Trophic Ecology | Biology | Visionlearning

<!DOCTYPE html> <html lang="en" dir="ltr"> <head>  <meta http-equiv="X-UA-Compatible" content="ie=edge"> <meta charset="utf-8"> <base href="https://www.visionlearning.com"> <title>Trophic Ecology | Biology | Visionlearning</title> <link rel="canonical" href="https://www.visionlearning.com/en/library/biology/2/trophic-ecology/293"> <meta name="description" content="Trophic ecology is the study of feeding relationship structures between organisms in a community. This module explores how scientists use various models like food chains and food webs to understand feeding relationships. We’ll also explore how scientists have tested theories on food chain and web length and how the different levels of a feeding structure interact to help define an ecosystem."> <meta name="keywords" content="ecosystem, food chain, food web, omnivore, herbivore, carnivore, ecosystem"> <meta name="viewport" content="width=device-width, initial-scale=1.0, shrink-to-fit=no"> <meta name="msvalidate.01" content="D8E20F39AD48052260032E56DE409970"> <script type="application/ld+json"> { "@context": "http://schema.org/", "@type": "Article", "mainEntityOfPage": { "@type": "WebPage", "@id": "https://visionlearning.com/en/library/biology/2/trophic-ecology/293" }, "name": "Trophic Ecology", "headline": "Trophic Ecology: Feeding relationships and energy transfer", "author": { "@type": "Person", "name": "Devin Reese, PhD." }, "datePublished": "2024-03-15 10:06:42", "dateModified": "2017-02-12T08:30:00+05:00", "image": { "@type": "ImageObject", "url": "/img/library/moduleImages/mod-image-293.jpg", "width": 696, "height": 464 }, "publisher": { "@type": "Organization", "name": "Visionlearning, Inc.", "logo": { "@type": "ImageObject", "url": "http://visionlearning.com/images/logo.png", "width": 278, "height": 60 } }, "description": "Trophic ecology is the study of feeding relationship structures between organisms in a community. This module explores how scientists use various models like food chains and food webs to understand feeding relationships. We’ll also explore how scientists have tested theories on food chain and web length and how the different levels of a feeding structure interact to help define an ecosystem.", "keywords": "ecosystem, food chain, food web, omnivore, herbivore, carnivore, ecosystem", "inLanguage": { "@type": "Language", "name": "English", "alternateName": "en" }, "copyrightHolder": { "@type": "Organization", "name": "Visionlearning, Inc." }, "copyrightYear": "2024"} </script> <meta property="og:url" content="https://visionlearning.com/en/library/biology/2/trophic-ecology/293"> <meta property="og:title" content="Trophic Ecology | Biology | Visionlearning" /> <meta property="og:type" content="website"> <meta property="og:site_name" content="Visionlearning"> <meta property="og:description" content="Trophic ecology is the study of feeding relationship structures between organisms in a community. This module explores how scientists use various models like food chains and food webs to understand feeding relationships. We’ll also explore how scientists have tested theories on food chain and web length and how the different levels of a feeding structure interact to help define an ecosystem."> <meta property="og:image" content="https://visionlearning.com/images/logo.png"> <meta property="fb:admins" content="100000299664514"> <link rel="stylesheet" type="text/css" href="/css/visionlearning.css">  <link rel="stylesheet" type="text/css" href="/css/visionlearning-icons.css">  <link rel="preload" href="https://fonts.gstatic.com"> <link rel="preload" href="https://fonts.googleapis.com/css2?family=Open+Sans:ital,wght@0,400;0,700;1,400;1,700&family=Schoolbell&display=swap"> <style> textarea.myEditor { width: 90%; height: 350px; } </style> <script type="text/x-mathjax-config" src="/js/mathjax-config.js"></script> <script id="MathJax-script" async src="/js/mathjax/tex-svg.js"></script> <script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-9561344156007092" 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<li><a href="/en/library/environmental-science/61/ecosystem-services/279">Ecosystem Services</a></li> <li><a href="/en/library/environmental-science/61/population-biology/287">Population Biology</a></li> </ul> </div> <button class="accordion__button" id="acc-button-earth-cycles" data-accordion="button" aria-controls="acc-panel-earth-cycles" aria-expanded="false"> <span class="accordion__button__label"> Earth Cycles </span> </button> <div class="accordion__panel" id="acc-panel-earth-cycles" data-accordion="panel" aria-labelledby="acc-button-earth-cycles" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/environmental-science/61/the-nitrogen-cycle/98">The Nitrogen Cycle</a></li> <li><a href="/en/library/environmental-science/61/the-carbon-cycle/95">The Carbon Cycle</a></li> <li><a href="/en/library/environmental-science/61/the-phosphorus-cycle/197">The Phosphorus Cycle</a></li> </ul> </div> <button class="accordion__button" id="acc-button-scientific-research" data-accordion="button" aria-controls="acc-panel-scientific-research" aria-expanded="false"> <span class="accordion__button__label"> Scientific Research </span> </button> <div class="accordion__panel" id="acc-panel-scientific-research" data-accordion="panel" aria-labelledby="acc-button-scientific-research" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/environmental-science/61/collaborative-research-in-the-arctic-towards-understanding-climate-change/183">Collaborative Research in the Arctic Towards Understanding Climate Change</a></li> <li><a href="/en/library/environmental-science/61/atmospheric-chemistry-research-that-changed-global-policy/211">Atmospheric Chemistry Research that Changed Global Policy</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-general-science" data-accordion="button" aria-controls="acc-panel-general-science" aria-expanded="false"> <span class="accordion__button__label"> General Science </span> </button> <div class="accordion__panel" id="acc-panel-general-science" data-accordion="panel" aria-labelledby="acc-button-general-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-methods" data-accordion="button" aria-controls="acc-panel-methods" aria-expanded="false"> <span class="accordion__button__label"> Methods </span> </button> <div class="accordion__panel" id="acc-panel-methods" data-accordion="panel" aria-labelledby="acc-button-methods" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/the-scientific-method/45">The Scientific Method</a></li> </ul> </div> <button class="accordion__button" id="acc-button-measurement" data-accordion="button" aria-controls="acc-panel-measurement" aria-expanded="false"> <span class="accordion__button__label"> Measurement </span> </button> <div class="accordion__panel" id="acc-panel-measurement" data-accordion="panel" aria-labelledby="acc-button-measurement" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/the-metric-system/47">The Metric System</a></li> </ul> </div> <button class="accordion__button" id="acc-button-physical-properties" data-accordion="button" aria-controls="acc-panel-physical-properties" aria-expanded="false"> <span class="accordion__button__label"> Physical Properties </span> </button> <div class="accordion__panel" id="acc-panel-physical-properties" data-accordion="panel" aria-labelledby="acc-button-physical-properties" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/temperature/48">Temperature</a></li> <li><a href="/en/library/general-science/3/density-and-buoyancy/37">Density and Buoyancy</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-math-in-science" data-accordion="button" aria-controls="acc-panel-math-in-science" aria-expanded="false"> <span class="accordion__button__label"> Math in Science </span> </button> <div class="accordion__panel" id="acc-panel-math-in-science" data-accordion="panel" aria-labelledby="acc-button-math-in-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-equations" data-accordion="button" aria-controls="acc-panel-equations" aria-expanded="false"> <span class="accordion__button__label"> Equations </span> </button> <div class="accordion__panel" id="acc-panel-equations" data-accordion="panel" aria-labelledby="acc-button-equations" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/unit-conversion/144">Unit Conversion</a></li> <li><a href="/en/library/math-in-science/62/linear-equations/194">Linear Equations</a></li> <li><a href="/en/library/math-in-science/62/exponential-equations-i/206">Exponential Equations I</a></li> <li><a href="/en/library/math-in-science/62/exponential-equations-ii/210">Exponential Equations II</a></li> <li><a href="/en/library/math-in-science/62/scientific-notation/250">Scientific Notation</a></li> <li><a href="/en/library/math-in-science/62/measurement/257">Measurement</a></li> </ul> </div> <button class="accordion__button" id="acc-button-statistics" data-accordion="button" aria-controls="acc-panel-statistics" aria-expanded="false"> <span class="accordion__button__label"> Statistics </span> </button> <div class="accordion__panel" id="acc-panel-statistics" data-accordion="panel" aria-labelledby="acc-button-statistics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/introduction-to-descriptive-statistics/218">Introduction to Descriptive Statistics</a></li> <li><a href="/en/library/math-in-science/62/introduction-to-inferential-statistics/224">Introduction to Inferential Statistics</a></li> <li><a href="/en/library/math-in-science/62/statistical-techniques/239">Statistical Techniques</a></li> </ul> </div> <button class="accordion__button" id="acc-button-trigonometric-functions" data-accordion="button" aria-controls="acc-panel-trigonometric-functions" aria-expanded="false"> <span class="accordion__button__label"> Trigonometric Functions </span> </button> <div class="accordion__panel" id="acc-panel-trigonometric-functions" data-accordion="panel" aria-labelledby="acc-button-trigonometric-functions" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/wave-mathematics/131">Wave Mathematics</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-physics" data-accordion="button" aria-controls="acc-panel-physics" aria-expanded="false"> <span class="accordion__button__label"> Physics </span> </button> <div class="accordion__panel" id="acc-panel-physics" data-accordion="panel" aria-labelledby="acc-button-physics" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-light-and-optics" data-accordion="button" aria-controls="acc-panel-light-and-optics" aria-expanded="false"> <span class="accordion__button__label"> Light and Optics </span> </button> <div class="accordion__panel" id="acc-panel-light-and-optics" data-accordion="panel" aria-labelledby="acc-button-light-and-optics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/physics/24/the-nature-of-light/132">The Nature of Light</a></li> <li><a href="/en/library/physics/24/electromagnetism-and-light/138">Electromagnetism and Light</a></li> </ul> </div> <button class="accordion__button" id="acc-button-mechanics" data-accordion="button" aria-controls="acc-panel-mechanics" aria-expanded="false"> <span class="accordion__button__label"> Mechanics </span> </button> <div class="accordion__panel" id="acc-panel-mechanics" data-accordion="panel" aria-labelledby="acc-button-mechanics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/physics/24/defining-energy/199">Defining Energy</a></li> <li><a href="/en/library/physics/24/waves-and-wave-motion/102">Waves and Wave Motion</a></li> <li><a href="/en/library/physics/24/gravity/118">Gravity</a></li> <li><a