Assessment:
Steps 1 to 5 are intended to be a quick method to assess students’ prior conceptions about the use of technology in biological science.

1. Begin by stating or writing on the board, “Technology is a means of extending human potential or of extending human senses.” Ask students to raise their hands if they agree with this statement.
2. Ask students to provide justification for their responses. Can students relate specific technologies to the extension of specific human attributes or senses?

Students will generally agree that technology extends human potential. Obvious examples include the wheel and other transportation innovations that extend our potential for movement, and electronic devices, such as TV, radio, and telephones, that extend our ability to communicate. Microscopes, telescopes, eyeglasses, and contact lenses extend and enhance our sense of vision. Computers and written materials can be seen as ways to extend memory. There are many other examples.

Tip from the field test: Some students correctly pointed out that technology is also used to extend animal potential.

3. Ask students to consider only technologies that have increased our understanding of living systems. Do they extend any human attributes? If they do, which attributes are extended?

Students will probably focus on those that extend vision, since they are the easiest to recognize. Examples could include radar, eyeglasses, contact lenses, and telescopes. Students also know that microscopes allow us to see objects that we cannot see with the naked eye. Students should be familiar with the light microscope, and many may have heard of electron microscopes. Through figures in textbooks, they may know X-ray crystallography as a technology that helped us “see” the structure of DNA. Other technologies might be mentioned. Accept all responses and write them on the board. This is an opportunity to identify students’ current understanding of these technologies.

A Gary Larson Far Side cartoon, “Early Microbiologists,” can be used to engage students. Pictured is a caveman “laboratory,” in which several cavemen peer intently into Petri dishes filled with agar. Since they do not have microscopes, they hold the dishes in various ways, such as very close to the face. One of the cavemen imitates binoculars by holding his hands to his eyes. (The cartoon can be found in several published works, including The Prehistory of the Far Side, by Gary Larson, copyright 1989 by FarWorks, Inc., distributed by Universal Press Syndicate, published by Andrews McMeel, Kansas City, Kansas.)

4. Ask students to focus on technologies as tools that allow us to “see” biological objects (the eye, microscopes of all kinds, and X-ray techniques). One at a time, ask the following questions:
1. What technologies would you use to study a whole (intact) organism and why?
2. What technologies would you use to study cells and why?
3. What technologies would you use to study molecules and why?

Accept all reasonable responses, but challenge those that are incorrect. Students should understand that no single technology is useful at all levels of organization of biological organisms. In other words, no single technology is able to resolve structural details from the intact organism to the molecules that make up that organism. This discussion introduces students to the idea that there is a right tool for the job.

Content Standard A:
Identify questions and concepts that guide scientific investigations.

5. Ask students why a single technology cannot provide information at all levels of organization of biological organisms.

You might remind students that at the conclusion of Lesson 1, they were asked to speculate on what would make one technology more useful than another in a given situation. If students need prodding, you can ask whether they would use a microscope to study a whole organism, or whether they would use their eyes alone to study molecules. While a microscope is required to study single-celled organisms, such as bacteria and protists, most multicellular organisms can be observed with the unaided eye. High-resolution technologies, such as X-ray crystallography, are required for investigations of molecular structure.

6. Tell students that what makes some technologies better than others for a given job relates to the concept of “resolution.” Ask them what resolution means.

Tip from the field test: Students generally had no concept of resolution as it relates to technologies used in biological science. Responses often related to resolution of computer monitors, personal resolve, or New Year’s resolutions.

7. Tell students that they will investigate resolution. Organize the class into groups of two and then pair two groups.

This activity works best if you have a minimum of six groups so that each can receive one of the six Masters 2.3 through 2.8.

8. Ask groups to arrange their seating so that one is directly opposite another:

Allow sufficient room between tables so that groups do not interfere with one another.

9. Explain to the class that this activity resembles the game Battleship, with which some of them might be familiar. Each group’s task is to locate and define the shape of an object or objects on the master held by the opposing group.

Tip from the field test: Field-testing indicated the need to point out that this activity is not exactly like Battleship. Students do not “sink” or “destroy” an opposition’s force. Rather, they use the Battleship strategy to locate and define the shape of a shaded region or regions on the master held by an opposing group.

10. Give each group a copy of Master 2.1, Probing for Answers Score Sheet.

Students use this sheet to record hits and misses as they probe for the location of the opposing group’s shaded region(s).

