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OAT SEED LAB

A Model Experiment

 

By Larry Flammer

PDF Version of This Page

 

THE NATURE OF SCIENCE

Basic Processes

 SYNOPSIS

  Oat seeds are "planted" in a particular environmental context, in the first week of the course, followed by an intensive introduction to the Nature of Science. Concurrent with that introduction, students record their daily measurements, process those data (graphically and statistically), and prepare a formal report, using sample reports as a model. Introduces the use of a simple statistical tool to measure significant differences.

 PRINCIPAL CONCEPT

  Processes in science include critical and quantitative observations limited to single variables whenever possible.

 ASSOCIATED CONCEPTS

 1. Experimental studies must use controls to assure that the effect of a single variable is being measured
2. Biological phenomena typically vary in their expression, requiring statistical analysis for clear interpretation.
3. Hypotheses provide generalized expectations or understanding based on logic and previous experience, while predictions based on hypotheses point to specific outcomes.
4. Experiment must be a fair test or the hypothesis: results could go either way, but must match or not match the predictions based on the hypothesis, thereby supporting or weakening the hypothesis.
5. Scientific reports must be clear and detailed enough to enable accurate repetition by others.

 ASSESSABLE OBJECTIVES

   Students will....

 1. Distinguish good and bad examples of controls, hypotheses, predictions, and scientific reports.
2. Recognize an experiment that actually does a fair test of a hypothesis and one that does not.
3. Analyze a graph of data for what it tells us vs what it does not tell us.
4. Analyze what the statistical t-Test tells us, and what it does not tell us.
5. Recognize the appropriate interpretation of different t-values at different levels of confidence.
6. Distinguish "significantly different" from "not significantly different."

 MATERIALS

See Oat Seed Lab: Teacher Notes (PDF) for details. Also, for the teacher rationale and the experimental rationale to share with students, be sure to read the Teacher Rationales.

1. Fresh oat seeds (Avena sativa), plastic vials, masking tape, marking pens, forceps, paper towels. (Plastic vials could be old and cleaned vials used for fruit fly studies.)
2. Blocks of wood (or suitable multiple vial holders, e.g., 1" PVC couplings - about 50 cents each - glued to flat plastic strips)
3. Prepared test solution (e.g., a plant food solution, or a 0.1% salt solution), and tap water
4. Metric rulers
5. Statistical Significance: T-Test Excel spreadsheet (for data input and t-Test calculation) on Computer. If you don't have Excel, or this file fails to download or open on your computer, use an online t-Test calculating program, or another one listed in the Other Resources (below), or contact the webmaster. If it DOES open, just use the LOWER data tables for entering the Values Measured (last day's measurements) in each group. Ignore the #DIV/0! items in the other spaces; they will show calculated results when all your measurements are entered. Be sure to type "omitted" for any seed that was not measured (didn't grow, or way too short). The t-value will be looked up and displayed automatically after all measurements are in, as will its proper interpretation. Be sure your students understand clearly what to enter, where to enter it, and how to record the results obtained.

 TIME

  About 30 minutes to set up, and 5-10 minutes a day to measure when shoots appear - for about 5 days.

 STUDENT HANDOUTS

 Oat Seed Lab: Instructions (3 pages)
Results (two Data Tables - 1 page)
Statistical Significance - t-Test: Information (2 pages + Data Sheet)
Statistical Analysis: Sample Data Sheet (add to Stat. Signif. packet)
Sample Research Report (Including Discussion Format and 2 Sample Discussions (4 pages)

 TEACHING STRATEGY

See Oat Seed Lab: Teacher Notes (PDF) for details. Also, for the teacher rationale and the experimental rationale to share with students, be sure to read the Teacher Rationales.

This two-week experiment is intended to be a guided model of a simple investigative study using a control set, providing detailed instructions with sample charts, statistical analysis, and examples of final reports. This should serve as an example for any future investigative studies that could be undertaken by the class or individual students.

Set up in the first week of school, it also serves as a vivid experience of a biological process (germination and growth) that many students may have never had, providing a point of reference in later class work in Biology or Life Science.

