Module-3.pdf

PALAWAN STATE UNIVERSITY College of Sciences BIO 106/L GENERAL ECOLOGY ENERGY FLOW IN ECOLOGICAL SYSTEM MODULE 3  Table of Contents Content Page Learning Objectives....................................

PALAWAN STATE UNIVERSITY College of Sciences BIO 106/L GENERAL ECOLOGY ENERGY FLOW IN ECOLOGICAL SYSTEM MODULE 3  Table of Contents Content Page Learning Objectives................................................ 3 Overview................................................................. 4 Initial Activity........................................................... 5 Discussion............................................................... 6 Learning Check....................................................... 23 Evaluation............................................................... 24 Rubrics................................................................... 25 Reflection................................................................ 26 References.............................................................. 27 2 2  Learning Objectives After going through in this module, you should be able to: ü LO1 Explain the fundamental concepts related to energy ü LO2 Construct a diagram showing the flow of energy in an ecosystem 3 3  Overview In the previous module, you learned about the structure and components of the environment. It is composed of both biotic and Abiotic components that interact together, forming a system. In this module, we will be discussing how the ecosystem continuously thrives from time to time. This module will tackle the fundamental concepts related to energy, solar radiation, and the energy in the environment, the concept of productivity, energy partitioning in food chains and food web, energy quality, and the ecological importance of photosynthesis in survival of an ecosystem. 4 4  Initial Activity Instruction: Complete the table below by listing the different biotic components of the ecosystem and come up with a simplified diagram of a food web. Producer Consumer Decomposer 1. Grass 1. Grasshopper 1. Bacteria and Fungi 1st trophic level 2nd trophic level 8th trophic level 5 5  Discussion Fundamental Concepts Related to Energy Energy is defined as the ability to do work. The following laws explain the behavior of energy: the first law of thermodynamics, or the law of conservation of energy, states that energy may be transformed from one form into another but is neither created nor destroyed. Light, for example, is a form of energy; it can be transformed into work, heat, or potential energy of food, depending on the situation, but none of it is destroyed. The second law of thermodynamics, or the law of entropy, may be stated in several ways, including the following: No process involving an energy transformation will spontaneously occur unless there is a degradation of energy from a concentrated form into a dispersed form. For example, heat in a hot object will spontaneously tend to become dispersed into cooler surroundings. The second law of thermodynamics may also be stated as follows: Because some energy is always dispersed into unavailable heat energy, no spontaneous transformation of energy (sunlight, for example) into potential energy (protoplasm, for example) is 100 percent efficient. 6 Entropy (from en = “in” and trope = “transformation”) is a measure of the unavailable energy resulting from transformations; the term is also used as a general index of the disorder associated with energy degradation. 6  Discussion Organisms, ecosystems, and the entire ecosphere possess the following essential thermodynamic characteristic: they can create and maintain a high state of internal order or a condition of low entropy (a low amount of disorder). Low entropy is achieved by continually and efficiently dissipating the energy of high utility (light or food, for example) into the energy of low utility (heat, for example). In the ecosystem, the order in a complex 7 biomass structure is maintained by the total community respiration. Which continually “pumps out disorder.” Accordingly, ecosystems and organisms are open, non-equilibrium thermodynamic systems that continuously exchange energy and matter with the environment to decrease internal entropy but increase external entropy (thus conforming to the laws of thermodynamics). 