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Living organism can not live isolated from their non-living environment because, latter provides materials and energy for the survival of the former. A natural functional ecological unit comprising of biotic community and their abiotic system. e.g. Pond, Lake, , , Meadow (Field), Forest etc. Structural and Functional Attribute (Characteristics) of an Ecosystem: (Organism of an Ecosystem) 1. Abiotic 2. Biotic 1. Abiotic Components; i) Climatic Factors – e.g. , Temperature, Light, Wind, Humidity etc. ii) Edaphic (related to soil) Factors – e.g. Soil, PH, Topography, Minerals etc. 2. Biotic Components – e.g. Plants, Animals and Micro-organism (bacteria, fungi) Classification of Biotic Components; 1. Producers 2. Consumers 3. Decomposers 1. Producers – green plants have chlorophyll – trap solar energy – change to chemical energy of carbohydrates using water and carbon dioxide – process is known as “Photosynthesis” Green plants manufacture their own food – known as Autotrophs (self-feeder) 2. Consumers – animal lack chlorophyll and are unable to synthesize their own food – known as Heterotrophs (i.e. other feeder) i) Primary Consumer or First Order Consumer or Herbivores e.g. Rabbit, Dear, Goat, etc. ii) Secondary Consumers or Second Order Consumers or Carnivores e.g. Cats, Foxes, etc. (feed on the herbivores) iii) Tertiary Consumers or Third Order Consumers – (feed on the secondary consumers) e.g. Wolves iv) Quaternary Consumers or Fourth Order Consumers or Omnivores – feed on the tertiary consumers and not eaten by any other animal e.g. Lions and Tigers 3. Decomposers or Reducers – Bacteria and Fungi – they break down the dead organic materials of producers (plants) and consumers (animals) for their food and release to the environment, inorganic and organic substances produced as by-products of their metabolism (chemical changes in living organisms) – the decomposers are known as Saprotrophs (i.e. rotten feeder) Biosphere as an Ecosystem and Ecological Balance in the Biosphere; (biosphere – the the earth’s crust and atmosphere occupied by living organisms) Biosphere as an Ecosystem – all types of plants and animals – starting from the minutest microscopic sized, like bacteria, fungi etc. to huge trees, whales, elephants, lions etc. - part of biotic components. The relative number of different types of organisms in the Biosphere is such that there in no scarcity of food for any organisms. In the natural environment in the biosphere – there, exists a perfect balance or equilibrium between the various organisms, and is well known as “ecological balance”. The ecological balance of may, however, get disturbed when there is any change in the natural environment. Environment – change in the physical factors such as temperature, precipitation, evaporation, light intensity, salinity of sea water etc. Food-chains and Food-webs of an Ecosystem; The linkage between the living organisms (plants and animals) for the transfer of food energy is known as food-chain. Plant (grass) → Herbivore (insect) → Carnivore (lizard or frog or bird) A single animal, during its development and growth, may be a part of different food chains. Such a food-chain is called food-web. Simple food chains rarely occur in nature – e.g. an insect may feed on a dozen of different plants instead of one. Similarly, a frog may eat several other insects – e.g. Tree → Beetle → Lizard → Bird Energy flow in the Ecosystem; Energy – capacity or ability to do work Energy is required for any activity in living beings. Every living organism contains energy and is called as an energy source. The first of thermodynamics explains that energy can neither be created nor destroyed. It merely transformed from one form to another. Various forms of energy are – i) Potential energy ii) Kinetic energy iii) Solar energy iv) Heat energy v) Atomic energy vi) Geothermal energy etc. Ecological pyramids; The energy pyramid is normally reflected by a pyramid of numbers whereby there more individuals in the primary producer trophic level than in the primary consumer level, more in the primary consumer level than in the secondary consumer level and so on. The top trophic levels are characterized by their lowest population size. The pyramid is also important for explaining how toxic compounds affect .

