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UNIT – I
ENVIRONMENT AND ECOSYSTEMS
ENVIRONMENTAL STUDIES
Introduction : Environment is derived from the French word ― Environ” which mean ―encircle or surround‖ Environmental Studies deals with every issue that affects an organism. So, Environment refers to surroundings which vary from place to place and continent depending upon Physiography, Topography, Climate and the available Natural resources. Since the beginning of the culture, the natural resources such as Soil, Land, Water etc are being over-exploited causing the environment gets polluted or degraded. This has resulted in multi – dimensional environmental crisis like soil erosion, landslides and in turn have created soil pollution, air pollution, water pollution, noise pollution etc. Definition: The sum total of all surroundings of a living organism, including natural forces and other living things, which provide conditions for development and growth. Importance of Environment: 1.Environment is concerned with day – to – day interaction with the surroundings with which human being is closely associated.
- Environmental Science is related to many branches of Sciences
- Environment is concerned with the importance of wild life and its protection.
- Environmental Science explains the significant role of biodiversity in establishing ecological balance.
- Environmental Science gives information relating to Population growth, Population explosion and impact on Population growth. Environmental Science also gives information about water conservation, watershed management and the importance of water Introduction of Ecology: The term ―Ecology‖ was derived from Greek words viz., Oikes means house or place and logs means a discussion or study. So, ecology is the scientific study of the distribution and the interactions between organisms and their natural environment. The environment (surroundings ) consists of: living organisms ( biotic ) and non-living things ( abiotic ) such as physical components of wind, temperature, rainfall, water, humidity , light, soil etc and chemical components of C,H,N,K,P,S etc..(in-organic components) and carbohydrates, proteins (organic components). Hence, Ecology involves studying the ecosystems. According to George Jackson, an Ecosystem is a natural unit consisting of all plants, animals and microorganisms in an area functioning together with all of the non-living things. An ecosystem is the smallest unit of biosphere that has all the characteristics to support life. Pond ecosystem, forest ecosystem, desert ecosystem, marine ecosystem, urban ecosystem are some of the examples for ecosystems. An ecosystem varies in sizes from a few square kms to hundreds of square kms. Similarly an ecosystem may be temporary like a fresh pool / agriculture field or permanent like a forest / ocean. Scope of ecosystem:
Ecology plays an important role in agriculture crop rotation, weed control (unwanted land); management of grasslands, forestry etc., biological surveys, fishery surveys, conservation of soil, wild life, surveys of water bodies like rivers, lakes; ponds etc... Concept of ecosystem: In an ecosystem, the interaction of life with its environment takes place at many levels. A single bacteria in the soil interacts with water, air around it within a small space while a fish in a river interacts with water and other animals, rivals in a large space. Considering the operational point of view; the biotic and biotic components of an ecosystem are so interlinked such that their separation from each other is practically difficult. So, in an ecosystem both organisms (biotic communities) and a biotic environment (rainfall, temperature, humidity) each influence the properties with other for maintenance of life. Types of Ecosystems : Ecosystem may be natural or artificial. Artificial Ecosystem: These are maintained or created artificially by man. The man tries to control bi otic community as well as physico chemical environment. Eg: Artificial pond, urban area development. Natural Ecosystem: It consists of Terrestrial and Aquatic Ecosystems which are maintained naturally. Terrestrial Ecosystem: This ecosystem relates to biotic components living on the land. Vegetation dominates the community and the types of vegetation affect the climate, soil structure & a rapid exchange of O 2 , water & CO 2 Aquatic Ecosystem: This ecosystem relates to biotic community living in water. The types of water (fresh water, saline water, polluted water) dominate and affect the pH of water, depth of water, temperature of water etc. Aquatic ecosystem has been sub-divided into fresh water and saline water based on the quality of water. Sturcture & Function of Ecosystem The two major aspects of an ecosystem are: (1) Structure and (2) Function together they illustrate the organization of an ecosystem. The Structure of an ecosystem consists of: Abiotic structure includes the non-living things of the ecosystem such as physical factors (soil, temperature, light & water) and chemical factors consisting the inorganic compounds (N, C, H, K, P,S) & organic compounds ( carbohydrates, proteins). Biotic structure includes plants, animals & microorganisms present in an ecosystem form the biotic component. These organisms have different nutritional behavior and status in the ecosystem and are known as Autotrophs Producers), Heterotrophy (Consumers) & Microconsumers (Decomposers) based on how they get their food. Hence, the structure of an ecosystem comprises: (a) The composition of biological community species (plants, animals, microorganisms), their population, life cycles, distribution in space etc.
