Unit III Ecosystems for BBA MT EM 1.pptx

Presentation for BBA, MT and EM

1. Unit III Ecosystems Dr S V Vageesha Campus Director, DSEU

2. Presentation Components Concept, Structure and function of an Ecosystem Components of ecosystem : Producers, Consumers, Decomposers Energy flow, food Chains, Food webs and ecological pyramids SVV 2

3. ECOSYSTEMS Ecology : Taylor (1936) defined ecology as “the science of the relations of all organisms to all their environments.” A. Macfadyen (1957) defined ecology as “ a science, which concerns itself with the inter-relationships of living organisms, plants and animals, and their environments.” R.L. Smith (1977), considers ecology as “a multidisciplinary science which deals with the organism and its place to live and which focuses on the ecosystems.” SVV 3

4. ECOSYSTEM An ecosystem is a structural and functional unit of ecology where the living organisms interact with each other and the surrounding environment. In other words, an ecosystem is a chain of interactions between organisms and their environment. The living community of plants and animals (Biotic Components) in any area together with the non- living components (Abiotic Components) of the environment such as soil, air and water, constitute the ecosystem. Ecosystems are equally vigorous and are less affected by a certain level of human disturbance. highly fragile and are quickly destroyed by human activities Ex Mountain System , Island System 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. SVV 4

5. ECOSYSTEM SVV 5

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7. Components of EcoSystem Biotic Components refer to all living components in an ecosystem. Based on nutrition, biotic components can be categorised into autotrophs, heterotrophs and saprotrophs (or decomposers). Producers include all autotrophs such as plants. They are called autotrophs as they can produce food through the process of photosynthesis. Consequently, all other organisms higher up on the food chain rely on producers for food. Consumers or heterotrophs are organisms that depend on other organisms for food. Consumers are further classified into primary consumers, secondary consumers and tertiary consumers. Primary consumers are always herbivores as they rely on producers for food. Secondary consumers depend on primary consumers for energy. They can either be carnivores or omnivores. Tertiary consumers are organisms that depend on secondary consumers for food. Tertiary consumers can also be carnivores or omnivores. Quaternary consumers are present in some food chains. These organisms prey on tertiary consumers for energy. Furthermore, they are usually at the top of a food chain as they have no natural predators. Decomposers include saprophytes such as fungi and bacteria. They directly thrive on the dead and decaying organic matter. Decomposers are essential for the ecosystem as they help in recycling nutrients to be reused by plants. SVV 7

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9. Components of EcoSystem Abiotic Components Abiotic components are the non-living component of an ecosystem. It includes air, water, soil, minerals, sunlight, temperature, nutrients, wind, altitude, turbidity, etc. SVV 9

10. Characteristics of Ecosystem The ecosystem is a major structural and functional unit of ecology. The structure of an eco-system is related to its species diversity; as such the more complex ecosystem has high species diversity. The relative amount of energy required to maintain an ecosystem depends on its structure. The more complex the structure, the lesser the energy it requires to maintain itself. The function of the ecosystem is related to energy flow in material cycling through and within the system. Ecosystems mature by passing from less complex to more complex states. Early stages of such succession have an excess of potential energy. Later (mature) stages have less energy accumulation. Both the environment and the energy fixation in any given ecosystem are limited. They cannot be exceeded in any way without causing serious undesirable effect. Alterations in the environments represent selective pressures upon the population to which it must adjust. Organisms, which fail to adjust to the changed environment, must vanish. SVV 10

11. TYPES OF ECOSYSTEM SVV 11

12. TERESTRIAL ECOSYSTEMS LAND BASED Forest Ecosystem A forest ecosystem consists of several plants, particularly trees, animals and microorganisms that live in coordination with the abiotic factors of the environment. Forests help in maintaining the temperature of the earth and are the major carbon sink. Grassland Ecosystem In a grassland ecosystem, the vegetation is dominated by grasses and herbs. Temperate grasslands and tropical or savanna grasslands are examples of grassland ecosystems. Tundra Ecosystem Tundra ecosystems are devoid of trees and are found in cold climates or where rainfall is scarce. These are covered with snow for most of the year. Tundra type of ecosystem is found in the Arctic or mountain tops. Desert Ecosystem Deserts are found throughout the world. These are regions with little rainfall and scarce vegetation. The days are hot, and the nights are cold. SVV 12

