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Notes for Teachers

This lesson takes place in a classroom and requires 90 minutes to gather accurate data.
Students work in groups of 4.
An emphasis is on limiting factors for yeast.
Presentations lab procedures and data collection strategies are important components.

List of Materials per team:

yeast - 3 Tbsp
empty soda or water bottles - 3 identical
sugar - ¼ cup
water
tea kettle
ice
thermometer (optional)
graduated cylinder - 100 ml
measuring spoon set
funnel
3 balloons
string
ruler
pipette
timer
Methylene blue or red food coloring
regular or digital microscope
slide
Growing Yeast lab report

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Arizona Science Standards

6.L2U1.13 Develop and use models to demonstrate the interdependence of organisms and their environment including biotic and abiotic factors.
U1: Scientists explain phenomena using evidence obtained from observations and or scientific investigations. Evidence may lead to developing models and or theories to make sense of phenomena. As new evidence is discovered, models and theories can be revised.
U2: The knowledge produced by science is used in engineering and technologies to solve problems and/or create products.
U3: Applications of science often have both positive and negative ethical, social, economic, and/or political implications.

Science and Engineering Practices

ask questions and define problems
develop and use models
plan and carry out investigations
analyze and interpret data
use mathematical and computational thinking
construct explanations and design solutions
engage in argument from evidence
obtain, evaluate and communicate information

Arizona ELA Standards

6.RI.1 Cite textual evidence to support analysis of what the text says explicitly as well as inferences drawn from the text.

6.RI.4 Determine the meaning of words and phrases as they are used in a text, including figurative, connotative, and technical meanings.

6.W.1 Write arguments to support claims with clear reasons and relevant evidence. a. Introduce claim(s) and organize the reasons and evidence clearly. b. Support claim(s) with clear reasons and relevant evidence, using credible sources and demonstrating an understanding of the topic or text. c. Use words, phrases, and clauses to clarify the relationships among claim(s) and reasons. d. Establish and maintain a formal style. e. Provide a concluding statement or section that follows from the argument presented.

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Objectives:

The student will be able to:

Read and annotate informational text.
Model limiting factors for a microorganism.
Design an experiment that demonstrates limiting factors.
Determine how to measure growth.
Set up experiment and collect, record, and graph accurate and repeatable data.
Write and present an analysis and conclusion.

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Agenda (90 Minutes and 45-60 minutes)

Day 1: 90 minutes

What is yeast? What do they need to grow? How do you know?
Introduce lab report
Students design test to show limiting factors for yeast, create their procedures, and determine how they measure growth.
Students set up their tests and collect data.

Day 2: 60 minutes

Students create their graph, write their analysis, and conclusion.
Students present their data to their peers.
Collect samples from each bottle, stain yeast, and look at under microscope. Count yeast if possible and record additional data.

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Intro

Place a pipette and a small amount of water, sugar, and yeast in separate containers at each table.

Have students place about ¼ tsp of yeast in the palm of their hand. Observe and discuss.

Add equal amount of water. Observe and discuss.

Add equal amount of sugar. Close hand and let it heat up. Open hand, observe and discuss. Students should smell the yeast activating and see it bubbling. Explain that this is the yeast coming alive and metabolizing the sugar for energy to grow and reproduce. The waste of that respiration is carbon dioxide or bubbles. This is called fermentation.

Explain that this experiment will demonstrate what yeast needs to grow the best, or what limits it’s growth. This is called a limiting factor. Explain that the students will be exploring with the limiting factors of sugar, temperature, water, and amount of yeast.

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Hands-on Activity Instructions - Day 1

Hands-on Activity Instructions - Day 2

Students should be in groups of 3-4.
Assign each student a role on their team.
Teams work together to determine if they will be testing the limiting factor of food, temperature, or amount of microbes.
Teams discuss how they will know if their yeast is growing and reproducing (the amount of bubbles).
Teams determine what they are measuring and how. (Will they measure the bubbles height in the bottle, the height of a balloon put over the bottle or the circumference of the balloon using the string.)
Teams determine how often they will measure the growth (bubbles).
Individuals complete the first page of the lab report.
Teams write procedures, set up lab, and collect data.

Students complete lab report by making sure their data is complete, graphing their data, and writing their analysis and conclusion. (Students may be surprised that the yeast seems to have “died” and will want to add sugar or yeast to see if they “come alive again”. This is a great way to demonstrate they they didn’t die, they just quite reproducing because they either got too cold or ran out of food. This is also a good opportunity for teams to do additional research on yeast.)
Students share findings with other teams, presenting their results to their peers. You can do this formally or informally.
Optional: Students take samples from each bottle, place a dropper of yeast solution on a blank slide, stain, and then look at sample under the microscope.

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Assessment

Informal:

Observe students as they work. Encourage accuracy in data collection, make certain they are only testing their independent variable and that their measuring techniques are consistent and valid.

Formal:

Use the lab report to grade students work:

Hypothesis - (thorough and it explains why) 5 points

Research - (Annotated and 3 cool facts) 5 points

Variables - 2 point each

Procedure - (specific, accurate, explains what they are measuring and how often, shows 1 independent variable) 5 points each

Data Chart - (accuracy, clarity) 5 points

Graph - (accurate, labeled, titled, neat) 5 points

Analysis - (complete, at least 5 sentences) 5 points

Conclusion - (complete and thorough, reflective and discusses knowledge of limiting factors, at least 5 sentences )- 5 points

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Differentiation

Use sentence starters for the analysis and conclusion.

Have students answer a series of questions to break down the analysis and conclusion.

Label and title the graph for students.

Put the graph on larger graph paper.

Prewrite the procedure and determine the independent variable.

Remediation

Extension/Enrichment

Compare the carbon dioxide growth in each bottle to an actual population growth of each test. After 20 minutes, collect a sample from each bottle, place a drop on a slide and use red food coloring or methylene blue to stain the yeast. Then use a digital or regular microscope to count the number of yeast seen in the microscope field. Repeat 3 times for each bottle. Compare to the growth seen in the bubbles in each of the bottles to the actual yeast count. More bubbles should mean more yeast counted under the microscope. Compare and discuss.

Reactive the yeast each day for several days to see if the same results are found. Determine through testing which limiting factor has more impact on yeast growth and reproduction?

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