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Grade 6 · Science · 30 minutes

Unit 1 · Investigating Living Systems · Lesson 1 of 2

What Can Seedling Data Tell Us?

Plan a fair light comparison and separate a measured pattern from a conclusion.

Mr. S Teaches · Original starter mini-lesson · MS6-SCI-01

Learning objective

Identify the changed, measured and controlled variables and write a limited explanation using two data points.

Before you begin

  • Read measurements in centimeters.

Gather your materials

  • Paper or notebook
  • Pencil and the passage, model directions or data printed in this lesson

Language to know

variable
A condition or measurement that can change.
control
A condition kept consistent so comparisons are useful.
replicate
Another trial using the same procedure.

Understand the concept

Original investigation report: Six seedlings of the same variety began at 2 cm. Three received eight hours of light daily and grew 4, 5 and 6 cm in ten days; three received two hours and grew 1, 2 and 3 cm. Soil, pot size and water were held constant. The averages suggest a light-related difference under these conditions. Small samples, measurement error and inherited differences still matter; these data do not prove that more light always causes more growth.

Teach it step by step

  1. Read the report and underline the light schedules and growth measurements in different colors.
  2. Name the question: how did daily light duration relate to growth over ten days? Separate growth from final height.
  3. Make a two-column table and calculate each group’s mean growth. Identify the three conditions held constant.
  4. Write an explanation using the two averages, then propose more plants and repeated measurements rather than a stronger unsupported claim.

Make the thinking visible

Worked example or model response

The eight-hour group averaged (4 + 5 + 6) ÷ 3 = 5 cm of growth; the two-hour group averaged 2 cm. A supported statement is: In this small comparison, seedlings receiving eight hours grew 3 cm more on average. It is not supported to claim every plant needs exactly eight hours.

Guided practice

Together, write a new fair-comparison plan that changes light duration only. State how growth will be measured at the same time each day.

Independent practice

Independently identify one possible source of measurement error. Explain why using different plant varieties in the two light groups would weaken the comparison. Cite a sentence from the report.

Quick assessment

Name the independent and dependent variables, and give one conclusion the data do not justify.

Answer key & assessment criteria

Answers and teaching guidance

  1. Guided plan: Use the same variety, initial conditions, pot, soil and water; compare the two daily light schedules; measure each seedling from the same starting point and calculate growth.
  2. Independent: An inconsistent ruler starting point is one possible error. Different varieties could influence growth as well as light, so the effect would be confounded. The report states that all plants were the same variety.
  3. Quick check: Daily light duration is changed; growth in centimeters over ten days is measured. The data do not establish the ideal light duration for every plant.

Look for: Look for a claim that answers this lesson’s question, accurate use of the supplied evidence and an explanation of a limit or alternative. Ask the learner to point to the detail supporting each inference.

Make it work for your learner

More support

Provide a three-column organizer labeled changed, measured and kept the same; calculate the first mean together.

Extension challenge

Add a second variety to both light groups and predict how a design could separate inherited and environmental influences.

Selected contributions · Official sources

Standards connections

Selected NGSS band contribution; not complete performance expectation coverage.

Contributes to NGSS performance expectation

MS-LS1-5

NGSS · Grades 6–8 band

Explain how inherited factors and surroundings influence growth.

Read the official performance expectation ↗

The lesson constructs a limited environmental-growth explanation from supplied data. It does not investigate genetic influences or provide the multiple independent evidence sources needed for a fuller performance.

Source and mapping checked 2026-11-04. This mini-lesson contributes selected skills; it does not claim full attainment.

Supporting Common Core literacy connection

RST.6-8.1

Common Core · Grades 6–8

Support scientific-text analysis with specific evidence.

Read the official standard ↗

The provided scientific passage/model is explicitly analyzed in the activity. This selected literacy practice does not establish subject-content alignment or complete coverage of the standard.

Source and mapping checked 2026-11-04. This mini-lesson contributes selected skills; it does not claim full attainment.