Observing Beyond our Senses – Unit Plan
In this unit, students are confronted with increasingly complex examples to build an understanding of how scientists measure what we cannot directly observe with our senses. Trade-offs in instrumentation design and generating meaningful inferences from observations are overarching themes connecting the activities.
Broad Overview: Students are introduced to the use of proxy variables to make inferences about phenomena beyond our immediate senses. Students evaluate the tradeoffs in instrumentation design related to accuracy, precision, resolution, sample size, signal amplification, signal and noise, and calibration.
More Specific Overview: Students are introduced to a formal design process through a wind speed measurement challenge. Inferences from proxy variables and issues of resolution and pattern prediction are explored with a mock Atomic Force Microscope. Trade-offs in signal and noise from proxy variables are examined with the use of semiphore and/or with a *student-built operational amplifier using a breadboard and audio input. The scattering and absorption properties of light are studied to evaluate differing concentrations of milk in a **student-made photometer. Student generated calibration curves for the photometer introduce quantitative inferences from proxy variables. The unit culminates with a case study which recognizes extremophiles (microbes) as an indicator species for the health of a saline environment impacted by mine tailings. Students use their photometers to count what they cannot see. The students, having limited resources, work together to develop a sampling strategy to map the microbial population and infer point pollution sources. Their findings and recommendations are presented as a water management plan.
*pre-made operational amplifier is available for loan, upon request.
**simple, pre-made photometers are available for loan, upon request.
- Environments of differing salinities form on earth.
- Human activities impact saline environments by altering the salinity and/or introducing pollution.
- Extremophilic organisms such as Halobacterium salinarum can live in high salinity environments.
- Evidence indicates similar saline environments once existed or now exist on other planets.
- Design is an iterative problem-solving process.
- Criteria are standards on which to judge success.
- Constraints are limitations on possible solutions or problems.
- Design solutions involve trade-offs.
- Application should drive criteria for instrumentation design (precision, accuracy, sampling, etc.).
- Observation is the skill of recognizing and noting some fact or occurrence in the natural world. Observation includes the act of measuring.
- To infer is to arrive at a decision or logical conclusion by reasoning from evidence.
- Scientists use observations to make inferences.
- Additional information can improve the validity of inferences.
- Proxy variables can be used to make observations.
- An Atomic Force Microscope (AFM) uses repulsive force as a proxy variable to make observations of surfaces at the atomic scale. Processing the data with visualization software allows scientists to infer surface structure from these observations.
- Increased resolution can provide additional information.
- Accuracy is the degree of closeness of a measured or calculated quantity to its actual value.
- Proxy variables can be quantitatively related to inferred properties through calibration.
- Measuring devices reference known standards.
- Measuring devices with a predictable pattern can be calibrated.
- Calibration curves can be used to determine unknown quantities.
- An offset or a blank is commonly needed to interpret calibration data.
- Measurements of indicator species can be used to make inferences about environmental conditions.
- Quantity and resolution of a data collection plan is limited by resources.
- Mine tailings are point sources of heavy metal pollution.
- Population density is a measurement of the number of individuals living in a given amount of space.
- Propose reasons why salinities of water bodies differ across the globe.
- Brainstorm how they could measure populations of microbes from these saline environments.
- Define criteria & constraints for a wind speed measurement challenge.
- Brainstorm possible solutions, weigh trade-offs, and carry out proposed methodology.
- Choose an appropriate number of significant digits to reflect the uncertainty in their data.
- Evaluate results and suggest improvements.
- Evaluate their current design’s suitability for a proposed application.
- Revise design criteria to meet the needs of the proposed application for a measurement.
- Make observations and generate inferences about differing types of data.
- Use “touch” data to draw an unknown object in a bag.
- Make inferences about the identify of the object from the drawings.
- Use a mock Atomic Force Microscope (AFM) to infer surface structure from “touch” data processed with Excel into a 3D graph.
- Brainstorm ways to improve the design of their mock AFM and evaluate the trade-offs.
- Evaluate the limitations of using proxy variables to take measurements.
- Evaluate the limitations of observation to infer patterns or make predictions.
- Generate operational definitions for signal and noise from common everyday experiences.
- Quantify Signal, Noise, and Signal to Noise ratio for a graphed radio transmission example.
- Analyze the trade-offs in amplifying a signal for measurements.
- Generate a calibration curve using a photoresistor to infer milk fat concentration.
- Determine an unknown concentration from their calibration curves.
- Generate a sampling plan based on limited resources.
- Share data with other student groups.
- Refine their sampling plan based on current observations.
- Analyze data about population density of indicator species to infer locations of point sources arsenic pollution and about freshwater springs.
- Analyze their findings to propose a watershed management plan for Middle Basin in Death Valley.
- Communicate their research and their proposal in a presentation.
- Communicate their findings and respond to questions and criticisms regarding their proposals.
- Use raw data to prepare GIS-like visual mapping products.
- Extension activities allow students to build an Operational Amplifier circuit on a bread board to amplify the signal from an iPod to a speaker and to collect and analyze signal and noise data for the built speaker circuit using voltage probes and real time graphing software such as LoggerPro from Vernier.
This approximately 3 week long unit consists of 6 (multi-day) lessons designed for 50-minute periods. If the Career Connections activities are included (see below), plan for an additional 1-6 class periods based on the activities you choose.
Lesson 1 Intro to Saline Environments and Halophiles (1 class period)
Main Question: How can we count halophilic microbes?
Lesson 2 Design Process-Measuring Wind Speed (2 class periods)
Main Question: How do scientists and engineers design and evaluate solutions to measuring problems?
Lesson 3 Inferences from Proxy Variables-Mock Atomic Force Microscope (2-3 class periods)
Main Question: How do we count or measure things we cannot observe directly?
Lesson 4 Signal and Noise (2 class periods)
Main Question: What are the trade-offs & benefits to amplifying a signal?
Lesson 5 Inferring Properties and Calibration (2 class periods)
Main Questions: How can we use light as a quantifiable proxy variable and how do we make our light measurements meaningful for population density?
Lesson 6 Mapping Death Valley Case Study (2-4 class periods)
Main Question: How can we make inferences from microbe populations to develop a water management plan?
Career Connections (Coming Soon!):
This module also contains career connected activities that are woven into each of the above lessons in order to provide a cohesive way to teach students about unique STEM careers. You can read about these activities within each of the 6 lessons, by clicking the "Career Connection" tab located within each of the lesson pages. In order to view a combined snapshot of all of the activites, see this compiled overview (link coming soon) and this pacing guide (link coming soon).
- Materials for each Lesson are found within the lesson links listed below. In addition, use this list for all needed materials.
Culminating project in the form of a watershed management plan (written) and/or student presentation.