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BSCS Biology: A Human Approach. Kendall/Hunt, 1997

Cell Structure and Function: Instructional Analysis

I: Providing a Sense of Purpose

Conveying unit purpose

Rating = Excellent
The material meets four indicators fully and mostly meets indicators 4 and 6.

Indicator 1: Met
Unit openers pose situations that convey to students the purpose of the unit. For example, Unit Two: Homeostasis: Maintaining Dynamic Equilibrium in Living Systems opens with a picture of an ice skater (pp. 76–77s). The text discusses how the skater is maintaining balance: “Think of a skater gliding across the ice: not only is he balancing on an edge of a blade, but his body is maintaining a balance in other less obvious ways. Although he is surrounded by ice and frigid air, his body temperature stays fairly constant. And as he exerts energy in spins and jumps, his heart rate and breathing rate accommodate these changes” (p. 77s).

The text then presents the unit purpose:

In this unit you will examine some of the processes involved in maintaining balance in the human body. You will consider the characteristics of the human life form that allow for stable internal conditions, and you will apply what you have learned by studying how the human body reacts when this balance is disrupted significantly.

p. 77s

Chapter openers also present purposes to students. For example, Chapter 4: The Internal Environment of Organisms compares astronauts’ attention to differences between their external and internal environments to the rest of us. Students then read, “In this chapter you will explore different systems in the human body, from the level of the cell to the body as a whole, to learn ways the human body maintains an internal balance” (p. 79s).

Indicator 2: Met
The problems, questions, or representations used to convey the unit and chapter purposes relate to observable phenomena rather than unfamiliar technical terms and hence are likely to be comprehensible to students. For example, the photograph used to introduce Unit Two: Homeostasis: Maintaining Dynamic Equilibrium in Living Systems shows an ice skater, one like many students have probably watched on television (pp. 76–77s). Similarly, the opener for chapter 4 uses non-technical language and an easily understandable comparison between the conscious efforts of astronauts and space suits in maintaining internal balance to intricate systems inside our bodies that do that work for us without our conscious awareness (p. 79s).

Indicator 3: Met
The problems, questions, and representations used to convey the unit and chapter purposes may be interesting to students. The purpose for Chapter 4: The Internal Environment of Organisms, for example, with its focus on astronauts and space suits, may appeal to some high school students (p. 79s). Immediately in the initial chapter activity students will read and discuss how a young man gets dehydrated, which may be interesting to high school students (pp. 80–81s).

Indicator 4: Mostly met
While students are not offered an opportunity to think about the purpose of the unit, they are given an opportunity to think about the purposes of chapters. Each chapter begins with an Engage activity that follows immediately after the chapter opening page, where the purpose has been presented. BSCS Biology: A Human Approach uses a progression from a general problem in the chapter opener to an example of this problem in the Engage activity. The purpose of the Engage activity in the material’s instructional model is, in part, to “focus students’ thinking on the learning outcomes” (p. xiiit). One purpose of Chapter 4: The Internal Environment of Organisms, for example, is to help students “learn ways the human body maintains an internal balance” (p. 79s). The initial chapter activity, Can You Stand the Heat?, engages students in considering ways the human body works to maintain its internal environment in the face of external stresses (p. 80s).

Indicator 5: Met
Chapters within units are consistent with the unit purposes identified. For example, in unit two all chapters deal with maintaining balance and homeostasis. Chapter 4 deals with this topic at the cellular and human levels, chapter 5 addresses it at the organism and human levels, and chapter 6 discusses health and disease.

Activities within chapters are consistent with the stated chapter purposes. For example, in Chapter 4: The Internal Environment of Organisms, after the initial activity considering how a young man becomes dehydrated (pp. 80–81s), the activity Cells in Action investigates how cells change in response to their surroundings. The activity A Cell Model uses dialysis tubing to explore how boundaries and compartments help living things maintain and regulate balance (pp. 86–88s). The next section, Regulating the Internal Environment, examines how the circulatory and urinary systems function to preserve and regulate balance in humans (pp. 88–90s). In the Evaluate activity for the chapter, Can You Stand the Heat—Again? revisits the initial story of the dehydrated young man in light of what has been learned in the chapter (pp. 90–91s).