- Grass→ Mouse→ Snake →Hawk.
- Grass→ Rabbit→ Man.
- Grass→ Mouse→ Hawk.
- Plant leaf →Caterpillar →Sparrow →Hawk. Explanation : A caterpillar eats a plant leaf, a sparrow eats the caterpillar, and a hawk eats the sparrow. When they all die, they are all consumed by micro organisms like bacteria (or) fungi which break down the organic matter and convert it into simple inorganic substances that can again be used by the plants. In nature, there are two basic types of food chains viz: 1. Grazing food chain and (2) Detritus food chain Grazing food chain: This food chain starts with green plants (primary producers) and goes to herbivores and on to carnivores.
- Phytoplankton‘s→ Zooplanktons →Small fish→ Tuna.
- Phytoplankton‘s→ Zooplanktons→ Fish→ Man.
- Grass→ Rabbit→ Fox→ Tiger. Detritus food chain: This food chain starts from dead organic matter (dead leaves/ plants / animals) and goes to Herbivores and on to Carnivores and so on….. Leaves or dead plants→ Soil mites→ Insects→ Birds. Dead organic matter → Bacteria → Insects. Dead leaves → Algae→ Fish→ Man.
FOOD WEB: Food web is a net work of food chains where different types of organisms are connected at different trophic levels so that there are a number of options of eating and being eaten at each trophic level. (A trophic level refers to an organism‘s position in the food chain).
- Grass→ Grasshopper→ Hawk
- Grass→ Grasshopper→ Lizard→ Hawk
- Grass→ Rabbit→ Hawk
- Grass→ Mouse→ Hawk
- Grass→ Mouse→ Snake→ Hawk ECOLOGICAL PYRAMID: Ecological pyramids were first studied by a British ecologist Charles Eltan (1927). An Ecological Pyramid is a graphical representation consisting varioustrophic levels with producers forming the base and top occupy the carnivores. In an ecological pyramid the huge number of tiny individuals form at the base and a few large individuals occupy the top / apex. This formation is known as ecological pyramid. Hence, all producers (micro & macro plants) belong to the I trophic level ; all primary consumers belong to II trophic level and organisms feeding on these consumers belong to the III trophic level and so on. The ecological pyramids are of three types. They are:
- The pyramid of Numbers (showing population).
- The pyramid of Biomass (showing total mass of organisms).
- The pyramid of energy (showing energy flow).
2. The Pyramid of Biomass: The amount of organic matter present in environment is called biomass. In pyramids of biomass, the relationship between different trophic levels is mentioned in terms of weight of organisms. The pyramid may be upright for grassland ecosystem and inverted for pond ecosystem. Example: Vegetation produces a biomass of 1000 kg. Out of this 100 kgs of biomass for herbivores, which in turn only 10 kg of biomass for primary carnivores that gives rise 1 kg of biomass for second order carnivores and so on… 1000 kgs 100 kgs 10 kgs 1 kg Vegetation Herbivores primary carnivores Secondary carnivores Hence, a vegetarian diet can support a larger population than a Non – vegetation diet.
