Unit 2
Basic Awareness on Various Ecosystems

Learning Outcomes

Prerequisites

Key words

Terrestrial, Aquatic Ecosystem, Freshwater and Marine, Wetland Ecosystem

Discussion

Do you know why an ecosystem can be as small as an oasis in a desert, or as big as an ocean? It is interesting.
An ecosystem consists of all the living and non-living things in a specific natural setting. Plants, animals, insects, microorganisms, rocks, soil, water and sunlight are the major components of many ecosystems. A community of living organisms of a particular region living in conjunction with non-living components is called an ecosystem. Ecosystems vary greatly in size from a small pond to a large forest or a sea. Many ecologists regard the entire biosphere as a global ecosystem, as a composite of all local ecosystems on Earth. Since this system is too big and complex to be studied at one time, it is convenient to di-vide it into two basic categories, namely the terrestrial and the aquatic. Terrestrial ecosystems are land-based, while aquatic are water-based. The major types of ecosystems are forests, grasslands, deserts, tundra, freshwater and marine. The word “biome” may also be used to describe terrestrial ecosystems which extend across a large geographic area, such as the tundra. There are different types of terrestrial ecosystems, which are widely distributed around the geological zones.

2.2.1 Terrestrial Ecosystem

The terrestrial ecosystem refers to the ecosystem of different land forms. Terrestrial ecosystems cover approximately 140 to 150 million Km2, which is about 25 to 30 percent of the total surface area of the earth. They are exclusively land-based ecosystems. There are different types of terrestrial ecosystems distributed around various geological zones. They are as follows:

1. Forest Ecosystems
2. Grassland Ecosystems
3. Tundra Ecosystems
4. Desert Ecosystem

2.2.1.1 Forest Ecosystems

These types of ecosystems include temperate deciduous forest, plantation forests and tropical rain forests. They serve as a natural habitat for a vast range of living species and also comprise the highest species diversity. Forests cover nearly 30 to 35 million square kilometres of the earth’s surface.
The Forest ecosystems are classified according to their climate type as tropical, temperate or boreal. In the tropics, rainforest ecosystems contain more diverse flora and fauna than eco-systems in any other region on earth. In these warm, moisture-laden environments, trees grow tall and foliage is lush and dense, with species inhabiting the forest floor all the way up to the canopy. In temperate zones, the forest ecosystems may be deciduous, coniferous or often times a mixture of both, in which some trees shed their leaves each autumn, while others remain evergreen year-round. In the far north, just south of the Arctic, boreal forests–also known as taiga– feature abundant conif-erous trees. There are different types of forest ecosystems based on climatic conditions such as tropical, temperate, boreal, etc. In a tropical ecosystem, we can find a large variety of vegetation as compared to another terrestrial ecosystem. This is the reason that you will always find tropical regions loaded with lush green landscapes. Forests are important. On the other hand, in the temperate regions the ecosystem may be coniferous, deciduous, or a combination of both. The forest ecosystem is one of the crucial terrestrial ecosystems that provide shelter to thousands of plant and animal species.

2.2.1.2 Grassland Ecosystem

Grasslands are the most dominant type of vegetation and these types of environments occur naturally in several parts of the world. These types of terrestrial ecosystems serve as a home for a wide diversity of animal species, such as elephants, giraffes, hyenas, jackrabbits, lions, rhinos, warthogs and zebras. Different types of grassland ecosystems can be found in prairies, savannas and steppes. Grassland ecosystems are typically found in tropical or temperate regions, although they can exist in colder areas as well, as is the case with the well-known Siberian steppe. Grasslands share the common climactic characteristic of semi-aridity. Trees are sparse or nonexistent, but flowers may be interspersed with the grasses. Grasslands pro-vide an ideal environment for grazing animals.
Types of grasslands include:

1. Tropical Grasslands and
2. Temperate Grasslands

As the name suggests, the grassland ecosystem mainly contains grasses along with some species of shrubs and trees. Grassland is a perfect region for grazing animals. The atmosphere in the grassland ecosystem is quite pleasant, and the climatic conditions are very similar to semi-arid regions. Organisms mostly found in the grassland ecosystem are grazing animals, herbivorous, insectivorous, etc. Tropical and temperate are typical regions of the grassland ecosystem.

