Covering about 70 per cent of the earth's surface ocean contains many communities. The life extends to all depths of the ocean, although life is much denser around the margins of continents and islands. However, all the oceans are interconnected. But temperature, salinity, and depths are the chief barrier to free movements of marine organisms. The sea is in continuous [...]
Apart from containing bacteria and perhaps fungi, the community of aphotic zone is characteristically animal. Bruun (1957) has called the abyssal the "world's largest ecological unit". It is of course an incomplete ecosystem because no producers exist in it. The oceanic portion of the aphotic zone has been divided by John D. Issacs (1969) into mesopelagic, bathypelagic and benthic zones. [...]
Progressive changes in temperature, solar radiation, and precipitation from the equator toward the poles and similarly from the low-lands to the mountain peaks control the distribution of certain major vegetation types and these, in turn, are accompanied by characteristic sets of plants and Associated animal species. As a result, we may recognize a series of life zones or terrestrial habitats [...]