Biology 2e is designed to cover the scope and sequence requirements of a typical two-semester biology course for science majors. The text provides comprehensive coverage of foundational research and core biology concepts through an evolutionary lens. Biology includes rich features that engage students in scientific inquiry, highlight careers in the biological sciences, and offer everyday applications. The book also includes various types of practice and homework questions that help students understand—and apply—key concepts. The 2nd edition has been revised to incorporate clearer, more current, and more dynamic explanations, while maintaining the same organization as the first edition. Art and illustrations have been substantially improved, and the textbook features additional assessments and related resources.
By the end of this section, you will be able to do the following:
Describe physical and chemical immune barriers
Explain immediate and induced innate immune responses
Discuss natural killer cells
Describe major histocompatibility class I molecules
Summarize how the proteins in a complement system function to destroy extracellular pathogens
Lysozyme is one of the major bactericidal agents in secretions and particularly helps to protect vulnerable sites such as the eyes and nasal passages. The lysoszyme exerts bactericidal effects by digesting bacterial cell walls. The complement system is a group of about 30 proteins within the body fluids of all vertebrates and some invertebrates. The main functions of complement are to promote phagocytosis or causes lysis of an invading organism.
Both the innate and adaptive immune systems use receptors to recognise foreign organisms. The innate immune system uses pattern recognition receptors which acts as an early warning system. The adaptive immune response is highly specific for each organism, as B and T cells have specialist surface immunoglobulin receptors which detect specific antigens on foreign pathogens. The Innate immune system is the body's first barrier of defence to infection. It relies on an older, more generic, and faster acting set of tools than the adaptive system. While the adaptive system is essential for a specific response to infection, it is ultimately the innate system that conquers foreign attackers through means of phagocytosis.