1Ecosystem: An ecosystem is a community of living organisms (plants and animals) sharing an environment. OR An ecosystem is complex set relationship among living resources, habitats and residents of an area. It includes animals, plants, trees, fishes, microorganisms, water, soil and people. The largest ecosystems are called biomes. A BIOME is a major ecosystem spread over a wide geographic area, and characterized by certain types of flora and fauna. Types of ecosystem There are basically two types of ecosystems; 1) Terrestrial ecosystem. 2) Aquatic ecosystem. A) Terrestrial ecosystems Terrestrial ecosystems are found everywhere apart from water bodies. They are broadly classified into: a) The Forest Ecosystem b) The Desert Ecosystem c) The Grassland Ecosystem d) The Mountain Ecosystem a) The Forest Ecosystem These are the ecosystems where abundance of flora (plants) is seen and they have a large number of organisms living in relatively small areas. Therefore, the density of life in forest ecosystems is very high. Any small change in the ecosystem can affect the whole balance and collapse the ecosystem. You can see wonderful diversity in the fauna of these ecosystems too. They occupy nearly 40% of the land. In India , the forest occupies roughly 19% of the total land area. They are again divided into few types. 1. Tropical evergreen forest: Tropical forests which receive an average rainfall of 80 to 400 inches in a year. These forests are marked by dense vegetation comprising of tall trees with different levels. Each level gives shelter to different kinds of animals. 2. Tropical deciduous forest: Dense bushes and shrubs rule here along with broad levels of trees. This type of forests is found in many parts of the world and large variety of flora and fauna are found here. 3. Temperate evergreen forest: Temperate evergreen forests are characterized by their hardy trees. Trees need to withstand sandy, rocky, and basically poor quality soil, occasional fires, droughts and cold weather. These forests are generally dominated by pine trees, but also support many other kinds of vegetation.These found in areas receiving more than 200 cm of rainfall and having a temperature of 15 °C to 30 °C. They occupy about seven per cent of the Earth's land surface and harbour more than half of the world’s plants and animals. 4. Temperate deciduous forest: This forest is found in the moist temperate regions with sufficient rainfall (75-126 cm). Winters and summers are well defined and dominated by broad – leaved hard wood trees (oak ,hickory) that lose their foliage annually during winter. They are found in areas where warm moist summers alternate with mild winters. These are the first biomes to be converted into agriculture use. 5. Taiga: Situated just south of the arctic regions, Taiga is distinguished by evergreen conifers. While the temperature is subzero for almost six months, the rest of the year it is buzzing with insects and migratory birds. Taiga is the world's largest land biome, and makes up 29% of the world's forest cover; the largest areas are located in Russia and Canada. The taiga is the terrestrial biome with the lowest annual average temperatures after the tundra and permanent ice caps. Extreme winter minimums in the northern taiga are typically lower than those of the tundra. 6. Tundra is a biome where the tree growth is hindered by low temperatures and short growing seasons. In tundra, the vegetation is composed of dwarf shrubs, sedges, grasses, mosses and lichens Scattered trees grow in some tundra. Functions of forest ecosystem: 1. Watershed protection 2. Atmospheric regulations 3. Soil erosion control 4. Wind erosion control 5. Noise pollution control II) The Desert Ecosystem Desert ecosystems are found in regions receiving an annual rainfall of less than 25cm. They occupy around 17 percent of all land on the planet. Due to very high temperature, intense sunlight and low water availability, flora and fauna are very poorly developed and scarce. Vegetation is mainly bushes, shrubs, few grasses and rarely trees. Leaves and stems of these plants are modified to conserve water. The best known desert plants are the succulents like spiny leaved cacti. Animal life includes insects, reptiles, birds, camels all of whom are adapted to the xeric (desert) conditions. Types of desert ecosystem 1.Sand desert 2.Rock desert 3.Cold desert 4. Stony desert 5. Plateau desert 6. Mountain desert. Functions of desert ecosystem 1. Solar energy resource 2. Mineral resource III) The Grassland Ecosystem Grasslands are found in both temperate and tropical regions of the world but the ecosystems are slightly varying. This area mainly comprises of grasses with very little amount of shrubs and trees. Main vegetation is grasses, legumes and plants belonging to composite family. Many grazing animals, herbivores and insectivores are found in grasslands. Two main types of grasslands ecosystems are: 1. Savanna: These tropical grasslands are seasonally dry with few individual trees. They support large number of grazers and predators. 