{"id":8587,"date":"2013-11-18T16:43:39","date_gmt":"2013-11-18T16:43:39","guid":{"rendered":"http:\/\/www.mometrix.com\/academy\/?page_id=8587"},"modified":"2026-03-26T09:18:12","modified_gmt":"2026-03-26T14:18:12","slug":"food-webs","status":"publish","type":"page","link":"https:\/\/www.mometrix.com\/academy\/food-webs\/","title":{"rendered":"Food Webs"},"content":{"rendered":"\n\t\t\t<div id=\"mmDeferVideoEncompass_VnIcepU7wqI\" style=\"position: relative;\">\n\t\t\t<picture>\n\t\t\t\t<source srcset=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2023\/01\/circle-play-duotone.webp\" type=\"image\/webp\">\n\t\t\t\t<source srcset=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2023\/01\/circle-play-duotone.png\" type=\"image\/jpeg\"> \n\t\t\t\t<img fetchpriority=\"high\" decoding=\"async\" loading=\"eager\" id=\"videoThumbnailImage_VnIcepU7wqI\" data-source-videoID=\"VnIcepU7wqI\" src=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2023\/01\/circle-play-duotone.png\" alt=\"Food Webs Video\" height=\"1080\" width=\"1920\" class=\"size-full\" data-matomo-title = \"Food Webs\">\n\t\t\t<\/picture>\n\t\t\t<\/div>\n\t\t\t<style>img#videoThumbnailImage_VnIcepU7wqI:hover {cursor:pointer;} img#videoThumbnailImage_VnIcepU7wqI {background-size:contain;background-image:url(\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2024\/01\/Food-Webs-thumbnail.webp\");}<\/style>\n\t\t\t<script defer>\n\t\t\t  jQuery(\"img#videoThumbnailImage_VnIcepU7wqI\").click(function() {\n\t\t\t\tlet videoId = jQuery(this).attr(\"data-source-videoID\");\n\t\t\t\tlet helpTag = '<div id=\"mmDeferVideoYTMessage_VnIcepU7wqI\" style=\"display: none;position: absolute;top: -24px;width: 100%;text-align: center;\"><span style=\"font-style: italic;font-size: small;border-top: 1px solid #fc0;\">Having trouble? <a href=\"https:\/\/www.youtube.com\/watch?v='+videoId+'\" target=\"_blank\">Click here to watch on YouTube.<\/a><\/span><\/div>';\n\t\t\t\tlet tag = document.createElement(\"iframe\");\n\t\t\t\ttag.id = \"yt\" + videoId;\n\t\t\t\ttag.src = \"https:\/\/www.youtube-nocookie.com\/embed\/\" + videoId + \"?autoplay=1&controls=1&wmode=opaque&rel=0&egm=0&iv_load_policy=3&hd=0&enablejsapi=1\";\n\t\t\t\ttag.frameborder = 0;\n\t\t\t\ttag.allow = \"autoplay; fullscreen\";\n\t\t\t\ttag.width = this.width;\n\t\t\t\ttag.height = this.height;\n\t\t\t\ttag.setAttribute(\"data-matomo-title\",\"Food Webs\");\n\t\t\t\tjQuery(\"div#mmDeferVideoEncompass_VnIcepU7wqI\").html(tag);\n\t\t\t\tjQuery(\"div#mmDeferVideoEncompass_VnIcepU7wqI\").prepend(helpTag);\n\t\t\t\tsetTimeout(function(){jQuery(\"div#mmDeferVideoYTMessage_VnIcepU7wqI\").css(\"display\", \"block\");}, 2000);\n\t\t\t  });\n\t\t\t  \n\t\t\t<\/script>\n\t\t\n<p><script>\nfunction FcM_Function() {\n  var x = document.getElementById(\"FcM\");\n  if (x.style.display === \"none\") {\n    x.style.display = \"block\";\n  } else {\n    x.style.display = \"none\";\n  }\n}\n<\/script><\/p>\n<div class=\"moc-toc hide-on-desktop hide-on-tablet\">\n<div><button onclick=\"FcM_Function()\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2024\/12\/toc2.svg\" width=\"16\" height=\"16\" alt=\"show or hide table of contents\"><\/button><\/p>\n<p>On this page<\/p>\n<\/div>\n<nav id=\"FcM\" style=\"display:none;\">\n<ul>\n<li class=\"toc-h2\"><a href=\"#What_is_an_Ecosystem\" class=\"smooth-scroll\">What is an Ecosystem?<\/a><\/li>\n<li class=\"toc-h2\"><a href=\"#Food_Chains\" class=\"smooth-scroll\">Food Chains<\/a><\/li>\n<li class=\"toc-h2\"><a href=\"#Ecosystem_Dynamics\" class=\"smooth-scroll\">Ecosystem Dynamics<\/a><\/li>\n<li class=\"toc-h2\"><a href=\"#Food_Webs\" class=\"smooth-scroll\">Food Webs<\/a><\/li>\n<li class=\"toc-h2\"><a href=\"#Review_Questions\" class=\"smooth-scroll\">Review Questions<\/a><\/li>\n<\/ul>\n<\/nav>\n<\/div>\n<div class=\"accordion\"><input id=\"transcript\" type=\"checkbox\" class=\"spoiler_button\" \/><label for=\"transcript\">Transcript<\/label>\n<div class=\"spoiler\" id=\"transcript-spoiler\">\n<p>We live in a complex world made up of communities, small and large, full of trends and other measurable behavior. But in terms of biology, how much difference does one species really make to an ecosystem? A lot, as it turns out. Today, we\u2019ll be talking about ecosystems and how they can be affected by food webs. Let\u2019s go eat!