13. AQUATIC ECOSYSTEM (Water Based) Fresh water Ecosystem The freshwater ecosystem is an aquatic ecosystem that includes lakes, ponds, rivers, streams and wetlands. These have no salt content in contrast with the marine ecosystem. Marine Ecosystem The marine ecosystem includes seas and oceans. These have a more substantial salt content and greater biodiversity in comparison to the freshwater ecosystem. SVV 13

14. ECOLOGICAL CONCEPTS Energy flow in Ecosystem SVV 14

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17. Energy Flow/Cycle Every ecosystem has numerous interconnected mechanisms that affect human life. Mechanisms : water cycle, the carbon cycle, the oxygen cycle, the nitrogen cycle and the energy cycle. While every ecosystem is controlled by these cycles, in each ecosystem its abiotic and biotic features are distinct from each other. All the functions of the ecosystem are in some way related to the growth and regeneration of its plant and animal species. These linked processes can be depicted as the various cycles. These processes depend on energy from sunlight. During photosynthesis carbon dioxide is taken up by plants and oxygen is released. Animals depend on this oxygen for their respiration. The water cycle depends on the rainfall, which is necessary for plants and animals to live. The energy cycle recycles nutrients into the soil on which plant life grows. Our own lives are closely linked to the proper functioning of these cycles of life. SVV 17

18. WATER CYCLE Water, air, and food are the most important natural resources to people. Humans can live only a few minutes without oxygen, less than a week without water, and about a month without food. Water also is essential for our oxygen and food supply. Plants breakdown water and use it to create oxygen during the process of photosynthesis. The water (or hydrologic) cycle shows the movement of water through different reservoirs, which include oceans, atmosphere, glaciers, groundwater, lakes, rivers, and biosphere. Solar energy and gravity drive the motion of water in the water cycle. From clouds, it falls as precipitation (rain and snow) on both water and land. The water on land can either return to the ocean by surface runoff, rivers, glaciers, and subsurface groundwater flow, or return to the atmosphere by evaporation or transpiration (loss of water by plants to the atmosphere). SVV 18

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21. Carbon Cycle The carbon cycle describes the flow of carbon between the biosphere, the geosphere, and the atmosphere, and is essential to maintaining life on earth. The physical cycle of carbon through the Earth’s biosphere, geosphere, hydrosphere and atmosphere that includes such processes as photosynthesis, decomposition, respiration and carbonification. Atmospheric Carbon Dioxide: Carbon in the earth’s atmosphere exists in two main forms: carbon dioxide and methane. Carbon dioxide leaves the atmosphere through photosynthesis, thus entering the terrestrial and marine biospheres. Carbon dioxide also dissolves directly from the atmosphere into bodies of water (oceans, lakes, etc.), as well as dissolving in precipitation as raindrops fall through the atmosphere. When dissolved in water, carbon dioxide reacts with water molecules and forms carbonic acid, which contributes to ocean acidity. Human activity over the past two centuries has significantly increased the amount of carbon in the atmosphere, mainly in the form of carbon dioxide, both by modifying ecosystems ability to extract carbon dioxide from the atmosphere and by emitting it directly, e.g. by burning fossil fuels and manufacturing concrete. SVV 21

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23. Oxygen Cycle The oxygen cycle is a fundamental biogeochemical process that plays a crucial role in maintaining oxygen balance in Earth’s atmosphere and sustaining life on our planet. the oxygen cycle describes the movement and transformation of oxygen through different components of the Earth’s atmosphere, lithosphere (Earth’s solid outer layer), and biosphere (all living organisms). SVV 23

24. Steps in Oxygen Cycle Step 1: Photosynthesis is the process through which all green plants make nourishment. Green plants use carbon dioxide, sun rays, chlorophyll, and water to make glucose during photosynthesis. As a byproduct of this mechanism, plants produce oxygen. Step 2: It is the process of aerobic organisms taking oxygen from the environment consuming and utilizing oxygen. The body uses oxygen for a variety of metabolic reactions. The availability and utilization of oxygen are required for several biological processes. Step 3: Aerobic organism that have taken in oxygen are emit carbon dioxide into the environment. The respiration process includes both inhaling oxygen and excretion of carbon dioxide. Any activity performed by aerobes requires the expenditure of energy. As a result of respiration, carbon dioxide is created and released into the atmosphere, while carbon dioxide returns to the atmosphere. SVV 24

