Immunity in living organisms

About this lesson

This unit introduces the concept of immunity in living organisms, focusing on plants and humans. It begins by defining immunity and the immune system, and distinguishes between innate (natural) and acquired (adaptive) immunity. For plants, it covers structural immunity (pre-existing and induced defenses such as cork formation, tyloses, gum deposition, and hypersensitive response) and biochemical immunity (antimicrobial chemicals, proteins, and receptors). For humans, it describes the lymphatic system and lymphoid organs (bone marrow, thymus, spleen, tonsils, Peyer's patches, lymph nodes), types of white blood cells (granulocytes and agranulocytes, including B cells, T cells, natural killer cells, macrophages), antibodies (structure, types, and mechanisms of action), and the two lines of natural defense (physical barriers and inflammatory response). It also explains acquired immunity through humoral (antibody-mediated) and cell-mediated mechanisms, including the roles of helper, cytotoxic, and suppressor T cells, and the primary and secondary immune responses. By the end, students should be able to compare natural and acquired immunity, describe plant defense mechanisms, identify human immune organs and cells, explain antibody action, and outline the immune response process.