Biology is designed for multi-semester biology courses for science majors. It is grounded on an evolutionary basis and includes exciting features that highlight careers in the biological sciences and everyday applications of the concepts at hand. To meet the needs of today’s instructors and students, some content has been strategically condensed while maintaining the overall scope and coverage of traditional texts for this course. Instructors can customize the book, adapting it to the approach that works best in their classroom. Biology also includes an innovative art program that incorporates critical thinking and clicker questions to help students understand—and apply—key concepts.

By the end of this section, you will be able to:Compare homologous and analogous traitsDiscuss the purpose of cladisticsDescribe maximum parsimony

By the end of this section, you will be able to:Discuss the need for a comprehensive classification systemList the different levels of the taxonomic classification systemDescribe how systematics and taxonomy relate to phylogenyDiscuss the components and purpose of a phylogenetic tree

By the end of this section, you will be able to:Describe horizontal gene transferIllustrate how prokaryotes and eukaryotes transfer genes horizontallyIdentify the web and ring models of phylogenetic relationships and describe how they differ from the original phylogenetic tree concept

This 13-minute video lesson looks at the science of taxonomy and where humans fit into the tree of life. [Biology playlist: Lesson 62 of 71].

This video demonstrates some of the features of PhyloTree. It then shows the early explosive discovery of mammal species (most major mammal groups were discovered early on), and then shows the slow and steady discovery of cnidarians (many cnidarians remain to be described). The tool can also be used to quickly find the first species that was described in a group. The first siphonophore to be described, for example, was Physalia physalis (the Portuguese man o’ war).

The evolutionary tree presented focuses on relationships among the ray-finned fishes (Actinopterygii). You can click on the colored logos to read about evolutionary innovations and see lists of characteristics that evolved in different lineages. Note that this tree has been pruned to focus on certain groups of interest.

Investigating a Deep Sea Mystery is based on Deep-sea mystery solved: astonishing larval transformation and extreme sexual dimorphism unite three fish families by Johnson, et al. (2009)* published in Biology Letters, Royal Society. The deep sea fishes at the heart of the investigation and this activity were historically classified into three families or clades based on the obvious morphological differences between the members of each group. Over time, as new data was accumulated, a new hypothesis was generated; the three fish clades were really one. Johnson, et al. found patterns in collection data that supported an alternative relationship; that they are the males, females, and larvae of a single family or clade, and that the morphological differences are the result of extreme ontogenetic (developmental) metamorphosis and sexual dimorphism. In this activity students follow the steps of the science team to unravel the mystery of the fishes' classification by analyzing some of the same morphological and phylogenetic data as the science team.