{"id":380,"date":"2017-08-23T05:42:25","date_gmt":"2017-08-23T05:42:25","guid":{"rendered":"http:\/\/americanboard.org\/Subjects\/elementary-education\/?page_id=380"},"modified":"2017-09-25T13:22:41","modified_gmt":"2017-09-25T13:22:41","slug":"natural-cycles","status":"publish","type":"page","link":"https:\/\/americanboard.org\/Subjects\/elementary-education\/natural-cycles\/","title":{"rendered":"Natural Cycles"},"content":{"rendered":"<div class=\"twelve columns\" style=\"margin-top: 10%;\">\n<div class=\"advance\"><a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/life-science-2\">\u2b05 Previous Lesson<\/a>\u00a0<a class=\"button\" href=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/life-science\">Workshop Index<\/a>\u00a0<a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/natural-cycles-2\">Next Lesson \u27a1<\/a><\/div>\n<p><!-- CONTENT BEGINS HERE --><\/p>\n<h1 id=\"title\">Natural Cycles<\/h1>\n<h4>Objective<\/h4>\n<p>In the coming pages, we\u2019ll examine several different natural cycles and see how they work in concert to promote and preserve life.<\/p>\n<p>When functioning properly, the environment and ecosystem cycle vital nutrients and energy, providing a renewable supply of necessary products and mechanisms. Many of the processes are very complex, with subtle background processes and interactions not readily apparent but highly important to the functioning of the system. Let\u2019s review some of the most important ones.<\/p>\n<h4>Previously Covered:<\/h4>\n<ul>\n<li>In the preceding section, we reviewed some of the body\u2019s defenses and examined the different systems of the body and their specific functions. We also brushed up on how cells divide in order to grow and heal the body.<\/li>\n<\/ul>\n<section>\n<h3>The Hydrologic Cycle<\/h3>\n<p>The water, or hydrologic, cycle is essential to life on earth, especially that of land animals including humans. Energy from the sun drives the process, through evaporation from oceans and surface water, photosynthesis in plants, and transpiration of water into the atmosphere. Because of the tilt of the earth\u2019s axis, surface water and air are not heated evenly, resulting in seasons, major ocean currents, and weather phenomena such as clouds, wind, and precipitation.<\/p>\n<p>As warm, moisture-laden air rises into the atmosphere, it is cooled and then falls back to earth as precipitation capable of replenishing ground and surface water supplies. Some returns to the oceans. Large areas of plant life, such as the tropical rainforests, are integral in transpiring water into the atmosphere and supplying much of the moisture needed for the rainfall that occurs at the tropical latitudes.<\/p>\n<p>Water helps carry nutrients through ecosystems as it filters through soil and rock. If too much water filters through soil and rock, it can cause <abbr title=\"The wearing away of the Earth\u2019s surface by wind, water, and other means.\">soil erosion<\/abbr>\u00a0or the removal of vegetation by wind or water. Soil erosion increases the sediment load of water, and nutrients are lost from the cycles in an ecosystem. <a class=\"inline cboxElement\" href=\"#hydro\">Click here to see the hydrologic cycle.<\/a><\/p>\n<div style=\"display: none;\">\n<div id=\"hydro\" style=\"padding: 10px; background: #fff;\">\n<h4>Hydrologic Cycle<\/h4>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/wp-content\/uploads\/sites\/4\/2017\/08\/hydrocycle.jpg\" alt=\"Hydrologic cycle\" \/><\/center><\/div>\n<\/div>\n<h3>The Carbon Cycle<\/h3>\n<p><abbr title=\"A plentiful nonmetallic element that occurs in many inorganic and in all organic compounds.\">Carbon<\/abbr> is stored, or sequestered, in several places, often called reservoirs. During aerobic respiration, carbon dioxide (CO2) is given off as waste, releasing carbon from cellular metabolism. Volcanic eruptions, weathering, and burning of fossil fuels, in particular, release large amounts of carbon into the atmosphere. Photosynthetic organisms take up large amounts of carbon for incorporation into carbohydrates and then release oxygen as a by-product of photosynthesis.<\/p>\n<p>Animals and other organisms utilize this oxygen in cellular respiration and excrete carbon dioxide as a waste product. As vegetation is removed through deforestation and as increasing amounts of carbon are released, photosynthetic uptake and carbon sequestering cannot keep up. The increase in carbon dioxide and other gases are believed to be responsible for increases in surface temperatures on earth. <a class=\"inline cboxElement\" href=\"#carbon\">Click here to see the carbon cycle.<\/a><\/p>\n<div style=\"display: none;\">\n<div id=\"carbon\" style=\"padding: 10px; background: #fff;\">\n<h4>Carbon Cycle<\/h4>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/wp-content\/uploads\/sites\/4\/2017\/08\/carboncycle.jpg\" alt=\"Carbon cycle\" \/><\/center><\/p>\n<p class=\"figcaption\">This NASA image shows the components of the carbon cycle.<\/p>\n<\/div>\n<\/div>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p>Rainforests move water into the atmosphere by<\/p>\n<ol>\n<li>saturation.<\/li>\n<li>transpiration.<\/li>\n<li>sublimation.<\/li>\n<li>condensation.