11. Randomly color several regions on a transparency of Master 2.1, Probing for Answers Score Sheet. Use this transparency and a 3 × 3 probe from Master 2.2, Probes, to demonstrate how this activity is done.
1. Use this probe to locate areas 3 squares by 3 squares on the transparency. To save time, you may instruct students to probe only the nine nonoverlapping 3 × 3 regions, as shown on the following diagram:
   
   
2. One group begins by calling out the location of the 3 × 3 area they wish to probe, such as A-C, 1-3.
3. If the opposing group’s Master (2.3, 2.4, 2.5, 2.6, 2.7, or 2.8) has a shaded square within the area called, they indicate this as a hit; if not, a miss.
4. The first group records the result on their score sheet. Draw an X in 3 × 3 squares that are misses, and put an O in the 3 × 3 squares that are hits.
5. It is then the opposing group’s turn to select an area to probe, which is then recorded as a hit or a miss.
6. Groups take turns trying to locate the opposing group’s shaded squares

12. Give each group a copy of one master selected from Masters 2.3 to 2.8. Instruct groups to hide this master from their opposing group.

Make sure that each of these six masters is used by at least one group. In larger classes, the same master may be used by more than one group. You may choose to place each master in a manila folder. Students can use the folder in various ways (for instance, opened and stood on its edge) to keep their master from being seen by the opposing group.

13. Give each group a 3 × 3 probe from Master 2.2, Probes. Instruct students to use this probe to locate areas 3 squares by 3 squares that contain the opposing group’s shaded area(s).

Limit the time allowed for this portion of the activity to no more than five minutes.

14. Ask students whether they believe they have gathered enough information to specify the exact shape(s) and location(s) of the opposing group’s shaded object(s).

Make sure students in opposing groups do not share information about their shaded patterns. Students should realize from looking at their own shaded pattern that the 3 × 3 probe is too large to identify the shape and location of smaller objects; that is, the large probe cannot resolve the size and shape of the smaller objects.

15. Ask students what would help them define the shape and location of the opposing group’s shaded object(s).

A smaller probe is required.

Tip from the field test: Field-testing indicated the importance of having students come to this conclusion on their own.

16. Next, give each group a 2 × 2 probe. Groups are to focus on those areas that were determined to be hits with the larger probe.

Students are to repeat with this probe what they did earlier (see Step 13 above) and try to determine the structure and location of the opposing group’s shaded pattern. Limit the time allowed for this portion of the activity to no more than several minutes.

17. Ask students whether they believe they now have enough information to specify the exact shape(s) and location(s) of the opposing group’s shaded object(s).

Make sure students in opposing groups do not share information about their shaded patterns. At this point, some students may believe they have sufficient information to predict the pattern held by the opposing group. Ask those willing to speculate on the opposing group’s pattern to provide their justification, especially how they know that all four squares in a 2 × 2 “hit” region are shaded.

18. Next give each group a 1 × 1 probe.

Students should focus only on those areas determined to be hits with the 2 × 2 probe. They should continue to define the structure and location of the opposing group’s shaded pattern. Limit the time allowed for this portion of the activity to no more than several minutes.

19. Ask students if they believe they now have gathered enough information to specify the exact shape(s) and location(s) of the opposing group’s shaded objects. Do they need another probe to complete the task?

Students should justify their responses. Students cannot know for sure what the opposing group’s pattern looks like, even though they see that their own pattern is composed of 1 × 1 squares. If they speculate that the opposing group’s pattern is constructed similarly, then no additional probes are required, since the objects being resolved (the 1 × 1 squares, both shaded and unshaded) are the same size as the final probe. Importantly, the final probe is not larger than the objects being resolved. If students believe that additional probes are required, they should justify this based on what they believe to be the size of the objects being resolved (shaded and unshaded). Their suggestion for an additional probe should indicate a probe size no larger than that of the objects being resolved. No matter what the response, ensure that students derive a general relationship between probe size and the size of the objects being resolved before proceeding. They should be able to explain that the size of the probe should be no larger than the objects being resolved.

Assessment:
Listening to students explain their answers, defend their reasoning, and modify their responses after listening to other students explain their logic will help you assess students’ understanding of resolution.

20. Have opposing groups confirm that after using the series of three probes, they were able to determine the correct pattern on one another’s master.

1. Why not use the smallest probe first?

A similar question is, Is there an advantage to using larger probes first and then using smaller probes? The larger probes allowed the students to quickly identify the general location of the object(s) being investigated. In some cases, even information about structure, albeit crude, can be obtained. Remind students of the procedure they follow when using a light microscope. They first use the lowest magnification to locate the object of interest and then switch to a higher magnification to gain more information. Using the smallest possible probe first can be time consuming and expensive. In some cases, using the smallest available probe also can be inappropriate—for example, when the probe is very much smaller than the objects being resolved. As an example, consider the time and expense involved in using an electron microscope rather than a light microscope to count yeast cells or to assess fruit fly traits in a genetics experiment.

2. On the board, write these wavelengths:

• visible light, 4 to 7 × 10^–7 m;
• electrons, 2.7 to 0.9 × 10^–10 m; and
• X-rays, 1 × 10^–8 to 1 × 10^–11 m.