href="/en/library/physics/24/thermodynamics-i/200">Thermodynamics I</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-process-of-science" data-accordion="button" aria-controls="acc-panel-process-of-science" aria-expanded="false"> <span class="accordion__button__label"> Process of Science </span> </button> <div class="accordion__panel" id="acc-panel-process-of-science" data-accordion="panel" aria-labelledby="acc-button-process-of-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-introduction" data-accordion="button" aria-controls="acc-panel-introduction" aria-expanded="false"> <span class="accordion__button__label"> Introduction </span> </button> <div class="accordion__panel" id="acc-panel-introduction" data-accordion="panel" aria-labelledby="acc-button-introduction" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-process-of-science/176">The Process of Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-the-culture-of-science" data-accordion="button" aria-controls="acc-panel-the-culture-of-science" aria-expanded="false"> <span class="accordion__button__label"> The Culture of Science </span> </button> <div class="accordion__panel" id="acc-panel-the-culture-of-science" data-accordion="panel" aria-labelledby="acc-button-the-culture-of-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-nature-of-scientific-knowledge/185">The Nature of Scientific Knowledge</a></li> <li><a href="/en/library/process-of-science/49/scientists-and-the-scientific-community/172">Scientists and the Scientific Community</a></li> <li><a href="/en/library/process-of-science/49/scientific-ethics/161">Scientific Ethics</a></li> <li><a href="/en/library/process-of-science/49/scientific-institutions-and-societies/162">Scientific Institutions and Societies</a></li> </ul> </div> <button class="accordion__button" id="acc-button-ideas-in-science" data-accordion="button" aria-controls="acc-panel-ideas-in-science" aria-expanded="false"> <span class="accordion__button__label"> Ideas in Science </span> </button> <div class="accordion__panel" id="acc-panel-ideas-in-science" data-accordion="panel" aria-labelledby="acc-button-ideas-in-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/theories-hypotheses-and-laws/177">Theories, Hypotheses, and Laws</a></li> <li><a href="/en/library/process-of-science/49/scientific-controversy/181">Scientific Controversy</a></li> <li><a href="/en/library/process-of-science/49/creativity-in-science/182">Creativity in Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-research-methods" data-accordion="button" aria-controls="acc-panel-research-methods" aria-expanded="false"> <span class="accordion__button__label"> Research Methods </span> </button> <div class="accordion__panel" id="acc-panel-research-methods" data-accordion="panel" aria-labelledby="acc-button-research-methods" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-practice-of-science/148">The Practice of Science</a></li> <li><a href="/en/library/process-of-science/49/experimentation-in-scientific-research/150">Experimentation in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/description-in-scientific-research/151">Description in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/comparison-in-scientific-research/152">Comparison in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/modeling-in-scientific-research/153">Modeling in Scientific Research</a></li> </ul> </div> <button class="accordion__button" id="acc-button-data" data-accordion="button" aria-controls="acc-panel-data" aria-expanded="false"> <span class="accordion__button__label"> Data </span> </button> <div class="accordion__panel" id="acc-panel-data" data-accordion="panel" aria-labelledby="acc-button-data" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/data-analysis-and-interpretation/154">Data Analysis and Interpretation</a></li> <li><a href="/en/library/process-of-science/49/uncertainty-error-and-confidence/157">Uncertainty, Error, and Confidence</a></li> <li><a href="/en/library/process-of-science/49/statistics-in-science/155">Statistics in Science</a></li> <li><a href="/en/library/process-of-science/49/using-graphs-and-visual-data-in-science/156">Using Graphs and Visual Data in Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-scientific-communication" data-accordion="button" aria-controls="acc-panel-scientific-communication" aria-expanded="false"> <span class="accordion__button__label"> Scientific Communication </span> </button> <div class="accordion__panel" id="acc-panel-scientific-communication" data-accordion="panel" aria-labelledby="acc-button-scientific-communication" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/understanding-scientific-journals-and-articles/158">Understanding Scientific Journals and Articles</a></li> <li><a href="/en/library/process-of-science/49/utilizing-the-scientific-literature/173">Utilizing the Scientific Literature</a></li> <li><a href="/en/library/process-of-science/49/peer-review-in-scientific-publishing/159">Peer Review in Scientific Publishing</a></li> <li><a href="/en/library/process-of-science/49/the-how-and-why-of-scientific-meetings/186">The How and Why of Scientific Meetings</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-scientists-and-research" data-accordion="button" aria-controls="acc-panel-scientists-and-research" aria-expanded="false"> <span class="accordion__button__label"> Scientists and Research </span> </button> <div class="accordion__panel" id="acc-panel-scientists-and-research" data-accordion="panel" aria-labelledby="acc-button-scientists-and-research" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-scientific-research" data-accordion="button" aria-controls="acc-panel-scientific-research" aria-expanded="false"> <span class="accordion__button__label"> Scientific Research </span> </button> <div class="accordion__panel" id="acc-panel-scientific-research" data-accordion="panel" aria-labelledby="acc-button-scientific-research" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/scientists-and-research/58/collaborative-research-in-the-arctic-towards-understanding-climate-change/183">Collaborative Research in the Arctic Towards Understanding Climate Change</a></li> <li><a href="/en/library/scientists-and-research/58/from-stable-chromosomes-to-jumping-genes/184">From Stable Chromosomes to Jumping Genes</a></li> <li><a href="/en/library/scientists-and-research/58/an-elegant-experiment-to-test-the-process-of-dna-replication/187">An Elegant Experiment to Test the Process of DNA Replication</a></li> <li><a href="/en/library/scientists-and-research/58/the-founding-of-neuroscience/233">The Founding of Neuroscience</a></li> <li><a href="/en/library/scientists-and-research/58/tracking-endangered-jaguars-across-the-border/189">Tracking Endangered Jaguars across the Border</a></li> <li><a href="/en/library/scientists-and-research/58/atmospheric-chemistry-research-that-changed-global-policy/211">Atmospheric Chemistry Research that Changed Global Policy</a></li> <li><a href="/en/library/scientists-and-research/58/revolutionizing-medicine-with-monoclonal-antibodies/220">Revolutionizing Medicine with Monoclonal Antibodies</a></li> <li><a href="/en/library/scientists-and-research/58/uncovering-the-mysteries-of-chronic-mountain-sickness/238">Uncovering the Mysteries of Chronic Mountain Sickness</a></li> </ul> </div> <button class="accordion__button" id="acc-button-profiles-in-science" data-accordion="button" aria-controls="acc-panel-profiles-in-science" aria-expanded="false"> <span class="accordion__button__label"> Profiles in Science </span> </button> <div class="accordion__panel" id="acc-panel-profiles-in-science" data-accordion="panel" aria-labelledby="acc-button-profiles-in-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/scientists-and-research/58/luis-e.-miramontes/232">Luis E. Miramontes</a></li> <li><a href="/en/library/scientists-and-research/58/bernardo-houssay/237">Bernardo Houssay</a></li> <li><a href="/en/library/scientists-and-research/58/craig-lee/256">Craig Lee</a></li> <li><a href="/en/library/scientists-and-research/58/david-ho/241">David Ho</a></li> <li><a href="/en/library/scientists-and-research/58/louis-tompkins-wright/244">Louis Tompkins Wright</a></li> <li><a href="/en/library/scientists-and-research/58/carlos-j.-finlay/217">Carlos J. Finlay</a></li> <li><a href="/en/library/scientists-and-research/58/cecilia-payne/290">Cecilia Payne</a></li> <li><a href="/en/library/scientists-and-research/58/jazmin-scarlett/291">Jazmin Scarlett</a></li> <li><a href="/en/library/scientists-and-research/58/ramari-stewart/292">Ramari Stewart</a></li> <li><a href="/en/library/scientists-and-research/58/johnson-cerda/300">Johnson Cerda</a></li> <li><a href="/en/library/scientists-and-research/58/ellen-ochoa/201">Ellen Ochoa</a></li> <li><a href="/en/library/scientists-and-research/58/ruth-benerito/205">Ruth Benerito</a></li> <li><a href="/en/library/scientists-and-research/58/franklin-chang-díaz/219">Franklin Chang Díaz</a></li> <li><a href="/en/library/scientists-and-research/58/percy-lavon-julian/221">Percy Lavon Julian</a></li> <li><a href="/en/library/scientists-and-research/58/luis-walter-alvarez/229">Luis Walter Alvarez</a></li> <li><a href="/en/library/scientists-and-research/58/france-anne-dominic-córdova/230">France Anne-Dominic Córdova</a></li> </ul> </div> </div> </div> </div> </div> </li> <li>  <button class="button" data-toggle="dropdown">Biology </button> <div class="nav__dropdown box-shadow-1 padding-1"> <div class="accordion accordion--secondary font-size-sm"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-sub-button-biological-molecules" data-accordion="button" aria-controls="acc-sub-panel-biological-molecules" aria-expanded="false"> <span class="accordion__button__label"> Biological Molecules </span> </button> <div class="accordion__panel" id="acc-sub-panel-biological-molecules" data-accordion="panel" aria-labelledby="acc-sub-button-biological-molecules" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/biology/2/carbohydrates/61">Carbohydrates</a></li> <li><a href="/en/library/biology/2/fats-and-proteins/62">Fats and Proteins</a></li> <li><a href="/en/library/biology/2/biological-proteins/243">Biological Proteins</a></li> <li><a href="/en/library/biology/2/blood-biology-i/242">Blood Biology I</a></li> <li><a href="/en/library/biology/2/lipids/207">Lipids</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-cell-biology" data-accordion="button" aria-controls="acc-sub-panel-cell-biology" aria-expanded="false"> <span class="accordion__button__label"> Cell Biology </span> </button> <div class="accordion__panel" id="acc-sub-panel-cell-biology" data-accordion="panel" aria-labelledby="acc-sub-button-cell-biology" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/biology/2/discovery-and-structure-of-cells/64">Discovery and Structure of Cells</a></li> <li><a href="/en/library/biology/2/respiration/285">Respiration</a></li> <li><a href="/en/library/biology/2/membranes-i/198">Membranes I</a></li> <li><a href="/en/library/biology/2/membranes-ii/204">Membranes II</a></li> <li><a href="/en/library/biology/2/cellular-organelles-i/195">Cellular Organelles I</a></li> <li><a href="/en/library/biology/2/cell-division-i/196">Cell Division I</a></li> <li><a href="/en/library/biology/2/cell-division-ii/212">Cell Division II</a></li> <li><a href="/en/library/biology/2/membranes-and-chemical-transport/106">Membranes and Chemical Transport</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-energy-in-living-systems" data-accordion="button" aria-controls="acc-sub-panel-energy-in-living-systems" aria-expanded="false"> <span