7  Discussion The fundamental concepts of thermodynamics are the most important natural laws that apply to all biological or ecological systems. So far as is known, no exceptions and no technological innovation can break these laws of physics. Any system of humankind or nature that does not conform to them is indeed doomed. The transfer of energy through the food chain of an ecosystem is termed the energy flow because, in accordance with the law of entropy, energy transformations are “ one way, “in contrast to the cyclic behavior of matter. Furthermore, energy quality, net energy, and an energy-based classification of ecosystems will be studied to demonstrate that energy is a common denominator for all kinds of systems, whether natural or designed by humans. Solar Radiation and the Energy Environment Organisms at or near the surface of the Earth are constantly irradiated by solar radiation and by long-wave thermal radiation from nearby surfaces. Both contribute to the climatic environment (temperature, evaporation of water, movement of air and water). Solar radiation reaching the surface of Earth consists of three components: visible light and two sensible components, short–wave ultraviolet and long-wave infrared. Because of its dilute, dispersed nature, only a tiny fraction (at most 5 percent) of visible light can be converted by photosynthesis into much more concentrated energy of organic matter for the biotic components of the ecosystem. 8 8  Discussion Figure 3. Spectral distribution of extraterrestrial solar radiation, of solar radiation at 9 the sea level on a clear day, of sunlight from a complete overcast, and of sunlight penetrating a stand of vegetation and diffuse light from the sky scattered by air molecules as distinguished from the direct radiation from the sun. Each curve represents the energy incident on a horizontal surface (Gates, 1965). 9  Discussion Extraterrestrial sunlight reaches the ionosphere at a rate of 2 gcal x cm-2 x min-1 (the solar constant)but is attenuated exponentially as it passes through the atmosphere; at most, 67 percent (1.34 gcal x cm -2 x min -1) may reach the surface level of the earth at sea level at noon on a clear summer day. Solar radiation is greatly altered as it passes through cloud cover, water, and vegetation. The daily input of sunlight to the autotrophic layer of an ecosystem averages about 300 to 4000 gcal/cm2 (=3000 to 4000 kcal/m2) for an area in the North temperature zone, such as the United States. The variation in total radiation flux between different strata of the ecosystem, and from one season or site to another surface of the Earth, is enormous, and the distribution of individual organisms responds accordingly. Concept of Productivity The primary productivity of an ecological system is defined as the rate at which radiant energy is converted by the photosynthetic and chemosynthetic activity of produces organisms (chiefly green plants) to organic substances. It is important to distinguish the four successive steps in the production process as follows: 1. Gross primary productivity (GPP) – The total rate of photosynthesis, including the organic matter used up in respiration during the period of measurement. This is also known as total photosynthesis. 2. Net primary productivity (NPP) – The rate of storage of organic matter in plant tissues that exceeds the respiratory use, R, by the plants during the period of measurement. This is also termed net assimilation. In practice, the amount of 10 plant respiration is usually added to the measurement of net primary productivity to estimate gross primary productivity (GPP = NPP = R). 10  Discussion Figure 4. World distribution of primary production in terms of annual gross production (103 kcal m-2 yr -1 of major ecosystem types (E.P. Odum 1963). 3. Net community productivity – The rate of storage of organic matter not used by heterotrophs ( net primary production minus heterotrophic consumption) during the period under consideration, usually the growing season or a year. 11 4. Secondary productivities – The rates of energy storage at consumer levels. Consumers use only food materials already produced with appropriate respiratory losses and convert this food energy to different tissues by one overall process. Secondary productivity should not be divided into gross and net amounts. The total energy flow at heterotrophic levels, which is analogous to the gross productivity of autotrophs, should be designated assimilation and not production. 11  Discussion In all these definitions, the terms productivity and the phrase rate of production may be used interchangeably. Even when the term production designates an amount of accumulated organic matter, a time element is always assumed or understood (for instance, a year in agricultural crop production). Thus, to avoid confusion, one should always state the time interval. In accordance with the second law of thermodynamics, the flow of energy decreases each step due to heat loss occurring with each transfer of energy from one to another. 