Food chains. Diversity-inter linkages between organisms. Nutrient cycles-biogeochemical cycles. Evolution. (e) Differentiate between primary and secondary pollutant? The Primary pollutants are passed into environment in the form they are produced or in other words it is directly released into the atmosphere from the sources. e.g. CO, SOx, NOx, etc. The Secondary pollutants are not emitted directly to the atmosphere as primary pollutants. Rather they are made in the air using other pollutants. Especially when primary pollutants react or interact with other molecules secondary pollutants are made. Therefore, by releasing primary pollutants to the air, not only it has direct effects, but it affects the atmosphere in an indirect way too. Most of the common secondary pollutants are ozone, acid rain, PAN, SMOG, etc. (f) What is the objective of 1972- Wildlife Protection Act? The objective of the Wildlife Protection Acts (1972) are for the protection of Wild animals, birds and plants and for matters connected therewith or ancillary or incidental thereto. (g) Name some greenhouse gases present in the atmosphere and their sources? Carbon dioxide (CO2) Combustion of fossil fuel, deforestation, industrialization, etc. Combustion of fossil fuel, and the decomposition of organic Methane (CH4) materials associated with wetlands, rice paddies, and livestock manure. production and/or use of foams, aerosols, refrigerants, and Ozone (O3) solvents Nitrous Oxide (N2O) Fertilizers, Deforestation, Burning of Biomass 2. What is Environmental Gradient? Draw the Universal tolerance curve for different levels of environmental factors? An environmental gradient is a continuous change in communities and environmental condition. Gradients can be related to environmental factors such as altitude, temperature, depth, ocean proximity, soil water content, soil pH, and moisture. Tolerance Level: Range of optimum: The range (Any Physical parameter , i.e., environment gradient) over which maximum population of a particular species will find Range of Intolerance: The range (Any Physical parameter, i.e., environment gradient) over which less population of a particular species will find but under a stress. Range of Physical Stress: The range (Any Physical parameter, i.e., environment gradient) over which a little or no population of a particular species will find.
3. Explain the structural and functional units of a natural ecosystem with suitable examples. An ecosystem is defined as a natural functional ecological unit comprising of living organisms (biotic community) and their non-living (abiotic or physio chemical) environment that interact to form a stable self-supporting system. e.g. pond, lake, desert, grassland, meadow, forest etc. are common examples of ecosystems. Structural unit of an Ecosystem: Each ecosystem has two main components: (1) Abiotic (2) Biotic (1) Abiotic Components: The non living factors or the physical environment prevailing in an ecosystem form the abiotic components (Lithosphere, Hydrosphere, and Atmosphere). They have a strong influence on the structure, distribution, behaviour and inter-relationship of organisms. The functions of important factors in abiotic components are given below: Soils are much more complex than simple sediments. They contain a mixture of weathered rock fragments, highly altered soil mineral particles, organic matter, and living organisms. Soils provide nutrients, water, a home, and a structural growing medium for organisms. The vegetation found growing on top of a soil is closely linked to this component of an ecosystem through nutrient cycling. The atmosphere provides organisms found within ecosystems with carbon dioxide for photosynthesis and oxygen for respiration. The processes of evaporation, transpiration and precipitation cycle water between the atmosphere and the Earth’s surface. Solar radiation is used in ecosystems to heat the atmosphere and to evaporate and transpire water into the atmosphere. Sunlight is also necessary for photosynthesis. Photosynthesis provides the energy for plant growth and metabolism, and the organic food for other forms of life. Most living tissue is composed of a very high percentage of water, up to and even exceeding 90%. The protoplasm of a very few cells can survive if their water content drops below 10%, and most are killed if it is less than 30-50%.Water is the medium by which mineral nutrients enter and are trans-located in plants. It is also necessary for the maintenance of leaf turgidity and is required for photosynthetic chemical reactions. Plants and animals receive their water from the Earth’s surface and soil. The original source of this water is precipitation from the atmosphere. (2) Biotic Components: The living organisms including plants, animals and micro-organisms (Bacteria and Fungi) that are present in an ecosystem form the biotic components. On the basis of their role in the ecosystem the biotic components can be classified into three main groups: (A) Producers