Indicator 6: Mostly met
Units do not return to the stated purpose at the end of the unit, but chapters do return to the stated purposes in the sense that final activities in the chapters are related to the problems and purposes posed at the beginning. For example, in Chapter 4: The Internal Environment of Organisms, the first student activity engages students in thinking about how a young man becomes dehydrated and in the final chapter activity, students revisit the opening story and re-examine how the young man’s decisions affected his internal balance.

Conveying lesson/activity purpose

Rating = Satisfactory
The material meets indicators 1 and 5 and somewhat meets indicators 2 and 4. It does not meet indicator 3.

Indicator 1: Met
The material conveys to students the purposes of all lessons, activities, and readings in the chapters reviewed. For example, for the activity A Cell Model, students read, “Your investigation will help you develop an explanation for how boundaries and compartments help living systems maintain and regulate the conditions necessary for life” (p. 86s). For the activity Regulating the Internal Environment, students read, “In this activity you will see how these two systems [circulatory and urinary systems] help regulate the internal environment in humans” (p. 89s). The purpose of reading essays in the back of the book is conveyed to students in brief directions such as this one, which is provided to students as a step in the procedures for the activity A Cell Model: “The essay Molecular Movement (page E53) may help with this step” (p. 87s).

Indicator 2: Somewhat met
In most cases, such as those discussed for indicator 1, the activity purpose is comprehensible. However, in some cases the purpose is not well-aligned to the activity, which may be confusing or misleading for students. For example, the purpose provided for one activity explains that: “Based on your examinations, you will begin to understand how living systems maintain an internal environment that is different from the external environment” (p. 80s). However, the activity does not show how the environment of a system maintains balance when the external environment changes. In fact, this activity uses a shell-less egg and plant cells to show how the internal environment of a cell changes when the external environment changes—it swells or shrinks depending on the solution it is in (pp. 80–86s).

Indicator 3: Not met
Opportunities are not provided for students to think about the purposes of activities.

Indicator 4: Somewhat met
At a few points throughout the chapters, this material includes statements or questions that convey how the activity relates to the chapter purpose. For example, as an introduction to the activity involving dialysis tubing and different solutions, the text explains:

You have been exploring examples of interactions between internal and external environments. In living systems, boundaries separate these environments.…In this activity you will use dialysis tubing and several solutions to build a cell model that you can use to investigate how cell boundaries affect the internal cellular environment.

p. 86s

Indicator 5: Met
The material consistently engages students in thinking about what they have learned so far and what they need to do next. For example, following an activity with dialysis tubing and different solutions, the text relates the activity to the next activity:

By now, you have begun to understand some of the processes that allow substances to move between internal and external environments. In addition, you have seen that the exchanges between compartments are influenced by the membranes that form boundaries around the contents of cells.

You might wonder whether the same processes of exchange, diffusion, and osmosis are important in large body systems as well. To begin to answer this question, consider two important compartments within the human body—the circulatory systems and the urinary system. In this activity you will see how these two systems help regulate the internal environment in humans.

pp. 88–89s

Justifying lesson/activity sequence

Rating = Fair
The material minimally meets the first indicator but does not meet the second indicator.

Indicator 1: Minimally met
Overall the sequence of readings and activities seems logical. However, only one key idea is presented, and the student activities are repetitive. Chapter 4: The Internal Environment of Organisms introduces homeostasis through a story about dehydration (Can You Stand the Heat?, pp. 80–81s). Then students investigate homeostasis in cells and cell models (pp. 80–88s) and return to the initial story of dehydration in more detail (the circulatory and urinary systems in humans, pp. 88–90s). The three student activities in this chapter address the same part of the key idea that “Every cell is covered by a membrane that controls what can enter and leave the cell” (Idea a). Activities involve (1) using a shell-less egg to model the control of a cell membrane, (2) observing cells in different solutions through a microscope, and (3) using dialysis tubing to model the control of a cell membrane.

Indicator 2: Not met
The Teacher’s Guide tells how the chapters are arranged in units but no rationale for this sequence is given. For example, the order of chapters in unit two is described as follows:

The learners begin the unit by exploring the concepts of internal environments, external environments, compartments, and membranes. Next learners investigate different systems in the human body, from the level of the cell to the body as a whole, in order to learn ways the human body maintains an internal balance. Then in Chapter 5, the learners extend their opportunity to learn about internal balance in the human body by applying the concept to some of the basic activities of life. In Chapter 6, the students study what happens when internal balance is disrupted in various ways. They also consider how humans can influence, both positively and negatively, their own health as well as the health of others.

p. 117t

However, nowhere is the teacher explicitly told the reasons for the sequence chosen. For each chapter, the sequence of activities is clearly presented in the Teacher’s Guide. However, while the material describes the sequence of activities in a chapter, no rationale for the sequence is provided, telling, for example, why a particular Elaborate activity precedes another.

