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 osmosis and explain its role within moleculesExplain why osmoregulation and osmotic balance are important body functionsDescribe active transport mechanismsExplain osmolarity and the way in which it is measuredDescribe osmoregulators or osmoconformers and how these tools allow animals to adapt to different environments

By the end of this section, you will be able to:Explain how the kidneys serve as the main osmoregulatory organs in mammalian systemsDescribe the structure of the kidneys and the functions of the parts of the kidneyDescribe how the nephron is the functional unit of the kidney and explain how it actively filters blood and generates urineDetail the three steps in the formation of urine: glomerular filtration, tubular reabsorption, and tubular secretion

By the end of this section, you will be able to:Explain why and how passive transport occursUnderstand the processes of osmosis and diffusionDefine tonicity and describe its relevance to passive transport

This work consists of original content and adapted OpenStax content. Each image is attributed with the source page in the figure description, in accordance with each respective license. OpenStax content has been remixed into the “Theory and Background,” “Lab Examples,” and “Relations to Health Sciences” sections of this work. OpenStax remixing consists of rearrangement and minor instructional design augmentations. All other sections within this work are originally created content.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"Salmon are famous for their swims upriver to spawn. Many people focus on this amazing feat of stamina, but even more remarkable is their ability to switch from living in freshwater to seawater, and back again. Most fish make their homes in just one type of water. So how do salmon do it? A team of biologists at Skidmore College, the U.S. Geological Survey, and the University of Gothenburg recently uncovered changes in the expression of certain genes that explain in part how Atlantic salmon make the transition. Atlantic salmon are born in freshwater, and between the ages of one and four migrate downstream to the sea. Before starting this migration, the fish undergo a months-long process preparing them for life in seawater. This is called smoltification. During this time, fish develop gill cells called ionocytes that contain specialized proteins that pump out excess salt..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.