Answers for Instructors
Campbell BIOLOGY IN FOCUS
by Lisa A. Urry, Michael L. Cain, Steven A. Wasserman,
Peter V. Minorsky, and Rebecca B. Orr
Appendix A of the book includes answers for students for Figure Questions, Concept Check
Questions, Summary of Key Concepts Questions, end-of-chapter multiple-choice questions, and
Draw It Questions. This document for instructors includes suggested answers and teaching tips
for the Scientific Skills Exercises and suggested answers for the Problem-Solving Exercises,
Interpret the Data Questions, and the short-answer essay questions at the end of each chapter.
The Scientific Skills Exercises, Problem-Solving Exercises, Interpret the Data Questions, and
additional questions for the Visualizing Figures can be assigned in Mastering Biology, where
they are graded automatically.
Tips for Grading Short-Answer Essays
The ability to communicate clearly in writing is essential for almost any profession your students
choose to pursue. As instructors, it is often frustrating to be faced with a large class full of
students who have had inadequate preparation in writing skills, knowing that you don’t have the
resources to help your students develop these skills.
The Focus on a Theme Questions at the end of each chapter are an attempt on the part of
the authors to partner with you in this endeavor. At the end of each chapter, we ask the student to
write a short essay of 100-150 words that relates the material they learned in the chapter to one
of the themes introduced in Chapter 1 and featured throughout the book. The Focus on a Theme
Questions can be used as in-class or outside-of-class assignments.
For ease of grading, sample key points and sample top-scoring answers for the Focus on a
Theme Questions are provided for instructors and TAs in this document. The list of key points
provides a guide to the ideas that students should include in their essays. In addition, suggested
answers to all of the end-of-chapter essay questions can be found in this document.
The time necessary to grade writing exercises has prohibited many instructors from
assigning them. Using a grading rubric, however, can streamline the process. Some instructors
have found they can train TAs or even students to grade short essays accurately. (Students can
grade their own essays or those of their classmates.) A suggested grading rubric for the Focus on
a Theme essays is shown at the end of these tips and in the Study Area of Mastering Biology.
This rubric can also be modified to use with the other end-of-chapter essay questions.
The simplest way to use the rubric is to read through each essay and determine how well
the writer has accomplished the four aims listed at the top of the columns. The essay can then be
graded as a 4, 3, 2, 1, or 0 based on the overall quality of the essay. Alternatively, you could
assign 0 to 4 points for each of the aims, and then total the points out of 16 possible points.
You can also weight one of the aims more highly. For example, if you want to focus
primarily on writing skills (aim #4: Quality of Writing) with the other aims weighted equally, the
score for each aim can be multiplied by a ―weighting factor.‖ Aim #4 could be assigned 40% of
the total points, with aims # 1, 2, and 3 each worth 20%. The score (out of 4) obtained for aim #4
,is multiplied by 40, and each of the others multiplied by 20, giving a total of 400 points (160 +
80 + 80 + 80 = 400).
To train TAs to grade essays in a large class, the instructor should first read through some
of the essays, looking for a representative example of each of the five scores (4, 3, 2, 1, and 0 for
the simplest grading scheme described above). Copies of the five representative essays (with
scores hidden) can be passed out to TAs, asking them to grade the essays based on the rubric and
a 0-4 grading scheme. Subsequent discussion with the TAs about their essay rankings should
clarify the standards, after which they can be given a few ―test‖ essays to grade to ensure
consistency in grading practices. This training exercise should take no more than 30-45 minutes.
Using a similar rubric and training scheme, the Montgomery County Public School System in
Maryland has been able to train a team of instructors to grade thousands of short essays
consistently in a relatively short time.
There is also a web-based program called Calibrated Peer Review (CPR) (developed at
UCLA with funding from the National Science Foundation and the Howard Hughes Medical
Institute) that trains students to evaluate their own work or that of their classmates (―peers‖). The
program is described at http://cpr.molsci.ucla.edu/.
When assigning essays, the instructor should point out the rubric to students (in the Study
Area of Mastering Biology) or provide a customized rubric to students. Students can then refer to
the rubric before writing to see what is expected of them. They can also check their essay before
submitting it to make sure they have met all the criteria in the rubric. Instructors should also
encourage students to read the Writing Tips provided under ―Additional Resources / Writing
Tips and Rubric‖ in the Study Area of Mastering Biology, which also includes the suggested
grading rubric.