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II: Taking Account of Student Ideas

Attending to prerequisite knowledge and skills

Rating = Poor
Indicators 1, 2, 3, and 5 are not met and indicator 4 is minimally met.

Indicator 1: Not met
The material does not alert the teacher to specific prerequisite ideas or skills.

Indicator 2: Not met
The material does not alert teachers to the specific ideas for which the prerequisites are needed.

Indicator 3: Not met
The material does not alert students to prerequisite ideas or experiences that are being assumed.

Indicator 4: Minimally met
Only one prerequisite idea is mentioned briefly. The prerequisite idea that “Atoms may stick together in well-defined molecules or may be packed together in large arrays” [4D(6-8)/1] is mentioned in an essay, Matter and Energy Are Related, when the term “chemical bonds” is defined. The text explains that “Chemical bonds hold atoms together in very predictable ways to form molecules; energy is stored within the structure of a molecule’s bonds and atoms” (p. E108s). No further explanation is provided. In fact, the text continues with a more difficult concept, describing how energy is stored in bonds.

Other important prerequisites—for example, that cells perform many of the same basic functions as organisms do, such as extracting energy from food and getting rid of waste [5C(6-8)/3] and that organs and tissues function to serve the needs of all cells [5C(6-8)/1]—are not mentioned. Although this material includes many essays on the structure of matter and basic chemistry, these ideas are not related to cellular functions. Even so, important prerequisite chemical concepts are not discussed, such as:

• The rate of reactions among atoms and molecules depends on how often they encounter one another, which is affected by the concentration, pressure, and temperature of the reacting materials. [4D(9-12)/9…]
• The configuration of atoms in a molecule determines the molecule’s properties. Shapes are particularly important in how large molecules interact with others. [4D(9-12)/8]

Both of these prerequisites are important for learning the idea that most cells function best within a narrow range of temperature and acidity.

Indicator 5: Not met
No links are made between the one prerequisite idea mentioned and the related key idea.

Alerting teachers to commonly held student ideas

Rating = Not rated
For the topic of cell structure and function, materials were not rated on this criterion because no research base outlines commonly held student ideas.

Assisting teachers in identifying their students’ ideas

Rating = Poor
The material meets no indicators.

Indicator 1: Not met
No questions are provided that could be used to elicit students’ ideas about cell structure and function before instruction. Some activities provide questions for students to answer before beginning the activity. For example, before students investigate what happens to a shell-less egg as it is placed in different solutions, they are asked to “[u]se the information in the introduction to generate questions about what might happen if you place the shell-less chicken egg in different solutions” (p. 82s). However, having students generate possible questions for investigation does not help the teacher better understand the students’ ideas about the key ideas for cell structure and function. Furthermore, since students are not directed to think about the function of the cell membrane, this question does not focus on these key ideas.

Similarly, before students investigate what happens to a model cell in different solutions (using dialysis tubing), they are asked to “[p]redict what will happen when you conduct the experiment, and record this information in your journal” (p. 87s). Although having students make predictions may help the teacher better understand their own students’ ideas, this question does not focus students on the function of the cell membrane (Idea a).

Indicator 2: Not met
Although the questions listed under indicator 1 are comprehensible, they do not focus on the key ideas for cell structure and function.

Indicator 3: Not met
The questions provided before activities are not identified as having the purpose of identifying students’ idea before instruction.

Indicator 4: Not met
Although one of the questions listed in indicator 1 involves students in making a prediction, the question does not focus on the key ideas for cell structure and function.

Indicator 5: Not met
The material does not suggest how teachers may probe beneath students’ initial responses to questions designed to find out what students think before instruction.

Addressing commonly held ideas

Rating = Not rated
For the topic of cell structure and function, materials were not rated on this criterion because no research base outlines commonly held student ideas.

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III: Engaging Students with Relevant Phenomena

Providing variety of phenomena

Rating = Poor
Since the rating scheme depends on how many phenomena meet both of the indicators, the report for this criterion is organized to reflect the overall rating rather than each indicator judgment.

