In this article, we will discuss about different types of ecosystems on our earth. Broadly speaking, there are two major types of ecosystems: the aquatic and the terrestrial.
Aquatic ecosystems can be subdivided into freshwater, estuarine and marine systems. These are differentiated on the basis of major chemical differences in water content. The terrestrial ecosystems consist of several major biomes such as forests, grasslands tundra, etc. these are determined largely by variations in climatic conditions between the poles and equator. These biomes can be differentiated on the basis of their predominant types of vegetation such as grasses, shrubs or trees.
The distribution of biomes appears to be governed by annual variation of temperature, i.e., maximum and minimum temperature, mineral availability, rainfall both average and minimum and availability of sunlight. For instance, forests are generally associated with heavy rainfall but the type is influenced by temperature and light; the same is true for deserts, which occur in regions where rainfall is very low.
Characteristics of some major biomes:
Biome - Tundra
Northern most regions adjoining the icebound poles. Similar communities at high altitudes. Devoid of all trees except stunted shrubs in the southern parts. Ground flora includes lichens, mosses and sedges. The soil is frozen for most part but top layer melts during summer allowing a short growing season. The typical animals are reindeer, arctic fox, polar bear, snowy bear, snowy owl, lemming, arctic hare, ptarmigan; reptiles and amphibians almost absent.
Mechanical abrasions, road building and oil pipelines threaten the tundras. Plants grow very slowly in the disrupted tundra, especially as decomposition occurs slowly in the soil.
Biome - Taiga
Also known as, boreal forests extend in a giant circle around northern Europe, Asia and North America but in areas of more moderate temperatures than tundra’s. The dominating vegetation is coniferous evergreens mostly spruce with some pine and firs. Amongst the animals are small seed eating birds and their predators such as hawks, fur bearing carnivores, little mink, elka, puma, Siberian tiger, wolverine, wolves etc.
Lumbering, unregulated hunting, trapping, and agricultural development.
Biome- Temperate Deciduous Forest
On an average, have moderate temperature and abundant rainfall through out the year. Most of the trees drop their leaves in winter. Extend over central and southern Europe, eastern North America, western China, Japan, New Zealand etc. the flora include trees like beach, oak, maple and cherry. Most animals are familiar vertebrates and invertebrates. These are generally the most productive agricultural areas of the earth, partly because of the controlled pace of decay and decomposition in the soil.
Agricultural activities and high human population densities have converted most of the forests into agricultural land. Thus very little of the original community is left.
Biome - Tropical Rain Forest
Tropical areas of high rainfall in the equatorial regions, which abound with life. Tropical rain forests cover only about 7% of the earth’s surface but house about 40% of the world’s plant and animal species. Habitat is dominated by multiple storeys of broad-leafed evergreen species. Most animals and epiphytic plants are concentrated in the canopy of tree-top zones; high temperatures result in very rapid decomposition of soil organic material which is taken up by the plants and the nutrient pool is tied up within the bodies of living organisms. Therefore, the soil quality is quite poor.
Unfortunately, most of us may never see the incredible beauty of the tropical rain forests as these are rapidly being cut down.
Biome - Savanna
Tropical region dominated by grasses with scattered trees and fire resisting thorny shrubs. The fauna include a great diversity of grazers and browsers such as antelopes, buffaloes, zebras, elephants and rhinoceros; the carnivores include lion, cheetah, hyaena, mongoose and many rodents. Savanna is most extensive in Africa.
Agriculture and pressures of human population have reduced the savanna to a great extent.
Biome - Desert
Continental interiors; with very low and sporadic rainfall with low humidity. The sun’s rays easily penetrate the atmosphere making ground temperatures very high but nights often cold by contrast. Drought resistant vegetation such as cacti, euphorbia’s, sagebrush, etc., present. Animals may be numerous but mostly nocturnal. Many species of reptiles and mammals and some birds present.
Threatened in some places by irrigation and residential industrial development, irrigation frequently accentuates the already high mineral content of soil leading to salinity.
Aquatic ecosystems cover more than 70% of earth’s surface and are as diverse in species as the biomes. Here, we will discuss characteristic features of fresh water, marine and estuarine ecosystems that are distinguished on the basis of their salt content.
