Biology How Life Works

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  • Major Content Changes and Updates in the Second Edition

    • We've greatly expanded the coverage of ecology in the second edition of Biology: How Life Works.
      • A new ecology chapter, Chapter 48: Biomes and Global Ecology, takes a broad look at ecology on the largest scale. It begins with how and why climates are distributed as they are around the world and introduces Earth's major biomes. The chapter is distinguished by extensive discussion of biomes in the aquatic realm, especially in the oceans.
      • Chapter 47 Species Interactions, Communities, and Ecosystems includes expanded coverage of the ways species interact with one another in communities. This chapter now has more detail on facilitation, herbivory, and biodiversity.
      • Chapter 49 The Anthropocene: Humans as a Planetary Force includes new discussions exploring how human activities affect ecology. The chapter now examines fracking and its effects on the carbon cycle, habitat loss and its effects on biodiversity, and the overexploitation of resources and its effects on community ecology. The chapter ends with a new section on conservation biology that explores how conservationists are working to preserve natural habitats.
      • Learn more about these changes by visiting the ecology section of this site.
    • A new Visual Synthesis figure on the flow of matter and energy through ecosystems illustrates, explores, and physically situates concepts from Chapters 25, 26, 47, and 48.


    New Topics and Other Revisions

    The following is a detailed list of content changes in this edition. These range from the very small (nucleotides shown at physiological pH) to quite substantial (an entire new chapter in the ecology section).  Especially important changes are indicated by boldface type. 

    • New coverage of functional groups (Chapter 2)
    • Nucleotides now shown at physiological pH (Chapter 3)
    • Amino acids now shown at physiological pH (Chapter 4)
    • The story of the evolution of photosynthesis now brought together in a single major section at the end of Chapter 8 (Section 8.5)
    • Chapters 9 and 10 streamlined to better match the mission statement
    • A new discussion of cellular response and what determines it (Chapter 9)
    •  New inclusion of the trombone model of DNA replication (Chapter 12)
    • Addition of CRISPR technology (Chapter 12)
    • Expanded coverage of retrotransposons and reverse transcriptase (Chapter 13)
    • A new How Do We Know? figure explaining Mendel's experimental results (Chapter 16)
    • New coverage of the mechanism of X-inactivation (Chapter 19)
    • An expanded discussion of nonrandom mating and inbreeding depression (Chapter 21)
    • Addition of the effect of mass extinctions on species diversity (Chapter 23)
    • Updated discussion of the relationship between Neanderthals and Homo sapiens, as well as Denisovans (Chapter 24) 
    • Significantly revised link between the carbon cycle, biodiversity, and ecology (Chapter 25)
    • New branching order of the eukaryote tree to reflect new research in the past three years (Chapter 27 and onward)
    • A new paragraph on ciliates (Chapter 27)
    • A new explanation of protist diversity (Chapter 27)
    • A new discussion of plant nutrients with a table (Chapter 29)
    • An enhanced discussion of seeds, including the development of the embryo and dispersal structures (Chapter 30)
    • New coverage of the genetic advantages of two generations, including how it allows inbreeding (Chapter 30)
    • Addition of apomixis (Chapter 30)
    • The section on the role of plant sensory systems in the timing of plant reproduction moved from Chapter 30 to Chapter 31
    • Completely revised explanation of the basis for angiosperm diversity (Chapter 33)
    • Brief descriptions of unfamiliar organisms and the major groups of organisms layered in the animal physiology chapters to make it easier to teach physiology before diversity (Chapters 35-42)
    • Brief review of organismal form and function in the plant and animal diversity chapters (Chapters 33 and 44), allowing these chapters to be used on their own or before the physiology chapters and giving instructors maximal flexibility
    • A new section on the composition of blood (Chapter 39)
    • New diagrams of hormone feedback loops in the menstrual cycle (Chapter 42)
    • A new introduction to the immune system (Chapter 43)
    • A new discussion of nematodes (Chapter 44)
    • Introduction of a newly-discovered species, Dendrogramma enigmatica (Chapter 44)
    • A new population growth equation (Chapter 46)
    • A new discussion of facilitation (Chapter 47)
    • An expanded discussion of herbivory (Chapter 47)
    • A new example of microbial symbionts (Chapter 47)
    • A new discussion of the importance of biodiversity (Chapter 47)
    • An entirely new chapter on physical processes that underlie different biomes (Chapter 48)  
      • Differential solar energy around the globe and seasonality
      • Wind and ocean currents
      • Effects of circulation and topography on rainfall
      • Expanded discussion of terrestrial biomes
      • Freshwater and marine biomes
      • Integration of concepts of biogeochemical cycles from Chapters 25 and 26 with ecological concepts
      • Global patterns of primary production
      • Global biodiversity
    • A new exploration of the effect of fracking on the carbon cycle (Chapter 49)
    • New coverage of habitat loss and biodiversity (Chapter 49)
    • New coverage of over-exploitation of resources and its effects on community ecology (Chapter 49)
    • A new Core Concept and discussion of conservation biology (Chapter 49)


  • Dan Hartl on Revising the Text, Media and Assessment

    From the start, Biology: How Life Works was envisioned not as a reference book for all of biology, but as a resource focused on foundational concepts, terms, and experiments. In preparing the second edition, we carefully considered the latest breakthroughs and incremental, but nevertheless significant, changes across the fields of biology. We also reached out to both adopters, instructors not using our book, and primary literature to determine what concepts and details would be relevant, important, and necessary additions. Hear author Dan Hartl explain the process of revising the text, media, and assessment for the second edition.