Biological and ecological hazards pose significant risks to human health and the environment. This unit examines various threats, including infectious diseases, pests, invasive species, and bioterrorism, exploring their origins, spread, and impacts on individuals and ecosystems. The unit emphasizes prevention, preparedness, and mitigation strategies to reduce risks. It highlights the role of public health, scientific research, and international cooperation in addressing these challenges, using real-world examples to illustrate the consequences of biological and ecological disasters.