The material provides almost no phenomena to support the key ideas about cell structure and function. In an Explore section in Chapter 4: The Internal Environment of Organisms, students examine how substances can move across a cell membrane of a shell-less egg in different solutions (pp. 80–84s). Students dissolve the shell of an egg in a vinegar solution, then place the shell-less egg in different solutions, one of corn syrup and another of pure water, and observe what happens to the mass of the egg. The link between this investigation and the idea that the cell membrane controls what can enter and leave the cell (Idea a) is mentioned in the introduction to the activity in a statement that explains that “this membrane allows certain substances to pass in and out of the egg” (p. 82s). However, none of the follow-up questions focuses the students on the role of the cell membrane in controlling what comes in or leaves the cell.

In an Elaborate section in Chapter 5: Maintaining Balance in Organisms, students investigate how living systems maintain internal conditions (pp. 102–107s). This activity could clarify the idea that most cells function best within a narrow range of acidity (Idea d). Students first observe pH changes as they add 0.1M HCl dropwise to a beaker of tap water. Next they observe pH changes as they add 0.1M NaOH dropwise to a beaker of tap water. Lastly they add 0.1M HCl dropwise to a solution of a homogenate (ground up liver or potato) while testing the pH and this is repeated with the 0.1M NaOH solution. Students are asked how the homogenate responds to the addition of acid and base and to compare what happened to the homogenate to what happened with the initial beakers of water. One question asks students “At what pH do you think the inside of liver and potato cells functions best? On what do you base this inference?” (p. 106s). However, there is no general statement made that focuses on the idea that all cells function best within a narrow range of acidity. Furthermore, this activity does not mention that cells also have only a narrow range of temperature at which they function best.

No phenomena are presented for the other three key ideas for the topic of cell structure and function:

• Within the cell are specialized parts for the transport of materials, energy capture and release, protein building, waste disposal, passing information, and even movement. (Idea b)
• The work of the cell is carried out by the many different types of molecules it assembles, mostly proteins. (Idea c)
• Cell functions are regulated. Complex interactions among different kinds of molecules in the cell cause distinct cycles of activities, such as growth and division. Cell behavior can also be affected by molecules from other parts of the organism or even other organisms. (Idea e)

Providing vivid experiences

Rating = Poor
Since the rating scheme depends on how many phenomena meet all of the indicators, the report for this criterion is organized to reflect the overall rating rather than each indicator judgment.

The material meets no indicators. Given that neither of the two provided phenomena were explained by the key ideas, there is essentially nothing to be judged for vividness.

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IV: Developing and Using Scientific Ideas

Introducing terms meaningfully

Rating = Poor
The material somewhat meets indicators 1 and 2.

Indicator 1: Somewhat met
In its opening page describing BSCS Biology: A Human Approach to learners, the text says:

When we defined the word “better,” we decided that a better high school biology program would mean the following:

• more emphasis on the big concepts of biology and less emphasis on the vocabulary words of biology….

p. xvs

However, the material is inconsistent in its treatment of technical terms. In the front section of the book, which focuses on student activities, terms are usually presented in connection with relevant experiences. For example, in an Explain section of Chapter 4: The Internal Environment of Organisms, students investigate how dialysis tubing models the behavior of the cell membrane. A boxed section called Background Information presents and defines several technical terms needed for the investigation, such as “dialysis tubing,” “glucose test strips,” “Lugol’s iodine solution,” “starch,” and “the size of a molecule” (p. 88s). These terms are presented in a relevant context for students but are not the focus of what is to be learned from the activity. Similarly, the terms “isotonic,” “solute,” “solvent,” “hypertonic,” and “hypotonic” are introduced in connection with another experiment on cell membranes (p. 83s).

The essays in the back section of the book are inconsistent in linking technical terms to experiences. On the positive side, the essays are introduced in connection with student activities presented in the front section. Therefore, many technical terms in the essays may be linked in student thinking to relevant experiences. For example, students are referred to the essays Membranes and Molecular Movement in connection with their firsthand experience modeling the cell membrane using dialysis tubing (pp. 86–88s). Thus, when the terms “selectively permeable” and “protein channel” are presented and defined in the essay Membranes, students may relate these terms to their own laboratory experiences, even though the essay does not state such relationships (pp. E52–E53s).

However, sometimes the essays present technical terms without links to relevant experiences. This is particularly true for terms used in illustrations. For example, one diagram presents the terms “stomate,” “mesophyll,” and “waxy cuticle” without establishing a relevant context for students (p. E51s).

