Biological structures refer to the physical components that make up living organisms. These structures can range from tiny cells, which are the basic units of life, to complex organs like the heart and lungs. Each structure has a specific function that contributes to the overall health and survival of the organism. In addition to cells and organs, biological structures also include systems such as the nervous system and circulatory system. These systems work together to maintain homeostasis and enable organisms to respond to their environment. Understanding these structures is essential for fields like biology and medicine.