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What is the earliest creature in the world?
One of the earliest creatures in the world is cyanobacteria.

Cyanobacteria appeared on the earth about 3.5 ~ 3.3 billion years ago, and it was the earliest photosynthetic oxygen-releasing organism, which played a great role in changing the surface of the earth from anaerobic atmosphere to aerobic environment. Many cyanobacteria (such as ANABAENA) can directly fix nitrogen in the atmosphere (reason: it contains nitrogenase, which can directly carry out biological nitrogen fixation) to improve soil fertility and increase crop yield.

Extended data:

Cyanobacteria can carry out photosynthesis and release oxygen. Its development makes the whole earth's atmosphere develop from anaerobic state to aerobic state, thus giving birth to the evolution and development of all aerobic organisms. Up to now, 120 kinds of cyanobacteria have nitrogen fixation ability, especially Azolla, an aquatic fern symbiotic with ANABAENA manjiangensis, is a good green manure.

Cyanobacteria are widely distributed in nature, including all kinds of water, soil and some internal and external organisms, and can even be found on rock surfaces and other harsh environments (high temperature, low temperature, salt lakes, deserts, ice sheets, etc.). ), and has the reputation of "pioneer". They play an important role in rock weathering, soil formation and water ecological balance.

Baidu encyclopedia-cyanobacteria