Introductory Lecture: What is Environment? What is Ecology? Dr.M. C.Dash

Environment- Includes water, air and land and the interrelationship which exists between water, air, land and human beings and other living creatures, plants, micro-organisms and property. [Section 2(b) of Environment (Protection) Act-1986, Government of India).

Biosphere:

Life in the planet-earth has become possible due to very favourable interactions between soil (Pedosphere), water (hydrosphere), and the air (atmosphere) in a zone, we call Biosphere. Biosphere includes these three spheres, and the biodiversity.

The Pedosphere

Earth has three layers; (a) the crust, which is in the solid state and has thickness varying from 16 to 50 km.The crust, contains soil of thickness ranging from few inches to a few feet. Soil is the abode of numerous organisms like bacteria, actinomycetes, fungi, protozoa and invertebrate fauna such as earthworms, collembola, mites, millipedes, centipedes, mollusks etc; b) The mantle, which is about 2900 km thick and made of hard rock containing mainly iron and magnesium, which respectively form 84% and 67 % of earth’s volume and weight; (c) The core, which is made of mainly iron and nickel with a temperature of about 8,000◦ C.

In a normal mineral soil, the profile has three horizons, usually termed A, B, and C layers. These soil horizons are differentiated by texture, physical structure, colour, porosity, and root growth,

nature of organic material and distribution of biodiversity. The A horizon includes the top soil, containing organic matter. The activity of microorganisms and soil fauna is greatest in this zone of soil. After breakdown of organic matter into smaller particles and undergoing decomposition, it forms humus, which gets mixed up with mineral particles. In some soils, such as coniferous forest soil the organic matter occurs in various stages of decomposition and forms a distinct zone called the O zone. The B zone is called subsoil and is more brightly coloured than the A zone. The brightness is usually due to present of iron oxides. This zone may contain clay. In poorly drained soils, water logging may happen. This may cause alternate reduction, mobilization and reoxidation of iron compounds. In such condition the B horizon may appear grey in colour.

The unchanged parent material is called the C -horizon. Soil texture depends upon the particle size of the constituent parts.

The atmosphere, which surrounds the earth, can be divided into five distinct layers:

(i) troposphere;

(ii) (ii) stratosphere;

(iii) (iii) mesosphere;

(iv) (iv) ionosphere; and

(v) exosphere, which is the uppermost layer extending to space

Hydrosphere

• Proportions of different types of water available in the hydrosphere

• Source of Water % Occurrence

• Ocean 97.389

• Glaciers & polar ice caps 02.01

• Ground water & soil moisture 0.58

• Rivers & lakes 0.02

• Atmospheric water as vapour 0.001

Total fresh water 2.611

Biodiversity

The living microorganisms, plants and animals, and microorganisms such as bacteria, fungi etc have specific requirements for existence, continuance and perpetuation. They interact among themselves (intra-specific and inter-specific interaction) and with the environment. All the living forms including man get their requirements of gases, other matter, and energy from the environment where they live.

Ecology: 1876 Ernst Haeckel (German Zoologist) Coined the word ecology (Oikos-home/house, logos-discourse). A.G.Tansley (British Ecologist)(1935) enumerated the concept of Ecosystem within the Biosphere. The concept was known to the people of India since Vedic Time.

Ecology deals with the understanding the natural order, which keeps so many living organisms in a dynamic coexistence. This raises many fundamental questions in human mind. What are the fundamental features of these natural systems? How the nutrients circulate and energy flow in natural systems? How efficient are the natural systems in comparison to manmade systems? Is there something called carrying capacity of an ecosystem? How can this knowledge be utilized to increase food, fodder and fuel production, to protect environment (landscape) from erosion, pollution etc. and manage the resources? The functioning of natural systems is based on certain principles. Understanding these principles will help man to solve many problems of the management and maintenance of natural and man-made systems. Ecological Science has three aspects namely (i) Theory ;(ii) Field and Lab observations; (iii) Socio-cultural- economic- aesthetic aspects. All forms of life owe their existence to the mother Earth and to the maintenance of ecological order (ecological balance) in nature. This balance is maintained by ( laws of Ecology) .(i) Rich bio-diversity, (Plants, Animals, Microbes,& Man ),(ii) Interdependence among the different life forms,(iii) Sustained productivity and food chain relationships,(iv) Maintenance of natural processes of nutrient cycling, energy, flow, homeostatic mechanisms and evolutionary process,(v) Adapted potentiality of the living forms to the changing environment, In the modern concept, principles of Ecology include:

(i) “Nothing comes from nowhere, everything comes from somewhere”. And

(ii) Nothing ever goes away, everything goes somewhere .

The environment of an organism has 2 components,

( i) Biotic, : Organism is in the state of dynamic equilibrium with environment ,which is in constant state of flux. Internal environment-stable, external environment- changes.- Tolerance

graph. Adaptation concept (two graphs). Convergence & Divergence concept-Adaptive radiations.

