Feeding a growing population is one of the majorchallenges of the twenty-first century. However,200 years ago, it was this very same challengethat initiated the foundation of the Universityof Hohenheim in 1818. Three years earlier, in1815, the volcano Tambora erupted in Indonesia.This local geological event had tremendousimpact on the global climate. The eruptionejected huge quantities of ash into the atmo-sphere, causing two ‘summers without sun’.In Europe, lower temperatures led to poor cropgrowth, resulting in famine and riots. On20 November 1818, King Wilhelm I ofWürttemberg founded an agricultural educationand research station at Hohenheim, with the aimof contributing to regional food security byeducating farmers and developing better agricultural production methods.

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:Describe how organisms acquire energy in a food web and in associated food chainsExplain how the efficiency of energy transfers between trophic levels affects ecosystem structure and dynamicsDiscuss trophic levels and how ecological pyramids are used to model them