Suggested Grading Rubric for “Focus on a Theme” Short-Answer Essays
Understanding of Use of Supporting Appropriate Use Quality of Writing
Theme and Examples or Details of Terminology
Relationship to Topic
4 Evidence of full and Examples well Accurate scientific Excellent
complete understanding chosen, details terminology organization,
accurate and applied enhances the essay sentence structure,
to theme and grammar
3 Evidence of good Examples or details Terminology is Good sentence flow,
understanding are generally well correctly used sentence structure,
applied to theme and grammar
2 Evidence of a basic Supporting examples Terminology used Some organizational
understanding and details are is not totally and grammatical
adequate accurate or problems
appropriate
1 Evidence of limited Examples and details Appropriate Poorly organized;
understanding are minimal terminology is not grammatical and
present spelling errors
detract from essay
0 Essay shows no Examples lacking or Terminology Essay is very poorly
understanding of theme incorrect lacking or incorrect written
,Suggested Answers and Teaching Tips
CHAPTER 1 INTRODUCTION: EVOLUTION AND THE FOUNDATIONS OF
BIOLOGY
Scientific Skills Exercise
Teaching objective: Students build scientific skills by interpreting data in a pair of bar graphs
and relating the data to the biological system it came from.
Teaching tips: A version of this Scientific Skills Exercise can be assigned in Mastering Biology.
If this is the first exercise the students are doing related to interpreting graphs, then you will need
to spend time reviewing independent and dependent variables. If the students are confused by
having two independent variables on one graph, have them cover one set of data while they look
at the other (for example, cover the ―full moon‖ portion of graph A while analyzing the ―no
moon‖ portion of it).
In these graphs, there are no statistical significance values given for comparisons between
treatments. In the original paper, there was a statistical difference between predation levels of
light brown versus dark brown mice in light-colored soil enclosures with no moon and in dark-
colored soil enclosures under a full moon. The other two combinations, light-colored soil under a
full moon and dark-colored soil with no moon, had no statistically significant difference between
light and dark mice.
Answers:
1. (a) The independent variables for each graph are the coat color of the mice (light or dark
brown) and the presence or absence of moonlight (full moon or no moon). These are on the x-
axis. Taking both graphs together, a third independent variable is the color of soil in the
enclosure. (b) The dependent variable is the amount of predation, measured as the number of
mice caught. The dependent variable is on the y-axis of the two graphs.
2. (a) About 19. (b) About 12. (c) Based on the data, the mouse would be more likely to escape
on dark soil. This might be because in the moonlight, a dark mouse on light soil would be more
noticeable than one on dark soil.
3. (a) Under a full moon (12 were caught vs. 20 under no moon). (b) Under no moon (11 were
caught vs. 18 under a full moon).
4. (a) Dark soil field with a full moon. (b) Light soil with no moon.
, 5. (a) No moon plus dark brown coat had the highest predation level in the light soil enclosure
(38 mice were caught). (b) Full moon plus light brown coat had the highest predation level in the
dark soil enclosure.
6. Being on the contrasting soil is most deadly for both colors of mice.
7. The total number of mice caught on moonlit nights was about 77, while the total caught on
nights without moonlight was about 95. This suggests that owls hunting on moonlit nights are
slightly less successful than are owls hunting on nights without moonlight.
Interpret the Data
Figure 1.21 In the beach habitat, approximately 14 light models and 36 dark models were
attacked. In the inland habitat, approximately 38 light models and 12 dark models were attacked.
Suggested Answers for End-of-Chapter Essay Questions
See the general information on grading short-answer essays and a suggested rubric at the
beginning of this document.
7. Scientific Inquiry
Many legitimate hypotheses could be proposed to extend the investigation. Here is one example.
If the camouflage color has arisen through the processes of natural selection due to visual
predators, then you might wonder what would happen if a population of beach mice lived in an
area where predators were absent. It might be possible to do a long-term study in an area where
you excluded predators. Mice have fairly short generation times, so if predation is ―naturally
selecting‖ lighter colored mice, then in the absence of predation you might predict the coat color
would not remain predominantly light in such an experimental population.
8. Scientific Inquiry
Students are asked to use a PubMed search to identify an abstract of an article authored or co-
authored by Hopi Hoekstra from 2016 forward. The range of abstracts from which students
might choose will grow as the Hoekstra lab generates additional publications.
9. Focus on a Theme: Evolution
Sample key points:
Darwin used reasoning based on observations to develop his theory of natural selection as a
mechanism for evolution.
His observations included:
o Heritable variations exist in each population.
o A population has more individuals than can be supported by the environment.
o Each species seems suited for its particular environment.
He proposed that the best-adapted individuals in a population would outcompete others for
resources and disproportionately survive and produce more offspring, leading to an increase
in the adaptations seen in the population.
