Biology

Biology investigates life and the processes associated with it. A biological question might concern the structure of a molecule, the activity of a cell, the development of an organism, a population's change over generations, or the functioning of an ecosystem. These levels are connected: molecules help build cells, organisms interact with other organisms and physical surroundings, and such interactions shape communities and ecosystems. Defining life in one sentence is not always straightforward. Viruses, for example, display some life-like properties but do not meet all criteria commonly used for cellular organisms, making them a useful boundary case in discussions of what counts as life.

Cells are the basic structural and functional units of known cellular life. Organisms may consist of one cell or many cells whose activities are coordinated. DNA carries genetic information, and genes are particular regions of DNA involved in heredity and cellular functions. Inherited variation provides the material on which evolution acts. Evolution, understood as descent with inherited modification, explains how populations change and helps account for the unity and diversity of organisms over Earth's history. Biology also examines how organisms regulate internal conditions, obtain and use energy, develop, reproduce, and interact with living and non-living parts of their environments.

Biologists use observation, field studies, experiments, measurement, models, and comparisons among organisms to investigate living systems. They formulate questions and test explanations against evidence; repeatable experiments are useful where variables can be controlled, while many questions about ecosystems, evolution, or past life also rely on carefully collected observations and multiple kinds of evidence. Microscopes and molecular methods reveal processes at small scales, while models and other technologies help researchers connect evidence across levels of organization. Biological explanations are refined as new evidence and methods become available.

Biology is a broad, interconnected discipline. Cell and molecular biology examine cells and their components; genetics studies heredity and variation; physiology investigates how organisms function; and evolutionary biology studies changes and relationships across generations. Ecology focuses on relationships among organisms and their environments. Botany, zoology, and microbiology concentrate respectively on plants, animals, and microorganisms. Fields such as biochemistry, neuroscience, paleontology, medicine, and biotechnology connect biological questions with chemistry, physics, Earth science, and engineering.

Biological knowledge contributes to medicine and public health, crop and food production, biotechnology, and efforts to understand and conserve biodiversity. It can help address challenges involving health, energy, food systems, and the environment. Applying biological research also raises ethical and societal questions, including how research involving people is conducted and how interventions may affect organisms and ecosystems. Responsible work therefore considers the quality of evidence as well as the consequences of research and its applications.