Question

The approximate quantity of organic matter produced per annum on the Earth by photoautotrophic organisms is

• A. 10 billion tons
• B. 1000 billion tons
• C. 100 billion tons
• D. 175 billion tons

Answer 1

Answer: (C)

• An autotroph is an organism able to make its own food. Photoautotrophs are organisms that carry out photosynthesis. Using energy from sunlight, carbon dioxide and water are converted into organic materials to be used in cellular functions such as biosynthesis and respiration. In an ecological context, they provide nutrition for all other forms of life (besides other autotrophs such as chemotrophs ).
• In terrestrial environments, plants are the predominant variety, while aquatic environments include a range of phototrophic organisms such as algae, protists, and bacteria. In photosynthetic bacteria and cyanobacteria that build up carbon dioxide and water into organic cell materials using energy from sunlight, starch is produced as final product.
• This process is an essential storage form of carbon, which can be used when light conditions are too poor to satisfy the immediate needs of the organism. Examples of phototrophs/photoautotrophs include Higher plants (maize plant, trees, grass etc), Euglena, Algae (Green algae etc), Bacteria (e.g. Cyanobacteria). Photoautotrophic organisms are present in a whole amount on earth about 100-125 billion tons per annum.

So, the correct option is option D.