Environmental Studies (SY) Past Paper PDF

Unit-II: VEC – CE202 – Environmental Studies (SY – Common for all Branches) 1. Ecosystems The word ecosystem means ecological systems. The term `eco' refers to a part of the world and `system' refers to the co-ordinating units. Ecology is the study of ecosystems. Sir Arthur George Tansley (1871 –195...

Unit-II: VEC – CE202 – Environmental Studies (SY – Common for all Branches) 1. Ecosystems The word ecosystem means ecological systems. The term `eco' refers to a part of the world and `system' refers to the co-ordinating units. Ecology is the study of ecosystems. Sir Arthur George Tansley (1871 –1955) was an English botanist who introduced the concept of the ecosystem into biology. “An ecosystem includes all the living things (plants, animals and organisms) in a given area, interacting with each other, and with their non-living environments (weather, earth, sun, soil, climate, atmosphere).” An ecosystem is a community of organisms and their physical environment interacting together. Environment involves both living organisms and the non-living physical conditions. These two are inseparable but inter-related. The living and physical components are linked together through nutrient cycles and energy flows. In an ecosystem, each organism has its own role to play. Ecosystems are the foundations of the Biosphere and they determine the health of the entire Earth system. The organisms in an ecosystem are usually well balanced with each other and with their environment. An ecosystem may be natural or artificial, land-based or water-based. Artificial systems may include a cropland, a garden, a park or an aquarium. Introduction of new environmental factors or new species can have disastrous results, eventually leading to the collapse of an ecosystem and the death of many of its native species. Some of the major non- living factors of an ecosystem are sunlight, water, temperature, oxygen, soil, air. 1.1 How big is an ecosystem? Ecosystems can be of any size, but usually they are places. An ecosystem may be of very different size. It may be a whole forest, as well as a small pond. An ecosystem may be as large as the Great Barrier Reef or as small as the back of a spider crab's shell, which provides a home for plants and other animals, such as sponges, algae and worms. Ecosystem boundaries are not marked (separated) by rigid lines. Ecosystems are often separated by geographical barriers such as deserts, mountains, oceans, lakes and rivers. As these borders are never rigid, ecosystems tend to blend into each other. Therefore, a lake can have many small ecosystems with their own unique characteristics. As a result, the whole earth can be seen as a single ecosystem, or a lake can be divided into several ecosystems, depending on the used scale. 1.2 Stability of ecosystems Many ecosystems are relatively stable and less influenced by some degree of human perturbation. Some are weak and quickly destroyed by human activity. Eg: Mountain ecosystems are extremely fragile, because degradation of forest cover contributes to significant soil erosion and changes in river courses. Island ecosystems are also easily affected by human activity which can contribute to the rapid extinction of many of their unique plant and animal species. Some species may have a significant impact on the environment if eliminated. These are called ‘keystone species’. Extinction is caused by land-use changes and other geographical changes. Forests are deforested for timber, wetlands are drained to create more agricultural 1 Unit-II: VEC – CE202 – Environmental Studies (SY – Common for all Branches) land and semi-arid grasslands are turned into irrigated fields. The pollution from industries and the waste from urban settings can also lead to poisoning and extinction of several species. 1.3 Scales of Ecosystems Ecosystems come in indefinite sizes. It can exist in a small area such as underneath a rock, a decaying tree trunk, or a pond in your village, or it can exist in large forms such as an entire rain forest. Technically, the Earth can be called a huge ecosystem. Ecosystems can be classified into three main scales. Micro: A small-scale ecosystem such as a pond, puddle, tree trunk, under a rock etc. Messo: A medium scale ecosystem such as a forest or a large lake. Biome: A very large ecosystem or collection of ecosystems with similar biotic and abiotic factors such as an entire Rainforest with millions of animals and trees, with many different water bodies running through them. 1.4 Structure of the Ecosystem The structure of an ecosystem is characterised by the organisation of both biotic and abiotic components. This includes the distribution of energy in our environment. It also includes the climatic conditions prevailing in that particular environment. The structure of an ecosystem can be split into two main components, namely: a. Biotic Components b. Abiotic Components