<\/p>\n<h2><span id=\"What_is_an_Ecosystem\" class=\"m-toc-anchor\"><\/span>What is an Ecosystem?<\/h2>\n<p>\nSo, what exactly is an ecosystem? Ecosystems are systems made up of many different types of species of plants, animals, and decomposers, and they also include resources like air, water, and sunlight for organisms to use.<\/p>\n<p>Ecosystems are very sensitive to change, so if one species goes extinct or if the climate changes, these systems can be thrown out of balance. Most animals are native to one place and largely remain in that system for generations unless weather or predation drives them to another location. <\/p>\n<h2><span id=\"Food_Chains\" class=\"m-toc-anchor\"><\/span>Food Chains<\/h2>\n<p>\nNow, before we get into food webs, let\u2019s talk about food chains, the building block of food webs.<\/p>\n<p>In any ecosystem, each member relies on all the others either directly or indirectly. A rabbit directly relies on grass so that it can eat. But the rabbit also indirectly relies on the sun because the rabbit eats the grass that converts sunlight into chemical energy via photosynthesis. When energy passes from one source to another, we call that an energy exchange. <\/p>\n<p>The simplest form of an energy exchange among <a class=\"ylist\" href=\"https:\/\/www.mometrix.com\/academy\/basic-characteristics-of-organisms\/\">organisms<\/a> can be represented through a diagram like this one, which we call a food chain:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/08\/Food-chain-color-corrected-logo-scaled.jpg\" alt=\"\" width=\"2560\" height=\"2293\" class=\"aligncenter size-full wp-image-87436\" srcset=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/08\/Food-chain-color-corrected-logo-scaled.jpg 2560w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/08\/Food-chain-color-corrected-logo-300x269.jpg 300w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/08\/Food-chain-color-corrected-logo-1024x917.jpg 1024w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/08\/Food-chain-color-corrected-logo-768x688.jpg 768w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/08\/Food-chain-color-corrected-logo-1536x1376.jpg 1536w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/08\/Food-chain-color-corrected-logo-2048x1834.jpg 2048w\" sizes=\"auto, (max-width: 2560px) 100vw, 2560px\" \/><\/p>\n<h2><span id=\"Ecosystem_Dynamics\" class=\"m-toc-anchor\"><\/span>Ecosystem Dynamics<\/h2>\n<p>\nFood chains can be made up of all kinds of different species within a system, but they all start with the sun as the initial energy source. The next level is usually a <strong>producer<\/strong> like a plant that can easily convert that energy into something nutritious and energy-rich that the next level can eat. So the following level with our rabbit, in this case, is known as the <strong>primary consumer<\/strong> level because the rabbit consumes the level before him. Primary consumers are usually herbivores or omnivores since they eat plants. If a snake eats the rabbit, the snake is known as a secondary consumer. <\/p>\n<p>We can also have <strong>tertiary <\/strong>and <strong>quaternary consumers<\/strong> based on the ecosystem, but in the end, there\u2019s always a <strong>predator<\/strong> to eat the last consumer and a <strong>decomposer<\/strong> to recycle the scraps.<\/p>\n<p>So in our food chain example we could have an owl as our predator and fungi as our decomposers. We know the owl is a predator because it preys on other consumers. Because the owl is a predator but isn\u2019t consumed herself, she\u2019s called an apex predator. When the owl is done having her snack, decomposers like fungi will convert any waste like scraps from the meal or anything the owl passes into nutrients to be put back into the soil, acting like food for plants. So in this way, food chains are really a misnomer because they are more like \u201cfood cycles.