The differences between active immunity and passive immunity and how they work. Active immunity, which involves the production of memory cells by the body, is triggered by exposure to a pathogen or a vaccine. In contrast, passive immunity, which only provides antibodies, is temporary and does not involve memory cells. The sources also discuss the key aspects of adaptive immunity, including the roles of B cells and T cells in producing antibodies and destroying infected cells. The sources further explain the important concept of antigens, which trigger the immune response, and their characteristics, such as epitopes and haptens. Finally, the sources detail the various functions of antibodies, which include neutralization, opsonization, agglutination, complement activation, and antibody-dependent cell-mediated cytotoxicity (ADCC).

Sources explore the importance of microbes, particularly prokaryotes, in various ecological niches. The first source focuses on the rhizosphere, the area surrounding plant roots, where a symbiotic relationship exists between plants, bacteria, and fungi. This relationship is crucial for nutrient exchange and plant growth, highlighting the vital role microbes play in soil health. The second source provides a broader overview of prokaryote habitats, highlighting their diversity and adaptability across various environments, including extreme conditions like hot springs and deep sea vents. The text emphasizes the positive contributions of prokaryotes, such as their roles in decomposition, nutrient cycling, and even the production of food and medicine. Both sources showcase the crucial role of prokaryotes in supporting life on Earth and the delicate balance of these microscopic ecosystems.

History of scientific thought regarding the origins of life and disease. Cell theory, which states that all cells come from other cells and are the basic units of life, was developed over several centuries by scientists like Robert Hooke, Matthias Schleiden, Theodor Schwann, Robert Remak, and Rudolf Virchow. The endosymbiotic theory explains the evolution of eukaryotic cells from ancestral bacteria and is supported by the work of Konstantin Mereschkowski, Ivan Wallin, and Lynn Margulis. In contrast to the prevailing miasma theory, which attributed disease to particles from decomposing matter, the germ theory of disease was established through the work of scientists like Ignaz Semmelweis, John Snow, Louis Pasteur, Joseph Lister, and Robert Koch, ultimately demonstrating that microbes cause disease.