Figure: Pyramid 1. Numbers and trophic level for an ecosystem. (trophic level-a division of an ecosystem consisting of all organisms whose food is obtained) 2. The concept of the energy pyramid and individual size of a food chain. i) Pyramid of Numbers ii) Pyramid of Biomass iii) Pyramid of Energy Concept of Connectance; All organisms are embedded in food webs – means – all organisms consume and are themselves consumed, C = t L/ [S (S - 1)/ 2] where, C – Connectance, t L – trophic link, S – number of species The concept is guided by the two laws; i) Link species scaling law – states that in a food web with a moderate number (around 50) of trophic species, the number of trophic links α (varies as) number of trophic species on an average food webs have twice the numbers of trophic links compared to trophic species. ii) Hyperbolic connectance law – According to this – in a food web (of moderate number of species), the product of the number of species and the connectance is approximately having a value of 4, (so it is hyperbolic function of the species) Ecological Succession; The communities of living biological species are not stable over time. The replacement of one community with the other is called the “ecological succession”. This is a continuous process until a final stage, called climax, is reached. The ecological succession process involves a series of steps or communities, called as a ‘sere’, (sere-a series of ecological communities succeeding each other and representing stages in the biological development of an area) The seres are classified according to the dominant force that is responsible for a particular sere. These forces are, biotic, climatic, physiographic and geological. If the dominant force is biotic – known as ‘bio-sere’ (here, we will discuss only the biotic succession involving ‘bioseres’) Process of Biotic Succession; i) Primary succession and ii) Secondary succession i) The living organisms establish themselves for the first time in that habitat. The said habitat or sub-stratum was lifeless (sterile) The cooled lava or sand etc. may provide such a sub-stratum. This first community of living organisms that develop in a habitat is called the ‘pioneer community’. The pioneer community modify the sub-stratum and the new community, known as secondary community will come up to replace the pioneers. Each community will exist for certain duration and then replaced. ii) Secondary succession differs from the primary in the sense that, the habitat or sub-stratum would have been previously occupied by a living community, but due to some catastrophic event like flood, fire or volcanic eruption etc., the previous community disappeared in the past and new organisms start inhabiting that habitat in the present time. The amount of water present, will govern the character of the succession pattern, whether primary or a secondary. The presence of water content in the habitat, we recognize the following succession; i) Hydrarch succession – where water is plentiful ii) Xerarch succession – where water is very scarce iii) Mesarch succession – water availability is moderate in between the two Autogenic type of primary succession; i) Conversion of a bare rock-land into a forest - Bare rock-land → lichens [any plant organism (crustose type/ fruticose type)] → progressive decomposition → minerals → (carbon dioxide + water → weak acid) → dissolves the rock by weakening its structure → further addition of the organic matter trapped in the soil

Thus, the environment now allows other organisms to settle Animal like mites and spiders begin to occupy the place. The soil comes as wind-blown dust. By the action of vegetation more mineral is added and layer of soil forms on rocky land. On the formation of the soil layer, the Moses will be replaced by weeds and grasses. Further, the grass community and shrubs spread their roots, which make the soil fertile to grow trees. “the forest or wood trees will be the final climax community”. ii) Conversion of a small lake into a forest - Large lake → (silting) smaller lake → pond → (a) or (b)→ (a) If water is less → low prairie → climax prairie (treeless/ grassland) (b) If water is plenty → marsh thicket (shrubs or trees) → climax forest Terrestrial (related to earth) and Aquatic Ecosystems: The ecosystems having land habitats are called the “terrestrial ecosystems” and the ecosystem having water habitats are called the “aquatic ecosystems”. e.g. on land – mountains, , ice-poles etc. on water – marine habitat and fresh water habitat. Both of these types of ecosystems are grouped into several larger units, called the ‘terrestrial ’. are larger ecosystems and may be called as mega-ecosystems or major ecosystems. The various types