Plantae is a large and diverse kingdom which includes all of the trees, grasses, ferns and mosses in the world. All plants are eukaryotes, with nucleated cells and organelles such as mitochondria and chloroplasts. Their cells have distinct cellulose walls that other organisms lack. All plants are descended from a common ancestor.
The world's 250,000 species of plants range over almost every biome on Earth and represent a huge fraction of life's total biomass. Plants have adapted to arid deserts, frozen mountainsides and the open ocean. Despite their diversity, however, all plants share some traits in common.
All plants are able to capture sunlight for use in synthesizing complex organic molecules. This process, known as photosynthesis, works on the cellular level and involves a symbiotic relationship with what was once a free-swimming variety of cyanobacteria called chloroplasts. Chloroplasts dwell inside the cells of plants and carry out the chemical heavy lifting of capturing sunlight with chlorophyll.
One byproduct of photosynthesis is free oxygen. All plants release oxygen as a waste gas after stripping electrons from water during the sunlight conversion process. Plants concentrate their chloroplasts in their leaves, which are perforated with microscopic holes called stoma that take up carbon dioxide and release oxygen.