Indicator 2: Somewhat met
The number of technical terms introduced in the student activities in the front section of the book is largely restricted to those needed to communicate intelligibly about the key ideas. This is not true of the essay section in the back of the book, where many more technical terms are presented than are needed for intelligible communication. Examples of unneeded terms are “prokaryotic” and “eukaryotic” organisms (p. E51s), “entropy,” “lipid bilayer,” “turgid,” “vacuole,” “passive transport,” “active transport,” and “protein channels” (pp. E53–E56s). However, it should be noted that many technical terms traditionally associated with these key ideas are not present in this curriculum material, such as nuclear pore, nuclear envelope, nucleolus, plastids, chromoplasts, cristae, peripheral proteins, integral proteins, thylakoid, grana, and lumen.

Representing ideas effectively

Rating = Poor
Since the rating scheme depends on how many representations meet all of the indicators, the report for this criterion is organized to reflect the overall rating rather than each indicator judgment.

There is only one representation that is used to clarify the key ideas about cell structure and function.

For the idea that the cell membrane controls what can enter and exit the cell (Idea a), one activity involves students in making a model of a cell membrane using dialysis tubing, which can illustrate the control the membrane has over what substances can enter and exit the cell (pp. 86–88s). Other, less useful representations include an analogy that compares the cell membrane to a beverage container (p. E52s). Although the essay concludes by explaining that cell membranes are more complex than the walls of an insulated beverage container, the analogy does not seem to convey many of the features of the cell membrane (beverage containers lack the flexibility and permeability that cell membranes have). Two diagrams of the cell membrane are included, but focus on the details of the membrane architecture, rather than the function of the membrane (e.g., Figure E4.4 on p. E53s and Figure E4.8 on p. E56s).

For the idea that cells have specialized parts for specific functions (Idea b), one diagram shows a cross-section of a cell with several organelles labeled (p. E51, Figure E4.3). However, this diagram does little to clarify the function of the labeled organelles. No other representations for any other key ideas were found.

Demonstrating use of knowledge

Rating = Poor
Demonstrating use of knowledge is not a feature of this material. The material meets no indicators.

Indicator 1: Not met
The material does not demonstrate the use of any of the key ideas. For example, it does not use any of the key ideas on the topic of cell structure and function to explain phenomena.

Indicator 2: Not met
No performances are provided.

Indicator 3: Not met
No performances are provided that could be identified as demonstrating the use of knowledge.

Indicator 4: Not met
No running commentary or criteria for judging a good explanation are presented.

Providing practice

Rating = Poor
Two kinds of questions and tasks were considered for this criterion: The Evaluate questions and the student tasks and questions requiring application of ideas presented in the text. However, only one question focuses on the key ideas for the topic of cell structure and function.

Indicator 1: Not met
The material provides only one question for one of the key ideas on cell structure and function. For the idea that the cell membrane controls what can enter and exit the cell (Idea a), a relevant question follows the activity in which students observe shell-less eggs in different solutions:

Question: A chicken egg is a single large cell. In this activity, how did the egg serve as a model of how cells function as containers in living organisms?

Suggested Response: The egg is a single, unusually large cell. Special treatment was required to dissolve the shell, but the tough membrane acted like a cell membrane in that it allowed water, but not corn syrup, to pass through it freely.

pp. 85s and 128t, Analysis, question 2

The suggested answer mentions that the cell membrane allowed water, but not corn syrup, to enter but does not focus on the control the membrane has over what can enter and exit in general terms. Most of the questions provided focus on experimental design, such as “Why is it useful to combine data from the entire class?” and “What controls did you use in your experimental design? Why?” (p. 83s). Other questions focus on boundaries or internal and external environments, but not on the key idea that “Every cell is covered by a membrane that controls what can enter and leave the cell” (Idea a). For example:

Question: What do the data tell you about the relationship between the internal contents of a shell-less egg and its external surroundings? Justify your response with specific evidence.

Suggested Response: Ask the learners to think about how the eggs responded to changes in their external environment. They should use the change in mass of the eggs to support their explanation.

pp. 83s and 127t, question 5b

Question: How would you account for any differences you noticed in the behavior of the three eggs under different external conditions?