3. The pyramid of energy : The amount of energy trapped per unit time and area at different trophic levels of a food chain with producers forming the base and the top carnivores at the apex 2 is called pyramid of energy. The energy content is generally expressed as K cal /m / year or KJ / 2 m / year. 2 Large Fish ---126 KJ / m / year 2 Small Fish ----840 – 126 KJ / m / year Zooplankton 2 ---- 7980 KJ / m / year Phytoplankton (producers) -- 2
- 31080 KJ / m / year Energy flow /Transformation of energy in Ecosystem The movement of energy (or) transfer of energy through a series of organisms in an ecosystem from the external environment and back to the external environment again is known as energy flow. In the universe, the main source of energy is SUN that produces energy in the form of light or solar radiation. Different ecosystems in the world receive variable quantities of solar energy depending upon their location on the globe. The other chief factors that control the amount of solar energy received by an ecosystem are Latitude and Longitude; Slope; Cloud formation; Pollutants in the atmosphere The transformation of energy in an ecosystem begin first with the input of energy from the sun by the process of photosynthesis. Carbon dioxide is combined with Hydrogen (derived from the splitting of water molecules) to produce carbohydrates (CH2O) and the energy is stored in the high energy bonds of Adenosine Tri Phosphate (ATP). Herbivores obtain their energy by consuming plants or plant products, Carnivores eat herbivores and micro-organisms consume the droppings and carcasses (dead bodies). In an ecosystem, the utility of energy is taken place in the following manner: The sun provides heat to maintain the required temperature in which proper Physical and chemical processes can take place. Certain bacteria obtain useful energy by oxidation of a few elements such as sulphur and iron. Bio – Geo-Chemical Cycles: In every ecosystem sunlight or solar radiant energy is accepted by producers (green plants) and the energy doesn‘t recycle through an ecosystem. But nutrients like Carbon; Nitrogen; Oxygen, Hydrogen; Water, Sulphur, Phosphorous etc move in circular paths through biotic and abiotic components and they are known as Bio-geochemical cycles. About forty chemical elements are considered to be essential for living organisms. They are macronutrients of C, H, O, P, K, I, N, S, Mg, Ca etc.. and micro nutrients of Cu, Fe, Co…… While all inorganic nutrients have cycles, we focus on the following: WATER CYCLE CARBON CYCLE NITROGEN CYCLE
NITROGEN CYCLE: Nitrogen is used by living organisms to produce a number of complex organic molecules like Amino acids; Proteins ; Nucleic acids ; Enzymes; Chlorophyll etc.. The largest reservoir of nitrogen is the atmosphere where it exists as a gas mainly N 2. But atmospheric nitrogen is not utilized directly. However, nitrogen gas undergoes many changes in the nitrogen cycle like: Nitrogen Fixation, Ammonification, Nitrification. Nitrogen fixation or conversion of free nitrogen into biologically acceptable form is referred to as Nitrogen Fixation. N 2 + 2(O) −electric discharge → 2 NO Nitrogen gas oxygen radical nitrogen oxide In physico chemical process; nitrogen combines with oxygen during lightning or electrical discharges in the clouds and produces different nitrogen oxides (N 2 O 5 ). These nitrogen oxides get dissolved in rain water and react with mineral compounds to form Nitrates and Nitrogenous compounds on the earth. N 2 O 5 + H 2 O → 2HNO 3 2 HNO 3 + CaCO 3 → Ca (NO 3 ) 2 + CO 2 + H 2 O Nitrogen fixation is also carried out by biological process by means of blue – green algae in the oceans. Examples: Rhizobium bacteria fix nitrogen in the roots of Leguminous plants Blue – green algae ( Nostoc, Anabena ) fix Nitrogen. Ammonification: when plants or animals die or release waste, the nitrogen is returned to the soil as ammonia. The bacteria ( nitrite bacteria ) in the soil and in the water which take up ammonia and convert it to Nitrite ( NO 2 ). Another bacteria ( Nitrate bacteria ) take nitrite and convert it to Nitrate (NO3) which can be taken up by plants to continue the cycle.
Nitrification means conversion of ammonia into nitrite by some of the bacteri as such as Nitrosmonas, Nitrococcus in oceans and soils.
Phosphorus cycle: Phosphorus cycle is the circulation of phosphorous among the rocks, soils,
water, and plants and animals of the earth. Human beings and all other organisms must have phosphorus to live. In nature, most phosphorus occurs in phosphate rock, which contains phosphate ions combined with calcium, magnesium, chlorine, and fluorine. It cannot be found in air in the gaseous. This is because phosphorous is usually liquid at normal
temperatures pressures.
The cycle basically starts out in the earth‘s soil. The soil contains phosphate and when
something grows out of the soil it should have phosphate as well.
When the plants grow they are consumed by herbivore and omnivore animals.
