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:Define species and describe how species are identified as differentDescribe genetic variables that lead to speciationIdentify prezygotic and postzygotic reproductive barriersExplain allopatric and sympatric speciationDescribe adaptive radiation

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

This 9-minute video lesson discusses what a species is and isn't. It considers ligers, tiglons, mule, hinnies, and dogs. [Biology playlist: Lesson 61 of 71].