Experiment takes a total of 14 days with minimal interactions necessary. Prep time is about 1 hour. With all the materials available and the simplest version of the experiment, preparation should take about half and hour. Additional materials necessary.Learn more about Teaching Climate Literacy and Energy Awareness»
See how this Activity supports the Next Generation Science Standards»
Middle School: 2 Performance Expectations, 2 Disciplinary Core Ideas, 6 Cross Cutting Concepts, 7 Science and Engineering Practices
High School: 1 Performance Expectation, 2 Disciplinary Core Ideas, 8 Cross Cutting Concepts, 6 Science and Engineering Practices
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Teaching Tips | Science | Pedagogy |
- Educators might want to emphasize to their students that the conditions simulated in this experiment do not represent the natural environment, since, so far, microalgae in the oceans have not been shown to be CO2 limited.
- The resource includes some suggestions on how to improvise seawater, nutrients and algal culture.
- Since this experiment takes several days to perform, it may be helpful to have students take photographs (as in the activity description) to illustrate the changes. Take pictures or drawings of culture flasks every two days.
- Students should do this experiment within the context of the ocean biological pump and its relationship to the global carbon cycle.
- Students may be led to think that phytoplankton will solve the problem of too much CO2 going into the water. Thus, it is very important that teachers talk about limiting factors (nutrients, iron etc) that are critical to phytoplankton population growth. Teachers should strongly consider including a nutrient-deficient experimental bottle with enhanced CO2.
- Dunalliela is not a toxic algae but if teachers feel uncomfortable with blowing CO2 into flask with a straw, they can produce extra CO2 simply using alka selzer and water in a flask with a simple tubing delivery system.
About the Science
- This experiment illustrates the importance of carbon dioxide for microalgal growth in the aquatic environment (in this case, the green microalga, Dunalliela sp, in seawater). Algae are grown in CO2 limited, CO2 enriched and control groups. It should be emphasized that the conditions simulated in this experiment do not represent the natural environment since, so far, microalgae in the oceans have not been shown to be CO2 limited.
- Comments from expert scientist: This resource is a description of an experiment showing that micro algae require CO2 for growth. The experiment is fairly simple and could be implemented at the later elementary school or middle school level. However, this resource is missing additional information on chlorophyll-a determination.
About the Pedagogy
- This activity offers a lot of flexibility to educators. It can be done qualitatively for younger students or quantitatively with instrumentation for older students. Variants of this set up can also be used to test the effects of light, temperature, nutrients, etc. on algal growth.
- The activity lacks an assessment strategy. It should be viewed as a class demonstration, unless the educator restructures it as a lab activity with a focus on good experimental design.
- Educators will need to create their own student protocol and data sheet if desired.
- There are experimental options for both qualitative and quantitative analyses.
Technical Details/Ease of Use
- Teachers will need to pull together the equipment and materials needed for this experiment. The easier one is qualitative whereas the one for more advanced students is quantitative and thus involves more equipment. For quantitative analysis, consider the Vernier colorimeter that uses light absorption to quantify the amount of algal growth if a spectrophotometer is unavailable.
Next Generation Science Standards See how this Activity supports:
Performance Expectations: 2
MS-LS2-1: Analyze and interpret data to provide evidence for the effects of resource availability on organisms and populations of organisms in an ecosystem.
MS-LS2-3: Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem
Disciplinary Core Ideas: 2
MS-LS2.A1:Organisms, and populations of organisms, are dependent on their environmental interactions both with other living things and with nonliving factors.
MS-LS2.A3:Growth of organisms and population increases are limited by access to resources.
Cross Cutting Concepts: 6
MS-C1.2: Patterns in rates of change and other numerical relationships can provide information about natural and human designed systems
MS-C1.3: Patterns can be used to identify cause and effect relationships.
MS-C2.2:Cause and effect relationships may be used to predict phenomena in natural or designed systems.
MS-C4.3:Models are limited in that they only represent certain aspects of the system under study.
MS-C5.2: Within a natural or designed system, the transfer of energy drives the motion and/or cycling of matter.
MS-C7.3:Stability might be disturbed either by sudden events or gradual changes that accumulate over time.
Science and Engineering Practices: 7
MS-P2.4:Develop and/or revise a model to show the relationships among variables, including those that are not observable but predict observable phenomena.
MS-P2.7:Develop and/or use a model to generate data to test ideas about phenomena in natural or designed systems, including those representing inputs and outputs, and those at unobservable scales.
MS-P3.2:Conduct an investigation and/or evaluate and/or revise the experimental design to produce data to serve as the basis for evidence that meet the goals of the investigation
MS-P4.3: Distinguish between causal and correlational relationships in data.
MS-P4.4:Analyze and interpret data to provide evidence for phenomena.
MS-P6.1:Construct an explanation that includes qualitative or quantitative relationships between variables that predict(s) and/or describe(s) phenomena.
MS-P6.3:Construct a scientific explanation based on valid and reliable evidence obtained from sources (including the students’ own experiments) and the assumption that theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future.
Performance Expectations: 1
HS-LS2-5: Develop a model to illustrate the role of photosynthesis and cellular respiration in the cycling of carbon among the biosphere, atmosphere, hydrosphere, and geosphere.
Disciplinary Core Ideas: 2
HS-LS2.B3:Photosynthesis and cellular respiration are important components of the carbon cycle, in which carbon is exchanged among the biosphere, atmosphere, oceans, and geosphere through chemical, physical, geological, and biological processes.
HS-LS2.C2:Moreover, anthropogenic changes (induced by human activity) in the environment—including habitat destruction, pollution, introduction of invasive species, overexploitation, and climate change—can disrupt an ecosystem and threaten the survival of some species.
Cross Cutting Concepts: 8
HS-C1.5:Empirical evidence is needed to identify patterns.
HS-C2.1:Empirical evidence is required to differentiate between cause and correlation and make claims about specific causes and effects.
HS-C2.2:Cause and effect relationships can be suggested and predicted for complex natural and human designed systems by examining what is known about smaller scale mechanisms within the system.
HS-C4.2:When investigating or describing a system, the boundaries and initial conditions of the system need to be defined and their inputs and outputs analyzed and described using models.
HS-C4.4:Models can be used to predict the behavior of a system, but these predictions have limited precision and reliability due to the assumptions and approximations inherent in models.
HS-C5.2:Changes of energy and matter in a system can be described in terms of energy and matter flows into, out of, and within that system.
HS-C5.4: Energy drives the cycling of matter within and between systems.
HS-C7.1:Much of science deals with constructing explanations of how things change and how they remain stable.
Science and Engineering Practices: 6
HS-P2.6:Develop and/or use a model (including mathematical and computational) to generate data to support explanations, predict phenomena, analyze systems, and/or solve problems.
HS-P3.2:Plan and conduct an investigation individually and collaboratively to produce data to serve as the basis for evidence, and in the design: decide on types, how much, and accuracy of data needed to produce reliable measurements and consider limitations on the precision of the data (e.g., number of trials, cost, risk, time), and refine the design accordingly.
HS-P3.4:Select appropriate tools to collect, record, analyze, and evaluate data.
HS-P3.5:Make directional hypotheses that specify what happens to a dependent variable when an independent variable is manipulated.
HS-P4.3:Consider limitations of data analysis (e.g., measurement error, sample selection) when analyzing and interpreting data
HS-P6.4:Apply scientific reasoning, theory, and/or models to link evidence to the claims to assess the extent to which the reasoning and data support the explanation or conclusion.