<\/li>\n<\/ol>\n<p><a class=\"q-answer button button-primary\">Reveal Answer<\/a><\/p>\n<p class=\"q-reveal\">The correct answer is B. Transpiration occurs as plants take in water through their roots and move it out into the atmosphere through their <abbr title=\"Tiny pores in the epidermis of a leaf or stem that allow water vapor and other gases to pass through.\">stomata<\/abbr>.<\/p>\n<\/section>\n<h3>The Nitrogen Cycle<\/h3>\n<p>Most of the air you breathe is nitrogen. Essential to living organisms, nitrogen is a critical component of proteins and nucleic acids and is often in short supply. Despite their dependence on nitrogen, very few organisms can make any use of the atmospheric N<sub>2<\/sub> form of nitrogen. They depend on the nitrogen cycle and the role of specific organisms to supply the nitrogen needed. There are several components of the nitrogen cycle, which converts atmospheric nitrogen to a useable form and eventually back to N<sub>2<\/sub>.<\/p>\n<p>Nitrogen fixation is the conversion of N<sub>2<\/sub> to ammonia (NH<sub>3<\/sub>) by several species of aquatic or terrestrial bacteria, either symbiotic with plants or living in the soil. NH<sub>3<\/sub> can dissolve quickly in water and is converted to ammonium, which is then taken into the tissues of plants, such as soybeans, as well as organisms feeding on these plants in a process called <abbr title=\"The taking in of digested substances from food into the tissues.\">assimilation<\/abbr>. Nitrogen is also released through waste products when these organisms die and decompose. Thus, without the essential nitrogen-fixing organisms, modern agriculture often must add sufficient nitrogen to soils in order for food crops to grow.<\/p>\n<p><abbr title=\"The production of ammonia when decomposition of organic matter occurs.\">Ammonification<\/abbr> occurs when bacteria convert nitrogen from wastes or decomposition to NH<sub>3<\/sub>, which again is dissolved to form ammonium. Nitrification is the process of converting some of the ammonium in the soil into nitrates or nitrites that can then be assimilated by plants or animals. Denitrification occurs when other bacteria convert nitrates back to N<sub>2<\/sub>, which is then released into the atmosphere. <a class=\"inline cboxElement\" href=\"#nitrogen\">Click here to see a NASA image of the nitrogen cycle.<\/a><\/p>\n<div style=\"display: none;\">\n<div id=\"nitrogen\" style=\"padding: 10px; background: #fff;\">\n<h4>Nitrogen Cycle<\/h4>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/wp-content\/uploads\/sites\/4\/2017\/08\/nitrocycle.gif\" alt=\"Nitrogen cycle\" \/><\/center><\/div>\n<\/div>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p>Rainforests move water into the atmosphere by<\/p>\n<ol>\n<li>the conversion of nitrogen by bacteria.<\/li>\n<li>the conversion of nitrates back to N<sub>2<\/sub>.<\/li>\n<li>the intake of ammonium by plants and the animals that eat them.<\/li>\n<li>the conversion of N<sub>2<\/sub> to ammonia.<\/li>\n<\/ol>\n<p><a class=\"q-answer button button-primary\">Reveal Answer<\/a><\/p>\n<p class=\"q-reveal\">The correct answer is C. Choices A, B, and D also describe different parts of the nitrogen cycle. Assimilation, however, refers to the taking in of nutrient material into the tissue of a living organism.<\/p>\n<\/section>\n<h3>Energy<\/h3>\n<p>If an ecosystem is composed of many interactions between organisms and their environment, the most essential of these interactions is the flow of energy throughout the system.<\/p>\n<p>As in the nitrogen cycle, sunlight is abundant on earth but available for use only by producers such as green plants and some bacteria and algae. Thus, while humans are the most evolved of species physiologically, we depend upon the actions of often very simple organisms for our survival.<\/p>\n<h4>Food Chains and Food Webs<\/h4>\n<p>The flow of energy from the sun to producers, consumers, and decomposers is often represented by a food chain, though the actual flow of energy is much more complex and is better represented by a still oversimplified food web.<\/p>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/wp-content\/uploads\/sites\/4\/2017\/08\/foodweb.jpg\" alt=\"Basic food web\" \/><\/center>The initial use of sunlight by producers is the same in either representation; however, in a food web, more pathways for energy flow from producers to different types of consumers and decomposers exist. Some consumers, such as herbivores, eat only plants but are themselves consumed by secondary or tertiary consumers. Other organisms eat both plants and animals, and all organisms will be decomposed. At each stage, much energy is consumed for metabolism and lost as heat.<\/p>\n<p>Another revealing representation of energy flow is the <em>energy pyramid<\/em>. With most energy from the sun available to the producers, they are given the bottom portion of the pyramid. As you can see, only a fraction of the energy received by plants is actually available to herbivores, and even less is available to carnivores and decomposers.<\/p>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p><em>Autotrophs<\/em> are organisms capable of producing their own \u201cfood.\u201d They would be considered<\/p>\n<ol>\n<li>tertiary consumers.<\/li>\n<li>predators.<\/li>\n<li>decomposers.<\/li>\n<li>primary producers<\/li>\n<\/ol>\n<p><a class=\"q-answer button button-primary\">Reveal Answer<\/a><\/p>\n<p class=\"q-reveal\">The correct answer is D. Primary producers are the first link in the food chain (and the first level of the food web). A plant is a good example of an autotroph\u2014it uses photosynthesis to produce its own nourishment. The energy created by the plant travels up the food chain until it reaches the top predator level.