Where does a growing plant get its material?

Why does a tree’s new material not come mostly from soil?

Submit: A labeled input model and revised evidence-based argument.

Related lesson: Ecosystems and Energy Flow

This is a teacher-led extension beyond the short lesson. The task supplies a performance opportunity; completion alone does not certify mastery, full NGSS coverage or state alignment.

Build the idea

Plants take in water through roots and carbon dioxide from air. Using light energy, they build sugars and other materials. Much of a fresh plant is water, and the carbon in its dry organic material comes chiefly from carbon dioxide. Soil supplies important mineral nutrients, but it is not the main source of all the plant’s new material. Sunlight supplies energy, not a supply of matter.

Evidence and model inputs

Original model case: a plant gains 20 g of fresh mass, of which a teacher’s dried sample analysis indicates 15 g is water. Its remaining increase is dry material. A mineral account alone is far smaller than that increase. These invented quantities illustrate mass accounting, not a reported experiment. Use the source reading to identify air and water as major material inputs; the numbers alone cannot identify an unmeasured source. NASA’s carbon-cycle reading explains that photosynthesis incorporates carbon dioxide into organic plant matter and that water and nutrient availability can limit growth. Use this source information alongside the hypothetical mass account.

Keep actual observations, published findings and invented model cases labeled separately. If a source or required equipment is unavailable, pause that part with a teacher; do not invent results.

Materials and preparation

Input cards, plant image or specimen, paper and the provided model case. No chemical drying or destructive experiments are required.

Grade-level scope

Use an argument about sources of plant material. Detailed photosynthesis reactions or biochemical steps are not required.

Do the work

1. Read the model case and separate fresh mass, water and dry material.
2. Make cards for air/carbon dioxide, water, mineral nutrients and sunlight. Sort them into material inputs and energy input.
3. Draw arrows from the material sources into the plant and label the role of each.
4. Compare “mostly soil” with a claim that uses both the reading and the mass-accounting model.
5. Revise the explanation to include needed minerals without confusing “small amount” with “unimportant.”

Learner worksheet

Write on paper or type here and print. Entries stay in this page’s memory and are lost when you leave or reload; they are not saved or submitted.

Check your reasoning

1. How much of the example fresh-mass increase is dry material?
2. Is sunlight counted as plant matter?
3. Are mineral nutrients unnecessary?
4. Do the invented mass values alone prove carbon came from air?

Teacher review guide

Review the actual deliverable and discuss the reasoning. For each criterion, use 0 when evidence is absent or fundamentally incorrect, 1 when partly supported with a material error or omission, and 2 when accurate, supported and complete for the stated task. Maximum 8 points is a task score, not a proficiency certification. Give feedback and allow revision.

1. Identifies air and water as major material sources.
2. Separates matter inputs from sunlight’s energy role.
3. Uses the source information and model account without overstating either.
4. Includes the necessary but smaller role of mineral nutrients.

Sources and standard reference

• Official NGSS 5-LS1-1 performance expectation — inspect the practice, core idea, crosscutting concept and assessment boundary.
• NASA: carbon cycle and plant growth

Instructional text and hypothetical cases are original. Linked source readings supply published evidence where specified. Teachers should judge fit with their course and state requirements.