Answer:
The theory of E.O. Wilson's theory of Island Biogeography was originally developed as island biogeography, to explain species richness of actual islands, surrounded by water.
It proposes that the number of species found in an undisturbed environment is determined by immigration and emigration. According to him, the species richness will be the same if this island will have an equal number of the immigration and extinction or emigration of species.
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Different types of species
Cyanobacteria, also known as blue-green algae, are found in vast quantities in fresh and salt water. Cyanobacteria are able to conduct photosynthesis. By utilising energy from the sun, they produce carbohydrates from water and carbon dioxide. As a byproduct, they produce oxygen. So cyanobacteria provided oxygen to the atmosphere that allowed other lifeforms to develop.