25. Production of Oxygen Photosynthesis: Photosynthesis is the conversion of light energy by phototrophs into chemical energy. Sugars, which are formed from water and carbon dioxide, are used to store chemical energy. Photodissociation: Oxygen molecules are created when sunlight interacts with the water vapor present. As a result of the water cycle, water vapor occurs in the atmosphere. The formation of molecular oxygen can occur as a result of many chemicals depleting the ozone layer. SVV 25

26. Oxygen Cycle SVV 26

27. Nitrogen Cycle Organic entities require numerous natural and inorganic substances to finish their life cycle. All such substances which are taken from outside comprise their nutrition. Based on their dietary necessities, life forms can be characterized as heterotrophs and autotrophs. All non-green plants and creatures, including individuals, are heterotrophs. Autotrophic green plants acquire their nourishment from inorganic substances which are available in the soil as minerals, which are known as mineral components or mineral supplements, and this kind of nutrition is called mineral nutrition. SVV 27

28. Nitrogen Cycle SVV 28

29. Nitrogen Cycle Carnivorous animals feed on herbivorous animals that live on plants. When animals defecate, this waste material is broken down by worms and insects mostly beetles and ants. These small ‘soil animals’ break the waste material into smaller bits on which microscopic bacteria and fungi can act. This material is thus broken down further into nutrients that plants can absorb and use for their growth. Thus, nutrients are recycled back from animals to plants. Similarly, the bodies of dead animals are also broken down into nutrients that are used by the plants for their growth. Thus, the nitrogen cycle on which life is dependent is completed. Nitrogen fixing bacteria and fungi in soil gives this important element to plants, which absorb it as nitrates. The nitrates are a part of the plant’s metabolism, which help in forming new plant proteins. This is used by animals that feed on the plants. The nitrogen is then transferred to carnivorous animals when they feed on the herbivores. Thus, our own lives are closely interlinked to soil animals, fungi and even bacteria in the soil. SVV 29

30. Nitrogen Cycle Nitrogen fixation: This process involves conversion of gaseous nitrogen into Ammonia, a form in which it can be used by plants. Atmospheric nitrogen can be fixed by the following three methods: - Atmospheric fixation: Lightening, combustion and volcanic activity help in the fixation of nitrogen. Industrial fixation: At high temperature (400 o C) and high pressure (200 atm.), molecular nitrogen is broken into atomic nitrogen which then combines with hydrogen to form ammonia. Bacterial fixation: There are two types of bacteria- ( i ) Symbiotic bacteria e.g. Rhizobium in the root nodules of leguminous plants. (ii) Freeliving or symbiotic e.g. 1. Nostoc 2. Azobacter 3. Cyanobacteria can combine atmospheric or dissolved nitrogen with hydrogen to form ammonia. Nitrification : It is a process by which ammonia is converted into nitrates or nitrites by Nitrosomonas and Nitrococcus bacteria respectively. Another soil bacteria Nitrobacter can covert nitrate into nitrite. Assimilation: In this process nitrogen fixed by plants is converted into organic molecules such as proteins, DNA, RNA etc. These molecules make the plant and animal tissue. Ammonification : Living organisms produce nitrogenous waste products such as urea and uric acid. These waste products as well as dead remains of organisms are converted back into inorganic ammonia by the bacteria This process is called ammonification. Ammonifying bacteria help in this process. Denitrification : Conversion of nitrates back into gaseous nitrogen is called denitrification. Denitrifying bacteria live deep in soil near the water table as they like to live in oxygen free medium. Denitrification is reverse of nitrogen fixation. SVV 30

31. Phosphorous Cycle Phosphorus is a major constituent of biological membranes, nucleic acids and cellular energy transfer systems. Many animals also need large quantities of this element to make shells, bones and teeth. The natural reservoir of phosphorus is rock, which contains phosphorus in the form of phosphates. When rocks are weathered, minute amounts of these phosphates dissolve in soil solution and are absorbed by the roots of the plants Herbivores and other animals obtain this element from plants. The waste products and the dead organisms are decomposed by phosphate- solubilising bacteria releasing phosphorus. Unlike carbon cycle, there is no respiratory release of phosphorus into atmosphere. The other two major and important differences between carbon and phosphorus cycle are firstly, atmospheric inputs of phosphorus through rainfall are much smaller than carbon inputs, and, secondly, gaseous exchanges of phosphorus between organism and environment are negligible. SVV 31