Fresh Water Ecosystems
Fresh water ecosystems are characterized as lotic (having flowing water) or lentic (still water). Lotic water systems which include freshwater streams, springs, rivulets, creaks, brooks and rivers etc., tend to become over their course from being narrow, shallow and relatively rapid to increasingly broad, deep and slow moving. Waterfalls are not uncommon features of lotic ecosystems. As would be expected only organisms well adapted to maintaining their position in flowing water and capable of adhering to an exposed surface are found in the upper reaches of a stream. Adhering organisms associated with large aquatic plants are termed periphyton.
Various types of fishes such as darters, trout, and salmon are found in mountain streams. Further downstream we also find warm water fish, such as carfish and carp. The most important primary producers of lotic systems are lagae but the major source of food is the organic matter brought in from the surrounding terrestrial ecosystems. Therefore, nutrient levels tend to the higher downstream because there is continual addition of nutrients.
Lentic bodies like pools, ponds, some swamps, bogs and lakes vary considerably in physical, chemical and biological characteristics. In general, they can be considered to have three zones – littoral, limnetic and profundal. The littoral zone extends from the shoreline to the innermost rooted plants, and is dominated by floating and emergent vegetation rooted in the bottom such as reeds and cattail, water lilies and some submerged but rooted species. Frogs, snakes, snails, clams and considerable variety of adult insects and their larvae are also found here. The limnetic zone is the open water, down to the depth where light penetrates. This zone contains phytoplankton that consists of diatoms, green and blue green algae, a variety of zooplankton from protozoan’s to micro arthropods. In this zone a variety of larger swimming organisms, in nekton, including fish, amphibians and larger insects are also found.
The profundal zone is found below the limnetic zone and in deep lakes this zone may constitute the largest water volume of the lake. Profundal zone gets its food from the limnetic zone. This zone consists mostly of decomposers. The nekton in this zone varies with the temperature and nutrient conditions.
Nearly three-quarters of the earth’s surface is covered by ocean with an average depth of 3,750 m and with salinity averaging 35 ppt (parts per thong), about 90 per cent of which is sodium chloride. Marine ecosystems are of singular ecological significance. Concentration of the nutrients in the ocean is low. The major zones in marine ecosystem are littoral, neurotic, pelagic and benthic. The littoral zone is the shoreline between land and the open sea. Waves and tides have maximum effect in this zone because sometimes extremes of temperature, moisture, and light intensity are felt by this zone, which results in a diversity of species. If the shore are rocky you will find more sessile organisms like algae, barnacles, starfish, etc., if sandy, organisms that have adapted by burrowing in or adhering to sand are dominant.
In bays where mud flats occur, algae are found on the surface. Often photosynthetic bacterial are found beneath the algae with abundance of clams, worms and crustaceans. Coral reefs and fringes of coral are formed by colonial coelenterates.
The neurotic zone is a region shallow enough to support plants rooted to the seafloor. Below it is the continental shelf, extending to a water depth of about 200 m. this zone constitutes about 7.5 per cent of the total ocean area and is relatively rich in species and high in productivity owing to the depth of light penetration and the presence of nutrients washed from land. Extensive communities of giant kelps as well as of smaller uni and multicellular forms, along with clams, snails, worms and echinoderms dominate the ocean bottom. Phytoplankton and zooplankton are relatively abundant and support some of the greatest fishing grounds in the world. However, the productivity of coastal oceans has its limits. Almost everywhere in the world and combined effects of extensive fishing and pollution have reduced the commercial fishing catch.
The pelagic zone is the open sea, constituting 90 per cent of total ocean surface. Photosynthesis on the surface of this zone is mainly carried out by various types of phytoplankton. In addition there are zooplankton along with shrimp, and jellyfish etc. this zone, although the largest in size, is low in nutrients, hence low in productivity.
Fin and blue whales are also found in this zone. The organisms in pelagic zone below the level of light penetration are completely dependent of the rain of detritus of upper regions for their nutrition. In deeper water many animals have poor vision, others including fishes are bioluminescent and some deep-water fish have light producing organs.
The benthic zone forms the floor of the ocean. It extends from the edge of the continental shelf to the deepest ocean trenches. Organisms here are heterotrophic. Rooted animals are sea laities, sea fan, sponges etc. Snails and clams remain embedded in the mud while starfish, sea cucumbers and sea urchins move on its surface.