12 Figure 5. Simplified energy flow diagram depicting three trophic levels in a linear food chain. Standard notations for successive energy flows are follows: La = Light absorbed by plant cover; GPP = gross primary production; A = total assimilation; NPP= net primary production; SP = secondary (consumer) production; NU = energy not consumed by next trophic level; E = energy not assimilated by consumers (egested); I = input (ingestion); B = standing crop biomass; and R = respiration. Bottom line in the diagram shows the order of magnitude of energy losses expected at major transfer points, starting with a solar input of 4000kcal per square meter per day. 12  Discussion High production rates, in both natural and cultured ecosystems, occur when physical factors are favorable, especially when energy subsidies (such as fertilizers) from outside the system enhance growth or reproduction rates within the system. Such energy subsidies may also be work of wind and rain in a forest, tidal energy in an estuary, or fossil fuels, animal, or human work energy used in cultivating a crop. In evaluating the productivity of an ecosystem, one must consider the nature and magnitude not only of the energy drains resulting from climates, harvest, pollution, and other stresses that divert energy away from the production process but also of the energy subsidies that enhance it by reducing the respiratory heat loss (the disorder pump-out) necessary to maintain biological structure. Photosynthesis is the process in which light energy is converted to chemical energy in the form of sugars. In a process driven by light energy, glucose molecules (or other sugars) are constructed from water and carbon dioxide, and oxygen is released as a by-product. The glucose molecules provide organisms with two crucial resources: energy and fixed—organic—carbon. Energy. The glucose molecules serve as fuel for cells: their chemical energy can be harvested through cellular respiration and fermentation, which generate adenosine triphosphate, a small, energy-carrying molecule—for the cell’s immediate energy needs. Fixed carbon. Carbon from carbon dioxide—inorganic carbon—can be incorporated into organic molecules; this process is called carbon fixation, and the carbon in organic molecules is also known as fixed carbon. The carbon that's fixed and incorporated into sugars during photosynthesis can be used to build other types of organic molecules needed by cells. 13 13  Discussion In photosynthesis, solar energy is harvested and converted to chemical energy in glucose using water and carbon dioxide. Oxygen is released as a by-product. Ecological importance of photosynthesis: Photosynthetic organisms, including plants, algae, and some bacteria, play a critical ecological role. They introduce chemical energy and fixed carbon into ecosystems by using light to synthesize sugars. Since these organisms produce their food—that is, fix their own carbon—using light energy, they are called photoautotrophs (literally, self-feeders that use light). Humans, and other organisms that can’t convert carbon dioxide to organic compounds themselves, are called heterotrophs, meaning different-feeders. Heterotrophs must get fixed carbon by eating other organisms or their by-products. Animals, fungi, and many prokaryotes and protists are heterotrophs. Photosynthesis also affects the makeup of the Earth’s atmosphere. Most photosynthetic organisms generate oxygen gas as a by-product, and the advent of photosynthesis—over 333 billion years ago, in bacteria resembling modern cyanobacteria—forever changed life on Earth. These bacteria gradually released oxygen into Earth’s oxygen-poor atmosphere. The increase in oxygen concentration has influenced the evolution of aerobic life forms—organisms that use oxygen for cellular respiration. Photosynthetic organisms also remove large quantities of carbon dioxide from the atmosphere and use carbon atoms to build organic molecules. Without Earth’s abundance of plants and algae to continually suck up carbon dioxide, the gas would build up in the atmosphere. Although photosynthetic organisms remove some of the 14 carbon dioxide produced by human activities, rising atmospheric levels are trapping heat and causing the climate to change. Many scientists believe that preserving forests and other expenses of vegetation are increasingly important to combat this rise in carbon dioxide levels. 14 Discussion 15 Figure 7. Leaf (Site photosynthesis in photosynthetic organism.) 15  Discussion At the level of the overall reactions, photosynthesis and cellular respiration are near- opposite processes. They differ only in the form of energy absorbed or released, as shown in the diagram below. Figure 8. Photosynthesis and Cellular Respiration process On a simplified level, photosynthesis and cellular respiration are opposite reactions to each other. In photosynthesis, solar energy is harvested as chemical energy in a 16 process that converts water and carbon dioxide to glucose. Oxygen is released as a by-product. In cellular respiration, oxygen is used to break down glucose, releasing chemical energy and heat in the process. Carbon dioxide and water are products of this reaction. 