32. FOOD CHAIN, FOOD WEB & ECOLOGICAL PYRAMIDS Food Chain A food chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another. In a food chain, each organism occupies a different trophic level, defined by how many energy transfers separate it from the basic input of the chain. In food chain each organism eats the smaller organisms and is eaten by the larger one. All those organisms which are interlinked with each other through food together constitute the ecosystem. The different levels in a food chain are called tropic levels, Each food chain has three main tropic levels:- Producer level, Consumer level, and decomposer level. If any of the intermediate stage of the food chain is removed, the succeeding links of the food chain will be affected. SVV 32

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35. Major Parts of Food Chain The Sun: The sun is the initial source of energy, which provides energy for everything on the planet. Producers: The producers in a food chain include all autotrophs such as phytoplankton, cyanobacteria, algae, and green plants. This is the first stage in a food chain. The producers make up the first level of a food chain. The producers utilise the energy from the sun to make food. Producers are also known as autotrophs as they make their own food. Producers are any plant or other organisms that produce their own nutrients through photosynthesis. SVV 35

36. Major Parts of Food Chain Consumers: Consumers are all organisms that are dependent on plants or other organisms for food. This is the largest part of a food web, as it contains almost all living organisms. It includes herbivores which are animals that eat plants, carnivores which are animals that eat other animals, parasites that live on other organisms by harming them and lastly the scavengers, which are animals that eat dead animals’ carcasses. Herbivores are known as primary consumers and carnivores are secondary consumers. The second trophic level includes organisms that eat producers. Therefore, primary consumers or herbivores are organisms in the second trophic level. Decomposers: Decomposers are organisms that get energy from dead or waste organic material. This is the last stage in a food chain. Decomposers are an integral part of a food chain, as they convert organic waste materials into inorganic materials, which enriches the soil or land with nutrients. SVV 36

37. Types of Food Chains Grazing Food Chain: This type of food chain starts from living green plants goes to grazing herbivores and onto carnivores. Ecosystem with such type of food chain directly depends upon the solar energy for their food requirements. Most of the ecosystem in nature follows this type of food chain. Detritus food Chain: This type of food chain goes from dead organic matter onto microorganisms and then to the organisms feeding on detritus and their predators. Such ecosystems are less dependent on direct solar energy. Parasitic Food Chain: This type of food chain starts from big hosts and ends with parasitic organisms SVV 37

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40. Food Webs The interconnected, interlocking pattern of food chain is known as food web. Under natural condition of the linear arrangement of food chain hardly occurs and they remain interconnected with each other through different types of organisms at different levels. Interconnected and interlocking pattern of food chain is known as food web.. SVV 40

41. SVV 41 Food Webs

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44. Ecological Pyramids The different species in a food chain are called tropic levels. Each food chain has 3 main trophic level : producer, consumer, and decomposers. Graphical representation of these trophic levels is called as Ecological Pyramids. The base of each pyramid represents the producers or the first trophic level while the apex represents tertiary or top level consumer. The three ecological pyramids that are usually studied are : pyramid of number; pyramid of biomass and pyramid of energy. SVV 44

45. Food Pyramid of Numbers A pyramid of numbers. shows the total number of individual organisms at each level in the food chain of an ecosystem. A pyramid of numbers does not always have a regular pyramid shape because it does not take into account the biomass of the organisms. Show the relationship between producers, herbivores, and carnivores at successive tropic levels in terms of their number. SVV 45

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47. Pyramid of Biomass The pyramid of biomass is usually determined by collecting all organisms occupying each trophic level separately and measuring their dry weight. This overcomes the size difference problem because all kinds of organisms at a trophic level are weighed. Each trophic level has a certain mass of living material at a particular time called the standing crop. In contrast, in many aquatic ecosystems, the pyramid of biomass may assume an inverted form. (In contrast, a pyramid of numbers for the aquatic ecosystem is upright) This is because the producers are tiny phytoplankton that grows and reproduces rapidly. SVV 47

48. Pyramid of Biomass SVV 48

49. Pyramid of Energy To compare the functional roles of the trophic levels in an ecosystem, an energy pyramid is most suitable. An energy pyramid represents the amount of energy at each trophic level and the loss of energy at each transfer to another . Hence the pyramid is always upward, with a large energy base at the bottom. The energy pyramid concept helps to explain the phenomenon of biological magnification. SVV 49

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51. Limitations of Food Pyramids SVV 51 It does not take into account the same species belonging to two or more trophic levels. Saprophytes are not given any place in ecological pyramids. It assumes a simple food chain and does not accommodate a food web.

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