Terrestrial Biome: 1. Tundra biome ( near ) 2. Taiga biome (coniferous forest biome) 3. Grassland biome 4. Deciduous forest biome (large broad leaf trees) 5. Highlands Icy Alpine biome () 6. Chapparal biome 7. Desert biome 8. Savanna biome (tropical Grassland biome-widely scattered trees and shrubs) 9. Tropical Rain-forest biome Grass land biome – grass land biome represents the land which is vegetated with grasses of various species. Earlier the grassland biome covered a large area of land, about 40 % of the total Earth’s surface. Now most of the have been turned into agricultural land or farm land for cultivation of food crops, or for growing pastures for our domestic animals. At present, the grasslands cover areas of , Russia, etc. Two types of grasslands; i) and ii) Prairies i) Steppes are the driest grasslands covered mainly by short grasses. The height of grasses or plants in steppes are not more than 0.3 m. ii) Prairies are those grasslands where the height of grasses and plants may reach up to 1.8 meters or more. The amount of rainfall decides the height of the grasses. Drier the climate – shorter the grasses If rainfall is ≯ 50 cm – only short grasses with small root system can survive. If rainfall is ≥ 100 cm – tall grasses grow e.g. blue grass, wheat grass, buffalo grass. The larger the grazers are generally animals that live in heard. Small grazers include grass hoppers, ants, leaf hoppers and other insects. The Desert Biome – any area with very small amount of rainfall and high evaporation, where vegetation is almost absent, becomes a desert. The hot deserts are the arid area with annual rainfall being < 25 cm or so. Such regions do have high evaporation potential as the skies are usually clear which reduces the scarce available water. Due to lack of vegetation and presence of winds and storms, tremendous soil erosion may occur, giving rise to ‘sand ’ (a mound or ridge of loose sand formed by high wind). The hot deserts occupy an area of about 14.9 MKm2 which is about 10.3 % of the total land area of the of the of 14.5 M Km2. These deserts include the greatest Desert of (Libya, Algeria, UAE etc.), The (South Africa), The Thar Desert ( – , ), The Desert of North America (USA and Western Mexico), The Great Victoria and the Great Sandy Deserts of . Desert plants vary in form from the prickly Pear Cactus to Giant Cacti. Many shrubs and two tree species also grow in the deserts. Such deserts plants enable to live among them by providing food and moisture. A cold desert as compared to a hot one, becomes much cooler during winter and may even get snowfall. Only a few grasses and mosses (growing in dense clusters) may grow here. Cold Deserts – area of about 4.1 M Km2 i.e. 2.8 % of total land of Earth. These include; of China and Kara Kum of South-West Russia. South American deserts, (Chile and Peru), Iranian desert (South Persia), (Argentina) Aquatic Ecosystems (the oldest ecosystem); Aquatic biomes are those major ecosystems which flourish under water. The life has itself originated from an aquatic environment. In all aquatic ecosystems, water is the medium in which the biotic and abiotic components co-exist. Various types of water bodies cover nearly 3/4th of the Earth’s surface. Major water bodies are – Oceans, Lakes, Rivers. Depending upon the salinity of the water body and the aquatic environment, the resulting ecosystem can be divided into the three categories. 1. Freshwater ecosystem 2. Estuarine ecosystem 3. Marine (concerned with the sea) ecosystem Marine water is the main Ocean water containing 3.5 % salt dissolved in water. The fresh water of rivers and lakes contain small amount of dissolved salts i.e. In between these two extremes, we have a water body called an estuary (transition zone from a river to sea). The water bodies which are more saline than the Oceans, may be called hyper saline. This may usually find in arid areas where rivers flow into a lake that has no outlet. The salt coming continuously with river’s flow, remains inside the lake. : diversity of plant and animal life. Biodiversity can be defined as an interacting system in a given habitat. It is the total sum of genes, species and ecosystems. Thus, biodiversity conservation encompasses (enclose) the whole spectrum of biota and their activities ranging from the macrolevel of ecosystems to the microlevel of DNA libraries. (DNA-deoxyribose nucleic acid – a self-replicating material which carries the genetic information in chromosomes) Biodiversity exists on the earth in eight broad realms with 193 biogeographical provinces. Each province is composed of ecosystem, which are constituted by communities of living species existing in an ecological region. Three fundamental levels of