(B) Consumers (C) Decomposers or Reducers. (A) Producers: The green plants have chlorophyll with the help of which they trap solar energy and change it into chemical energy of carbohydrates using simple inorganic compounds namely water and carbon dioxide. This process is known as photosynthesis. As the green plants manufacture their own food they are known as Autotrophs (i.e. auto = self, trophos = feeder) The chemical energy stored by the producers is utilised partly by the producers for their own growth and survival and the remaining is stored in the plant parts for their future use. (B) Consumers: The animals lack chlorophyll and are unable to synthesise their own food. Therefore, they depend on the producers for their food. They are known as heterotrophs The consumers are of four types, namely: (a) Primary Consumers or First Order Consumers or Herbivores: These are the animals which feed on plants or the producers. They are called herbivores. Examples are rabbit, deer, goat, cattle etc. (b) Secondary Consumers or Second Order Consumers or Primary Carnivores: The animals which feed on the herbivores are called the primary carnivores. Examples are cats, foxes, snakes etc. (c) Tertiary Consumers or Third Order Consumers: These are the large carnivores which feed on the secondary consumers. Example are Wolves. (d) Quaternary Consumers or Fourth Order Consumers or Omnivores: These are the largest carnivores which feed on the tertiary consumers and are not eaten up by any other animal. Examples are lions and tigers. (C) Decomposers or Reducers: Bacteria and fungi belong to this category. They breakdown the dead organic materials of producers (plants) and consumers (animals) for their food and release to the environment the simple inorganic and organic substances produced as by-products of their metabolisms. These simple substances are reused by the producers resulting in a cyclic exchange of materials between the biotic community and the abiotic environment of the ecosystem. The decomposers are known as Saprotrophs Functional unit of an Ecosystem: The functional units of an ecosystem include such things as the amount of energy that is produced by photosynthesis, how energy or materials flow along the many steps in a food chain, or what controls the rate of decomposition of materials or the rate at which nutrients are recycled in the system. Functional attributes Energy cycles. Food chains. Diversity-interlinkages between organisms. Nutrient cycles-biogeochemical cycles. Evolution. 4. Explains nitrogen cycle with various steps involve in it. The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out through both biological and physical processes. In other words, it can be defined as the global circulation of nitrogen between organisms and the abiotic environment. Atmospheric nitrogen (N2) is so stable that it must first be broken apart in a series of steps before it can combine with other elements to form biological molecules Nitrogen is an essential part of proteins and nucleic acids (DNA)
The atmosphere is 78% nitrogen gas (N2) There are various steps in the nitrogen cycle 1. Nitrogen fixation Conversion of gaseous nitrogen (N2) to ammonia (NH3) Nitrogen-fixing bacteria (including cyanobacteria) fixes nitrogen in soil and aquatic environments (anaerobic process) N2 + 8 H+ 2 NH3 + H2 Combustion, volcanic action, lightning discharges, and industrial processes also fix nitrogen 2. Nitrification a. Conversion of ammonia (NH3) or ammonioum (NH4+ ) to nitrate (NO− 3) b. Soil bacteria perform nitrification in a two-step process − NH3 or NH4+ is converted to nitrite (NO− 2 -) then to NO3 ) c. Nitrifying bacteria is used in this process 3 𝑁𝐻3 + 𝑂2 NO− 2 + H2 O 2 NO− 2 + 1 𝑂 NO− 3 2 2 3. Assimilation + Plant roots absorb NO− 3 , NO3 or NO4 and assimilate the nitrogen of these molecules into plant proteins and nucleic acids Animals assimilate nitrogen by consuming plant tissues (conversion of aminio acids to proteins) This step does not involve bacteria 4. Ammonification; Conversion of biological nitrogen compounds into NH3 and NO+ 4. NH3 is released into the abiotic environment through the decomposition of nitrogen-containing waste products such as urea and uric acid (birds), as well as the nitrogen compounds that occur in dead organisms. Ammonifying bacteria is used in this process 5. Denitrification a. Reduction of NO− 3 to N2 b. Anaerobic denitrifying bacteria reverse the action of nitrogen-fixing and nitrifying bacteria − + NO− 3 + 10e + 12H N2 + 6H2 O 5. What do you mean by energy flow through an ecosystem? Explain how energy transformation through an ecosystem can be explained by two laws of thermodynamics. In an ecosystem, the energy flow, also called the calorific flow, refers to the flow of energy through a food chain from one tropic level to another tropic level.