Refer to Master 1.1, Searching for Scale, and ask students which of these they think would be appropriate probes (that is, provide the appropriate level of resolution) for the objects listed.

Visible light could be used to resolve cells, bacteria, and mitochondria. Longer-wavelength electrons are potential probes for viruses, small cell organelles such as ribosomes, and large molecules such as proteins. Shorter-wavelength electrons and short-wavelength X-rays are potential probes for molecules, even small ones like glucose. They also may be used to resolve adjacent atoms in molecules (which requires probes smaller than 2 × 10^–10 m).

Teacher note: Whether or not a probe is useful in a given situation also depends on whether the technology actually exists to make use of the probe. For instance, are appropriate sample preparation techniques available? Are appropriate sample handling technologies available (for example, can the sample be rotated if necessary, and in a way that does not interfere with the rest of the procedure)? Can the probe be focused sufficiently? Is there technology to view and evaluate the results of such analyses?

1. Begin by holding one of the bread rolls up to the class. Make sure that no dye is showing. Ask students to describe what they see.

Students will recognize the object, and they may describe it by noting its color, shape, and apparent external texture. They should indicate that the roll is a three-dimensional object.

2. Do students have maximum information about the roll? Is there anything they do not know about the bread roll from just looking at it?

Student responses will vary from, “Is it tasty?” and “Where does it come from?” to “What is inside?” Some students may realize that although they might have made an assumption about the roll’s interior (for example, it is just plain bread), they actually know nothing about what is under the crust.

3. Focus discussion on what is inside the bread roll. Ask students how they would get that information.

Students will suggest cutting or tearing the roll.

4. Slice the roll to reveal the presence of dye in one of the two dye locations. Hold the roll so the class can see the two cut edges. Do the students now feel they have complete information about this object? If not, what questions do they have?

Even though they know there is a dyed region inside the roll, students should realize that they do not know what this region looks like. What is the shape of the dyed region and how far does it extend in any given direction? Is there only a single dyed region, or are there multiple regions? If there is more than one dyed region, is it the same color as the region they can see?

Tip from the field test: Some students suggested cutting the roll as one would if making a sandwich. The second bread roll is helpful if this possibility is raised.

5. Ask students how they could obtain information to answer these questions.

A simple approach would be to make additional slices in the roll. Students may suggest more exotic means (for example, use a fiber optic light source connected to a minivideo device to view the roll’s interior on a remote screen). If suggestions fall in the latter category, congratulate students for their ingenuity. Ask them to think about how to gain the information required quickly and using simple, available technology. In the end, focus student attention on increasing the number of slices. This requires only a knife and can be done quickly.

6. Ask the students how many slices would be required to define the dyed region(s) in the roll’s interior. What are their considerations in providing an answer to this question?

The actual number of slices that the students believe is correct is not the important issue. If students do provide a specific answer, ask them to justify it. It is important for them to understand the following. First, multiple slices are required to define the object’s properties. The size of the slices will determine the resolution used to define the object’s properties. Thicker slices will provide less resolution, just as the 3 × 3 probes provided low resolution in Activity 1. Thinner slices will provide greater resolution, just as the 1 × 1 probes did in Activity 1.

7. Ask students to have their group’s Master 2.3 to 2.8 available. Explain that the “level” designation below the grid (Level 1, 2, 3, 4, 5, or 6) on the master indicates the location of a slice through an object.

Level 1 is the top slice, followed by 2, 3, 4, 5, and 6 (at the bottom).

8. Ask students to visualize their pattern in three dimensions by imagining that their shaded pattern represents the top of a stack of gray blocks. Their level is a slice two blocks thick.
9. Ask the groups to share their data (that is, the location of the shaded regions) and try to reconstruct the three-dimensional object that has been cut into six slices.

Do not provide additional guidance. Give students about five minutes to do this. Students may or may not be able to reconstruct the object in this time.

10. Show students a transparency of Master 2.9, Solution to Probing for Answers. Were they able to arrive at this solution? What might have made their task easier?

Some students do well thinking in three dimensions, and others do not. Many may recognize the need for additional technology, such as a computer and appropriate software, to make the job of reconstruction easier. Even a simple technology, such as wooden blocks or Legos, could have been used to construct a three-dimensional model of the intact object.

1. As a follow-up, ask students, “Have these activities expanded your understanding of technology? If they have, how?”

Activity 1 demonstrates the use of multiple probes to achieve different levels of resolution. It also demonstrates that the right tool, in this case a probe of appropriate size, must be selected to solve a problem (resolving the structure of an unknown object). Therefore, students should realize that there is an appropriate technology for a given problem (that is, the right tool for the job). Activity 2 demonstrates that solutions to a problem may involve more than one technology (the use of slices to determine the structure of a three-dimensional object and technologies to collect and analyze the data).