2.2.1.3 Desert Ecosystems

The common defining feature among desert ecosystems is low precipitation, generally less than 25 centimeters, or 10 inches, per year. Not all deserts are hot desert ecosystems; they can exist from the tropics to the arctic, but regardless of latitude, deserts are often windy. Some deserts contain sand dunes, while others feature mostly rock. Vegetation is sparse or nonexistent, and any animal species, such as insects, reptiles and birds, must be highly adapted to the dry conditions. A high amount of flora and fauna are found in this region. The desert ecosystem covers almost 17% of the Earth’s surface. Excessive temperature, extreme sunshine, less water availability, etc. do not allow a variety of plants and animals to live in a desert ecosystem. You can find some plants such as cactus in the desert ecosystem. These types of plants can conserve water to a large extent. In this region, we can find animals like camels, reptiles, a few insects, etc.

Depending on the climate and temperature, deserts can be classified into hot deserts and cold deserts. There are many life forms well-adapted to life in the desert. Animals include camels, foxes, hyenas, jackals, scorpions, a few varieties of snakes and lizards. The common plants are acacia, cactus and date palms. Sahara is an example of a hot desert, which is characterised by high temperatures associated with little rainfall and complicated life for both plants and animals. Ladakh is an example of a cold desert, which is found on the eastern side of Jammu and Kashmir near the Great Himalayas.

2.2.1.4 Aquatic Ecosystem

Aquatic ecosystems are ecosystems present in a body of water. These can be further divided into two types, namely:

1. Freshwater Ecosystem
2. Marine Ecosystem

Freshwater Ecosystem

The freshwater ecosystem is an aquatic ecosystem that includes lakes, ponds, rivers, streams, wetlands bogs and freshwater swamps. These have no salt content in contrast with the marine ecosystem. They are subdivided into two classes those in which the water is nearly stationary, such as ponds, and those in which the water flows, such as creeks. Freshwater eco-systems are home to more than just fish: algae, plankton, insects, amphibians and underwater plants also inhabit them. Freshwater covers less area as compared to the marine ecosystem. The freshwater ecosystem covers almost 0.8% of the Earth’s surface.

The major kinds of freshwater ecosystems are lentic, lotic, and wetlands. Lentic ecosystem refers to stagnant water bodies such as ponds, lakes, etc. whereas the lotic ecosystem means fast-flowing water bodies such as a river. On the other hand, in wetland areas, the land becomes saturated and remains water logged for a long period. The freshwater ecosystem is a home for various fishes, reptiles, amphibians, etc. The fast-flowing water bodies have more dissolved oxygen as compare to slow-flowing water bodies. Hence, the fast-flowing water bodies support significant diversity of life.

Marine Ecosystems

The Marine ecosystems differ from freshwater ecosystems in that they contain saltwater, which usually supports more different types of species than the fresh water. The Marine ecosystems are the most abundant types of ecosystems in the world. They encompass not only the ocean floor and surface but also tidal zones, estuaries, salt marshes and saltwater swamps, mangroves and coral reefs. Marine ecosystem covers almost 70% of the area on the Earth’s surface; hence it is known as one of the biggest kinds of ecosystems on the Earth. Water is the main component of the marine ecosystem, which contains various minerals and salts dissolved in it. Many organisms such as sharks, cephalopods, brown algae, echinoderm, corals, dinoflagellates, etc .populate the marine ecosystem.

Wetland Ecosystems

Wetlands comprise areas that are transitional between terrestrial (land) areas and aquatic (water) areas. The wetlands ecosystem represents a richly diverse web of plants and animals interacting together. They also exhibit great sensitivity to disturbance from outside influence, particularly by human development and environmental damage. Wetlands ecosystems provide the world with natural storm barriers, environmental cleansers, and food and water resources for many forms of life. The water in wetlands ecosystems can be freshwater, saltwater, brackish water or flowing water. Wetlands contain wet soils and typically anaerobic environments, and rooted plants and other forms of life used to those conditions. While remaining distinct, the characteristics of wetlands may blend both terrestrial and aquatic environments. The characteristics and functions of any given wetland are deter-mined by climate, hydrology, and substrate, as well as by position and dominance in the landscape. In many cases, wetlands occupy a small portion of the total landscape (usually less than 10%), but have extensive boundaries with both terrestrial and aquatic ecosystems. In some cases, they occupy virtually the entire landscape. Despite their great range in size and other features, wetlands share specific characteristics, some of which are structural (water, substrate, biota), while others are functional (nutrient cycling, water balance, organic production).

Recap

Objective type questions

Answer to Objective type questions

Self Assessment Questions

Assignment

Suggested Reading

Reference