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:Name and describe the distinguishing features of the three main groups of mammalsDescribe the proposed line of descent that produced mammalsList some derived features that may have arisen in response to mammals’ need for constant, high-level metabolism

Each mammary complex consists of 5-20 mammary units and their corresponding ducts. The ducts open separately on the tip of the teat. Shallow grooves indicate the border between complexes. An intermammary sulcus divides the right from the left row.

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:

"In lactating mammals, the mammary glands are responsible for milk production and secretion. Low energy levels in mammary gland cells are known to reduce milk synthesis by activating AMPK, an energy-sensing protein. However, the exact mechanism by which energy status affects lactation efficiency isn’t clear. To learn more, researchers recently examined AMPK’s role in milk synthesis in mouse mammary epithelial cells. Energy (glucose) deficiency indeed activated AMPK, which reduced milk fat and protein synthesis in the cells. AMPK inhibited milk production partly by inhibiting the classic mTORC1 signaling pathway, but it primarily reduced milk protein synthesis by blocking the signaling pathway of the lactation hormone prolactin. Specifically, AMPK triggered degradation of the prolactin receptor (PrlR) in lysosomes to halt prolactin signaling..."

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

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:

"A new study shows that abnormal production of nitric oxide in the body leads to the progression of breast cancer in mice. This finding could open the door to new treatments for early-stage breast cancer that stabilize the production of this pivotal molecule. Nearly one-third of newly diagnosed breast cancers in the US are early-stage lesions. Though technically pre-cancerous, about 40% of these lesions could progress to invasive cancers. Researchers don’t yet fully understand what drives these insidious formations. But various studies have reported a common link between cancer risk factors related to lifestyle—such as a high-fat diet, high alcohol consumption, and low physical activity—and abnormal production of nitric oxide. Normally, physiological stress triggers the production of large amounts of nitric oxide. This activates tissue-specific functions of neurons, muscles, immune cells, blood vessels and other specialized cells..."

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

The mammary gland is a modified sweat gland that nourishes the young. It consists of the mamma and the teat. Undeveloped in both the male and female at birth, the female mammary gland begins to develop as a secondary sex characteristic at puberty.

The mammary gland is a modified sweat gland that nourishes the young. It consists of the mamma and the teat. Undeveloped in both the male and female at birth, the female mammary gland begins to develop as a secondary sex characteristic at puberty.

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:

"Mastitis is a severe disease in cows that decreases milk yield and quality in dairy farms around the world. Although pathogenic infection of the mammary gland is a major cause, the gut microbiota is also thought to play a critical role. Studies have shown that mastitis is associated with gastrointestinal imbalance caused by the acid build-up associated with a high-grain diet, but the direct link between gut microbes and mastitis remains unclear. To address this gap, researchers investigated the microbes and their metabolites in the gut of cows fed a high-grain diet. Findings revealed elevated levels of sialic acid. Separate experiments in mice showed that supplementation with sialic acid aided the proliferation of Enterobacteriacea. These microbes damage the gut barrier, allowing toxins to enter the intestine and cause local inflammation, which then progresses to systemic inflammation when the toxins enter the blood..."

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