With growth measurements taking only several minutes each day, other lab activities can be done concurrently, labs that illustrate other key components of the Nature of Science that can be selected from the Nature of Science index on this site.

 

PROCEDURES


Click for More Images

 1. Optional, day before or day of lab, introduce use of metric ruler to measure in mm and cm. See Meaningful Metrics with Dramatic Demos

2. On the first Wednesday or Thursday of the semester, have materials 1-4 available to all students. Introduce the rationale for doing this study (read from the Problem and Background in the Sample Report). Demonstrate and describe procedures as described in Teacher Notes. Students prepare the vials, plant the seeds, add fluids, and place them in the wood blocks.

3. Friday: have students add more water and test solution (each to level just below lower ends of seeds). Hand out the Instructions Packet to read for homework, insert in notebook, and bring each day.

4. First day of measurements (Monday following planting): provide metric ruler and Results sheet (with data tables) for each student. Demonstrate how, where to measure, and where to record.
5. Students are to measure each numbered shoot (cotyledon) in mm and record in data tables. Each student should measure and record all shoots that have started growing above the vial's edge, in both vials. If a team is absent, a neighbor team must measure those vials. Add water or solution (appropriate for each vial) to maintain proper level. Replace in wood block. Last person in row to return vial to block places block back in assigned spot on windowsill or other lighted area. If time is short, students could just measure their own vial, then copy each other's data for the other vial.
6. Repeat step 5 each day of the week at the beginning of the period (should take only 5-10 minutes).

7. After the next weekend, you may continue measuring for a few days, unless lots of seedlings are so long that they are bending and breaking. When that happens, students make final measurements, and clean up the vials: pour out the fluids, pull out the wet towel with the seedlings and discard into wastebasket. Rinse the vials with water, and place upside down to drain and dry in wire baskets.
8. Hand out graph paper, and have students prepare their Summary Tables and make their Graphs.
9. Assign the Statistical Significance pages to read for homework.

10. Provide computers with Excel spreadsheet for students to input their last day's data and get their t-Test results. Hand out Sample Research Report packet to read for homework. This provides instructions and models for the formal report that each student must prepare, using their team data and the collective results obtained by the other teams. This can be expedited by asking one person from each team to raise hand when you ask for "who got... significantly faster growth of experimental seeds," "significantly slower growth of experimental seeds," or "no significant difference of growth in the two vials." Place the tally results on the board or overhead for each student to record the numbers of teams reporting each kind of result obtained in the class. These data must be included in the report as being from a larger, and therefore more reliable, sample size. All data taken together (team data and class data) must contribute to the discussion and statement of conclusion.

 ASSESSMENT

  See Assessable Objectives for focus of assessment.

 EXTENSIONS

& VARIATIONS   

 See Alternative Studies in the Teacher Notes, and see the Recommendations at the end of first Sample Discussion page. Encourage students to continue (individually or in pairs) with one of the seed-growing recommendations, or even something different, as the course continues, using the materials provided in this model. This could be required, or done for extra credit.

 OTHER RESOURCES

Statistical Significance and using the t-Test

Online t-Test calculating program
http://graphpad.com/quickcalcs/ttest1.cfm

Explanation and a data-input online solution
http://www.physics.csbsju.edu/stats/t-test.html

Includes procedure and a t-test table:
http://helios.bto.ed.ac.uk/bto/statistics/tress4a.html

Explains, shows diagrams and formula:
http://www.socialresearchmethods.net/kb/stat_t.htm

Experimental Biosciences (explanation, formula, table):
http://www.ruf.rice.edu/~bioslabs/tools/stats/ttest.html

 ATTRIBUTIONS

Some of the ideas in this lesson may have been adapted from earlier, unacknowledged sources without our knowledge. If the reader believes this to be the case, please let us know, and appropriate corrections will be made. Thanks.

Created by: Larry Flammer, 1966
Adapted for ENSI site by Larry Flammer. August 2009

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