Biology is the study of living organisms and their interactions with each other and their environment. It encompasses topics from cells, which are the basic unit of life, to evolution, which is the process by which species change over time in response to environmental pressures. Other important areas of biology include genetics, which studies heredity and trait expression, and ecology, which examines how organisms interact within ecosystems. Biology is a diverse field that has led to advances in medicine, agriculture, and environmental science.