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  1. 21 hours ago · The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinters, distinguishing them from the organism's own healthy tissue. Many species have two major subsystems of ...

  2. 21 hours ago · e. Human history, also called world history, is the narrative of humanity 's past. It is understood and studied through archaeology, anthropology, genetics, and linguistics. Since the invention of writing, human history has been studied through primary and secondary source documents. Humanity's written history was preceded by its prehistory ...