|Introduction |Similarities |Differences |

It is not easy to compare terrestrial and aquatic systems because there is such a large variety of these environments. It is possible to recognize in the terrestrial part of the biosphere a small number of units with distinctive vegetation and climate, each with a complex of communities of large extent. These units are known as biomes and six major biomes are usually recognized, namely the:

1. Tundra,
2. Taiga ( coniferous forests ),
3. Deciduous Forests,
4. Grasslands,
5. Tropical Rain Forests,
6. Deserts.

The Major Biomes of the World:

In this section we will focus on the similarities and differences between terrestrial and aquatic ecosystems.

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• in both terrestrial and aquatic environments the ecosystems include communities made up of a variety of species,
• within both terrestrial and aquatic communities there are populations at the different trophic levels,
• a great deal of mutual interdependence exists between species in both terrestrial and aquatic environments,
• in undisturbed terrestrial and aquatic ecosystems equilibrium is reached, i.e. very few major changes are observed over a period of time,
• in both ecosystems stratification (vertical zonation) occurs.

The Knysna forest in South Africa, an example of an terrestrial ecosystem.	A marine aquatic ecosystem

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• because aquatic environments are so rich in nutrients they support more live than equivalent terrestrial ecosystems. The small drifting photosynthetic organisms of the oceans, referred to collectively as phytoplankton are regarded as the major photosynthesizers, or primary producers, of the earth,
• aquatic environments are much more stable than terrestrial environments, with smaller fluctuations in temperature and other variables,
• aquatic organisms are seldom exposed to desiccation while terrestrial organisms are often exposed to desiccation and are usually relatively resistant to drying out,
• oxygen (because there is very much less present) is sometimes a limiting factor an aquatic habitats but this is seldom the case in terrestrial habitats,
• light can be a limiting factor in some aquatic habitats, but in most terrestrial environments there is hardly ever a a shortage of light,
• terrestrial animals are influenced far more by gravity, while water supports aquatic organisms.