Question

The first photoautotrophs organism were-
(a)Bryophytes
(b)Algae
(c)Cyanobacteria
(d)Bacteria

Answer 1

They are small, single-celled organisms that live in their millions, both within and outside of other organisms in any environment. Some of them are negative, but most have a beneficial function. Many types of life, both plant, and animal are assisted and used in industrial and medicinal procedures.

Complete answer:
Chemosynthesis has contributed to an accumulation in the primitive sea of organic compounds. These organic molecules, supposed to be the first organism on earth, acted as a source of carbon and an energy source for chemoheterotrophs. Owing to the limited supply of organic compounds, photosystems were formed by organisms to absorb sunlight to be used as an energy source, thereby contributing to the origin of photoautotrophs. Reduced inorganic compounds (hydrogen sulfide, ammonia, etc) were used by the first photoautotrophs as an energy source and carbon dioxide as their primary source of carbon. Since an inorganic molecule such as hydrogen sulfide is the source of electrons, oxygen is not produced and the process is called non-oxygenic photosynthesis. Non-oxygenic bacteria, i.e. the purple bacteria, were thus the first photoautotrophs.

Additional Information: The removal of inorganic compounds leads to the creation of oxygen photoautotrophs that use light as an energy source and carbon dioxide as the main source of carbon. During photophosphorylation, these photoautotrophs use water as an electron donor, resulting in oxygen production; thus the term oxygenic bacteria, which in turn added oxygen to the otherwise primitive reducing atmosphere. Cyanobacteria were the first oxygenic photoautotrophs. The accumulation of oxygen in the atmosphere of the planet contributed to the origin of algae, the first photosynthetic eukaryotes. It came to light about 3.4 billion years ago. During the Ordovician period, Bryophytes appeared much later.
So, the correct answer is ‘bacteria’.

Note: Bacteria are small, single-celled organisms that occur in their millions, both within and outside of other organisms in any environment. It is harmful to certain bacteria, but most serve a helpful function. Many types of life, both plant, and animal are assisted and used in industrial and medicinal procedures.