Immunity, Reproduction, and Development
A body must recognize threats while also controlling growth and maintaining its own tissues. Defense and development both depend on communication among cells, although they solve different biological problems. Immunity protects the body through barriers, innate responses, and adaptive responses with antigen-specific recognition and memory. Sexual reproduction brings genetic material from gametes together at fertilization. […]
Nervous and Endocrine Control of Movement
Touching something unexpectedly hot can trigger withdrawal before you consciously decide to move. The response still requires organized signaling: receptors detect a change, neural circuits process it, and muscles act. Body control depends on detecting conditions, processing information, and activating effectors. Nervous signaling uses electrical changes and communication between cells, often producing rapid targeted responses. […]