16  Discussion At the level of individual steps, photosynthesis isn't just cellular respiration that runs in reverse. Instead, as we'll see in the rest of this section, photosynthesis takes place in its own unique series of steps. However, there are some notable similarities between photosynthesis and cellular respiration. For instance, photosynthesis and cellular respiration both involve a series of redox reactions (reactions involving electron transfers). In cellular respiration, electrons flow from glucose to oxygen, forming water and releasing energy. In photosynthesis, they go the opposite direction, starting in water and winding up in glucose—an energy-requiring process powered by light. Energy Partitioning in Food Chains and Food Webs The transfer of food energy from its source in autotrophs (plants) through a series of organisms that consume and are consumed is termed the food chain. At each transfer, a proportion (often as high as 80 or 90 percent) of the potential energy is lost as heat. Therefore, the shorter the food chain or the nearer the organism to the producer or trophic level, the greater the energy available to that population. However, whereas the quantity of energy declines with each transfer, the quality or concentration of the transferred energy increases. Food chains are two basic types: (1) The grazing food chain, which, starting from the green plant base, goes to grazing herbivores (organisms eating living plant cells or tissues) and on to carnivores (animal eaters); and (2) the detritus food chain, which goes from non-living organic matter to microorganisms and then detritus-feeding organisms (detrivores) and their predators. Food chains are not isolated sequences; they are interconnected. The interlocking pattern is often spoken of as the food web (Figure). In complex natural communities, organisms whose nourishment is obtained from the sun through the 17 same number of steps are said to belong to the same trophic level. Thus, green plants occupy the first trophic level (the producer trophic level), Plant eaters (herbivores) occupy the second level (the primary consumer trophic level). Primary carnivores occupy the third level(the secondary consumer trophic level), and secondary carnivores occupy the fourth trophic level (the tertiary consumer trophic level). This trophic classification is one of function and not one of the species as such. A given species population may occupy one or more trophic levels according to the energy source actually assimilated. 17 Discussion 18 Figure 9. Typical food web for terrestrial ecosystem. 18  Discussion 19 Figure 10. Detritus food web based on mangrove leaves that fall into shallow estuarine waters. Leaf fragments acted on by saprotrophs and colonized by algae are eaten and re-eaten (copropagy) by a key group of small detritus consumers, which in turn provide the main food for game fish, herons, storks, and ibis (redrawn from W.E Odum and Heald 1975). 19  Discussion Energy Quality Energy has quality as well as quantity. Not all calories(or whatever unit of energy quantity is employed) are equal because equal quantities of different forms of energy vary widely in work potential. Highly concentrated forms of energy, such as fossil fuels, have a much higher quality than more dispersed forms of energy, such as sunlight. We can express quality or concentration in terms of the amount of one type of energy (such as sunlight) required to develop the same amount of another type (such as soil). The term eMergy (spelled with a capital M) has been proposed for this measure; eMergy can be defined in a general way as the sum of the available energy already used directly or indirectly to create a service or product. In comparing energy sources for direct use by humankind, one should consider the quality as well as the quantity of energy available and, wherever possible, match the quality of the source either the quality of the use. 20 20  Discussion 21 Figure 11. Diagram showing how increasing energy concentration (quality) accompanies decreasing energy quantity in (A) food chains, (B) energy flows, (C) electric energy generation, and (D) spatial energy concentration from input to output involves to 5 orders of magnitude (102).Data are in kcal/m2 (H.T Odum 1983, 1996). 21  Discussion Learning Enrichment To enrich your knowledge on how the energy flows in the ecological system of the earth: https://www.youtube.com/watch?v=QHh1DVeB5FI https://www.youtube.com/watch?v=Rnh7Pc24_fI https://www.youtube.com/watch?v=rC8TwL49RFA https://www.youtube.com/watch?v=iqK_PVK3svE https://www.youtube.com/watch?v=CsKZvVvTba4 https://www.youtube.com/watch?v=jzjx7zRvhQE https://www.youtube.com/watch?v=t9B8gGQtJzo https://www.youtube.com/watch?v=lnAKICtJIA4 NOTE:Watch this video for you to acquire additional information about the topics. 