same after years. Claim or evidence?
Plants are built mostly from air and water. Claim or evidence?
Blue water climbed into the celery leaves. Claim or evidence?

What soil does and does not do

Soil still matters to most plants. It holds the roots steady.

It holds water between rains. It gives tiny amounts of minerals a plant needs.

But the wood, the leaves and the stems are not made of soil.

They are made from sugar. The sugar comes from carbon dioxide and water.

A seed is small. A tree is huge. Almost all of the difference came from the air and the water.

BUILD THE ARGUMENT IN ORDER
  • ?Evidence: the willow grew heavy, but the soil barely changed.
  • ?Evidence: water climbs the stem, and air enters the leaves.
  • ?Claim: plants are built mostly from air and water.
  • ?Reasoning: the plant must build itself from what goes in, water and air.
WHY THIS EXERCISEClaim, then evidence, then reasoning. That is how scientists argue.
StatementTrue or false?
Soil is where most of the stuff of a plant comes from.?
Soil holds roots steady and stores water.?
A claim needs evidence to back it up.?
Reasoning explains how the evidence supports the claim.?
WHY THIS EXERCISESoil holds and stores. Air and water build. Claims need evidence and reasoning.
Facts that support a claim are called ____.
Plants build their parts from ____ and carbon dioxide.
Plants take in carbon dioxide from the ____.
Try it
Tell your grown-up the claim. Then give them two pieces of evidence.
Ask them: are you convinced? If not, which evidence would help?
Name one thing soil DOES do for a plant.
WHY THIS EXERCISESoil holds roots steady, stores water and gives small amounts of minerals.
Draw a tiny seed next to a giant tree. Add arrows showing where the extra material came from.

A real scientific argument! Tomorrow is Explorer Day: you compare two plants outdoors.

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