Sample top-scoring answer:
Campbell BIOLOGY IN FOCUS
by Lisa A. Urry, Michael L. Cain, Steven A. Wasserman,
Peter V. Minorsky, and Rebecca B. Orr
Appendix A of the book includes answers for students for Figure Questions, Concept Check
Questions, Summary of Key Concepts Questions, end-of-chapter multiple-choice questions, and
Draw It Questions. This document for instructors includes suggested answers and teaching tips
for the Scientific Skills Exercises and suggested answers for the Problem-Solving Exercises,
Interpret the Data Questions, and the short-answer essay questions at the end of each chapter.
The Scientific Skills Exercises, Problem-Solving Exercises, Interpret the Data Questions, and
additional questions for the Visualizing Figures can be assigned in Mastering Biology, where
they are graded automatically.
Tips for Grading Short-Answer Essays
The ability to communicate clearly in writing is essential for almost any profession your students
choose to pursue. As instructors, it is often frustrating to be faced with a large class full of
students who have had inadequate preparation in writing skills, knowing that you don’t have the
resources to help your students develop these skills.
The Focus on a Theme Questions at the end of each chapter are an attempt on the part of
the authors to partner with you in this endeavor. At the end of each chapter, we ask the student to
write a short essay of 100-150 words that relates the material they learned in the chapter to one
of the themes introduced in Chapter 1 and featured throughout the book. The Focus on a Theme
Questions can be used as in-class or outside-of-class assignments.
For ease of grading, sample key points and sample top-scoring answers for the Focus on a
Theme Questions are provided for instructors and TAs in this document. The list of key points
provides a guide to the ideas that students should include in their essays. In addition, suggested
answers to all of the end-of-chapter essay questions can be found in this document.
The time necessary to grade writing exercises has prohibited many instructors from
assigning them. Using a grading rubric, however, can streamline the process. Some instructors
have found they can train TAs or even students to grade short essays accurately. (Students can
grade their own essays or those of their classmates.) A suggested grading rubric for the Focus on
a Theme essays is shown at the end of these tips and in the Study Area of Mastering Biology.
This rubric can also be modified to use with the other end-of-chapter essay questions.
The simplest way to use the rubric is to read through each essay and determine how well
the writer has accomplished the four aims listed at the top of the columns. The essay can then be
graded as a 4, 3, 2, 1, or 0 based on the overall quality of the essay. Alternatively, you could
assign 0 to 4 points for each of the aims, and then total the points out of 16 possible points.
You can also weight one of the aims more highly. For example, if you want to focus
primarily on writing skills (aim #4: Quality of Writing) with the other aims weighted equally, the
score for each aim can be multiplied by a ―weighting factor.‖ Aim #4 could be assigned 40% of
the total points, with aims # 1, 2, and 3 each worth 20%. The score (out of 4) obtained for aim #4
,is multiplied by 40, and each of the others multiplied by 20, giving a total of 400 points (160 +
80 + 80 + 80 = 400).
To train TAs to grade essays in a large class, the instructor should first read through some
of the essays, looking for a representative example of each of the five scores (4, 3, 2, 1, and 0 for
the simplest grading scheme described above). Copies of the five representative essays (with
scores hidden) can be passed out to TAs, asking them to grade the essays based on the rubric and
a 0-4 grading scheme. Subsequent discussion with the TAs about their essay rankings should
clarify the standards, after which they can be given a few ―test‖ essays to grade to ensure
consistency in grading practices. This training exercise should take no more than 30-45 minutes.
Using a similar rubric and training scheme, the Montgomery County Public School System in
Maryland has been able to train a team of instructors to grade thousands of short essays
consistently in a relatively short time.
There is also a web-based program called Calibrated Peer Review (CPR) (developed at
UCLA with funding from the National Science Foundation and the Howard Hughes Medical
Institute) that trains students to evaluate their own work or that of their classmates (―peers‖). The
program is described at http://cpr.molsci.ucla.edu/.
When assigning essays, the instructor should point out the rubric to students (in the Study
Area of Mastering Biology) or provide a customized rubric to students. Students can then refer to
the rubric before writing to see what is expected of them. They can also check their essay before
submitting it to make sure they have met all the criteria in the rubric. Instructors should also
encourage students to read the Writing Tips provided under ―Additional Resources / Writing
Tips and Rubric‖ in the Study Area of Mastering Biology, which also includes the suggested
grading rubric.