Suggested Response: The learners should be able to infer that the decrease in mass of the eggs in corn syrup solution was due to fluid loss. The eggs in distilled water must have gained fluid because their mass increased.

pp. 83s and 127t, question 5c

Question: What do eggs, animal cells, plant cells, and the human body have in common?

Suggested Response: Each is a container that has a boundary that separates the internal and external environments and allows the two environments to differ from each other.

pp. 85s and 129t, Analysis, question 3

No other questions or tasks were provided for the other key ideas.

Indicator 2: Not met
The practice task described under indicator 1 is novel. However, since there is only one task, the number of tasks is insufficient for the set of key ideas. The material as a whole does not meet this indicator.

Indicator 3: Not met
The material does not provide sequences of questions or tasks in which complexity is progressively increased.

Indicator 4: Not met
The material does not provide students first with opportunities for guided practice with feedback and then with practice in which the amount of support is gradually decreased.

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V: Promoting Students’ Thinking about Phenomena, Experiences, and Knowledge

Encouraging students to explain their ideas

Rating = Fair
Questions examined in the Engage, Explore, and Explain activities are designed to encourage students to express their own ideas. This material provides some opportunities for students to express their ideas by writing their ideas in journals, discussing with a partner, or drawing a diagram. However, very few of the questions in these sections focus on the key ideas about cell structure and function.

Indicator 1: Minimally met
The material provides very few opportunities for students to express their ideas about the key ideas for cell structure and function. Questions often focus, instead, on aspects of experimental design, such as “Why is it useful to combine data from the entire class?” and “What controls did you use in your experimental design? Why?” (p. 83s).

Indicator 2: Not met
The material does not provide questions that ask students to clarify, justify, and represent their ideas on this topic.

Indicator 3: Not met
The material does not provide opportunities for each student to express ideas on this topic.

Indicator 4: Not met
The material does not provide students with feedback.

Indicator 5: Not met
The material does not include suggestions on how to diagnose student errors, explanations about how these errors may be corrected, and recommendations for how students’ ideas may be further developed.

Guiding student interpretation and reasoning

Rating = Poor
The material meets no indicators.

Indicator 1: Not met
After each student activity, the material includes a set of Analysis questions. However, very few questions are relevant to the key ideas, such as:

Question: A chicken egg is a single large cell. In this activity, how did the egg serve as a model of how cells function as containers in living organisms?

Suggested answer: The egg is a single, unusually large cell. Special treatment was required to dissolve the shell, but the tough membrane acted like a cell membrane in that it allowed water, but not corn syrup, to pass through it freely.

pp. 85s and 128t, Analysis, question 2

Other questions either focus on the experimental design or on unrelated ideas.

The essays in the back of the student text are referenced in the activities. For example, in the activity Cells in Action, Part B Observing Cell Activity, students are told, “The essay Compartments on page E50 will be a helpful resource for this Analysis and for the next activity” (p. 85s). However, the material does not provide specific questions to guide student interpretation of the essays.

Indicator 2: Not met
No questions have helpful characteristics that will guide student reasoning.

Indicator 3: Not met
Since only one relevant question is provided for the key ideas on cell structure and function, no carefully scaffolded sequences were found. This question was found in a group of questions that relate to a wide range of ideas rather than being scaffolded to help students move gradually toward understanding a particular key idea.

Encouraging students to think about what they have learned

Rating = Poor
The material meets no indicators.

Indicator 1: Not met
This material includes no instances in which students are asked to reconsider their initial ideas.

Indicators 2 and 3: Not met
The material does not engage students in monitoring how their ideas have changed.

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VI: Assessing Progress

BSCS Biology: A Human Approach provides a variety of tools to assess students’ progress at the end of instruction. The Teacher’s Resource Book (TRB) specifies “Opportunities for Summative Assessment” (TRB, p. AP-2), among which it lists “Evaluate Activities” (which appear in each chapter), “Model Chapter Assessment” (provided only for chapter 2), “Unit Assessments,” and the “Evaluate Section,” which is presented at the end of the entire program. These components of chapter four—the chapter that treats the key ideas related to cell structure and function—were examined for the first two criteria.

In addition to these components, teachers are encouraged to have students write in their portfolios at the end of each unit: “Ask the students to choose works that represent key points in their own learning process—points at which a concept became clear to them” (TRB, p. AP-3). While if done properly, students’ entries in their portfolios might demonstrate their understanding of the key ideas, this is not guaranteed; therefore, the portfolios were not taken into account in judging the sufficiency of relevant assessment tasks.

