The dandelions shown in is an embryo surrounded by a store of food and a protective coat. The dan- Figure 1.1 send their seeds aloft for dispersal. A seed delion’s seeds, shown at the lower left, are borne on the wind by parachute-like structures made from modified flower parts. The parachutes harness the wind, which carries such seeds to new locations where conditions may favor sprouting and growth. Dandelions are very successful plants, found in temperate regions worldwide. An organism’s adaptations to its environment, such as the dandelion seed’s parachute, are the result of evolution. Evolution is the process of change that has transformed life on Earth from its earliest beginnings to the diversity of organisms living today. Because evolution is the fundamental organizing principle of biology, it is the core theme of this book. Although biologists know a great deal about life on Earth, many mysteries remain. For instance, what processes led to the origin of flowering among plants such as the ones pictured above? Posing questions about the living world and seeking answers through scientific inquiry are the central activities of biology, the scientific study of life. Biologists’ questions can be ambitious. They may ask how a single tiny cell becomes a tree or a dog, how the human mind works, or how the different