Marine Biology: Function, Biodiversity, Ecology (3rd Edition) Edit edition

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The azoic theory was proposed by one of the earliest marine biologists named Edward Forbes.

Edward Forbes observed that the number of organisms decreased with increasing depth of the ocean. He also observed that different organisms are distributed at different depths of the ocean. He proposed that the width of the depth zone of a species was directly proportional to its geographical extent.

Based on his observations, he proposed the azoic theory. The azoic theory stated that no life forms existed on seabeds deeper than 1,800 ft.

A statement that can be tested is called as hypothesis. Hypothesis can be tested by experimentation or sampling. The azoic theory was a testable hypothesis. Hence, it could be tested by other scientists and in fact proved to be wrong.

One of the evidence against the azoic theory was provided by the Norwegian marine biologist named Michael Sars. He collected number of species from Norwegian fjords below the depth of 1,800 ft.

Additional evidence against the azoic theory was provided W. B. Carpenter and C. Wyville Thomson. They detected marine life below the depth of 1,800 ft during their expedition of the northern waters of the British Isles.