What is the primary focus of the field of biology?

The primary focus of the field of biology is the study of living things. This encompasses a vast array of topics, including the structure, function, growth, evolution, distribution, and taxonomy of organisms. Biology seeks to understand the various forms of life on Earth—from the simplest microorganisms to complex multicellular organisms like plants and animals—along with their interactions with one another and their environments.

By studying living organisms, biologists can explore essential principles such as genetics, ecology, physiology, and behavior, providing insights into how life operates and adapts over time. This foundational understanding is critical for advancements in medicine, environmental science, and many other fields.

In contrast, other options pertain to different disciplines: the study of chemical reactions is central to chemistry, the study of physical laws relates to physics, and the study of planetary systems is associated with astronomy. These areas may intersect with biology, especially in fields like biochemistry and astrobiology, but they do not represent the core focus of the biological sciences.