TAMU BIOL111 Exam 1 Practice Exam

The basic unit of life is the cell. Cells are the smallest structural and functional units of an organism, capable of performing all life processes. They can carry out metabolism, respond to stimuli, grow, reproduce, and maintain homeostasis. This concept is a fundamental principle of biology, specifically encapsulated in the cell theory, which states that all living organisms are made up of cells, and all cells arise from pre-existing cells. In contrast, atoms are the smallest units of matter but do not exhibit the characteristics of life. Tissues, while important, are groups of similar cells working together for a common function and thus are considered a higher level of organization than cells. Organs, composed of various tissues, also function at an even more complex level. Therefore, while both tissues and organs are essential for the functioning of multicellular organisms, they are built from cells, reinforcing the idea that cells are the fundamental units that define life.