The animal‘s waste or the animal‘s body when it dies becomes detritus. Detritus is non-living organic material. When the detritus goes deep into the soil, detrivores in the soil decompose and become the soil‘s phosphate and the cycle repeats.
Phosphorus cycle Biomagnification: Biomagnification is also known as bioamplification or biological magnification. Increase in the concentration of a pollutant as it passes from one trophic level to the next.^ Small amount in environment → Large concentration at top of food chain.
Water depth Amount of light Temperature Salinity of water Amount of oxygen and Carbondioxide. Aquatic ecosystems are broadly classified into fresh water and marine water ecosystems. In some regions, the marine and fresh water environments overlaps creating ― Estuaries ‖. Fresh Water: Eg: lakes, ponds streams, rivers water Marine: Eg: salt lakes, seas, oceans Estuaries: Eg: water bodies mix of fresh & sea I. Ponds & Lake Ecosystems : A pond is a small area of still water, especially is artificial whereas a lake is a large area of water body and the water is natural. The life span of ponds range from a few weeks or months and whereas the life span for lakes depend upon their location, size and depth. Depending upon temperature, the upper part of the lake becomes warm and is called eplimnion and the lower part of the lake becomes cold which is called as hypolimnion. These two zones are separated by thermocline zone which acts as a barrier to exchange of material / nutrients within the pond. During rainy season, entire water body gets same temperature due to mixing of water while in non-rainy season very small amount of mixing occurs by surface waves due to wind blow. The non-living ( abiotic ) components of a pond include Heat; light, pH value of water; organic compounds ( water, CO 2 , O 2 , Ca, N, P) and living (biotic) component s of Autotrophs or producers ( green plants, bacteria, rooted plants of Trapa, Typha, Sagi Haria ), Consumers ( Herbivores, insects and large fish ) and micro cosumers ( bacteria, fungi).
2. Stream & River Ecosystems : Rivers and streams are flowing fresh water bodies. Out of all natural ecosystems, rivers are the most intensively used ecosystems by man. The organization of river and stream ecosystem include: Abiotic Components : include volume of water, speed of water flow, dissolved oxygen content, temperature etc. The energy flow usually the organic matter which is being imported from adjacent terrestrial ecosystems. Biotic Components: include Producers ( algae, grass, amphibians ); consumers ( leaches, water insects, snails, fishes, crocodiles, reptiles ) and Decomposers ( bacteria, fungi, protozoa). 3. Ocean or Marine Ecosystems: The marine environment is characterized by its high concentration of salts and minerals. The major oceans of the world are Atlantic; Pacific; Indian, Arctic and Antarctic. These are deep and life extends to all its depths. The sea water contains salt o o content in the form of NaCl and rest are Mg, Ca, K. Temperature ranges from 0 to 30 C and pressure of 1 ATM at surface and 1000 ATM at bottom of oceans. The ocean ecosystem consists of the following; Biotic components of Producers (phytoplanktons, marine plants, Ruppia, Zostera, Halophile are true marine angiospers), Consumers of Molluscas, fishes and Decomposers of bacteria and Fungi. Abiotic components include Na, Cl, Mg, Ca, Sulphur, Dissolved oxygen content, light, temperature, pressure variations etc.