2. Prairies: This is temperate grassland. It is completely devoid of trees and large shrubs. Prairies can be categorized as tall grass, mixed grass and short grass prairie. Functions of grassland ecosystems. 1. These are breading areas 2. These provide food. 3. Human habitat IV) The Mountain Ecosystem Mountain lands provide a scattered but diverse array of habitats in which a large range of plants and animals are found. At higher altitudes harsh environmental conditions generally prevail, and only treeless alpine vegetation is found. The animals living here have thick fur coats for prevention from cold and hibernate in winter months. Lower slopes commonly are covered by coniferous forests. B) Aquatic Ecosystems An aquatic ecosystem is an ecosystem located in a body of water. It comprises aquatic fauna, flora and the properties of water too. There are three types of aquatic ecosystems 1. Marine 2. Freshwater. 3. Wetlands 1.) The Marine Ecosystem Marine ecosystems are the largest ecosystems with coverage of nearly 71% of the Earth's surface and containing 97% of the planet's water. The water in Marine ecosystems has salts and minerals dissolved in them in high amounts. Different divisions of marine ecosystems are: 1. Oceanic: The relatively shallow part of the ocean that lies over the continental shelf. It is the edge of a continent that lies under the ocean. 2. Profundal: Bottom or deep water. 3. Benthic Bottom substrates. 4. Inter-tidal: The area between high and low tides. 5.Estuaries, Salt marshes 6.Coral reefs 7. Hydrothermal vents- chemosynthetic bacteria form the food base. 2.) Wetlands: Places where the soil is saturated or inundated for at least some time. These ecosystems are home to amphibians, reptiles and almost 41% of world’s fish species. Faster moving turbulent water typically contains greater concentrations of dissolved oxygen, which supports greater biodiversity than the slow moving water of pools. 3) The Freshwater Ecosystem: In contrast to the Marine ecosystem, freshwater ecosystems only cover 0.8% of the Earth's surface and contain 0.009% of its total water. There are three basic types of freshwater ecosystems: Lentic: Still or slow-moving water like pools, ponds, and lakes. Lotic: Fast-moving water like streams and rivers. The Food Chain: Definition: A linear sequence of feeding relationships. OR The sequence of the transfer of food energy from one organism to another in an ecological community. A food chain begins with a producer (autotrophs), usually a green plant or alga that creates its own food through photosynthesis. In the typical predatory food chain, producers are eaten by primary consumers (herbivores) which are eaten by secondary consumers (carnivores), some of which may in turn be eaten by tertiary consumers (the top carnivore in the chain). Many species of animals in an ecological community feed on both plants and animals and thus play multiple roles in the chain. Parasites feed on living tissues, generally without killing their hosts, and may themselves be hosts to smaller parasites. In addition, organisms that die without being eaten are consumed by detrivores, some of which serve as prey for other consumers. The complex system of interrelated food chains in an environment is known as a food web. There are two kinds of food chains 1) Grazing food chains. 2) Detritus food chains. 3) Parasitic food chain. 1) Grazing food chains: Grazing food chains derive their energy directly from the sun. These are the chains that we are familiar with because we can see them, and because they are more frequently described in articles about energy flow through food chains. Characteristics of Grazing Food Chain 1. These are directly dependent upon solar radiations as the primary source of energy and the producers (green plants) synthesize their plant biomass by the process of photosynthesis. Producers form the first trophic level. 2. Herbivores or primary consumers eat upon the producers and form the second trophic level. 3. Herbivores are in-turn eaten by different categories of carnivores forming the higher trophic levels. 4. Grazing food chains are longer food chains and they always end at decomposer level. EX. of grassland ecosystem Grass→ Rabbit→ Fox→ Wolf→ Tiger Grass→ Grasshopper→ Frog → Snake → Hawk EX. of aquatic ecosystem Phytoplankton →Zooplankton→ Fish→ Hawk 2) Detritus food chains: A detritus food chain is one in which the primary consumer feeds on dead plant matter. OR This type of food chain starts from dead organic matter and so it is less dependent on solar energy. The dead organic matter is broken down into simple nutrients by microorganisms like fungi and bacteria. This type of food chain is found in forest ecosystem. ( This is decomposer organism based ) Dead organic matter→ Detritivores → Predators Characteristics of Detritus Food Chain 1.