Aligning assessment to goals

Rating = Poor
Since the rating scheme depends on how many assessment tasks meet both of the indicators, the report for this criterion is organized to reflect the overall rating rather than each indicator judgment.

BSCS Biology: A Human Approach provides no assessment items that focus on the key ideas for cell structure and function. Although one question focuses on the results of an experiment using dialysis tubing, it does focus on how the dialysis tubing could be a model for the cell membrane:

Question: A researcher has just placed some dialysis tubing containing a solution of molecule X into a beaker that contains the same type of solution, but in a higher concentration. The tubing is permeable to X.

1. Draw a sketch of what this set up would look like initially. Use Xs to show the relative concentrations of solutions.

Suggested Response: The students’ sketches should depict more Xs closer together in the beaker and fewer Xs father [sic] apart inside the tubing (See Figure TUA2.1 left).

2. Make a prediction about what will happen in the beaker and in the dialysis tubing after 24 hours, and provide another sketch.

Suggested Response: Expect the students to predict that during a 24 hour period, Xs will move from the solution in the beaker into the tubing (See Figure TUA2.1 right).

3. Explain your prediction.

Suggested Response: Expect the students to explain that molecules of X will move from the area of higher concentration to an area of lower concentration until they are equal.

TRB, p. AP-35, question 8

Testing for understanding

Rating = Poor
Since the rating scheme depends on how many items meet both of the indicators, the report for this criterion is organized to reflect the overall rating rather than each indicator judgment.

The material provides no assessment items that focus on the key ideas for cell structure and function.

Using assessment to inform instruction

Rating = Poor
The material meets no indicators.

Indicator 1: Met
BSCS Biology: A Human Approach provides formal opportunities for ongoing, formative assessment (indicated by check-mark icons in the Teacher’s Guide). In addition, teachers are encouraged to assess students informally—for example, based on “the learners’ contributions to both team and class discussions” (TRB, p. AP-4). The Teacher’s Resource Book states: “Use the learners’ responses, writing, and performance as cues to modify your instruction. For instance, if a class discussion reveals persistent misconceptions at the Explain phase…you might decide to spend a full class period in direct instruction to clarify the misconceptions” (TRB, p. AP-4). The text then identifies a variety of tools in the material that can be used to evaluate student progress to inform instruction at each phase of the instructional model.

None of the formal tasks focuses on key ideas for cell structure and function.

Indicator 2: Not met
The material does not assist the teacher in interpreting student responses. The sample answers provide teachers with more guidance than is found in many teacher guides. For example, teachers are often alerted to the purpose of the question and to key points that students should address in their answers. However, these suggestions will not help teachers interpret student responses to diagnose what learning difficulties may remain.

Indicator 3: Not met
The material does not provide specific suggestions about how teachers can use student responses to make instructional decisions about what ideas need to be addressed by further activities.

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VII: Enhancing the Science Learning Environment

Providing teacher content support

Rating = Some support is provided.
The material provides minimal support in alerting teachers to how ideas have been simplified for students to comprehend and what the more sophisticated versions are. Background notes provide sophisticated versions of ideas for selected student text and activity sections (e.g., pp. 177–178t; p. 442t). The advanced explanations sometimes briefly elaborate on one or a few student text concepts (e.g., p. 123t). Overall, the Background notes may be used as a selective but not a comprehensive content resource by the teacher.

The material generally provides sufficiently detailed answers to questions in the student book for teachers to understand and interpret various student responses (e.g., p. 133t, Step 11; p. 165t, Analysis, answer 1). However, there are some limitations to the responses provided in the teacher notes, which occasionally are brief and require further explanation (e.g., p. 127t, Step 5, answer 5b; p. 163t, Process and Procedures, answer 3b).

The material provides minimal support in recommending resources for improving the teacher’s understanding of key ideas. A reference list without annotations subdivided by unit and chapter is provided at the end of the Teacher’s Guide (pp. 591–603t). In addition, the Teacher’s Resource Book has reference lists about biology content and general learning (pp. IG-51 to IG-53) as well as assessment strategies (pp. AP-8 to AP-9, 2.6 Resources on Assessment). While these resources might help teachers improve their understanding of the key ideas, the lists lack annotations about what kind of specific information the resources provide.