The biotic and abiotic components are interrelated in an ecosystem. It is an open system where the energy and components can flow throughout the boundaries. Ecosystem Abiotic Biotic Components Components Climatic Producers (Rain, light, wind, temperature) Consumers Edaphic (Soil, pH, minerals, topography) Decomposers Fig. 1: Schematic representation of structure of an ecosystem a. Biotic Components The living organisms including plants, animals and micro-organisms (Bacteria and Fungi) that are present in an ecosystem form the biotic components. From nutrition point of view, the biotic components can be grouped into two basic components: Autotrophic components and Heterotrophic components 2 Unit-II: VEC – CE202 – Environmental Studies (SY – Common for all Branches) The autotrophic components include all green plants which fix the radiant energy of sun and manufacture food from inorganic substances. The heterotrophic components include non-green plants and all animals which take food from autotrophs. On the basis of their role in the ecosystem, the biotic components can be classified into three main groups: i. Producers, ii. Consumers, iii. Decomposers or Reducers i. Producers Green plants have chlorophyll with the help of which they trap 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 utilized partly by the producers for their own growth and survival and the remaining is stored in the plant parts for their future use. ii. Consumers Animals lack chlorophyll and are unable to synthesize their own food. Therefore, they depend on the producers for their food. They are known as heterotrophs (i.e. heteros= other, trophos= feeder). 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. Eg: 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 carvivores. Eg: cat, fox, snake etc. (c) Tertiary Consumers or Third Order Consumers: These are the large carnivores which feed on the secondary consumers. E.g. wolf. (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: Eg: lion and tiger. iii. 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 byproducts 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 (i.e., sapros=rotten, trophos=feeder). b. Abiotic Components The non-living factors or the physical environment prevailing in an ecosystem form the abiotic components. They have a significant impact on the structure, distribution, behavior and inter- relationship of organisms. Abiotic components are primarily of two types: i. Climate Factors which include rain, temperature, light, wind, humidity etc. ii. Edaphic Factors which include soil, pH, topography, minerals etc. 3 Unit-II: VEC – CE202 – Environmental Studies (SY – Common for all Branches) 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 topsoil is closely linked to this component of an ecosystem through nutrient cycling. The atmosphere provides carbon dioxide for photosynthesis and oxygen for respiration for the organisms found within ecosystems. 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 tissues are 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% of their saturation level and most are killed if it is less than 30-50% below the saturation level. 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. Fig. 2: Relationship within an ecosystem 1.5 Functions of Ecosystem The functions of the ecosystem are as follows: a. It regulates the essential ecological processes, supports life systems and renders stability. b. It is also responsible for the cycling of nutrients between biotic and abiotic components. c. It maintains a balance among the various trophic levels in the ecosystem. d. It cycles the minerals through the biosphere. e. The abiotic components help in the synthesis of organic components that involve the exchange of energy. 4 Unit-II: VEC – CE202 – Environmental Studies (SY – Common for all Branches) 1.6 Food Chain It is a transfer of energy from one organism to another organism through a repeated process of eating and being eaten. A food chain is a linear network of links in a food web, often starting with an autotroph, also called a producer, and typically ending at an apex predator, detritivore, or decomposer. The sun is the ultimate source of energy on earth. It provides the energy required for all plant life. The plants utilise this energy for the process of photosynthesis, which is used to synthesise their food. During this biological process, light energy is converted into chemical energy and is passed on through successive trophic levels. The flow of energy from a producer, to a consumer and eventually, to an apex predator or a detritivore is called the food chain. Dead and decaying matter, along with organic debris, is broken down into its constituents by scavengers. The reducers then absorb these constituents. After gaining the energy, the reducers liberate molecules to the environment, which can be utilised again by the producers. Fig. 3: Food chain Threats to Ecosystems 5