22 22  Learning Check Instruction: Answer the following questions. How energy flows in the ecosystem? ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ __________________________________________________ What will happen if environmental fluctuation occurs in an ecosystem? ___________________________________________________ ___________________________________________________ ___________________________________________________ 23 ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ 23  Evaluation Construct a diagram showing the flow of energy and discuss its role in an ecosystem. Discussion: _____________________________________________________ _____________________________________________________ _____________________________________________________ 24 _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ 24  Rubrics Mark Criteria 10 6-9 3-5 1-2 Integration of The model demonstrates The model demonstrates The model demonstrates The model does not knowledge that the student fully that the student, for the that the student, to a demonstrate that the understands the scientific most part, understands certain extent, understands student understands the concepts being utilized. the the scientific concepts being These concepts are scientific concepts being Scientific concepts are utilized. integrated and utilized. being utilized. contextualized into the These concepts, to a student’s own insights. certain extent, are integrated and contextualized into the student’s own insights. Clarity of content In-depth In-depth The student has omitted Cursory or hasty discussion and discussion and important components of discussion in all elaboration in elaboration in most the natural and man-made components of the natural all components of the components of the natural environments. and man-made natural and man-made and man-made environments. environments. environments. Clear and attractive Simple and very easy to Simple but not easy to tell Complex and Impossible to tell what illustration understand what what component is difficult to tell what component is being component is being illustrated. component is being illustrated. being illustrated. illustrated. 25 25  Reflection Energy flow is critical for ecological balance to be maintained. Food is synthesized by producers through the process of photosynthesis. Plants store a portion of the energy. The remainder of the energy is used by plants for growth and development. When primary consumers feed on producers, this stored energy is transferred to them. This energy is then passed on to secondary consumers who consume the primary consumers, and so forth. 26 26  References Book Angsalud, P.S.L. et al. Environment ScienceI 2014. Published by: Jimczyville Publication. ISBN 978-971-0161-37-9 (Available at College of Sciences- BPS Department) Berg, Linda R. Visualizing Environmental Science. Copyright at 2014,2011,2008 John Wiley & sons, INC. ISBN: 978-11181-69834 Botkin, Edward B., and Keller, Edward A. 1992. Environmental Science: Earth As a Living Planet Barker, T., Mortimer, M. &Perrings, Charles (2010). Biodiversity, Ecosystems and ecosystem Services. The Economics of Ecosystems and Biodiversity: The Ecological and Economic Foundation. Cunningham, W. P. & Cunningham, M. (2017). Environmental Science: A Global Concern. Mc Graw Hill Education. Fourteenth Edition (Downloadable at Google Classroom) Cunningham, W. P. & Cunningham, M. (2017). Principles of Environmental Science Inquiry & Application. Mc Graw Hill Education. Eighth Edition (Downloadable at Google Classroom) Hallare, A.V. 2001. General Ecology: Concepts and Selected Exercises. UP Manila @ Busybook Distributors: Manila Lee, Sergio J and Anes, Myrna L. 2008. Environmental Science: The Economy of Nature and Ecology of Man Odum, E.P. and G.W. Barret. 2005. Fundamentals of Ecology. 5th edition. Thomson Brooks/Cole: Singapore. Skinner, B. & Murch, B. (2011). The Blue Planet: An introduction to Earth System Science. John Wiley & Sons Inc., Third Edition. Internet 27 http://www.ecologyessays.com/ecosyst https://www.biotecharticles.com/Biology-Article/Technoecosystems-and-Modern- Conservation-Strategies-646.html https://www.encyclopedia.com/environment/energy-government-and-defense- magazines/ecosystem-diversity https://www.tutorialspoint.com/environmental_studies/environmental_studies_functions_ of_ecosystem.htm https://courses.lumenlearning.com/boundless-biology/chapter/energy-flow-through- ecosystems/ https://umich.instructure.com/courses/181737/files/6072083/download?verifier=sbMqBZ CGHIqlLKuz6a4gMZmewbTCqx8iH6yehR95&wrap=1 https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.2307/1937607 27