List of Changes

What we did in this revision:

Ecology and Evolution
Professor Jonathan Losos, our colleague at Washington University, has revised the Evolution and Ecology sections of the text, bringing more of everyday experimental science into our discussions. Presentation of the experimental data used to derive key conclusions and concepts is key to this revision. Our goal is to better aid students to understand how the concepts arose from the research. For this reason you will see that graphs and charts are more plentiful in these chapters.

Botany
Professor Susan Singer of Carleton College has revised the botany chapters. The Botany sections have benefited from a new approach where plant development takes center stage. A plant developmental biologist, she has placed the traditional discussions of evolutionary influences on plant form and function into a developmental context. Thus while evolution is still presented as the underlying explanation for the character of vascular tissue, seeds, flowers, and fruits, the developmental processes that produce these organs are now given more prominence. This does not lessen the evolutionary character of the treatment, but rather serves to amplify it. Throughout all the botany chapters, there is an enhanced emphasis on the molecular aspects of plant life. Understanding the molecular underpinnings of plant form and function allows students to more clearly understand the evolutionary changes that have shaped them.

New Chapter: Conservation Biology (Chapter 31)
In the fifth edition, we presented a discussion of conservation biology on the Biology web site, as an "enhancement chapter". The response was so overwhelming that we have included such a chapter in this edition of our text. In our own classroom teaching we find students to be keenly aware of the problems of dwindling natural resources, and the need to tackle the issue concretely. We feel a chapter focusing on conservation biology will be appreciated by students and useful to professors.

Genomics "Enhancement Chapter"
The rapidly advancing field of Genomics is so key to the future of biology that we felt it necessary to discuss it in some way in this sixth edition. Including a chapter in the text seemed rather pointless--so much of what we would cover will have changed after the first year. So, we turn again to an "enhancement chapter." We used enhancement chapters to expand information for the fifth edition of Biology and as you see from above, after fine-tuning the Conservation Biology chapter, we now include it in this edition. This new chapter expands upon the discussion of gene technology to present and explain the advances now being made with genomics. While the chapter discusses the technology involved and the genomes that have been uncoded, it focuses on the significance of this information to biology as a science, and on what it could mean to the future of medicine, agriculture and many other fields.

Real People Doing Real Science (Inquiry-Based Learning)
We have added an inquiry-based learning experience at the beginning of every Part that walks a student through the process of scientific inquiry by examining a particular experiment. After briefly reviewing the significance of the experimental question being addressed, we take the student through the actual experiment, discussing experimental design in depth, and then briefly describe the results and conclusion. This is but the first part of the learning experience. The student is then directed to the Biology, sixth edition web site for an in-depth examination of the experiment. There a student can read the actual published research paper, allowing students to become more familiar with the primary literature. Then the student can carry out a "Virtual Experiment" where he or she is able to manipulate the parameters of the experiment and obtain data for analysis. We provide on-line questions and discussions to help the student better understand the thought process behind the experiment.

A Thorough Revision
In addition to the extensive revisions of the Ecology, Evolution, and Botany sections of the text, and new chapters on genomics and conservation biology, we have thoroughly revised the rest of the text as well. Many chapters now sport radically different organizations, benefiting from extensive reviewer input. Pedagogy has been improved as well. We have included phylogenetic guideposts throughout the discussions of diversity to clarify for the student where each group fits in the tree of life (You will find these guideposts in chapters 35, 36, 37, and 44-48).

The Chemical Building Blocks of Life (Chapter 3)
The organization of this chapter has been turned on its head, presenting lipids before carbohydrates. This gives a greatly improved sense of the relative biological importance of these macromolecules, and actually makes the material easier to learn.

The Origin and Early History of Life (Chapter 4)
The discussion of ideas about the origin of life is now much more open-ended, stressing competing hypotheses and the key role of assumptions for which there is little data.

Photosynthesis (Chapter 10)
The internal organization of this chapter has been reworked to make it easier for students to understand how the many concepts covered in this chapter relate to one another.

Patterns of Inheritance (Chapter 13)
This chapter has been reorganized to incorporate the discussion of human genetics earlier in the chapter and then to use human examples as a means of explaining Mendelian principles.

Cellular Mechanisms of Development (Chapter 17)
We have moved the discussion of cellular development up earlier in the text, immediately following the discussion of gene expression, to reinforce key molecular concepts.

Altering the Genetic Message (Chapter 18)
Many recent advances in cancer research are highlighted, with greater emphasis on genes governing metastasis and angiogenesis.

Gene Technology (Chapter 19)
New topics such as Biochips and Transgenic rice have been included and rapidly advancing areas such as Stem cells and Ethics and Regulations have been updated.

The Evidence for Evolution (Chapter 21)
We have expanded this chapter to include a complete discussion of the evolution of the horse, and have expanded the discussion of artificial selection as a means of showing the power of selection on the evolution of species.

Population Ecology (Chapter 24)
We have added and expanded the discussions of population distributions, ranges, dispersal mechanisms and human effects in examples replete with actual data.

Animal Behavior (Chapter 26) and Behavioral Ecology (Chapter 27)
We have amplified these two chapters, moving them to the ecology section, a more logical place to teach these topics.

Dynamics of Ecosystems (Chapter 28)
We have greatly expanded discussions of interactions among trophic levels and the controversial matter of how species richness influences community stability.

The Biosphere (Chapter 29)
We have expanded the discussion of evolutionary responses to environmental variation.

Evolutionary History of Plants (Chapter 37)
We now include a discussion of the "Deep Green Project" that demonstrated the green algal origin of all plants.

The Plant Body (Chapter 38)
We included a discussion of the genes involved in development of stomata, trichomes, root tissues and leaves.

How Plants Grow in Response to the Environment (Chapter 41)
This chapter was extensively reworked and many new topics were added and expanded such as: acid growth hypothesis of auxin actions, plant defense responses, cytokinins involvement in organ regeneration and crown gall tumors, brassinosteroids and oligosaccharins, transgenic tomatoes, initiating flowering and circadian clocks.

The Noncoelomate Animals (Chapter 44)
This chapter now includes a molecular reevaluation of the evolution of the metazoan body plan.

Arthropods (Chapter 46)
New molecular data calls into question traditional classification of arthropods based on external characteristics.

Locomotion (Chapter 50)
We have added a discussion of modes of locomotion that ties together the concepts presented in the chapter.

Circulation (Chapter 52)
We have added a section on heart disease, explaining that heart disease is preventable and begins with establishing a heart-healthy lifestyle early.

Sensory Systems (Chapter 55)
We have broadened the coverage in this chapter to include more examples of nonmammalian sensory systems.

The Immune System (Chapter 57)
This chapter has been completely reorganized to improve clarity and understanding. The presentation of topics now more logically follows the process of the immune response in the body.