The diverse plant life on Earth—consisting of nearly 400,000 species—can be divided into three broad categories based on biological characteristics: nonvascular, seedless vascular, and seed plants.

From Water to Land

Most plants are seed plants—characterized by seeds, pollen, and reduced gametophytes. Seed plants include gymnosperms and angiosperms.

Genetic variations accumulating within populations over generations give rise to biological evolution. Evolutionary changes can result in the formation of novel varieties and entire new species. These changes are responsible for the diverse forms of life inhabiting the planet. The evidence for evolution suggests that all living organisms descended from common ancestors.

Plant morphogenesis—the development of a plant’s form and structure—involves several overlapping developmental processes, including growth and cell differentiation. Precursor cells differentiate into specific cell types, which are organized into the tissues and organ systems that make up the functional plant.

Crop cultivation has a long history in human civilization, with records showing the cultivation of cereal plants beginning at around 8000 BC. This early plant breeding was developed primarily to provide a steady supply of food.