biological organizations; 1. Ecosystem or ecosystem diversity i) Forests ii) Grassland systems iii) Semi-arid and desert systems iv) Aquatic systems v) Wetlands and Swamps (low water logged ground) 2. Species of species diversity 3. Genes or genetic diversity Global diversity; All together 1.4 million species at present known to science in the world. The number is likely to be about 30 to 50 million as plants, insects and other forms of life are continually being identified in the world’s ‘hot-spot’ of diversity. At the present rate of extinction about 25 percent of the world’s species will undergo extinction during the next 20 or 30 years. Species extinction (destruction/ suppression/ no longer existing) may occur at the rate of 10 to 20 thousand per year. The loss of wild habitats due to rapid human population growth and short-term economic development are major contributions to rapid global destruction of diversity. The value of Biodiversity; Direct values – most important values of biological resources are providing the food. - The wild species became the foundation for agriculture. - Traditional medical practices like, Ayurveda (plants or their extracts are consumed) - In modern medicine, around 199 pure chemical substances extracted from 90 species of plants are used in medicines. - Domesticated animals have given us hormones, enzymes and food products while the fungi and microbes provide life-saving drugs (e.g. antibiotics). - Microbial, antiviral, cardioactive and neurophysiological substances have been derived from marine . - Sources of wood, firewood and several industrial products, ornamental plants are a lucrative commodity. Indirect values – i) Carbon fixation through photosynthesis ii) Pollination (fertilization), gene (unit of DNA) flow etc. iii) Maintaining water cycles, recharging ground water, protecting water sheds and suffering from extreme conditions such as flood and draught. iv) Soil formation and protection from erosion. v) Maintaining essential nutrient cycles. vi) Absorbing and decomposing pollutants. vii) Regulating climate at both macrolevel and microlevel. viii) Preserving recreational, aesthetic, socio-cultural, scientific, educational, ethical and historical value of natural environments. Biodiversity Hot Spots; The areas which are severely threatened by human activities are known as hot-spots. All the areas that support rich biodiversity, because of geologic formations and endemic (confined to a particular area) flora (vegetable life) and fauna (animal life) and exhibit exceptional scientific interest are called hot-spots. At the global level, 10 hot-spots of tropical forests has been identified by Myens (1988). Later on, he added 8 another area. These areas include 49,955 endemic species which constitute 20 % of the world’s total plant species. The Eastern Himalaya and the from India are included as hot-spots. Global Hot-spots and the Number of Endemic Species;

Region No. of plants Cape Region (South Africa) 6000 Upland Western Amazonia 5000 Madagascar 4900 Philippines 3900 Borneo 3700 SW Australia 2830 Western Ecuador 2500 Colombian Choco 2500 Peninsular Malaysia 2400 Californian Floristic Province 2140 Western Ghats (India) 1600 Central Chile 1450 New Caledonia 535 Eastern Arc Mts (Tanzania) 535 SW Sri Lanka 500 SW Coted Tvorie 200 Total = 49,995

The botanical hot-pots lie in – i) Western Ghats ii) North- iii) and iv) Andaman and Nicobar Islands Biodiversity Conservation; The need to save biodiversity is of utmost urgency. The maintenance of species and ecosystems is a keynote to sustainable development. Two types of Conservation – i) In situ conservation ii) Ex situ conservation Bio-wealth of India; Biodiversity is not distributed uniformly across the Globe. India has over 108,276 species of bacteria, fungi, plants and animals identified and described. Number of species of Bacteria, Fungi, Plants and Animals –

Type No. of species Bacteria 850 Fungi 23000 Algae 2500 Bryophyta (a non-vascular plant) 2564 Pteridophyte 1022 Angiosperms (plant producing flowers and 15000 reproducing by seeds enclosed within a carpel) Gymnosperms (plants having seeds 64 unprotected by an ovary) Insecta 53430 Mollusca (a hard shell, snails) 5050 Pisces (large fishes) 2546 Amphibia (living both on land and in water) 204 Reptilia 446 Aves (road with trees at regular intervals) 1228 Mammalia [species (4000), which produce 372 milk to feed their young, 3 species are egg laying mammals] Total = 108,276 tenth among the plant rich countries of the world, fourth among the Asian countries, eleventh according to the number of endemic species of higher vertebrates (amphibia, birds and mammals) and tenth in the world as far as richness in moments is concerned.