Encouraging curiosity and questioning

Rating = Some support is provided.
The material provides a few suggestions for how to encourage students’ questions and guide their search for answers. In some experiments, students are asked to generate questions for experimentation (e.g., p. 82s, Process and Procedures, item 1; p. 86s, Process and Procedures, item 1).

The material provides many suggestions for how to respect and value students’ ideas. Teacher and student notes often stress that multiple student answers should be acceptable for questions (e.g., pp. 148–149t, Analysis, item 2; p. 165t, Analysis, item 1). Many tasks elicit students’ ideas about particular concepts and issues (e.g., p. 80s, Process and Procedures, item 2; p. 87s, Process and Procedures, item 6). In addition, students are often asked to design their own experiments (e.g., p. 82s, Process and Procedures, item 2; p. 87s, Process and Procedures, item 3).

The material provides many suggestions for how to raise questions such as “How do we know? What is the evidence?” and “Are there alternative explanations or other ways of solving the problem that could be better?” The material includes many tasks that ask students to provide evidence or reasons in their responses (e.g., p. 80s, Process and Procedures, item 2; p. 83s, Process and Procedures, item 5b; p. 85s, Analysis, item 1).

The material provides many suggestions for how to avoid dogmatism. The first chapter explicitly discusses the nature of science as a durable yet dynamic human enterprise in which all people can participate (e.g., pp. 3–13s). In addition, the material discusses historical contributions (e.g., pp. 287–288s) as well as the work of current scientists (e.g., p. E67s and pp. E75–E77s). Throughout the material, the writing avoids dogmatism by being explicitly directed to students (e.g., pp. E56–E57s) and including some narratives (e.g., p. 113s).

The material does not provide examples of classroom interactions (e.g., dialogue boxes, vignettes, or video clips) that illustrate appropriate ways to respond to student questions or ideas. However, some sense of desirable interactions may be gained from general guidelines (e.g., p. xivt, Cooperative Learning and TRB, pp. CL-1 to CL-22, Chapter 3, A Guide to Cooperative Learning) and particular directions for cooperative group activities (e.g., pp. 80–86s, 126–129t, Explore: Cells in Action; pp. 90s, 139t, Analysis; pp. 103–106s, 163–165t, Process and Procedures).

Supporting all students

Rating = Some support is provided.
The material generally avoids stereotypes or language that might be offensive to a particular group. For example, photographs include a diverse cultural mix of students and adults (e.g., pp. 84s, 101s, E50s). In one instance, the subject matter of alcohol consumption may be offensive to some students (e.g., p. 81s, A Pause That Refreshes?).

For this topic, the material does not provide illustrations of the contributions of women and minorities to science and as role models.

The material suggests multiple formats for students to express their ideas during instruction and assessment, including individual journal writing (e.g., pp. 85–86s, Analysis), pair work (pp. 86–88s, Explain: A Cell Model), cooperative group activities and laboratory investigations (e.g., pp. 80–86s, Explore: Cells in Action), whole class discussions (e.g., p. 80s, Analysis), essay questions (e.g., p. 87s, Process and Procedures, item 11; p. 91s, Analysis), written reports (e.g., p. 88s, Analysis), and visual projects (e.g., pp. 84–85s, Part B Observing Cell Activity, items 4 and 6). For a few activities, the material provides alternatives for the same task (e.g., p. 89s, Process and Procedures, item 1).

The material does not routinely include specific suggestions about how teachers can modify activities for students with special needs. However, the student text, Teacher’s Guide, and Teacher’s Resource Book provide some additional activities for students. Within each chapter, there are Further Challenges (e.g, p. 86s) and Extensions (e.g., pp. 129–130t) in which students may further study a related interest. The Teacher’s Resource Book includes a few optional extension activities similar in complexity to those in the student text (e.g., pp. OA-13 to OA-15, Elaborate, Optional Activity: Cell Size and Diffusion).

The material provides some strategies to validate students’ relevant personal and social experiences with scientific ideas. Some text sections relate specific personal experiences students may have had to the presented scientific concepts (e.g., pp. E50–E51s). In addition, some tasks (e.g., p. 124t, Analysis; p. 105s, Part A pH Is Everywhere, item 3b; p. 107s, Analysis, item 2) ask students about particular personal experiences they may have had or suggest specific experiences they could have. However, the material rarely encourages students to contribute relevant experiences of their own choice to the science classroom. Overall, the tasks are well integrated with students’ personal and social experiences with scientific ideas.

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