Plants produce food in their leaves through photosynthesis, a process that uses chlorophyll to synthesize sustenance through carbon dioxide, sunlight, water and mineral-related nutrients. Chemical energy from photosynthesis is stored as carbohydrate molecules. Chloroplasts are the cellular structures responsible for photosynthesis, and oxygen is a byproduct of this chemical process.
Plants are multicelluar, eukaryotic organisms belonging to the kingdom Plantae. More than 300,000 species of plants are known to exist. The first ancestors of plants are believed to have evolved approximately 1.2 billion years ago in the form of primitive algae, while the first land plants appeared around 450 million years ago, during the Ordovician period.