Summer Research Program for Science Teachers
Joanne T. Giordano
Village Community School
Using the Scientific Method to Determine Which Conditions Best Favor Plant Growth
7th grade (Life Science)
PROJECTED LEARNING OUTCOMES:
(A) Students will develop an understanding of how environmental conditions affect biological processes.
(B) Students will determine the optimal conditions for the germination of bean seeds by tracking and recording growth patterns under variable conditions in a lab notebook using the scientific method format.
(C) Students will be able to define what a variable is, and specifically name which ones we are manipulating in this experiment. *(The conditions which will be considered include light, moisture, oxygen concentration, and temperature.)
(D) Students will write about their observations in narrative form in order to analyze the variables as represented by their data and draw meaningful conclusions from it.
Day 1: 30-40 minutes
Days 2 & 3: 10 minutes
Day 4: 20 minutes
PRE-LAB PREP (for the teacher):
(1) Obtain viable bean seeds from a local garden center.
(2) Make a list of student teams for the experiment (2-3 per group).
(3) Review the following terms: viable, germination, seedling, cotyledon. Show a visual of how a germinating bean seed looks and elicit questions and responses. (i.e.: Viable seeds germinate and grow by receiving nourishment from the cotyledon. What other factors contribute to their growth?) [5-8 Content Standard C- Structure and function in living systems]
(4) Arrange to use a refrigerator or get a cooler of ice to use over the three-day lab period. Keep replenishing ice as needed; don't allow melted ice water to seep into seed cups placed on the ice.
(5) On lab day, check each team's setup to make sure the conditions have been properly represented. You may also want to discuss what the five setups represent:
Cup 1: Seeds deprived of water at room temperature.
Cup 2: Seeds that are watered at room temperature.
Cup 3: Seeds that are watered at cold temperature.
Cup 4: Seeds that are watered in room temperature with no light.
Cup 5: Seeds that are watered in room temperature with no oxygen.
Note: The Data Table may vary among teams, but should reveal that seeds fail to germinate when deprived of oxygen, water and warm temperatures.
Five small paper cups per team
Fifteen viable bean seeds per team
One black piece of felt (large enough to drape over one cup) per team
Refrigerator or cooler
[Teaching Standard D- Make accessible science materials]
(1) Add potting soil to the cups so that each is about ½ full.
(2) Plant 3 bean seeds in each cup at a depth equal to the length of the seeds. Space seeds around the edge of the cup.
(3) Label the cups 1-5.
(4) Add the following:
Cup 1: Don't add anything to this cup during the experiment other than the seeds.
Cup 2: Add water until the soil is damp. Don't soak the soil. Water this cup each day for the next 2 days.
Cup 3: Add water until the soil is damp. Water this cup each day for the next 2 days. Place this container in a refrigerator or in an ice chest for the rest of the experiment. *(Make sure team members have their names on the cup to avoid mix-ups.)
Cup 4: Add water until the soil is damp. Water this cup each day for the next two days. Place a piece of black felt over this cup except for when you are watering it.
Cup 5: Add water until the soil is damp. Place several cotton balls that have been thoroughly covered with vaseline, so they completely cover the soil surface. Smear a layer of petroleum jelly around the top rim of the cup. Place a piece of plastic wrap on top of the petroleum jelly so that it completely covers the opening of the cup. Use a rubber band to firmly hold the seal in place and to keep out oxygen.
(5) Place the cups in a location where they will not be disturbed for the next 3 days.
(6) Each day for the next 2-3 days, observe what is occurring in each cup and record it in a data table in your lab notebook. It should have a title such as "Conditions for Germination", and should be set up in 3 rows by 5 columns. The five columns should be labeled with each cup number. The three rows should be labeled: "After 24 hours", "After 48 hours" and "After 72 hours". The total number of seeds that have germinated in each cup should be recorded in the proper column corresponding to the associated time interval. *(Students should be asked to comment on their observations each day, beginning to reflect on why certain things are happening or not.)
(7) A conclusion should be written in narrative form following an analysis of the data. Some questions that can serve as an outline for this statement are as follows:
In what cups did germination occur? Why do you think so? [5-8 Content Standard A- Cause and effect relations]
Is light required for germination? Explain your reasoning.
Is oxygen required for germination? Explain.
Is water require for germination? Explain.
Can seeds germinate under cold conditions? Explain.
List the conditions necessary for the germination of a seed. [5-8 Content Standard C- Regulation]
At what point in their development do you think plants must receive light to survive? Why?
How could you manipulate the variables to design a new experimental trial? [Teaching Standard B- Orchestrate scientific discourse]
Using the "Learning Outcomes" as a guide, students can be asked to design a new experiment manipulating the given variables by degree or in new combinations, or to set up a new trial using a hydroponics medium in place of the soil. [5-8 Content Standard A- Design a scientific investigation]
I would also ask students to write something that applies their knowledge, such as a discussion of other fluids that might be substituted for water if we were trying to germinate seeds on another planet.
This lesson plan was obtained from Scientific Investigations: A Middle School Teacher Resource Book, written by Elaine Wood and Pam Walker, and published by Instructional Fair - TS Denison (Grand Rapids, MI), 1997. ISBN: 1-56822-424-9.
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