\u201d<\/p>\n<h2><span id=\"Food_Webs\" class=\"m-toc-anchor\"><\/span>Food Webs<\/h2>\n<p>\nThese are great for honing in the habits of a few related organisms, but they\u2019re not great when the rabbit decides she wants something else for lunch outside of that specific chain. When we want to consider how other species interact, we can use a food web. A food web is basically like a bunch of food chains together in one diagram that considers more feeding options.<\/p>\n<p>Wildlife biologists can use this to see what kind of trickle-down effect the addition or removal of a species can have on the ecosystem. However, a lot of times this isn\u2019t so easily predictable. A good example is the recent reintroduction of wolves into Yellowstone National Park.<\/p>\n<h3><span id=\"Yellowstone_National_Park_Experiment\" class=\"m-toc-anchor\"><\/span>Yellowstone National Park Experiment<\/h3>\n<p>\nIn 1995, Yellowstone decided to bring wolves back to one of their native habitats. The wolves had previously been hunted off the land and biologists didn\u2019t know how impactful reintroducing them would be. Within just 10 years, they saw a lot of surprising changes in the food web with wolves being the new apex predator. Let\u2019s take a look. <\/p>\n<p>This is a partial food web that shows the main species involved in, or affected by, the wolf\u2019s feeding habits:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2025\/01\/Food-Web.webp\" alt=\"Illustration of a food web showing interactions among animals such as a mouse, beaver, wolf, and deer, along with plants like grass and trees, indicated by arrows and symbols.\" width=\"1836\" height=\"1198\" class=\"aligncenter size-full wp-image-238831\" style=\"box-shadow: 1.5px 1.5px 3px;\" srcset=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2025\/01\/Food-Web.webp 1836w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2025\/01\/Food-Web-300x196.webp 300w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2025\/01\/Food-Web-1024x668.webp 1024w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2025\/01\/Food-Web-768x501.webp 768w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2025\/01\/Food-Web-1536x1002.webp 1536w\" sizes=\"auto, (max-width: 1836px) 100vw, 1836px\" \/><\/p>\n<p>As with any food web, the primary source of energy comes from the sun. This energy is transferred to our bottom row of producers: grasses, aspen trees, cottonwood trees, and willow trees. All of these plants are then food sources for the next row of primary consumers: mice, beavers, elk, and mule deer. <\/p>\n<p>Notice how mice are shown to only eat grass in this partial web, while the elk eats all of the available plants. The next row up shows rough-legged hawk and coyote as predators to the mice and beavers. But the wolf occupies the top-most spot because it is the apex predator, meaning nothing is above it in the food web and nothing will eat it. <\/p>\n<p>To see how wolves have changed how all of these organisms interact, let\u2019s first look at the relationship between wolves and elk. The web shows that wolves are the main predator for elk. So when the wolves were reintroduced, biologists found that the wolves put pressure on the elk, so the elk moved around more to avoid being prey for the wolves. This kept the elk from overgrazing in any certain area and allowed more native grasses and trees to grow back\u2013trees like the aspen, cottonwood, and willow trees. Before the wolves were brought back, elk would eat stems of willow trees so much so that a lot of them couldn\u2019t grow back in the spring. Post-wolf, the willow trees were able to grow back. <\/p>\n<p>Scientists noticed how important willow trees were