Allen, Bergman, Gloger’s observations (rules): Allen’s Rule states that Tails, bills, ears etc of animals are relatively shorter for a species in cooler region of the range of the environmental gradient than in the warmer regions, Bergman’s Rule states that Races of species having a larger body size are generally found in the cooler parts of the range while those having a smaller body size are found in the warmer parts. This rule is applicable to both poikilotherms and homothermic animals. Gloger’s Rule states that in homotherms, black pigments increase in warmer and humid climatic conditions,red and brown-yellow pigments in arid climates. These pigments over the skin are greatly reduced in cold climates,

Abiotic (nonliving): (i) Atmosphere ;(ii) Hydrosphere,(iii) Pedosphere(Soil)

Biotic (living): Diverse organisms, Interactions ( Interspecific, Interspecific interactions,- Associations- competition, favourable and unfavourable associations like symbiosis,commensaliosm and parasitism etc)- Genotype-& Phenotypes

Concept of Stress and Strain

Environmental Scientists/Ecologists agree that any environmental factor that is potentially unfavorable to organism functioning can be called stress. Pollutants can be classified as stress factors. An organism’s ability to survive in a particular environmental complex depends upon its evolutionary history. Resistance to stress is defined as the ability of living organisms to survive and grow in the presence of unfavorable factors.

If a body X exerts force on body Y, then Y must also exert a counter force on X. In Newtonian terms, these two forces are termed action and reaction. Taken together, they may be called stress. A body remains in a state of strain if subjected to stress. The magnitude of stress can be measured as the force per unit area. The magnitude of strain is measured as the change in dimensions such as length or volume of the body.

The elastic strain produced by a body is proportional to the stress applied on it. Therefore the Modulus of elasticity (M) of the body is defined as:

M = Stress / Strain,

A higher M implies more elasticity. A body is considered sensitive for a stress factor, if little stress is required to produce a unit strain.

The upper and lower limits of tolerance are the intensity levels of an environmental factor at which only 50% of the organism can survive. Species vary in their limits of tolerance to the same factor and these limits are usually difficult to determine. The prefix steno means that an individual or a species population has a narrow range of tolerance, while the prefix Eury means that it has a wide range of tolerance. Thus, the terms stenothermal and Eurythermal have been developed with regard to temperature, stenohaline and Euryhaline in respect of salinity and stenoecious and euryoecious in the context of habitat or niche have been developed.

Terminology Environmental Factors

Steno & Eurythermal Temperature

Steno & Euryhaline Salinity

Steno & Euryhydric Water

Stenobathic & Eurybathic Water depth

Stenocious &Euroecious Habitat selection/distribution

Stenophagic &Euryphagic Food selection

Concept of law of minimum, limiting factors, interacting factors etc (Liebig, 1840, Shelford, 1952, Blackman, 1905, Taylor,1930.The practical importance of ecology results from the presence of man in the ecosystem.

Man’s evolution, its dependence on environment and environmental phenomena, his relationship with nature and the development of his position from one of struggle against natural forces to the recent influence, control and use of environment for human welfare are included in ecology.Pre-agricultural human society, Agriculture based Society, Urban-industrialized Society, The Current atomic age and the electronic age society, and The global warming- climate change have brought the science of ecology to the forefront of human knowledge.

Population increase and demand for food and other resources necessitate the need of increased food productivity.

Landscape Ecology

Diversity of Landscape- mountains, hills, valleys, plateau, plains and other physical landscapes- cumulative effect of geological, geomorphological and meteorological processes of millions of years. These have been formed along with Earth’s evolution and along water resources. They have sustained Biodiversity including human settlements and civilization for thousands of years. Definition: German geologist, Carl Troll(1971) defined it as ‘The total natural and human living space’ -Three dimensional- space,time,biodiversity & human interactions. Alexander Van Humboldt, German Geographer defined it as ‘ The total character of a region’.The basic unit is the Ecotype.Socio-cultural aspects have also shaped landscapes.

Landscapes-Tangible Gestalt Systems of total Human Ecosystem

India’s land area is about 329 million ha., Population 1230 million, per capita land area- 329/1230=0.267 ha,

Assuming 50% productive area, per capita productive lansd-0.134 ha.

What is the significance?

1.The biosphere including all the ecotypes are dependent on solar energy for functioning.2.The human modified semi-natural ecotypes are dependent on solar energy & on fertilizer & pesticides,3.The intensive agro-industrial ecotypes are dependent on fossil fuels(subsidized),4.The urban-industrial techno-sphere ecotypes and their techno-systems ( Highway, flyover,bridges,mines,power plants etc),Landuse policy, Forest policy,(33% forest cover),Ecocity concept(the theme of the World Habitat Day in 1999-’The cities for all,-20% tree cover, Housing –energy conservation, soil waste management etc.

Recent Trends of Study (1) Understanding of the pattern and functioning of natural systems along with life cycle analysis of biodiversity. 2. Impacts of modern technological developments (Agriculture, Industry,etc chemicals, energy use) on natural systems. Adoption of Green Technology,3.Conservation of natural systems vis-a--vis resource conservation, to increase production,discourge consumerism, population control, sustainable Development & science-technology input to achieve sustainable development.

Environmental Movements/Consciousness

In the Last century unprecedented deterioration in the state of Environment occurred mainly due to loss of habitats, unscientific land use, industrialization and Urbanization. This led to discharge of high volumes of effluents and municipal sewage to water bodies and polluted the rivers and water bodies. Huge quantity of Industrial emissions to the atmosphere causing environmental pollution and health hazards.The extent of deterioration could be judged due to pollution, global warming, ozone depletion in stratosphere, acid rain, eutrophication, loss

of habitat, vegetal cover and biodiversity, excessive concentration of harmful chemicals and magnification through food chain, growing risk of environmental accidents, and threat to Life support systems.

Government of India actively participated in1972conference and follow-up conferences. The Indian Parliament enacted many environmental laws to prevent and control pollution, conserve biodiversity and wild life etc.(The Water Act-1972,The Air Act-1981,The Environmental Protection Act-1986, etc, and the Forest Act-1980,amended 1988,Wildlife Act-1972 etc.