<\/p>\n<\/section>\n<h3>Seasonal Cycles<\/h3>\n<p>Within many ecosystems outside of the tropics, the flow of energy changes dramatically throughout the year. Winter represents the highest stress time for many organisms; most plants either die or become dormant, while animals either migrate, hibernate, or deal with the harsh conditions. Nutrients are still available in dormant or even dead plants but often the plants are buried under snow or are very scarce. Some species will switch diets, while others will live off of fat reserves built up during the warmer seasons and feed very little.<\/p>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/wp-content\/uploads\/sites\/4\/2017\/08\/seasons.png\" alt=\"Tilt of the earth against the Sun for seasons\" \/><\/center>As the daylight begins to lengthen in springtime, increased sunlight is available. Soil temperatures warm and plants begin moving stored nutrients from the roots to the branches to supply buds and developing stems and leaves. Seeds lying dormant can begin to germinate, and food for primary consumers becomes abundant again. Many organisms, such as deer, time the birth of their young to coincide with peak vegetation growth in late spring.<\/p>\n<p>Summer and fall are critical times for hibernating and non-hibernating organisms to obtain sufficient energy to recover from winter stress, breed, raise young, and gain fat levels needed to survive the next winter.<\/p>\n<p>In some animals, such as elk, insufficient fall preparation creates a much lower chance of surviving the winter. Some will not breed in the fall because their nutritional level is so poor. The length of daylight hours drives migration patterns of many birds, but as global temperatures have increased so have soil temperatures and vegetation emergence. Insect emergence is beginning to occur before some migratory species move through; The peak availability of food is no longer in sync with the hatching of young.<\/p>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p>How might the energy pyramid look if it showed the actual number of organisms in an ecosystem instead of the amount of energy available to each?<\/p>\n<ol>\n<li>It would look essentially the same.<\/li>\n<li>It would be inverted.<\/li>\n<li>It would be narrower at the bottom and wider at the top.<\/li>\n<li>None of the above<\/li>\n<\/ol>\n<p><a class=\"q-answer button button-primary\">Reveal Answer<\/a><\/p>\n<p class=\"q-reveal\">The correct answer is A. Because less energy is available to top consumers, an ecosystem can support far fewer of these organisms than it can plants and herbivores.<\/p>\n<\/section>\n<h3>Review<\/h3>\n<ul>\n<li>Energy from the sun drives the hydrologic cycle, photosynthesis in plants, and transpiration of water.<\/li>\n<li>Few organisms can make any use of the atmospheric N<sub>2<\/sub>, making them dependent on the nitrogen cycle.<\/li>\n<li>The food chain is arranged by trophic levels: producers, consumers (primary, secondary, etc.), and decomposers.<\/li>\n<li>The varying temperatures of the seasonal cycle have a dramatic effect on the operation of the food chain (or food web).<\/li>\n<\/ul>\n<\/section>\n<p><!-- CONTENT ENDS HERE --><\/p>\n<div class=\"advance\"><a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/life-science-2\">\u2b05 Previous Lesson<\/a>\u00a0<a class=\"button\" href=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/life-science\">Workshop Index<\/a>\u00a0<a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/natural-cycles-2\">Next Lesson \u27a1<\/a><\/div>\n<p><a class=\"backtotop\" href=\"#title\">Back to Top<\/a><\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>\u2b05 Previous Lesson\u00a0Workshop Index\u00a0Next Lesson \u27a1 Natural Cycles Objective In the coming pages, we\u2019ll examine several different natural cycles and see how they work in concert to promote and preserve life. When functioning properly, the environment and ecosystem cycle vital nutrients and energy, providing a renewable supply of necessary products and mechanisms. Many of the [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-380","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/americanboard.org\/Subjects\/elementary-education\/wp-json\/wp\/v2\/pages\/380","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/americanboard.org\/Subjects\/elementary-education\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/americanboard.org\/Subjects\/elementary-education\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/americanboard.org\/Subjects\/elementary-education\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/americanboard.org\/Subjects\/elementary-education\/wp-json\/wp\/v2\/comments?post=380"}],"version-history":[{"count":11,"href":"https:\/\/americanboard.org\/Subjects\/elementary-education\/wp-json\/wp\/v2\/pages\/380\/revisions"}],"predecessor-version":[{"id":1326,"href":"https:\/\/americanboard.org\/Subjects\/elementary-education\/wp-json\/wp\/v2\/pages\/380\/revisions\/1326"}],"wp:attachment":[{"href":"https:\/\/americanboard.org\/Subjects\/elementary-education\/wp-json\/wp\/v2\/media?parent=380"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}