class="accordion__button__label"> Energy in Living Systems </span> </button> <div class="accordion__panel" id="acc-sub-panel-energy-in-living-systems" data-accordion="panel" aria-labelledby="acc-sub-button-energy-in-living-systems" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/biology/2/energy-metabolism-i/215">Energy Metabolism I</a></li> <li><a href="/en/library/biology/2/energy-metabolism-ii/225">Energy Metabolism II</a></li> <li><a href="/en/library/biology/2/photosynthesis-i/192">Photosynthesis I</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-evolutionary-biology" data-accordion="button" aria-controls="acc-sub-panel-evolutionary-biology" aria-expanded="false"> <span class="accordion__button__label"> Evolutionary Biology </span> </button> <div class="accordion__panel" id="acc-sub-panel-evolutionary-biology" data-accordion="panel" aria-labelledby="acc-sub-button-evolutionary-biology" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/biology/2/origins-of-life-i/226">Origins of Life I</a></li> <li><a href="/en/library/biology/2/origins-of-life-ii/227">Origins of Life II</a></li> <li><a href="/en/library/biology/2/extinction/295">Extinction</a></li> <li><a href="/en/library/biology/2/mass-extinctions/294">Mass Extinctions</a></li> <li><a href="/en/library/biology/2/charles-darwin-i/110">Charles Darwin I</a></li> <li><a href="/en/library/biology/2/charles-darwin-ii/111">Charles Darwin II</a></li> <li><a href="/en/library/biology/2/charles-darwin-iii/112">Charles Darwin III</a></li> <li><a href="/en/library/biology/2/adaptation/68">Adaptation</a></li> <li><a href="/en/library/biology/2/taxonomy-i/70">Taxonomy I</a></li> <li><a href="/en/library/biology/2/taxonomy-ii/89">Taxonomy II</a></li> <li><a href="/en/library/biology/2/introduction-to-paleoanthropology/258">Introduction to Paleoanthropology</a></li> <li><a href="/en/library/biology/2/the-piltdown-hoax/263">The Piltdown Hoax</a></li> <li><a href="/en/library/biology/2/future-of-human-evolution/259">Future of Human Evolution</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-genetics" data-accordion="button" aria-controls="acc-sub-panel-genetics" aria-expanded="false"> <span class="accordion__button__label"> Genetics </span> </button> <div class="accordion__panel" id="acc-sub-panel-genetics" data-accordion="panel" 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data-accordion="panel" aria-labelledby="acc-sub-button-ecology" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/biology/2/biodiversity-i/276">Biodiversity I</a></li> <li><a href="/en/library/biology/2/ecosystem-services/279">Ecosystem Services</a></li> <li><a href="/en/library/biology/2/animal-ecology/283">Animal Ecology</a></li> <li><a href="/en/library/biology/2/biodiversity-ii/281">Biodiversity II</a></li> <li><a href="/en/library/biology/2/animal-behavior/286">Animal Behavior</a></li> <li><a href="/en/library/biology/2/population-biology/287">Population Biology</a></li> <li class="current">Trophic Ecology</li> </ul> </div> </div> </div> </div> </li> </ul> </nav>  <div id="theTop"></div> <main id="skip-header-content"> <div class="margin-bottom-5"> <article class="container wide module"> <header class="grid grid--sidebar-right module__header"> <div class="module__header__title"> <span class="subcategory"> <strong><em>Ecology</em></strong> </span> <h1>Trophic Ecology: <sub><em>Feeding relationships and energy transfer</em></sub></h1> <p class="byline">by Devin Reese, PhD.</p> <nav class="module__header__tabs"> <ul class="tabs-nav tabs-nav--horizontal library"> <li> <a href="/en/library/biology/2/trophic-ecology/293/reading" aria-current="page" >Reading</a> </li> <li> <a href="/en/library/biology/2/trophic-ecology/293/quiz">Quiz</a> </li> <li> <a href="/en/library/biology/2/trophic-ecology/293/resources">Teach with this</a> </li> </ul> </nav> </div> </header> <hr class="divider"/>   <div class="grid grid--sidebar-right grid--divider"> <div class="order-2 order-1--lg module__main"> <div class="narrow margin-x-auto margin-y-5"> <div class="accordion margin-bottom-5">  <button class="accordion__button" id="acc-button-key-concepts" data-accordion="button" aria-controls="acc-panel-key-concepts" aria-expanded="true" tabindex="0"> Did you know? </button> <div class="accordion__panel shown show" id="acc-panel-key-concepts" data-accordion="panel" aria-labelledby="acc-button-key-concepts" role="region"> <div class="accordion__panel__content"> <p>Did you know that by removing blackbirds from a meadow ecosystem, you can disrupt the entire community? Even nonliving disturbances, like tornadoes and hurricanes, can significantly alter the relationships in a community. Through the study of trophic ecology, scientists are gaining a greater understanding of how feeding structures work and what impacts them most.</p> </div> </div>  <button class="accordion__button" id="acc-button-terms-you-should-know" data-accordion="button" aria-controls="acc-panel-terms-you-should-know" aria-expanded="false" tabindex="0"> Terms you should know </button> <div class="accordion__panel" id="acc-panel-terms-you-should-know" data-accordion="panel" aria-labelledby="acc-button-terms-you-should-know" role="region" aria-hidden="true"> <div class="accordion__panel__content"> <dl> <dt><a href="/en/glossary/view/photosynthesis">photosynthesis </a></dt> <dd> The process through which plants use sunlight, hydrogen, and carbon dioxide to create oxygen and energy in the form of sugar. </dd> <dt>carnivore </dt> <dd> An organism that feeds primarily on other animals. </dd> <dt>herbivore </dt> <dd> An organism that feeds primarily on plants. </dd> <dt>omnivore </dt> <dd> An organism that feeds on both plants and animals. </dd> <dt><a href="/en/glossary/view/ecosystem">ecosystem </a></dt> <dd> A complex of a community of organisms and its environment, functioning as a unit. </dd> <dt>metabolize </dt> <dd> The biochemical process of an organism converting food into energy used in other biological processes. </dd> <dt><a href="/en/glossary/view/matter">matter </a></dt> <dd> The substance that makes up physical objects. </dd> <dt><a href="/en/glossary/view/variable">variable </a></dt> <dd> A condition or parameter that may be manipulated, fixed, measured, or observed during scientific research.</dd> </dl> </div> </div> </div> <hr class="border-color-dark" /> <section> <div class="container narrow"> <p>A worm wiggles through the brush, eating little bits of oak leaves. Just as we get closer for a look, a robin swoops in and snaps up the worm in its beak. As the robin swallows the worm, a Cooper’s hawk flies down and catches the bird in its claws. Watching the hawk fly off with the unlucky bird, we wonder whether the hawk will get nutrition not only from the bird, but also from the worm and the leaf <mark class="term" data-term="matter" data-term-def="The substance that makes up physical objects." data-term-url="/en/glossary/view/matter/8264">matter</mark> it ate.</p> <p><section id="toc_1" class=""> <h2>Food chains: Understanding basic feeding relationships</h2></p> <p>A “community” is a <mark class="term" data-term="group" data-term-def="A column of elements in the periodic table." data-term-url="/en/glossary/view/group/8566">group</mark> of <mark class="term" data-term="organism" data-term-def="Any connected living system, such as an animal, plant, fungus, or bacterium. Organisms may be composed of a single cell or&hellip;" data-term-url="/en/glossary/view/organism/2171">organisms</mark> living in the same area and interacting with each other. The oak tree, the worm, the robin, and the Cooper’s hawk are all members of a meadow community. How they interact is largely shaped by what they eat. As English ecologist Charles Elton put it, “Food is the burning question in animal <mark class="term" data-term="society" data-term-def="A group of people who belong to an organization that has been formed because of shared interest in a specific field." data-term-url="/en/glossary/view/society/8249">society</mark>, and the whole structure… of the community is based on the food supply.” (1927).</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox=""> <img src="/img/library/modules/mid293/Image/VLObject13212-24031510030213.png" alt="Figure 1: Meadow community food chain showing feeding relationships with arrows pointing in the direction of the eaters." /> </button> <figcaption> <p><strong>Figure 1:</strong> Meadow community food chain showing feeding relationships with arrows pointing in the direction of the eaters.</p> <span class="credit">image ©Visionlearning</span> </figcaption> </figure> </div> <p>Elton coined the term “food chain” to describe a linear sequence of feeding relationships in a community. Figure 1 shows just one of the many food chains you could encounter in a natural meadow or urban grassy patch. Decaying material in the <mark class="term" data-term="soil" data-term-def="The loose top layer of Earth’s surface where plants grow, made up of particles of rocks, minerals, and organic material." data-term-url="/en/glossary/view/soil/8563">soil</mark> is eaten by earthworms, which are eaten by ground-feeding birds, which are preyed on by hawks. Wherever different <mark class="term" data-term="species" data-term-def="1. In biological classifications, it is the lowest and most basic unit of the Linnaean taxonomic hierarchy (although it is also&hellip;" data-term-url="/en/glossary/view/species/893">species</mark> co-exist, there are food chains. Elton recognized that these feeding relationships are largely what structure communities.</p> <p>Elton was by no <mark class="term" data-term="mean" data-term-def="In statistics, mean commonly refers to the arithmetic mean, also called the average, which is one measure of the mid-point of&hellip;" data-term-url="/en/glossary/view/mean/4221">means</mark> the first to recognize the feeding relationships that shape community interactions. Forty years earlier, American entomologist Stephen Forbes published “The Lake as a Microcosm,” (Forbes, 1887). In his paper, Forbes described how the “animals of such a body of water are …closely related among themselves in all their interests.” And even before Forbes, Native American ways of life involved an understanding of the feeding relationships in the <mark class="term" data-term="ecosystem" data-term-def="The complex of a community of organisms and its environment, functioning as a unit." data-term-url="/en/glossary/view/ecosystem/2174">ecosystems</mark> they inhabited, a necessity for living sustainably with the <mark class="term" data-term="organism" data-term-def="Any connected living system, such as an animal, plant, fungus, or bacterium. Organisms may be composed of a single cell or&hellip;" data-term-url="/en/glossary/view/organism/2171">organisms</mark> around them.</p><blockquote class="blockquote-hanging"> <p>Many tribes were agriculturists, while others were more migratory and prolific hunters/fishers and gatherers.</p> <cite> <strong>Mark Ford,</strong> Chiricahua Apache and Tewa/Tiwa, 2021 </cite></p></blockquote><p>Elton formalized the term “trophic relationships,” or feeding relationships (trophic = related to feeding, from the Greek word for food). Every <mark class="term" data-term="organism" data-term-def="Any connected living system, such as an animal, plant, fungus, or bacterium. Organisms may be composed of a single cell or&hellip;" data-term-url="/en/glossary/view/organism/2171">organism</mark> can be assigned to a “trophic level,” or feeding level relative to other <mark class="term" data-term="species" data-term-def="1. In biological classifications, it is the lowest and most basic unit of the Linnaean taxonomic hierarchy (although it is also&hellip;" data-term-url="/en/glossary/view/species/893">species</mark> of organism in its community.</p> <p>For example, as shown in the meadow food chain pictured in Figure 1, plants form the <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">base</mark> level of every community on dry land. On the next level above plants are herbivores like worms, which are eaten by carnivores. There can be multiple levels of carnivores. For instance, primary carnivores, such as blackbirds, eat herbivores, while secondary carnivores, such as hawks, eat the primary carnivores. The animals at the very top of a food chain are called top predators or “apex predators.”</p> <p>Knowing this, why do you think photosynthesizers are at the base of the food chain?</p> <p>To answer that question, consider what would happen if you removed plants from the food chain in Figure 1. Through <mark class="term" data-term="photosynthesis" data-term-def="Formation of carbohydrates from carbon dioxide and a source of hydrogen (as water) in the chlorophyll-containing tissues of plants exposed to light." data-term-url="/en/glossary/view/photosynthesis/2194">photosynthesis</mark>, plants harvest <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> from the sun to produce energy-rich <mark class="term" data-term="organic" data-term-def="Originating from a living organism; a compound that contains hydrocarbons." data-term-url="/en/glossary/view/organic/8530">organic</mark> <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecules</mark> such as <mark class="term" data-term="sugar" data-term-def="A water-soluble crystalline carbohydrate. There are many types of sugar of varying degrees of sweetness, including fructose, which occurs naturally in&hellip;" data-term-url="/en/glossary/view/sugar/5309">sugar</mark>, which then feed the other organisms in the chain (see our module <a href="https://www.visionlearning.com/en/library/Biology/2/Photosynthesis-I/192">Photosynthesis I: Harnessing the energy of the sun</a>). No plants <mark class="term" data-term="mean" data-term-def="In statistics, mean commonly refers to the arithmetic mean, also called the average, which is one measure of the mid-point of&hellip;" data-term-url="/en/glossary/view/mean/4221">mean</mark> less food for worms. Fewer worms result in less food for blackbirds, meaning less food for hawks, and so on.</p> <p>Since plants and other photosynthetic organisms don’t have to eat to gain energy, they are called “autotrophs” (or producers, since they produce their own food). Organisms that must eat other organisms to get energy are called “heterotrophs” (or consumers).</p> <p>In the food chain pictured in Figure 2, which organisms are autotrophs and which are heterotrophs?</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox=""> <img src="/img/library/modules/mid293/Image/VLObject13208-24031310030357.jpg" alt="Figure 2: Depiction of a river food chain." /> </button> <figcaption> <p><strong>Figure 2:</strong> Depiction of a river food chain.</p> <span class="credit">image ©<a href="https://commons.wikimedia.org/wiki/File:Figure_46_01_03.jpg"> Adapted from CC BY 4.0 DEED CNX OpenStax</a> </span> </figcaption> </figure> </div> <p>In <mark class="term" data-term="terrestrial" data-term-def="In Environmental Science: related to, located on, or living on land. Not aquatic. <br> <br> In Astronomy: related to or occurring on Earth. Not&hellip;" data-term-url="/en/glossary/view/terrestrial/5618">terrestrial</mark> (land-based) <mark class="term" data-term="ecosystem" data-term-def="The complex of a community of organisms and its environment, functioning as a unit." data-term-url="/en/glossary/view/ecosystem/2174">ecosystems</mark>, plants are the primary producers at the <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">base</mark> of the food chain. However, in <mark class="term" data-term="aquatic" data-term-def="Related to, located in, or living in or on a body of water. Not terrestrial. Aquatic includes both freshwater and saltwater&hellip;" data-term-url="/en/glossary/view/aquatic/5619">aquatic</mark> (water-based) ecosystems, seaweed, <mark class="term" data-term="algae" data-term-def="(plural form of <b>alga</b>) Mostly aquatic plantlike organisms that range in size from one cell to large multi-celled seaweed and are photosynthetic." data-term-url="/en/glossary/view/algae/8678">algae</mark>, and other <mark class="term" data-term="phytoplankton" data-term-def="Microscopic plants, such as algae, that float freely in the water column of an aquatic system (e.g., lake, ocean)." data-term-url="/en/glossary/view/phytoplankton/7074">phytoplankton</mark> (microscopic photosynthesizers) are the autotrophs that produce the food consumers rely on. Figure 2 depicts a river food chain where green algae are autotrophs. Like plants, green algae use chlorophyll <mark class="term" data-term="pigment" data-term-def="A light-absorbing molecule that gathers energy from the sun; a molecule that gives color and is involved in vital functions within&hellip;" data-term-url="/en/glossary/view/pigment/8522">pigment</mark> to capture the sun’s <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> and turn it into food. The herbivorous snails eat the green algae and then become prey for fish, which are ultimately prey for black bears.</p> <p>There can be various layers and <mark class="term" data-term="organism" data-term-def="Any connected living system, such as an animal, plant, fungus, or bacterium. Organisms may be composed of a single cell or&hellip;" data-term-url="/en/glossary/view/organism/2171">organisms</mark> in a food chain, but at the base are always the producers, like plants, algae, and other photosynthesizers. The energy they harvest from the sun is then passed up the food chain as chemical energy.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc13169"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">All consumer organisms, whether herbivores or carnivores, are heterotrophic.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-13169-0-option-a" name="quiz-option-13169" type="radio" value="True" > <span class="option__label"> <span class="screen-reader-only">a.</span> True </span> </label> <span class="quiz__response" id="response-13169-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-13169-1-option-b" name="quiz-option-13169" type="radio" value="False" > <span class="option__label"> <span class="screen-reader-only">b.</span> False </span> </label> <span class="quiz__response" id="response-13169-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_2"> <h2>What limits the number of trophic levels?</h2><p>The food chains we’ve examined so far each have 4-5 trophic levels. In nature, food chains tend to have no more than five trophic levels, encompassing the autotrophs, the herbivores, and the carnivores. Another category of feeders - the decomposers or “detritivores” - feed on dead <mark class="term" data-term="matter" data-term-def="The substance that makes up physical objects." data-term-url="/en/glossary/view/matter/8264">matter</mark>, returning <mark class="term" data-term="nutrient" data-term-def="A chemical substance (e.g., minerals, vitamins, proteins) that is needed by an organism to survive and grow. See also: macronutrient and micronutrient." data-term-url="/en/glossary/view/nutrient/7058">nutrients</mark> to the <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">base</mark> of the food chain. These include scavenging vultures, hyenas, and other <mark class="term" data-term="organism" data-term-def="Any connected living system, such as an animal, plant, fungus, or bacterium. Organisms may be composed of a single cell or&hellip;" data-term-url="/en/glossary/view/organism/2171">organisms</mark> that feed on decaying animal and plant matter. Fungi and <mark class="term" data-term="bacteria" data-term-def="(plural of bacterium) A large group of one-celled organisms that are found almost everywhere." data-term-url="/en/glossary/view/bacteria/8679">bacteria</mark> <mark class="term" data-term="absorb" data-term-def="Take in or soak up (energy, liquids, or other substances), usually gradually, through a chemical or physical action." data-term-url="/en/glossary/view/absorb/11219">absorb</mark> the remaining chemical <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> that is inaccessible to other heterotrophs. Animal waste, animal bones, decaying plants, fallen trees, and more are all eventually recycled down to <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecules</mark>, a key part of materials cycling through food chains.</p> <p>If you’re wondering why there aren’t more trophic levels in food chains, you’re not alone. Ecologists have developed several <mark class="term" data-term="hypothesis" data-term-url="/en/glossary/view/hypothesis" data-term-def="From the Greek word <em>hypothesis</em> meaning assumption or the basis of an argument, a hypothesis is a proposal intended to explain&hellip;">hypotheses</mark> about what limits the number of trophic levels to no more than five.</p></section> <section id="toc2_1"><h3>Hypothesis 1: Energy-Productivity</h3><blockquote class="blockquote-hanging"> <p> The amount of energy flowing to top trophic levels depends on primary production and the efficiency at which it is converted to production at each trophic level. </p> <cite> <strong>American ecologist Freya E. Rowland,</strong> 2015 </cite> </p></blockquote> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox=""> <img src="/img/library/modules/mid293/Image/VLObject13174-24022703020607.png" alt="Figure 3: Energy pyramid." /> </button> <figcaption> <p><strong>Figure 3:</strong> Energy pyramid.</p> <span class="credit">image ©<a href="https://commons.wikimedia.org/wiki/File:Ecological_Pyramid.png"> CC-BY-SA Swiggity.Swag.YOLO.Bro</a> </span> </figcaption> </figure> </div> <p>The <mark class="term" data-term="hypothesis" data-term-def="From the Greek word <em>hypothesis</em> meaning assumption or the basis of an argument, a hypothesis is a proposal intended to explain&hellip;" data-term-url="/en/glossary/view/hypothesis/3727">hypothesis</mark> suggests that food-chain length is limited by available <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark>. Food contains energy, and each trophic level consumes some of this energy to build, maintain, and perform all its activities. As a result, only a small portion of the energy is passed up to the next level. The amount of energy transferred to the next level is called the “trophic transfer efficiency” (TTE).</p> <p>Chinese fisheries biologist Long-qi Sun attempted to calculate the TTE for Sanggou Bay (Sun et al., 2020). The bay is an <mark class="term" data-term="ecosystem" data-term-def="The complex of a community of organisms and its environment, functioning as a unit." data-term-url="/en/glossary/view/ecosystem/2174">ecosystem</mark> connected to the Yellow Sea containing a mix of wild marine <mark class="term" data-term="species" data-term-def="1. In biological classifications, it is the lowest and most basic unit of the Linnaean taxonomic hierarchy (although it is also&hellip;" data-term-url="/en/glossary/view/species/893">species</mark> and aquaculture (or farmed) species such as kelp, scallops, and oysters. With the assistance of ecosystem modeling software, Sun and colleagues came up with a TTE of 10.76% from primary producers to first-level consumers . Studies of other <mark class="term" data-term="habitat" data-term-def="The place or type of environment where a wild plant, animal, or other organism naturally lives or grows." data-term-url="/en/glossary/view/habitat/5593">habitats</mark> have given similar results, leading ecologists to conclude that in natural ecosystems, roughly 10% of the energy required at one trophic level is available for consumption by the next level.</p> <p>But the <mark class="term" data-term="law" data-term-def="In science, a principle that describes a phenomenon, often mathematically." data-term-url="/en/glossary/view/law/8686">laws</mark> of physics tell us that energy is conserved; it cannot disappear. So, where does the rest of the energy go?</p> <p>Besides powering the growth, maintenance, and physical activity of the <mark class="term" data-term="organism" data-term-def="Any connected living system, such as an animal, plant, fungus, or bacterium. Organisms may be composed of a single cell or&hellip;" data-term-url="/en/glossary/view/organism/2171">organisms</mark> at each level, energy is also lost as <mark class="term" data-term="heat" data-term-def="A measure of the total internal energy of a substance that can be increased or decreased when objects with different temperatures&hellip;" data-term-url="/en/glossary/view/heat/1506">heat</mark> and decomposition. As animals metabolize, heat is lost as a byproduct. This metabolic heat is what animals use to keep their bodies warm. In addition, every organism consumes energy as it performs the basic <mark class="term" data-term="work" data-term-def="A process that occurs when a force acts over a distance, as when an object is moved. Work equals the multiple&hellip;" data-term-url="/en/glossary/view/work/1502">work</mark> of life, from maintaining <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark> and tissues to running, playing, and hunting. Also, organisms die at each level of the Energy Pyramid (see Figure 3) before they’re eaten. Their energy is not lost altogether since every community includes detritivores that help <mark class="term" data-term="recycle" data-term-def="To cause to appear again in a new form or function; to adapt to a new use, form, or function." data-term-url="/en/glossary/view/recycle/8560">recycle</mark> dead <mark class="term" data-term="matter" data-term-def="The substance that makes up physical objects." data-term-url="/en/glossary/view/matter/8264">matter</mark> back into the ecosystem.</p> <p>If the Energy Hypothesis is correct, “productivity”—or the amount of energy available as food at the <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">base</mark> of the food chain—should positively correlate to the number of trophic levels.</p> <p><em>More energy available at the base → more trophic levels can be supported </em></p> <p>Laboratory studies conducted during the 1990s showed that food chain length correlated with productivity. Specifically, researchers manipulated the <mark class="term" data-term="nutrient" data-term-def="A chemical substance (e.g., minerals, vitamins, proteins) that is needed by an organism to survive and grow. See also: macronutrient and micronutrient." data-term-url="/en/glossary/view/nutrient/7058">nutrients</mark> in a growth medium for <mark class="term" data-term="aquatic" data-term-def="Related to, located in, or living in or on a body of water. Not terrestrial. Aquatic includes both freshwater and saltwater&hellip;" data-term-url="/en/glossary/view/aquatic/5619">aquatic</mark> <mark class="term" data-term="bacteria" data-term-def="(plural of bacterium) A large group of one-celled organisms that are found almost everywhere." data-term-url="/en/glossary/view/bacteria/8679">bacteria</mark> and protists. They found that the longest food chains—three levels—persisted only at high nutrient conditions, which boosted the bacteria <mark class="term" data-term="population" data-term-def="In biology, the population is all individuals of a certain kind of plant or animal that live in a particular habitat.&hellip;" data-term-url="/en/glossary/view/population/8283">population</mark> (Kaunzinger and Morin, 1998). However, <mark class="term" data-term="research" data-term-def="A study or an investigation." data-term-url="/en/glossary/view/research/8257">research</mark> in the field has so far failed to confirm energy transfer (TTE) between trophic levels as the factor limiting food chain length.</p></section> <section id="toc2_2"><h3>Hypothesis 2: Disturbance</h3><p>In the 1970s, scientists proposed another <mark class="term" data-term="hypothesis" data-term-def="From the Greek word <em>hypothesis</em> meaning assumption or the basis of an argument, a hypothesis is a proposal intended to explain&hellip;" data-term-url="/en/glossary/view/hypothesis/3727">hypothesis</mark> to explain food chain length called the Dynamic Constraints Hypothesis. The hypothesis holds that frequent disturbances to the <mark class="term" data-term="ecosystem" data-term-def="The complex of a community of organisms and its environment, functioning as a unit." data-term-url="/en/glossary/view/ecosystem/2174">ecosystem</mark> lead to shorter food chains (Pimm and Lawton, 1977). Recovery from disturbances takes time and begins at the bottom of a food chain before moving up. As a result, disturbances are often most disruptive to the highest trophic levels since they depend on all the lower levels being intact.</p> <p>For example, in an ecosystem disturbed by frequent <mark class="term" data-term="hurricane" data-term-def="Also called tropical cyclone; "hurricane" is the name used more commonly for tropical cyclones in the northern Atlantic Ocean basin and&hellip;" data-term-url="/en/glossary/view/hurricane/5216">hurricanes</mark> or fires, each level will take time to recover. The highest level, the top predators, are likely to starve before the recovery has progressed enough to provide for them. On the other hand, more stable <mark class="term" data-term="environment" data-term-def="The conditions that surround and affect an organism." data-term-url="/en/glossary/view/environment/8270">environments</mark> could allow longer food chains to persist.</p> <p>However, <mark class="term" data-term="research" data-term-def="A study or an investigation." data-term-url="/en/glossary/view/research/8257">research</mark> in the field has generated inconsistent results. Some early studies found that North American rivers with steadier flows had longer food chains (Sabo et al., 2010), but more recent studies yielded conflicting conclusions.</p> <p>Australian evolutionary biologist Nicholas P. Moran compared the Great Artesian Basin, which has highly stable <mark class="term" data-term="groundwater" data-term-def="Water that fills pore space in rocks and sediments and forms a subsurface aquifer. Groundwater is distinct from soil moisture, which&hellip;" data-term-url="/en/glossary/view/groundwater/2119">groundwater</mark> springs, to the Lake Eyre Basin, which has highly <mark class="term" data-term="variable" data-term-def="In math, an expression that can be assigned any set of values. Variables are written as symbols, such as x, y&hellip;" data-term-url="/en/glossary/view/variable/3797">variable</mark> rivers influenced by seasonal water availability (Moran et al., 2022). Contrary to predictions of the Dynamic Constraints Hypothesis, the contrasting water bodies displayed similar food chain lengths. Instead, the study results suggested that ecosystem size was a better predictor, with the largest groundwater spring and the largest river having longer food chains.</p> <p>Moran’s studies directly relate to a third hypothesis below.</p></section> <section id="toc2_3"><h3>Hypothesis 3: <mark class="term" data-term="ecosystem" data-term-def="The complex of a community of organisms and its environment, functioning as a unit." data-term-url="/en/glossary/view/ecosystem/2174">Ecosystem</mark> size</h3><p>The Productive Space <mark class="term" data-term="hypothesis" data-term-def="From the Greek word <em>hypothesis</em> meaning assumption or the basis of an argument, a hypothesis is a proposal intended to explain&hellip;" data-term-url="/en/glossary/view/hypothesis/3727">Hypothesis</mark> proposes that food chain length is determined by <mark class="term" data-term="ecosystem" data-term-def="The complex of a community of organisms and its environment, functioning as a unit." data-term-url="/en/glossary/view/ecosystem/2174">ecosystem</mark> size, as found by Moran (2022). It seems logical: Small <mark class="term" data-term="habitat" data-term-def="The place or type of environment where a wild plant, animal, or other organism naturally lives or grows." data-term-url="/en/glossary/view/habitat/5593">habitats</mark> have fewer resources, which may be too limited to provide enough resources for top predators. Larger ecosystems have greater total availability of resources starting at the bottom, promoting longer food chains as the resources travel upward through the <mark class="term" data-term="system" data-term-def="A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for&hellip;" data-term-url="/en/glossary/view/system/3904">system</mark>.</p> <p>This Productive Space Hypothesis, like the <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">Energy</mark> Hypothesis, presumes certain dynamics: The baseline resources are the plants or other food-producing autotrophs. And, in tandem with energy lost at each food chain level (see Figure 3), total <mark class="term" data-term="biomass" data-term-def="The combined mass of living or once-living organisms in a given area." data-term-url="/en/glossary/view/biomass/2175">biomass</mark> (the <mark class="term" data-term="mass" data-term-def="A fundamental property of matter which is a numerical measure of the inertia of an object or the amount of matter&hellip;" data-term-url="/en/glossary/view/mass/3417">mass</mark> of living things) diminishes at each trophic level. Thus, the biomass of an ecosystem, sorted by trophic levels, should also have a pyramid shape (see Figure 4).</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox=""> <img src="/img/library/modules/mid293/Image/VLObject13180-24022709022109.png" alt="Figure 4: Hypothetical biomass pyramids for aquatic and terrestrial ecosystems. " /> </button> <figcaption> <p><strong>Figure 4:</strong> Hypothetical biomass pyramids for aquatic and terrestrial ecosystems. </p> <span class="credit">image ©<a href="https://commons.wikimedia.org/wiki/File:Biomass_Pyramid.svg"> Adapted from CC-BY-SA Swiggity.Swag.YOLO.Bro</a> </span> </figcaption> </figure> </div> <p>The Productive Space <mark class="term" data-term="hypothesis" data-term-def="From the Greek word <em>hypothesis</em> meaning assumption or the basis of an argument, a hypothesis is a proposal intended to explain&hellip;" data-term-url="/en/glossary/view/hypothesis/3727">Hypothesis</mark>, then, predicts that more initial plant <mark class="term" data-term="biomass" data-term-def="The combined mass of living or once-living organisms in a given area." data-term-url="/en/glossary/view/biomass/2175">biomass</mark> should sustain more levels. Japanese biologist Gaku Takimoto (Takimoto, 2008) and colleagues found field <mark class="term" data-term="evidence" data-term-def="Support for an idea, opinion, or hypothesis." data-term-url="/en/glossary/view/evidence/8243">evidence</mark> that <mark class="term" data-term="ecosystem" data-term-def="The complex of a community of organisms and its environment, functioning as a unit." data-term-url="/en/glossary/view/ecosystem/2174">ecosystem</mark> size determines food chain length. They examined trophic levels on islands ranging from 500 m2 to 300000 km2. Food chain length increased by about one trophic level from the smallest to the largest islands.</p> <p>But, other field studies show no effect of ecosystem size. American community ecologist Hillary S. Young and colleagues (Young et al., 2013) found no effect of ecosystem size on food chain length in a set of coral islands in the central Pacific Ocean (the Palmyra Atoll). Clearly, the determinants of trophic levels are varied and complex.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc13182"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">Which is a better definition of “primary productivity?”</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-13182-0-option-a" name="quiz-option-13182" type="radio" value="How much energy is produced by autotrophs" > <span class="option__label"> <span class="screen-reader-only">a.</span> How much energy is produced by autotrophs </span> </label> <span class="quiz__response" id="response-13182-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-13182-1-option-b" name="quiz-option-13182" type="radio" value="How much energy is consumed by heterotrophs" > <span class="option__label"> <span class="screen-reader-only">b.</span> How much energy is consumed by heterotrophs </span> </label> <span class="quiz__response" id="response-13182-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_3"> <h2>Visualize complex feeding relationships with food webs</h2><blockquote class="blockquote-hanging"> <p> Most theoretical studies to date have assumed that communities are organized into neat trophic levels, in the simplest case represented as simple, linear unbranched food chains...However, food webs are more complex than this, because of omnivory, where species’ trophic roles in effect straddle multiple levels. </p> <cite> <strong>Gaku Takimoto,</strong> Japanese ecologist, 2012 </cite> </p></blockquote><p>None of the three <mark class="term" data-term="hypothesis" data-term-url="/en/glossary/view/hypothesis" data-term-def="From the Greek word <em>hypothesis</em> meaning assumption or the basis of an argument, a hypothesis is a proposal intended to explain&hellip;">hypotheses</mark> above adequately explains the length of food chains. The hypotheses were derived theoretically and make good sense, but studies of actual communities have not produced <mark class="term" data-term="data" data-term-def="(plural form of <b>datum</b>) A collection of pieces of information, generally taking the form of numbers, text, bits, or facts, that&hellip;" data-term-url="/en/glossary/view/data/3729">data</mark> to resolve the questions fully.</p> <p>Why not? <mark class="term" data-term="reflect" data-term-def="To change direction in response to hitting a surface; to bounce off in a different direction." data-term-url="/en/glossary/view/reflect/8276">Reflect</mark> on that question while looking at Figure 5.</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox=""> <img src="/img/library/modules/mid293/Image/VLObject13186-24022811021328.jpeg" alt="Figure 5: Depiction of a freshwater food web." /> </button> <figcaption> <p><strong>Figure 5:</strong> Depiction of a freshwater food web.</p> <span class="credit">image ©<a href="https://www.google.com/url?q=https://commons.wikimedia.org/wiki/File:Aquatic_food_web.jpg&sa=D&source=docs&ust=1710185353693481&usg=AOvVaw2L_U3Wt46vg0GUkoWJfYZN"> CC-BY-SA Missouri Department of Conservation</a> </span> </figcaption> </figure> </div> <p>A “food web” shows the complex feeding relationships within a natural <mark class="term" data-term="ecosystem" data-term-def="The complex of a community of organisms and its environment, functioning as a unit." data-term-url="/en/glossary/view/ecosystem/2174">ecosystem</mark> that a simplified food chain fails to represent. For instance, in Figure 5, every brown arrow shows a feeding relationship. While a food chain demonstrates one direct set of feeding relationships, it lacks the complexity of trophic dynamics in natural ecosystems.</p> <p>As Figure 5 shows, nearly all the animals feed on more than one type of food. By definition, an omnivore feeds at more than one level of the food web. Although there are food specialists in every community, most animals eat a mix of foods.</p> <p>Within a food web, animals may also feed on other animals at their trophic level. For example, the boy in Figure 5 fishes for both green sunfish and largemouth bass, but the largemouth bass also eats the green sunfish. These feeding relationships within a trophic level are called “intraguild predation” (because a guild is a <mark class="term" data-term="group" data-term-def="A column of elements in the periodic table." data-term-url="/en/glossary/view/group/8566">group</mark> of animals feeding at a similar trophic level) and give the visual an even more weblike form with horizontal connections.</p></section> <section id="toc2_4"><h3>Food web complexity</h3><p>The complexity of trophic relationships in a food web, coupled with other <mark class="term" data-term="variable" data-term-def="In math, an expression that can be assigned any set of values. Variables are written as symbols, such as x, y&hellip;" data-term-url="/en/glossary/view/variable/3797">variables</mark> like abiotic (nonliving) conditions, further complicates the question of what determines food chain length.</p> <p>Canadian ecologist Tiffany A. Schriever studied nine Ontario ponds over two years to find any relationships between environmental variables (such as <mark class="term" data-term="ecosystem" data-term-def="The complex of a community of organisms and its environment, functioning as a unit." data-term-url="/en/glossary/view/ecosystem/2174">ecosystem</mark> size and the <mark class="term" data-term="frequency" data-term-def="The rate at which a vibration occurs that constitutes a wave, either in a material or in an electromagnetic field, usually&hellip;" data-term-url="/en/glossary/view/frequency/2210">frequency</mark> of disturbance) and the length of food chains (Schriever, 2015). Schriever characterized the food webs based on the amphibian, <mark class="term" data-term="invertebrate" data-term-def="An organism without a backbone. Invertebrates account for 95-99% of all animal species on Earth and include organisms like worms, insects,&hellip;" data-term-url="/en/glossary/view/invertebrate/5270">invertebrate</mark>, and detritus communities and relative to physical-chemical <mark class="term" data-term="data" data-term-def="(plural form of <b>datum</b>) A collection of pieces of information, generally taking the form of numbers, text, bits, or facts, that&hellip;" data-term-url="/en/glossary/view/data/3729">data</mark> like dissolved oxygen, <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark>, temperature, and water depth. She found that multiple variables affect food web structure, with no single variable explaining food chain length in all cases. Instead, food chain length varied depending on <mark class="term" data-term="habitat" data-term-def="The place or type of environment where a wild plant, animal, or other organism naturally lives or grows." data-term-url="/en/glossary/view/habitat/5593">habitat</mark>, such as small wetlands versus large ponds.</p> <p>Scientists like Takimoto have come up with more sophisticated <mark class="term" data-term="model" data-term-def="A representation, pattern, or mathematical description that can help scientists replicate a system." data-term-url="/en/glossary/view/model/8236">models</mark> to <mark class="term" data-term="reflect" data-term-def="To change direction in response to hitting a surface; to bounce off in a different direction." data-term-url="/en/glossary/view/reflect/8276">reflect</mark> the complexity of food webs (Takimoto et al., 2012). Takimoto and colleagues included intraguild predation (preying on competitors occupying a similar trophic level) in a food web model, which generated more complex <mark class="term" data-term="hypothesis" data-term-url="/en/glossary/view/hypothesis" data-term-def="From the Greek word <em>hypothesis</em> meaning assumption or the basis of an argument, a hypothesis is a proposal intended to explain&hellip;">hypotheses</mark>. Overall, their model predicts that if intraguild predation is weak, then higher productivity, large ecosystems, and lower disturbance rates support longer food chains. However, if intraguild predation is strong, then productivity and disturbance actually limit food chain length.</p> <p>This <mark class="term" data-term="work" data-term-def="A process that occurs when a force acts over a distance, as when an object is moved. Work equals the multiple&hellip;" data-term-url="/en/glossary/view/work/1502">work</mark> showed how different hypotheses might explain food webs under different conditions, getting us closer to a complete understanding of ecosystems.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc13190"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">How does a food web model build on models of food chains?</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-13190-0-option-a" name="quiz-option-13190" type="radio" value="A food web extends a food chain vertically to show more trophic levels." > <span class="option__label"> <span class="screen-reader-only">a.</span> A food web extends a food chain vertically to show more trophic levels. </span> </label> <span class="quiz__response" id="response-13190-0"> <strong>Incorrect.</strong> </span> </div> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-13190-1-option-b" name="quiz-option-13190" type="radio" value="A food web extends a food chain horizontally to show more complexity." > <span class="option__label"> <span class="screen-reader-only">b.</span> A food web extends a food chain horizontally to show more complexity. </span> </label> <span class="quiz__response" id="response-13190-1"> <strong>Correct!</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_4"> <h2>Food web dynamics</h2><blockquote class="blockquote-hanging"> <p> The different hypotheses developed by various scholars of the community ecology have to be considered in an integrated fashion in order to clearly understand and explain the plausible mechanisms that influence the community structure and trophic level interactions in the terrestrial ecosystems. </p> <cite> <strong>Solomon Ayele Tadesse,</strong> Ethiopian ecologist, 2017 </cite> </p></blockquote><p>Food webs are dynamic because feeding relationships respond to many environmental changes, such as drought or the introduction of a new <mark class="term" data-term="species" data-term-def="1. In biological classifications, it is the lowest and most basic unit of the Linnaean taxonomic hierarchy (although it is also&hellip;" data-term-url="/en/glossary/view/species/893">species</mark>.</p> <p>For example, ecologists studying grassland food webs found that the <mark class="term" data-term="biomass" data-term-def="The combined mass of living or once-living organisms in a given area." data-term-url="/en/glossary/view/biomass/2175">biomass</mark> pyramids (see Figure 4) varied depending on the amount of rainfall (Chase et al., 2020). More rainfall meant more grasses, resulting in larger <mark class="term" data-term="population" data-term-def="In biology, the population is all individuals of a certain kind of plant or animal that live in a particular habitat.&hellip;" data-term-url="/en/glossary/view/population/8283">populations</mark> of herbivores eating them. When ecologists excluded large herbivores, by preventing cattle from grazing, for example, grasses flourished. This proved that herbivores <mark class="term" data-term="control" data-term-def="In science, a control is a system for which the expected change or outcome is well known and is measured or&hellip;" data-term-url="/en/glossary/view/control/3801">control</mark> grasses. However, excluding the cattle made little difference when rainfall was low and water scarcity limited the grasses.</p> <p>If food webs respond to abiotic conditions, such as rainfall, and their effects on producers and consumers, their stability likely also depends on these interactions.</p></section> <section id="toc2_5"><h3>Ecosystem stability</h3><blockquote class="blockquote-hanging"> <p>Trophic interactions underpin an extensive range of crucial ecosystem functions characterizing a large proportion of total ecosystem performance …and have been a central tenet of ecology since Elton’s pioneering work.</p> <cite> <strong>Andrew D. Barnes,</strong> New Zealand ecologist, 2021 </cite></p></blockquote><p>It has become increasingly clear that food web trophic dynamics—including the flow of <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark>, <mark class="term" data-term="nutrient" data-term-def="A chemical substance (e.g., minerals, vitamins, proteins) that is needed by an organism to survive and grow. See also: macronutrient and micronutrient." data-term-url="/en/glossary/view/nutrient/7058">nutrients</mark>, and biomass—support <mark class="term" data-term="ecosystem" data-term-def="The complex of a community of organisms and its environment, functioning as a unit." data-term-url="/en/glossary/view/ecosystem/2174">ecosystem</mark> <mark class="term" data-term="function" data-term-def="Adaptations that influence how the animal interacts with other species. For example, animal function typically serves genetic and reproductive success." data-term-url="/en/glossary/view/function/13151">function</mark>. The way ecosystems function determines the services they naturally provide to humans (see our <a href="https://www.visionlearning.com/en/library/Biology/2/Ecosystem-Services/279">Ecosystem Services module</a>). In Figure 6, Barnes (2021) details eight ecosystem services resulting from trophic web interactions within a community.</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox=""> <img src="/img/library/modules/mid293/Image/VLObject13197-24022811022756.jpeg" alt="Figure 6: Trophic energy fluxes (arrows) and ecosystem services (numbers)." /> </button> <figcaption> <p><strong>Figure 6:</strong> Trophic energy fluxes (arrows) and ecosystem services (numbers).</p> <span class="credit">image ©<a href="https://pubmed.ncbi.nlm.nih.gov/29325921/"> Used with permission from Elsevier</a> </span> </figcaption> </figure> </div> <p>Consider what would happen if a <mark class="term" data-term="species" data-term-def="1. In biological classifications, it is the lowest and most basic unit of the Linnaean taxonomic hierarchy (although it is also&hellip;" data-term-url="/en/glossary/view/species/893">species</mark> disappeared from the community. For example, in Figure 6, how might the community change if there were no birds at the top of the web?</p> <p>According to the diagram, the birds feed on several types of <mark class="term" data-term="invertebrate" data-term-def="An organism without a backbone. Invertebrates account for 95-99% of all animal species on Earth and include organisms like worms, insects,&hellip;" data-term-url="/en/glossary/view/invertebrate/5270">invertebrates</mark> (wasps, beetles, worms and <mark class="term" data-term="aquatic" data-term-def="Related to, located in, or living in or on a body of water. Not terrestrial. Aquatic includes both freshwater and saltwater&hellip;" data-term-url="/en/glossary/view/aquatic/5619">aquatic</mark> insects). If the birds are lost, this could free those invertebrate <mark class="term" data-term="population" data-term-def="In biology, the population is all individuals of a certain kind of plant or animal that live in a particular habitat.&hellip;" data-term-url="/en/glossary/view/population/8283">populations</mark> from predation, causing them to grow (see our <a href="https://www.visionlearning.com/en/library/Biology/2/Population-Biology/287">Population Biology module</a>). Rising invertebrate populations would provide more food for other animals that rely on them, causing those populations to grow. But it might also reduce the population of the <mark class="term" data-term="organism" data-term-def="Any connected living system, such as an animal, plant, fungus, or bacterium. Organisms may be composed of a single cell or&hellip;" data-term-url="/en/glossary/view/organism/2171">organisms</mark> that the invertebrates feed on. Because these trophic relationships structure the community, any disruption changes it—sometimes drastically—which can threaten the entire community.</p> <p>Food webs are controlled both bottom-up (by primary productivity) and top-down (by predators). Any factors that alter one food web level can cause disturbances on other levels. Russian ecologist Anton M. Potapov and colleagues studied trophic dynamics in Indonesia’s tropical rainforests and compared them to nearby <mark class="term" data-term="ecosystem" data-term-def="The complex of a community of organisms and its environment, functioning as a unit." data-term-url="/en/glossary/view/ecosystem/2174">ecosystems</mark> that had been altered by the creation of rubber or palm oil plantations (Potapov et al., 2019). They found that the plantations had smaller populations of small <mark class="term" data-term="soil" data-term-def="The loose top layer of Earth’s surface where plants grow, made up of particles of rocks, minerals, and organic material." data-term-url="/en/glossary/view/soil/8563">soil</mark> invertebrates (such as beetles) but more large earthworms. <mark class="term" data-term="biomass" data-term-def="The combined mass of living or once-living organisms in a given area." data-term-url="/en/glossary/view/biomass/2175">Biomass</mark> and <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> were concentrated in these large decomposers in the altered ecosystems, altering energy conversions at other trophic levels.</p> <p>Consider Figure 7. What differences do you notice in decomposition, herbivory, and predation in the natural rainforests versus the altered ecosystems?</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox=""> <img src="/img/library/modules/mid293/Image/VLObject13199-24022811024420.jpeg" alt="Figure 7: Graph showing changes in energy flux from plant eating - herbivory - with conversion of rainforest (F) into jungle rubber (J), rubber(R), and oil palm plantations (O)." /> </button> <figcaption> <p><strong>Figure 7:</strong> Graph showing changes in energy flux from plant eating - herbivory - with conversion of rainforest (F) into jungle rubber (J), rubber(R), and oil palm plantations (O).</p> <span class="credit">image ©<a href="https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2656.13027"> Used with permission from John Wiley & Sons</a> </span> </figcaption> </figure> </div> <p>Potapov and colleagues compared the rainforest (F) to the altered <mark class="term" data-term="ecosystem" data-term-def="The complex of a community of organisms and its environment, functioning as a unit." data-term-url="/en/glossary/view/ecosystem/2174">ecosystems</mark> (J, R, and O) based on “energy flux” (movement of <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> through the system). They noticed that the movement of energy from herbivory was lower in the plantations compared to the natural rainforest. When rainforest is converted into monoculture (single-crop) plantations, the trophic dynamics are disrupted. This results in less energy flow into higher trophic levels, such as the herbivores and carnivores that inhabit natural rainforests.</p></section> <section id="toc2_6"><h3>Humans in trophic systems</h3><p>Humans are the most successful predators on Earth. When you add them to an <mark class="term" data-term="ecosystem" data-term-def="The complex of a community of organisms and its environment, functioning as a unit." data-term-url="/en/glossary/view/ecosystem/2174">ecosystem</mark> as top predators, the feeding relationships change substantially. For example, Figure 8 shows five trophic levels of the ocean food web and how the fishing industry affects 165 different marine <mark class="term" data-term="species" data-term-def="1. In biological classifications, it is the lowest and most basic unit of the Linnaean taxonomic hierarchy (although it is also&hellip;" data-term-url="/en/glossary/view/species/893">species</mark>.</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox=""> <img src="/img/library/modules/mid293/Image/VLObject13203-24022811025109.jpeg" alt="Figure 8: Food web diagram showing ocean trophic relationships related to fisheries." /> </button> <figcaption> <p><strong>Figure 8:</strong> Food web diagram showing ocean trophic relationships related to fisheries.</p> <span class="credit">image ©<a href="https://ri.conicet.gov.ar/handle/11336/171847"> CC BY-NC-SA 2.5 Conicet Digital</a> </span> </figcaption> </figure> </div> <p>In Figure 8, how many marine <mark class="term" data-term="species" data-term-def="1. In biological classifications, it is the lowest and most basic unit of the Linnaean taxonomic hierarchy (although it is also&hellip;" data-term-url="/en/glossary/view/species/893">species</mark> impacted by the fishing industry can you count?</p> <p>The fishing industry impacts just about every marine species directly or indirectly. And other human activities also change trophic <mark class="term" data-term="system" data-term-def="A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for&hellip;" data-term-url="/en/glossary/view/system/3904">systems</mark>.</p> <p>For example, Brazilian environmental scientist Maria A. L. Lima studied the effects of the 2011 dam construction on the Amazon’s Madeira River. The river boasts the highest fish species richness (number of species in an ecosystem) in the world (see our <a href="https://www.visionlearning.com/en/library/Biology/2/Biodiversity-I/276">Biodiversity I module</a>). Lima compared the trophic structure of a river <mark class="term" data-term="ecosystem" data-term-def="The complex of a community of organisms and its environment, functioning as a unit." data-term-url="/en/glossary/view/ecosystem/2174">ecosystem</mark> before and after the dam’s construction. Using known trophic relationships, she estimated the <mark class="term" data-term="biomass" data-term-def="The combined mass of living or once-living organisms in a given area." data-term-url="/en/glossary/view/biomass/2175">biomass</mark> and <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> flows pre- and post-damming and found the following:</p> <ul class="bulleted"> <li>More detritus after damming, supporting more decomposer organisms</li> <li>Less total biomass of fish after damming</li> <li>Lower energy transfer efficiency between trophic levels</li> <li>Shifts in which fishes were top predators</li> </ul> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc13205"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">Understanding trophic relationships is sufficient for predicting food web dynamics.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-13205-0-option-a" name="quiz-option-13205" type="radio" value="True" > <span class="option__label"> <span class="screen-reader-only">a.</span> True </span> </label> <span class="quiz__response" id="response-13205-0"> <strong>Incorrect.</strong> </span> </div> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-13205-1-option-b" name="quiz-option-13205" type="radio" value="False" > <span class="option__label"> <span class="screen-reader-only">b.</span> False </span> </label> <span class="quiz__response" id="response-13205-1"> <strong>Correct!</strong> </span> </div> </div> </div> </div> </form> </div> <p>Feeding relationships give structure to communities and respond to changes in environmental conditions. As such, each chain of relationships is part of a dynamic <mark class="term" data-term="system" data-term-def="A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for&hellip;" data-term-url="/en/glossary/view/system/3904">system</mark>. Understanding the trophic system requires multiple perspectives on its <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> and <mark class="term" data-term="biomass" data-term-def="The combined mass of living or once-living organisms in a given area." data-term-url="/en/glossary/view/biomass/2175">biomass</mark> fluxes.</p> <p>Think back to the earthworms in Figure 1. They’re not just herbivores feeding on plant seedlings but also decomposers feeding on fallen leaves and other bits of dead or dying <mark class="term" data-term="organic" data-term-def="Originating from a living organism; a compound that contains hydrocarbons." data-term-url="/en/glossary/view/organic/8530">organic</mark> <mark class="term" data-term="matter" data-term-def="The substance that makes up physical objects." data-term-url="/en/glossary/view/matter/8264">matter</mark>. If an earthworm can select both seedlings and detritus off the menu, you can envision how a linear food chain is just the beginning of the full story of this <mark class="term" data-term="ecosystem" data-term-def="The complex of a community of organisms and its environment, functioning as a unit." data-term-url="/en/glossary/view/ecosystem/2174">ecosystem</mark>.</p> </div> </section> <hr class="border-color-dark" /> <footer class="module__footer"> <p class="citation"> <em> Devin Reese, PhD. “Trophic Ecology” Visionlearning Vol. BIO-6 (3), 2024. </em> </p>  <div class="title-list" id="refs" name="refs"> <p class="h6 title-list__title"> References </p> <ul class="title-list__list"> <li><p> Barnes, A. D., Jochum, M., Lefcheck, J. S., Eisenhauer, N., Scherber, C., O’Connor, M. I., ... & Brose, U. (2018). Energy flux: the link between multitrophic biodiversity and ecosystem functioning. <em>Trends in ecology & evolution, 33</em>(3), 186-197.</li> <li>Chase, J. M., Leibold, M. A., Downing, A. L., & Shurin, J. B. (2000). The effects of productivity, herbivory, and plant species turnover in grassland food webs. <em>Ecology, 81</em>(9), 2485-2497.</li> <li>Elton, C. S. (1927). <em>Animal Ecology.</em> London, UK.: Sidgwick and Jackson. ISBN 0-226-20639-4. https://archive.org/details/animalecology00elto/mode/2up?view=theater</li> <li>Forbes, S.A. (1887). The lake as a microcosm. Bull. Sci. Assoc., Peoria, Illinois pp 77-87. Reprinted in Illinois Nat. Hist. Survey Bulletin 15, art. 9,537-550.</li> <li>Ford, M. (2021, November 17). The Need to Support Native American Food Sovereignty. <em>Hunger and Health.</em> 2023, https://hungerandhealth.feedingamerica.org/2021/11/the-need-to-support-native-american-food-sovereignty/</li> <li>Hairston, N. G., Smith, F. E., & Slobodkin, L. B. (1960). Community structure, population control, and competition. <em>The American Naturalist, 94</em>(879), 421-425.</li> <li>Kaunzinger, C. M., & Morin, P. J. (1998). Productivity controls food-chain properties in microbial communities. <em>Nature, 395</em>(6701), 495-497.</li> <li>Lima, M. A., Doria, C. R., Carvalho, A. R., & Angelini, R. (2020). Fisheries and trophic structure of a large tropical river under impoundment. <em>Ecological Indicators, 113,</em> 106162.</li> <li>Lindeman, R. L. (1942). The trophic-dynamic aspect of ecology. <em>Ecology, 23</em>(4), 399-417.</li> <li>Pimm, S. L., & Lawton, J. H. (1977). Number of trophic levels in ecological communities. <em>Nature, 268</em>(5618), 329-331.</li> <li>Potapov, A. M., Klarner, B., Sandmann, D., Widyastuti, R., & Scheu, S. (2019). Linking size spectrum, energy flux and trophic multifunctionality in soil food webs of tropical land‐use systems. <em>Journal of Animal Ecology, 88</em>(12), 1845-1859.</li> <li>Rowland, F. E., Bricker, K. J., Vanni, M. J., & González, M. J. (2015). Light and nutrients regulate energy transfer through benthic and pelagic food chains. <em>Oikos, 124</em>(12), 1648-1663.</li> <li>Sabo, J. L., Finlay, J. C., Kennedy, T., & Post, D. M. (2010). The role of discharge variation in scaling of drainage area and food chain length in rivers. <em>Science, 330</em>(6006), 965-967.</li> <li>Sabo, J.L., & Gerber, L.R. (2021, January). Trophic ecology. <em>AccessScience.</em> Retrieved October 18, 2022, from https://doi.org/10.1036/1097-8542.711650. https://www.accessscience.com/content/article/a711650</li> <li>Schriever, T. A. (2015). Food webs in relation to variation in the environment and species assemblage: a multivariate approach. <em>PloS one, 10</em>(4), e0122719.</li> <li>Sun, L. Q., Liu, H., Gao, Y. P., Jiang, Z. J., Lin, F., Chang, L. R., & Zhang, Y. T. (2020). Food web structure and ecosystem attributes of integrated multi-trophic aquaculture waters in Sanggou Bay. <em>Aquaculture Reports, 16,</em> 100279.</li> <li>Tadesse, S. A. (2017). Community structure and trophic level interactions in the terrestrial ecosystems: a review. <em>Int J Avian & Wildlife Biol, 2</em>(6), 00040.</li> <li>Takimoto, G., & Post, D. M. (2013). Environmental determinants of food-chain length: a meta-analysis. <em>Ecological Research, 28,</em> 675-681.</li> <li>Takimoto, G., Spiller, D. A., & Post, D. M. (2008). Ecosystem size, but not disturbance, determines food‐chain length on islands of the Bahamas. <em>Ecology, 89</em>(11), 3001-3007.</li> <li>Warfe, D. M., Jardine, T. D., Pettit, N. E., Hamilton, S. K., Pusey, B. J., Bunn, S. E., ... & Douglas, M. M. (2013). Productivity, disturbance and ecosystem size have no influence on food chain length in seasonally connected rivers. <em>PloS one, 8</em>(6), e66240.</li> <li>Young, H. S., McCauley, D. J., Dunbar, R. B., Hutson, M. S., Ter-Kuile, A. M., & Dirzo, R. (2013). The roles of productivity and ecosystem size in determining food chain length in tropical terrestrial ecosystems. <em>Ecology, 94</em>(3), 692-701.</li> </ul> </div>  <div class="title-list" name="further"> <p class="h6 title-list__title"> Further Reading </p> <ul class="grid grid--column-2--md grid--column-3--md gap-1"> <li> <a class="no-hover-focus height-100" href="/en/library/Biology/2/Ecosystem-Services/279"> <article class="flex-row align-items-center flex-column--md align-items-start--md height-100 theme-light padding-2 gap-2"> <div class="width-30 width-auto--md"> <img class="border-radius box-shadow-1" src="/img/library/moduleImages/featured_image_279-23061209063850.jpeg" alt="Ecosystem Services"> </div> <div class="flex-grow-shrink"> <h2 class="h6 font-weight-normal"> Ecosystem Services: <em>Categories and valuation</em> </h2> </div> </article> </a> </li> <li> <a class="no-hover-focus height-100" href="/en/library/Biology/2/Biodiversity-II/281"> <article class="flex-row align-items-center flex-column--md align-items-start--md height-100 theme-light padding-2 gap-2"> <div class="width-30 width-auto--md"> <img class="border-radius box-shadow-1" src="/img/library/moduleImages/featured_image_281-23061209063903.jpg" alt="Biodiversity II"> </div> <div class="flex-grow-shrink"> <h2 class="h6 font-weight-normal"> Biodiversity II: <em>Changing habits and habitats</em> </h2> </div> </article> </a> </li> <li> <a class="no-hover-focus height-100" href="/en/library/Biology/2/Photosynthesis-I/192"> <article class="flex-row align-items-center flex-column--md align-items-start--md height-100 theme-light padding-2 gap-2"> <div class="width-30 width-auto--md"> <img class="border-radius box-shadow-1" src="/img/library/moduleImages/featured_image_192-23061209063006.jpg" alt="Photosynthesis I"> </div> <div class="flex-grow-shrink"> <h2 class="h6 font-weight-normal"> Photosynthesis I: <em>Harnessing the energy of the sun</em> </h2> </div> </article> </a> </li> <li> <a class="no-hover-focus height-100" href="/en/library/Biology/2/Population-Biology/287"> <article class="flex-row align-items-center flex-column--md align-items-start--md height-100 theme-light padding-2 gap-2"> <div class="width-30 width-auto--md"> <img class="border-radius box-shadow-1" src="/img/library/moduleImages/featured_image_287-23061209063942.jpg" alt="Population Biology"> </div> <div class="flex-grow-shrink"> <h2 class="h6 font-weight-normal"> Population Biology: <em>Carrying capacity, demographics, and cycles</em> </h2> </div> </article> </a> </li> </ul> </div> </footer> </div>   </div>  <div class="order-1 order-2--lg module__tools"> <div class="narrow margin-x-auto position-sticky-top font-size-md"> <div class="padding-2 border-radius box-shadow-1--lg"> <div class="tabs" role="tablist"> <nav> <button class="button button--icon-label" id="tab-button-in-this-module" aria-label="Table of Contents" aria-controls="tab-panel-module__tools" aria-selected="true" role="tab"> <span class="icon icon-list" aria-hidden="true"></span> <span class="button__text">Contents</span> </button> <button class="button button--icon-label" id="tab-button-toggle-terms" aria-controls="tab-panel-toggle-terms" aria-selected="false" role="tab"> <span class="icon icon-glossary-highlight"></span> <span class="button__text">Glossary Terms</span> </button> </nav> <hr class="divider" /> <div class="tabs__panel shown" id="tab-panel-module__tools" aria-labelledby="tab-button-module__tools" role="tabpanel"> <p class="font-weight-bold margin-bottom-1"> Table of Contents </p> <div class="table-of-contents" id="module-toc"> <ul> <li><a href="/en/library/biology/2/trophic-ecology/293#toc_1">Food chains: Understanding basic feeding relationships</a> </li> <li><a href="/en/library/biology/2/trophic-ecology/293#toc_2">What limits the number of trophic levels?</a> </li> <li> <ul> <li><a href="/en/library/biology/2/trophic-ecology/293#toc2_1">Hypothesis 1: Energy-Productivity</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/biology/2/trophic-ecology/293#toc2_2">Hypothesis 2: Disturbance</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/biology/2/trophic-ecology/293#toc2_3">Hypothesis 3: Ecosystem size</a> </li> </ul> </li> <li><a href="/en/library/biology/2/trophic-ecology/293#toc_3">Visualize complex feeding relationships with food webs</a> </li> <li> <ul> <li><a href="/en/library/biology/2/trophic-ecology/293#toc2_4">Food web complexity</a> </li> </ul> </li> <li><a href="/en/library/biology/2/trophic-ecology/293#toc_4">Food web dynamics</a> </li> <li> <ul> <li><a href="/en/library/biology/2/trophic-ecology/293#toc2_5">Ecosystem stability</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/biology/2/trophic-ecology/293#toc2_6">Humans in trophic systems</a> </li> </ul> </li> </ul> </div> </div>   <div class="tabs__panel" id="tab-panel-toggle-terms" aria-labelledby="tab-button-toggle-terms" role="tabpanel"> <div class="reading-toggle"> <div 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