to the ecosystem by studying beaver populations within the park. Beaver were scarce in the park when the elk were still munching on the willow trees, because, as it turns out, willow trees are also a food and shelter source for beavers. Beaver populations were able to bounce back pretty quickly with fewer elk and more willow trees. <\/p>\n<p>Other changes that were recorded but not listed in the food web here include a boost for scavengers like ravens and grizzly bears who were able to eat more scraps from what wolves left behind. <\/p>\n<h4 style=\"margin-bottom: 0em;\"><span id=\"Trophic_Cascade\" class=\"m-toc-anchor\"><\/span>Trophic Cascade<\/h4>\n<p>\nEssentially one small change, like bringing one species back to its native habitat, caused a rippling effect for the entire ecosystem. This effect is known as a trophic cascade. In reality, hundreds of species were affected by this change and, so far, the wolf has helped balance out Yellowstone\u2019s ecosystem. Their introduction is relatively new, however, so any other conclusions have yet to be drawn. <\/p>\n<p>Ok, now that we\u2019ve discussed food webs and their impact on ecosystems, let\u2019s look at a review question to test your memory.<\/p>\n<hr>\n<\/hr>\n<h2><span id=\"Review_Questions\" class=\"m-toc-anchor\"><\/span>Review Questions<\/h2>\n<p>An omnivore, like an American black bear, most likely occupies which level of the food web?<\/p>\n<ol style=\"list-style: upper-alpha;\">\n<li>Primary producer<\/li>\n<li>Primary consumer<\/li>\n<li>Secondary producer<\/li>\n<li>Secondary consumer<\/li>\n<li>Predator<\/li>\n<li>More than one<\/li>\n<\/ol>\n<div style=\"text-align: center; margin-bottom: 20px;\">\n   <button class=\"buttontranscript\" onClick=\"toggle('Answer1')\">Show Answer<\/button>\n<\/div>\n<div id=\"Answer1\" class=\"showanswer\">\n   <strong>The correct answer is F.<\/strong><\/p>\n<p style=\"text-align: left;\">American black bears are a great example of why we need food webs. Black bears are omnivores, so they eat berries and other plants making them primary consumers, but they also eat meat so they could also occupy the secondary consumer or predator tier in some ecosystems.<\/p>\n<\/div>\n<p>\n&nbsp;<\/p>\n<p>I hope this review was helpful! Thanks for watching, and happy studying!<\/p>\n<ul class=\"citelist\">\n<li><a href=\"https:\/\/www.yellowstonepark.com\/things-to-do\/wolf-reintroduction-changes-ecosystem\"target=\"_blank\">Farquhar, Brodie. 2020. \u201cWolf Reintroduction Changes Ecosystem.\u201d My Yellowstone Park<\/a><\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n<div class=\"home-buttons\">\n<p><a href=\"https:\/\/www.mometrix.com\/academy\/biology\/\">Return to Biology Videos<\/a><\/p>\n<\/div>\n<p><script>\nfunction toggle(obj) {\n          var obj=document.getElementById(obj);\n          if (obj.style.display == \"block\") obj.style.display = \"none\";\n          else obj.style.display = \"block\";\n}\n<\/script><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Return to Biology Videos<\/p>\n","protected":false},"author":1,"featured_media":211789,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"open","template":"","meta":{"footnotes":""},"class_list":{"0":"post-8587","1":"page","2":"type-page","3":"status-publish","4":"has-post-thumbnail","6":"page_category-organisms-biology-videos","7":"page_type-video","8":"subject_matter-science"},"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/pages\/8587","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/comments?post=8587"}],"version-history":[{"count":6,"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/pages\/8587\/revisions"}],"predecessor-version":[{"id":260725,"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/pages\/8587\/revisions\/260725"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/media\/211789"}],"wp:attachment":[{"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/media?parent=8587"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}