4. Estuarine Ecosystem : Estuary is the area at the mouth of the river joins the sea and continents. It has a free connection with the open sea and is thus strongly affected by tidal action. Estuaries are mixed with fresh water from land drainages. River mouth, coastal bay etc are the examples for estuarine ecosystem. Estuaries are one among the naturally fertile in the world. The components of estuarine ecosystem are giv en below: Abiotic components : Estuaries have their own ecological characteristics. Physical factors such as salinity, temperature, tidal activity etc are variable in estuaries when compared to the sea or ocean. Biotic components include Producers, consumers and Decomposers. Producers: Three major life forms of Autotrophs play a significant role in grass production. They are (c) macrophytes ( sea weeds, sea grass, spartina,Thalassia, marsh grass, nagrove trees ) (d) Phytoplankton and ( e) Benthic flora (algae). Consumers include a number of zooplankton, oysters, crabs and some species of fishes capable of surviving in estuarine conditions form primary, secondary, tertiary consumers of the estuarine ecosystem. Decomposers include bacteria and fungi which actively take part in the breaking down the complex and dead organic matter (Fungi of actinomycites ). FOREST ECOSYSTEM Introduction: Forest is a type of terrestrial ( land ) ecosystem. It consists of trees, shrubs or woody vegetation occupying an extensive area of land. Forests are important renewable resources. A different types of forests are seen on this earth. The type of forest depend upon its geographical location and environment factors ( Temperature and moisture ) that influence the kind of vegetation that occur in an area. Types of forests: 1. Savannas: These forests develop where a seasonal rainfall occurs. The grass lands of North Africa are known as savannas. Eg: North Africa, America, Burma & India. 2. Tropical forests: These exits in areas of good rainfall (>200cm per year) with uniform warm temperature. The Soils found in there forests are ol d, acidic in nature & poor in nutrients. Eg: Amazon rain forest (South America, India). 3. Deciduous forests (or) Temperate forests: Deciduous forests consists of broad leaved trees & occur where rainfall is plenty (750 - 1000 cms per year). Eg: Europe & North -East America. 4. Coniferous forest: These occur in areas with long winters with heavy snowfall. In other words, where moisture is limited & rainfall is low. Herbivores (animals eating plants) & insects exist in these forests. Eg: Mosc ow. (5) Tundras : These are the large flat Arctic regions of Northern Europe, Asia and North America where no trees grow and where the soil below the surface of the ground is always frozen. The growing season is short and plants grow very slowly. Following are the types of forests present in India :
- Tropical, forests present in Western Ghats of Maharashtra, Karnataka, Kerala.
- Deciduous forests present at Dehradun, Eastern Ghats of Andhra Pradesh, Tamil Nadu, M.P.
- Littoral and swamp forests present at Sunderbans in West Bengal and Andaman islands.
- Tropical Thorn forests present in New Delhi, Punjab and Gujarat.
The desert plants have adapted to the dry conditions and conserve water by having few or no leaves. Examples: (1) A plant namely Saguaro cactus has a stem that can expand to store water (2) Many desert plants have thorns or toxins to protect themselves from being grazed by animals. (3) Some desert plants have wax – coated leaves that minimize the loss of moisture. (4) Some desert plants have deep roots that reach the ground water. (5) A few desert plants have shallow roots that collect water after any rain and store it in spongy tissues. Desert ecosystem is characterized by scanty flora and fauna. The organisms which with stand the extreme temperatures can survive here. Desert animals are usually small in size and come out during the nights for food. Human impact on deserts: Slow rate of growth of vegetation if topsoil is eroded due to heavy vehicle transportation across the desert. Desert cities, depletion of ground water, land disturbance, pollution from mining, storage of toxic wastes are some of the human activities that cause damage. Abiotic components include temperature, rainfall, soil, water etc plays a major role to control the desert ecosystem. Biotic components include producers ( shrubs, bushes, grasses, a few trees and plants namely Cacti, Acacias, Euphorbias ). Consumers of insects, reptiles, rodents of rats & rabbits; birds, camels which are capable of living under desert conditions. Decomposers include Bacteria, Fungi due to poor vegetation and the less quantity of dead organic matter. A Case study of Desert ecosystem: The Thar desert (the Great Indian Desert) is spread over four states in India __ Punjab; Haryana; Rajasthan and Gujarat and two states in Pakistan. Thar desert covers an area of about 4,46,000 sq kms. Though the Thar desert is smaller than the Sahara desert in Africa and the Gobi desert in Russia, the Thar desert is most populated in the world with about 13 million people. The average rainfall is between 100 mm and 500 mm. The only river in the region is the Ghaggar which enters Rajasthan from Punjab and dries up in the forest. The Thar desert has no Oasis. Flowering plants like shrubs, grasses, trees (Khejra, Babul, Rohida ); fruit trees ( Ber; Pilu ) are found in Thar desert. Sheep, goats, camels are the common animals found in the Thar desert. In addition, wild ass, black buck deer, hare, red lynx, Jackal, Wild dog etc.. About 23 species of Lizard and 25 species of snakes are found in Thar desert region. part, is gleaning insects. The community provides the habitat—the place where particular plants or animals live. Within the habitat, organisms occupy different niches.