Suggested Grading Rubric for “Focus on a Theme” Short-Answer Essays
Understanding of Use of Supporting Appropriate Use Quality of Writing
Theme and Examples or Details of Terminology
Relationship to Topic
4 Evidence of full and Examples well Accurate scientific Excellent
complete understanding chosen, details terminology organization,
accurate and applied enhances the essay sentence structure,
to theme and grammar
3 Evidence of good Examples or details Terminology is Good sentence flow,
understanding are generally well correctly used sentence structure,
applied to theme and grammar
2 Evidence of a basic Supporting examples Terminology used Some organizational
understanding and details are is not totally and grammatical
adequate accurate or problems
appropriate
1 Evidence of limited Examples and details Appropriate Poorly organized;
understanding are minimal terminology is not grammatical and
present spelling errors
detract from essay
0 Essay shows no Examples lacking or Terminology Essay is very poorly
understanding of theme incorrect lacking or incorrect written
,Suggested Answers and Teaching Tips
CHAPTER 1 INTRODUCTION: EVOLUTION AND THE FOUNDATIONS OF
BIOLOGY
Scientific Skills Exercise
Teaching objective: Students build scientific skills by interpreting data in a pair of bar graphs
and relating the data to the biological system it came from.
Teaching tips: A version of this Scientific Skills Exercise can be assigned in Mastering Biology.
If this is the first exercise the students are doing related to interpreting graphs, then you will need
to spend time reviewing independent and dependent variables. If the students are confused by
having two independent variables on one graph, have them cover one set of data while they look
at the other (for example, cover the ―full moon‖ portion of graph A while analyzing the ―no
moon‖ portion of it).
In these graphs, there are no statistical significance values given for comparisons between
treatments. In the original paper, there was a statistical difference between predation levels of
light brown versus dark brown mice in light-colored soil enclosures with no moon and in dark-
colored soil enclosures under a full moon. The other two combinations, light-colored soil under a
full moon and dark-colored soil with no moon, had no statistically significant difference between
light and dark mice.
Answers:
1. (a) The independent variables for each graph are the coat color of the mice (light or dark
brown) and the presence or absence of moonlight (full moon or no moon). These are on the x-
axis. Taking both graphs together, a third independent variable is the color of soil in the
enclosure. (b) The dependent variable is the amount of predation, measured as the number of
mice caught. The dependent variable is on the y-axis of the two graphs.
2. (a) About 19. (b) About 12. (c) Based on the data, the mouse would be more likely to escape
on dark soil. This might be because in the moonlight, a dark mouse on light soil would be more
noticeable than one on dark soil.
3. (a) Under a full moon (12 were caught vs. 20 under no moon). (b) Under no moon (11 were
caught vs. 18 under a full moon).
4. (a) Dark soil field with a full moon. (b) Light soil with no moon.
, 5. (a) No moon plus dark brown coat had the highest predation level in the light soil enclosure
(38 mice were caught). (b) Full moon plus light brown coat had the highest predation level in the
dark soil enclosure.
6. Being on the contrasting soil is most deadly for both colors of mice.
7. The total number of mice caught on moonlit nights was about 77, while the total caught on
nights without moonlight was about 95. This suggests that owls hunting on moonlit nights are
slightly less successful than are owls hunting on nights without moonlight.
Interpret the Data
Figure 1.21 In the beach habitat, approximately 14 light models and 36 dark models were
attacked. In the inland habitat, approximately 38 light models and 12 dark models were attacked.
Suggested Answers for End-of-Chapter Essay Questions
See the general information on grading short-answer essays and a suggested rubric at the
beginning of this document.
7. Scientific Inquiry
Many legitimate hypotheses could be proposed to extend the investigation. Here is one example.
If the camouflage color has arisen through the processes of natural selection due to visual
predators, then you might wonder what would happen if a population of beach mice lived in an
area where predators were absent. It might be possible to do a long-term study in an area where
you excluded predators. Mice have fairly short generation times, so if predation is ―naturally
selecting‖ lighter colored mice, then in the absence of predation you might predict the coat color
would not remain predominantly light in such an experimental population.
8. Scientific Inquiry
Students are asked to use a PubMed search to identify an abstract of an article authored or co-
authored by Hopi Hoekstra from 2016 forward. The range of abstracts from which students
might choose will grow as the Hoekstra lab generates additional publications.
9. Focus on a Theme: Evolution
Sample key points:
Darwin used reasoning based on observations to develop his theory of natural selection as a
mechanism for evolution.
His observations included:
o Heritable variations exist in each population.
o A population has more individuals than can be supported by the environment.
o Each species seems suited for its particular environment.
He proposed that the best-adapted individuals in a population would outcompete others for
resources and disproportionately survive and produce more offspring, leading to an increase
in the adaptations seen in the population.
Sample top-scoring answer:
