{"id":214,"date":"2015-07-21T05:01:32","date_gmt":"2015-07-21T05:01:32","guid":{"rendered":"https:\/\/courses.candelalearning.com\/bio2labsxmaster2\/?post_type=chapter&#038;p=214"},"modified":"2016-01-08T22:22:05","modified_gmt":"2016-01-08T22:22:05","slug":"community-ecology","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-bio2labs\/chapter\/community-ecology\/","title":{"raw":"Community Ecology Lab","rendered":"Community Ecology Lab"},"content":{"raw":"<p class=\"p1\"><em><span class=\"s1\">Lab adapted by Staci Forgey and Dr. James Holden, Tidewater Community College biology faculty, with permission from Dr. William Edwards, biology faculty at Niagara University.<\/span><\/em><\/p>\r\n\r\n<div class=\"textbox shaded\">\r\n<h2 class=\"p3\"><span class=\"s1\"><b>Learning Objectives<\/b><\/span><\/h2>\r\n<ul>\r\n\t<li class=\"p3\"><span class=\"s1\">Describe the processes of primary succession and secondary succession<\/span><\/li>\r\n\t<li class=\"p3\"><span class=\"s1\">Explain what makes a community and an ecosystem different<\/span><\/li>\r\n\t<li class=\"p3\"><span class=\"s1\">Describe the differences between abiotic and biotic factors<\/span><\/li>\r\n\t<li class=\"p3\"><span class=\"s1\">Explain why disturbances play an important role in the progression of succession<\/span><\/li>\r\n\t<li class=\"p3\"><span class=\"s1\">Define a climax community<\/span><\/li>\r\n\t<li class=\"p3\"><span class=\"s1\">Describe why most areas will not make it to a climax community<\/span><\/li>\r\n\t<li class=\"p3\"><span class=\"s1\">Describe the plant communities present after glacial succession and how they change the environment<\/span><\/li>\r\n\t<li class=\"p3\"><span class=\"s1\">Explain the stages of succession of milk<\/span><\/li>\r\n\t<li class=\"p3\"><span class=\"s1\">Describe how pH changes as milk goes through successional stages<\/span><\/li>\r\n\t<li class=\"p3\"><span class=\"s1\">Explain the difference between gram negative and positive bacteria<\/span><\/li>\r\n\t<li class=\"p3\"><span class=\"s1\">Draw and describe the shapes of bacteria<\/span><\/li>\r\n\t<li class=\"p3\"><span class=\"s1\">Formulate a hypothesis based on background data<\/span><\/li>\r\n<\/ul>\r\n<\/div>\r\nhttp:\/\/www.slideshare.net\/CandelaContent\/succession-51120026\r\n<h2 class=\"p3\">Ecological Succession of Bacteria in Milk<\/h2>\r\n<p class=\"p3\"><span class=\"s1\">The communities within ecosystems develop over time, from very simple species assemblages, to complex, rich ecosystems.<span class=\"Apple-converted-space\">\u00a0<\/span>In this process, called succession, each <i>succeeding<\/i> species facilitates changes in environment which allow new species to come into the ecosystem.<span class=\"Apple-converted-space\">\u00a0<\/span>As the community becomes more and more complex, the biodiversity of the ecosystem also increases.<span class=\"Apple-converted-space\">\u00a0<\/span>Both biotic and abiotic processes can reset the succession process.<span class=\"Apple-converted-space\">\u00a0<\/span>That is, events cause by both the community itself, and outside events can return the community to an earlier succession state.<span class=\"Apple-converted-space\">\u00a0<\/span>The gradual changes in the community are both orderly and predictable in many ecosystems.<span class=\"Apple-converted-space\">\u00a0<\/span>The peak or most complex, advanced community that can develop in any abiotic environment is called the climax community.<span class=\"Apple-converted-space\">\u00a0<\/span>The picture below describes the developing communities as a series of steps, each of which can be driven against the succession process by disturbances:<\/span><\/p>\r\n<p class=\"p3\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/745\/2015\/07\/23081107\/Screen-Shot-2015-07-20-at-10.42.23-PM.png\"><img class=\"alignnone wp-image-215 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/745\/2015\/07\/23081107\/Screen-Shot-2015-07-20-at-10.42.23-PM.png\" alt=\"Succession of ecosystems. It shows bare ground leading toward pioneer stage then secondary succession towards the climax.\" width=\"498\" height=\"216\" \/><\/a><\/p>\r\n\r\n<div class=\"textbox shaded\">\r\n<h3>Question<\/h3>\r\n<ol>\r\n\t<li class=\"p3\"><span class=\"s1\">What types of events could \"reset\" a succession process? Name at least one biotic and one abiotic disturbance.<\/span><\/li>\r\n<\/ol>\r\n<\/div>\r\n<p class=\"p3\"><span class=\"s1\">One example of a severe disturbance, reducing the land to bare ground, is the passage of a glacier.<span class=\"Apple-converted-space\">\u00a0<\/span>Though glaciers have not covered this part of North America for ten thousand years, there are parts of the continent that are even now becoming uncovered by receding glaciers.<span class=\"Apple-converted-space\">\u00a0<\/span>One area is the pacific northwest.<span class=\"Apple-converted-space\">\u00a0<\/span>From Juneau to Glacier Bay, many glaciers which have previously fallen directly into the ocean are now leaving bare soil which has not been exposed for more than fifty thousand years.<span class=\"Apple-converted-space\">\u00a0<\/span>Because the glaciers retreat very slowly, we can watch communities change across time in a single snap shot.<span class=\"Apple-converted-space\">\u00a0<\/span>Take the glaciers of Glacier Bay National Park, midway between Juneau and Anchorage, Alaska.<span class=\"Apple-converted-space\">\u00a0<\/span>The glaciers there have been retreating since the explorer Vancouver\u2019s first expedition in 1794.<span class=\"Apple-converted-space\">\u00a0<\/span>Since then, the retreat has covered over 100 km, including new coastline, meadows and mountains:<\/span><\/p>\r\n<p class=\"p3\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/745\/2015\/07\/23081109\/Screen-Shot-2015-07-20-at-10.48.13-PM.png\"><img class=\"alignnone wp-image-216 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/745\/2015\/07\/23081109\/Screen-Shot-2015-07-20-at-10.48.13-PM.png\" alt=\"Map of the retreating glaciers at Glacier Bay National Park\" width=\"346\" height=\"394\" \/><\/a><\/p>\r\n\r\n<div class=\"textbox shaded\">\r\n<h3><span class=\"s1\">Question<\/span><\/h3>\r\n<ol>\r\n\t<li><span class=\"s1\">Explain how this retreat will result in different communities along the glacier\u2019s retreat, though in similar environments.<span class=\"Apple-converted-space\">\u00a0<\/span>Hint: what is the difference between exposed soil at point A and point B.<\/span><\/li>\r\n<\/ol>\r\n<\/div>\r\n<p class=\"p9\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/745\/2015\/07\/23081110\/Screen-Shot-2015-07-20-at-10.52.12-PM.png\"><img class=\"alignnone wp-image-217 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/745\/2015\/07\/23081110\/Screen-Shot-2015-07-20-at-10.52.12-PM.png\" alt=\"Image showing the progression of the ecosystem, beginning at exposed rocks and progressing towards a mature forest and then a climax forest.\" width=\"624\" height=\"319\" \/><\/a><\/p>\r\n<p class=\"p3\"><span class=\"s1\">As the glacier retreats, it leaves nutrient poor soil which can only support simple plants such as liverworts, lichens, and other primitive plants.<span class=\"Apple-converted-space\">\u00a0<\/span>As they photosynthesize and die, we see them enter the decomposer pathway and increase the quality of the soil for later plants.<span class=\"Apple-converted-space\">\u00a0<\/span>However, this slow glacier retreat is a unique situation.<span class=\"Apple-converted-space\">\u00a0<\/span>To set up an experiment to test our understanding of succession would require hundreds of years, longer than a scientists lifetime.<span class=\"Apple-converted-space\">\u00a0<\/span>However, some organisms and communities proceed at a much faster rate, within your own refrigerators.\u00a0The process of milk decomposition from a community of bacteria can test the same processes and theories in a much more reasonable time frame.<span class=\"Apple-converted-space\">\u00a0<\/span>This substitution of a simpler and faster community for experimental purposes is called a \u2018model\u2019 system. <\/span><\/p>\r\n<p class=\"p3\"><span class=\"s1\">Milk is a highly nutritious food containing carbohydrates (lactose, or milk sugar), proteins (casein, or curd), and lipids (butterfat). This high level of nutrition makes milk an excellent medium for the growth of bacteria.<span class=\"Apple-converted-space\">\u00a0<\/span>Pasteurizing milk does not sterilize it (sterilizing kills <i>all <\/i>bacteria) but merely destroys pathogenic bacteria, leaving many bacteria that can multiply and these bacteria will begin to grow and bring about milk spoilage. Biologists have discovered that as milk ages, changing conditions in the milk bring about a predictable, orderly succession of microorganism communities. <\/span><\/p>\r\n<p class=\"p3\"><span class=\"s1\">In this laboratory exercise, you will observe successional patterns in several types of milk.<span class=\"Apple-converted-space\">\u00a0<\/span>You will record changes in the environmental conditions of the types of milk as they age.<span class=\"Apple-converted-space\">\u00a0<\/span>These changes are a result of changes in the bacterial communities.<span class=\"Apple-converted-space\">\u00a0Here are s<\/span>ome of the major bacteria found at various stages.<\/span><\/p>\r\n\r\n<h3 class=\"p3\"><span class=\"s1\">Stages of Milk Succession<\/span><\/h3>\r\n<ol>\r\n\t<li class=\"p3\"><span class=\"s1\"><i>Psuedomonas <\/i>and <i>Achromobacter<\/i> (gram-negative rods) digest butterfat and give milk a putrid smell<\/span><\/li>\r\n\t<li class=\"p3\"><span class=\"s1\"><i>Lactobacillus<\/i> (gram-positive rod) and <i>Streptococcus <\/i>(gram-positive coccus) ferment lactose to lactic acid and acetic acid.<\/span><\/li>\r\n\t<li class=\"p3\"><span class=\"s1\">Acidity sours milk and converts casein to curd.<\/span><\/li>\r\n\t<li class=\"p3\"><span class=\"s1\">Yeast (fungi) thrive in acidic conditions and metabolize the acids into non-acidic compounds.<\/span><\/li>\r\n\t<li class=\"p3\"><span class=\"s1\"><i>Bacillus<\/i> metabolize proteins into ammonia products and raise the milk\u2019s pH. Spoiled milk odor is very noticeable at this stage.<\/span><\/li>\r\n<\/ol>\r\n<div class=\"textbox shaded\">\r\n<h3>Questions<\/h3>\r\n<ol>\r\n\t<li><span class=\"s1\">What are some advantages to using bacteria as opposed to plants in this experiment?<\/span><\/li>\r\n\t<li>What factors might speed or delay a successional process? Apply your example to succession in milk.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<p class=\"p3\"><span class=\"s1\">Locate the milk samples available in the lab.<span class=\"Apple-converted-space\">\u00a0<\/span>Take a look at the samples and form two conditions you would like to study.<span class=\"Apple-converted-space\">\u00a0<\/span>Develop a short design for studying the first condition, state the dependent and independent variable, control and experimental group, the hypothesis and any variables which have been controlled.<span class=\"Apple-converted-space\">\u00a0<\/span>Then develop a short design for studying the second condition, state the dependent and independent variable, control and experimental group, the hypothesis and any variables which have been controlled.\u00a0<\/span><\/p>\r\n<p class=\"p3\"><span class=\"s1\">Just as in any of our experiments, you must use effective scientific method<b>.<span class=\"Apple-converted-space\">\u00a0<\/span><\/b>Develop hypotheses (at least 2\u2014one with different milk types and one with either temperature or time as an independent variable) that you can test in the process of the milk community succession.<\/span><\/p>\r\n<p class=\"p3\"><span class=\"s1\">We will be performing a gram stain on our milk samples.<span class=\"Apple-converted-space\">\u00a0<\/span>Remember from our microbiology section that bacteria can be either gram negative (pink) or gram positive (purple).<span class=\"Apple-converted-space\">\u00a0<\/span>We will also look at these bacteria under a microscope to identify their shapes.<span class=\"Apple-converted-space\">\u00a0<\/span>Recall that bacteria can be cocci, bacilli, or spirillum.\u00a0<\/span><\/p>\r\n\r\n<div class=\"textbox shaded\">\r\n<h3 class=\"p3\">Questions<\/h3>\r\n<ol>\r\n\t<li><span class=\"s1\">What hypotheses are you testing?\u00a0List both here.\u00a0<\/span><\/li>\r\n\t<li><span class=\"s1\">What information led you to ask these hypotheses?<\/span><\/li>\r\n\t<li><span class=\"s1\">Make predictions about your hypotheses. i.e. How will you know if the data supports or refutes your hypotheses?<\/span><\/li>\r\n\t<li><span class=\"s1\">Be sure to identify the variables you will <i>test<\/i>, and those you will <i>control<\/i> for each experiment.<\/span><\/li>\r\n\t<li><span class=\"s1\">Prepare a table for data collection.<span class=\"Apple-converted-space\">\u00a0<\/span>You will be recording the pH, smell, consistency, and bacteria shapes and colors present in your milk samples.\u00a0<\/span><\/li>\r\n<\/ol>\r\n<\/div>\r\n<p class=\"p3\"><span class=\"s1\">On each lab bench are several small beakers.<span class=\"Apple-converted-space\">\u00a0<\/span>You will obtain a sample of the milk samples you need for your experimental design and test the pH, color, consistency, smell and other characteristics of each sample.<span class=\"Apple-converted-space\">\u00a0<\/span>For each milk sample:\u00a0<\/span><\/p>\r\n\r\n<ol>\r\n\t<li class=\"p3\"><span class=\"s1\">Using the Vernier, take the pH of each flask. Record your results.<\/span><\/li>\r\n\t<li class=\"p3\"><span class=\"s1\">Record the color, odor (sour, putrid), and consistency (coagulation slight, moderate, chunky) for the milk in each flask.<\/span><\/li>\r\n\t<li class=\"p11\"><span class=\"s1\">Perform Gram Staining as outlined below.<span class=\"Apple-converted-space\">\u00a0<strong>Note: We will be using\u00a0chemicals\u00a0and open flames. Exercise caution when\u00a0performing this portion of the lab.<\/strong><\/span><\/span><\/li>\r\n<\/ol>\r\n<h3 class=\"p12\"><span class=\"s1\">Materials<\/span><\/h3>\r\n<ul>\r\n\t<li class=\"p11\"><span class=\"s1\">Microscope slide<\/span><\/li>\r\n\t<li class=\"p11\"><span class=\"s1\">Bunsen burner and tubing<\/span><\/li>\r\n\t<li class=\"p11\"><span class=\"s1\">Crystal violet (primary stain)<\/span><\/li>\r\n\t<li class=\"p11\"><span class=\"s1\">Iodine solution\/Gram's Iodine (mordant that fixes crystal violet to cell wall)<\/span><\/li>\r\n\t<li class=\"p11\"><span class=\"s1\">Decolorizer (e.g. ethanol)<\/span><\/li>\r\n\t<li class=\"p11\"><span class=\"s1\">Safranin (secondary stain)<\/span><\/li>\r\n\t<li class=\"p11\"><span class=\"s1\">Water (preferably in a squirt bottle)<\/span><\/li>\r\n<\/ul>\r\n<h3>Procedure<\/h3>\r\n<ol>\r\n\t<li class=\"p11\"><span class=\"s1\">Make a slide with your milk sample to be stained. Heat fix the sample to the slide by carefully passing the slide with a drop or small piece of sample on it through a Bunsen burner three times.<\/span><\/li>\r\n\t<li class=\"p11\"><span class=\"s1\">Add the primary stain (crystal violet) to the sample\/slide and let sit for 15 seconds. Rinse slide with a gentle stream of water for a maximum of 5 seconds to remove unbound crystal violet.<\/span><\/li>\r\n\t<li class=\"p11\"><span class=\"s1\">Add Gram's iodine for 15 seconds - this is an agent that fixes the crystal violet to the bacterial cell wall.<\/span><\/li>\r\n\t<li class=\"p11\"><span class=\"s1\">Rinse sample\/slide with acetone or alcohol for ~3 seconds and <b>rinse with a gentle stream of water<\/b>. The alcohol will decolorize the sample if it is Gram negative, removing the crystal violet. However, <b>if the alcohol remains on the sample for too long, it may also decolorize Gram positive cells<\/b>.<\/span><\/li>\r\n\t<li class=\"p11\"><span class=\"s1\">Add the secondary stain, safranin, to the slide and incubate for 15 seconds.<span class=\"Apple-converted-space\">\u00a0 <\/span>Wash with a gentle stream of water for a maximum of 5 seconds. If the bacteria is Gram positive, it will retain the primary stain (crystal violet) and not take the secondary stain (safranin), causing it to look violet\/purple under a microscope. If the bacteria is Gram negative, it will lose the primary stain and take the secondary stain, causing it to appear red when viewed under a microscope.<\/span><\/li>\r\n<\/ol>\r\n<div class=\"textbox shaded\">\r\n<h3 class=\"p3\"><span class=\"s1\"><b>Questions<\/b><\/span><\/h3>\r\n<ol>\r\n\t<li class=\"p14\"><span class=\"s1\">Describe the changing sequence of organisms and corresponding environmental changes during succession in the milk samples.<span class=\"Apple-converted-space\">\u00a0<\/span>Which bacteria are in each of your milk samples?<\/span><\/li>\r\n\t<li class=\"p14\"><span class=\"s1\">Describe the changing sequence of organisms and corresponding environmental changes during succession in chocolate milk. Do the results of your investigation match your hypothesis?<\/span><\/li>\r\n\t<li class=\"p14\"><span class=\"s1\">Compare succession in one or more types milk. Propose reasons for differences.<\/span><\/li>\r\n\t<li class=\"p14\"><span class=\"s1\">Propose another experiment to test the environmental factors and\/or organisms changing in your proposed scenario for milk succession.<\/span><\/li>\r\n\t<li class=\"p14\"><span class=\"s1\">How could you improve your test of the hypotheses?<span class=\"Apple-converted-space\">\u00a0<\/span>Be specific!<\/span><\/li>\r\n\t<li class=\"p14\"><span class=\"s1\">Identify what happened to the pH of the milk as time passed.<\/span><\/li>\r\n\t<li class=\"p14\"><span class=\"s1\">Infer what the change in pH means about the populations of microorganisms in the milk.<\/span><\/li>\r\n<\/ol>\r\n<\/div>","rendered":"<p class=\"p1\"><em><span class=\"s1\">Lab adapted by Staci Forgey and Dr. James Holden, Tidewater Community College biology faculty, with permission from Dr. William Edwards, biology faculty at Niagara University.<\/span><\/em><\/p>\n<div class=\"textbox shaded\">\n<h2 class=\"p3\"><span class=\"s1\"><b>Learning Objectives<\/b><\/span><\/h2>\n<ul>\n<li class=\"p3\"><span class=\"s1\">Describe the processes of primary succession and secondary succession<\/span><\/li>\n<li class=\"p3\"><span class=\"s1\">Explain what makes a community and an ecosystem different<\/span><\/li>\n<li class=\"p3\"><span class=\"s1\">Describe the differences between abiotic and biotic factors<\/span><\/li>\n<li class=\"p3\"><span class=\"s1\">Explain why disturbances play an important role in the progression of succession<\/span><\/li>\n<li class=\"p3\"><span class=\"s1\">Define a climax community<\/span><\/li>\n<li class=\"p3\"><span class=\"s1\">Describe why most areas will not make it to a climax community<\/span><\/li>\n<li class=\"p3\"><span class=\"s1\">Describe the plant communities present after glacial succession and how they change the environment<\/span><\/li>\n<li class=\"p3\"><span class=\"s1\">Explain the stages of succession of milk<\/span><\/li>\n<li class=\"p3\"><span class=\"s1\">Describe how pH changes as milk goes through successional stages<\/span><\/li>\n<li class=\"p3\"><span class=\"s1\">Explain the difference between gram negative and positive bacteria<\/span><\/li>\n<li class=\"p3\"><span class=\"s1\">Draw and describe the shapes of bacteria<\/span><\/li>\n<li class=\"p3\"><span class=\"s1\">Formulate a hypothesis based on background data<\/span><\/li>\n<\/ul>\n<\/div>\n<p>http:\/\/www.slideshare.net\/CandelaContent\/succession-51120026<\/p>\n<h2 class=\"p3\">Ecological Succession of Bacteria in Milk<\/h2>\n<p class=\"p3\"><span class=\"s1\">The communities within ecosystems develop over time, from very simple species assemblages, to complex, rich ecosystems.<span class=\"Apple-converted-space\">\u00a0<\/span>In this process, called succession, each <i>succeeding<\/i> species facilitates changes in environment which allow new species to come into the ecosystem.<span class=\"Apple-converted-space\">\u00a0<\/span>As the community becomes more and more complex, the biodiversity of the ecosystem also increases.<span class=\"Apple-converted-space\">\u00a0<\/span>Both biotic and abiotic processes can reset the succession process.<span class=\"Apple-converted-space\">\u00a0<\/span>That is, events cause by both the community itself, and outside events can return the community to an earlier succession state.<span class=\"Apple-converted-space\">\u00a0<\/span>The gradual changes in the community are both orderly and predictable in many ecosystems.<span class=\"Apple-converted-space\">\u00a0<\/span>The peak or most complex, advanced community that can develop in any abiotic environment is called the climax community.<span class=\"Apple-converted-space\">\u00a0<\/span>The picture below describes the developing communities as a series of steps, each of which can be driven against the succession process by disturbances:<\/span><\/p>\n<p class=\"p3\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/745\/2015\/07\/23081107\/Screen-Shot-2015-07-20-at-10.42.23-PM.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-215 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/745\/2015\/07\/23081107\/Screen-Shot-2015-07-20-at-10.42.23-PM.png\" alt=\"Succession of ecosystems. It shows bare ground leading toward pioneer stage then secondary succession towards the climax.\" width=\"498\" height=\"216\" \/><\/a><\/p>\n<div class=\"textbox shaded\">\n<h3>Question<\/h3>\n<ol>\n<li class=\"p3\"><span class=\"s1\">What types of events could &#8220;reset&#8221; a succession process? Name at least one biotic and one abiotic disturbance.<\/span><\/li>\n<\/ol>\n<\/div>\n<p class=\"p3\"><span class=\"s1\">One example of a severe disturbance, reducing the land to bare ground, is the passage of a glacier.<span class=\"Apple-converted-space\">\u00a0<\/span>Though glaciers have not covered this part of North America for ten thousand years, there are parts of the continent that are even now becoming uncovered by receding glaciers.<span class=\"Apple-converted-space\">\u00a0<\/span>One area is the pacific northwest.<span class=\"Apple-converted-space\">\u00a0<\/span>From Juneau to Glacier Bay, many glaciers which have previously fallen directly into the ocean are now leaving bare soil which has not been exposed for more than fifty thousand years.<span class=\"Apple-converted-space\">\u00a0<\/span>Because the glaciers retreat very slowly, we can watch communities change across time in a single snap shot.<span class=\"Apple-converted-space\">\u00a0<\/span>Take the glaciers of Glacier Bay National Park, midway between Juneau and Anchorage, Alaska.<span class=\"Apple-converted-space\">\u00a0<\/span>The glaciers there have been retreating since the explorer Vancouver\u2019s first expedition in 1794.<span class=\"Apple-converted-space\">\u00a0<\/span>Since then, the retreat has covered over 100 km, including new coastline, meadows and mountains:<\/span><\/p>\n<p class=\"p3\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/745\/2015\/07\/23081109\/Screen-Shot-2015-07-20-at-10.48.13-PM.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-216 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/745\/2015\/07\/23081109\/Screen-Shot-2015-07-20-at-10.48.13-PM.png\" alt=\"Map of the retreating glaciers at Glacier Bay National Park\" width=\"346\" height=\"394\" \/><\/a><\/p>\n<div class=\"textbox shaded\">\n<h3><span class=\"s1\">Question<\/span><\/h3>\n<ol>\n<li><span class=\"s1\">Explain how this retreat will result in different communities along the glacier\u2019s retreat, though in similar environments.<span class=\"Apple-converted-space\">\u00a0<\/span>Hint: what is the difference between exposed soil at point A and point B.<\/span><\/li>\n<\/ol>\n<\/div>\n<p class=\"p9\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/745\/2015\/07\/23081110\/Screen-Shot-2015-07-20-at-10.52.12-PM.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-217 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/745\/2015\/07\/23081110\/Screen-Shot-2015-07-20-at-10.52.12-PM.png\" alt=\"Image showing the progression of the ecosystem, beginning at exposed rocks and progressing towards a mature forest and then a climax forest.\" width=\"624\" height=\"319\" \/><\/a><\/p>\n<p class=\"p3\"><span class=\"s1\">As the glacier retreats, it leaves nutrient poor soil which can only support simple plants such as liverworts, lichens, and other primitive plants.<span class=\"Apple-converted-space\">\u00a0<\/span>As they photosynthesize and die, we see them enter the decomposer pathway and increase the quality of the soil for later plants.<span class=\"Apple-converted-space\">\u00a0<\/span>However, this slow glacier retreat is a unique situation.<span class=\"Apple-converted-space\">\u00a0<\/span>To set up an experiment to test our understanding of succession would require hundreds of years, longer than a scientists lifetime.<span class=\"Apple-converted-space\">\u00a0<\/span>However, some organisms and communities proceed at a much faster rate, within your own refrigerators.\u00a0The process of milk decomposition from a community of bacteria can test the same processes and theories in a much more reasonable time frame.<span class=\"Apple-converted-space\">\u00a0<\/span>This substitution of a simpler and faster community for experimental purposes is called a \u2018model\u2019 system. <\/span><\/p>\n<p class=\"p3\"><span class=\"s1\">Milk is a highly nutritious food containing carbohydrates (lactose, or milk sugar), proteins (casein, or curd), and lipids (butterfat). This high level of nutrition makes milk an excellent medium for the growth of bacteria.<span class=\"Apple-converted-space\">\u00a0<\/span>Pasteurizing milk does not sterilize it (sterilizing kills <i>all <\/i>bacteria) but merely destroys pathogenic bacteria, leaving many bacteria that can multiply and these bacteria will begin to grow and bring about milk spoilage. Biologists have discovered that as milk ages, changing conditions in the milk bring about a predictable, orderly succession of microorganism communities. <\/span><\/p>\n<p class=\"p3\"><span class=\"s1\">In this laboratory exercise, you will observe successional patterns in several types of milk.<span class=\"Apple-converted-space\">\u00a0<\/span>You will record changes in the environmental conditions of the types of milk as they age.<span class=\"Apple-converted-space\">\u00a0<\/span>These changes are a result of changes in the bacterial communities.<span class=\"Apple-converted-space\">\u00a0Here are s<\/span>ome of the major bacteria found at various stages.<\/span><\/p>\n<h3 class=\"p3\"><span class=\"s1\">Stages of Milk Succession<\/span><\/h3>\n<ol>\n<li class=\"p3\"><span class=\"s1\"><i>Psuedomonas <\/i>and <i>Achromobacter<\/i> (gram-negative rods) digest butterfat and give milk a putrid smell<\/span><\/li>\n<li class=\"p3\"><span class=\"s1\"><i>Lactobacillus<\/i> (gram-positive rod) and <i>Streptococcus <\/i>(gram-positive coccus) ferment lactose to lactic acid and acetic acid.<\/span><\/li>\n<li class=\"p3\"><span class=\"s1\">Acidity sours milk and converts casein to curd.<\/span><\/li>\n<li class=\"p3\"><span class=\"s1\">Yeast (fungi) thrive in acidic conditions and metabolize the acids into non-acidic compounds.<\/span><\/li>\n<li class=\"p3\"><span class=\"s1\"><i>Bacillus<\/i> metabolize proteins into ammonia products and raise the milk\u2019s pH. Spoiled milk odor is very noticeable at this stage.<\/span><\/li>\n<\/ol>\n<div class=\"textbox shaded\">\n<h3>Questions<\/h3>\n<ol>\n<li><span class=\"s1\">What are some advantages to using bacteria as opposed to plants in this experiment?<\/span><\/li>\n<li>What factors might speed or delay a successional process? Apply your example to succession in milk.<\/li>\n<\/ol>\n<\/div>\n<p class=\"p3\"><span class=\"s1\">Locate the milk samples available in the lab.<span class=\"Apple-converted-space\">\u00a0<\/span>Take a look at the samples and form two conditions you would like to study.<span class=\"Apple-converted-space\">\u00a0<\/span>Develop a short design for studying the first condition, state the dependent and independent variable, control and experimental group, the hypothesis and any variables which have been controlled.<span class=\"Apple-converted-space\">\u00a0<\/span>Then develop a short design for studying the second condition, state the dependent and independent variable, control and experimental group, the hypothesis and any variables which have been controlled.\u00a0<\/span><\/p>\n<p class=\"p3\"><span class=\"s1\">Just as in any of our experiments, you must use effective scientific method<b>.<span class=\"Apple-converted-space\">\u00a0<\/span><\/b>Develop hypotheses (at least 2\u2014one with different milk types and one with either temperature or time as an independent variable) that you can test in the process of the milk community succession.<\/span><\/p>\n<p class=\"p3\"><span class=\"s1\">We will be performing a gram stain on our milk samples.<span class=\"Apple-converted-space\">\u00a0<\/span>Remember from our microbiology section that bacteria can be either gram negative (pink) or gram positive (purple).<span class=\"Apple-converted-space\">\u00a0<\/span>We will also look at these bacteria under a microscope to identify their shapes.<span class=\"Apple-converted-space\">\u00a0<\/span>Recall that bacteria can be cocci, bacilli, or spirillum.\u00a0<\/span><\/p>\n<div class=\"textbox shaded\">\n<h3 class=\"p3\">Questions<\/h3>\n<ol>\n<li><span class=\"s1\">What hypotheses are you testing?\u00a0List both here.\u00a0<\/span><\/li>\n<li><span class=\"s1\">What information led you to ask these hypotheses?<\/span><\/li>\n<li><span class=\"s1\">Make predictions about your hypotheses. i.e. How will you know if the data supports or refutes your hypotheses?<\/span><\/li>\n<li><span class=\"s1\">Be sure to identify the variables you will <i>test<\/i>, and those you will <i>control<\/i> for each experiment.<\/span><\/li>\n<li><span class=\"s1\">Prepare a table for data collection.<span class=\"Apple-converted-space\">\u00a0<\/span>You will be recording the pH, smell, consistency, and bacteria shapes and colors present in your milk samples.\u00a0<\/span><\/li>\n<\/ol>\n<\/div>\n<p class=\"p3\"><span class=\"s1\">On each lab bench are several small beakers.<span class=\"Apple-converted-space\">\u00a0<\/span>You will obtain a sample of the milk samples you need for your experimental design and test the pH, color, consistency, smell and other characteristics of each sample.<span class=\"Apple-converted-space\">\u00a0<\/span>For each milk sample:\u00a0<\/span><\/p>\n<ol>\n<li class=\"p3\"><span class=\"s1\">Using the Vernier, take the pH of each flask. Record your results.<\/span><\/li>\n<li class=\"p3\"><span class=\"s1\">Record the color, odor (sour, putrid), and consistency (coagulation slight, moderate, chunky) for the milk in each flask.<\/span><\/li>\n<li class=\"p11\"><span class=\"s1\">Perform Gram Staining as outlined below.<span class=\"Apple-converted-space\">\u00a0<strong>Note: We will be using\u00a0chemicals\u00a0and open flames. Exercise caution when\u00a0performing this portion of the lab.<\/strong><\/span><\/span><\/li>\n<\/ol>\n<h3 class=\"p12\"><span class=\"s1\">Materials<\/span><\/h3>\n<ul>\n<li class=\"p11\"><span class=\"s1\">Microscope slide<\/span><\/li>\n<li class=\"p11\"><span class=\"s1\">Bunsen burner and tubing<\/span><\/li>\n<li class=\"p11\"><span class=\"s1\">Crystal violet (primary stain)<\/span><\/li>\n<li class=\"p11\"><span class=\"s1\">Iodine solution\/Gram&#8217;s Iodine (mordant that fixes crystal violet to cell wall)<\/span><\/li>\n<li class=\"p11\"><span class=\"s1\">Decolorizer (e.g. ethanol)<\/span><\/li>\n<li class=\"p11\"><span class=\"s1\">Safranin (secondary stain)<\/span><\/li>\n<li class=\"p11\"><span class=\"s1\">Water (preferably in a squirt bottle)<\/span><\/li>\n<\/ul>\n<h3>Procedure<\/h3>\n<ol>\n<li class=\"p11\"><span class=\"s1\">Make a slide with your milk sample to be stained. Heat fix the sample to the slide by carefully passing the slide with a drop or small piece of sample on it through a Bunsen burner three times.<\/span><\/li>\n<li class=\"p11\"><span class=\"s1\">Add the primary stain (crystal violet) to the sample\/slide and let sit for 15 seconds. Rinse slide with a gentle stream of water for a maximum of 5 seconds to remove unbound crystal violet.<\/span><\/li>\n<li class=\"p11\"><span class=\"s1\">Add Gram&#8217;s iodine for 15 seconds &#8211; this is an agent that fixes the crystal violet to the bacterial cell wall.<\/span><\/li>\n<li class=\"p11\"><span class=\"s1\">Rinse sample\/slide with acetone or alcohol for ~3 seconds and <b>rinse with a gentle stream of water<\/b>. The alcohol will decolorize the sample if it is Gram negative, removing the crystal violet. However, <b>if the alcohol remains on the sample for too long, it may also decolorize Gram positive cells<\/b>.<\/span><\/li>\n<li class=\"p11\"><span class=\"s1\">Add the secondary stain, safranin, to the slide and incubate for 15 seconds.<span class=\"Apple-converted-space\">\u00a0 <\/span>Wash with a gentle stream of water for a maximum of 5 seconds. If the bacteria is Gram positive, it will retain the primary stain (crystal violet) and not take the secondary stain (safranin), causing it to look violet\/purple under a microscope. If the bacteria is Gram negative, it will lose the primary stain and take the secondary stain, causing it to appear red when viewed under a microscope.<\/span><\/li>\n<\/ol>\n<div class=\"textbox shaded\">\n<h3 class=\"p3\"><span class=\"s1\"><b>Questions<\/b><\/span><\/h3>\n<ol>\n<li class=\"p14\"><span class=\"s1\">Describe the changing sequence of organisms and corresponding environmental changes during succession in the milk samples.<span class=\"Apple-converted-space\">\u00a0<\/span>Which bacteria are in each of your milk samples?<\/span><\/li>\n<li class=\"p14\"><span class=\"s1\">Describe the changing sequence of organisms and corresponding environmental changes during succession in chocolate milk. Do the results of your investigation match your hypothesis?<\/span><\/li>\n<li class=\"p14\"><span class=\"s1\">Compare succession in one or more types milk. Propose reasons for differences.<\/span><\/li>\n<li class=\"p14\"><span class=\"s1\">Propose another experiment to test the environmental factors and\/or organisms changing in your proposed scenario for milk succession.<\/span><\/li>\n<li class=\"p14\"><span class=\"s1\">How could you improve your test of the hypotheses?<span class=\"Apple-converted-space\">\u00a0<\/span>Be specific!<\/span><\/li>\n<li class=\"p14\"><span class=\"s1\">Identify what happened to the pH of the milk as time passed.<\/span><\/li>\n<li class=\"p14\"><span class=\"s1\">Infer what the change in pH means about the populations of microorganisms in the milk.<\/span><\/li>\n<\/ol>\n<\/div>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-214\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Original<\/div><ul class=\"citation-list\"><li>Community Ecology Lab. <strong>Authored by<\/strong>: Dr. William Edwards. <strong>Provided by<\/strong>: Niagara University. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/www.niagara.edu\/\">https:\/\/www.niagara.edu\/<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em><\/li><\/ul><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Biology 102 Labs. <strong>Authored by<\/strong>: Lynette Hauser &amp; Dr. James Holden. <strong>Provided by<\/strong>: Tidewater Community Colleg. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/www.tcc.edu\/\">http:\/\/www.tcc.edu\/<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/about\/pdm\">Public Domain: No Known Copyright<\/a><\/em><\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":74,"menu_order":1,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Biology 102 Labs\",\"author\":\"Lynette Hauser & Dr. James Holden\",\"organization\":\"Tidewater Community Colleg\",\"url\":\"http:\/\/www.tcc.edu\/\",\"project\":\"\",\"license\":\"pd\",\"license_terms\":\"\"},{\"type\":\"original\",\"description\":\"Community Ecology Lab\",\"author\":\"Dr. William Edwards\",\"organization\":\"Niagara University\",\"url\":\"https:\/\/www.niagara.edu\/\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"\"}]","CANDELA_OUTCOMES_GUID":"","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-214","chapter","type-chapter","status-publish","hentry"],"part":213,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/suny-bio2labs\/wp-json\/pressbooks\/v2\/chapters\/214","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/suny-bio2labs\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/suny-bio2labs\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-bio2labs\/wp-json\/wp\/v2\/users\/74"}],"version-history":[{"count":11,"href":"https:\/\/courses.lumenlearning.com\/suny-bio2labs\/wp-json\/pressbooks\/v2\/chapters\/214\/revisions"}],"predecessor-version":[{"id":777,"href":"https:\/\/courses.lumenlearning.com\/suny-bio2labs\/wp-json\/pressbooks\/v2\/chapters\/214\/revisions\/777"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/suny-bio2labs\/wp-json\/pressbooks\/v2\/parts\/213"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/suny-bio2labs\/wp-json\/pressbooks\/v2\/chapters\/214\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/suny-bio2labs\/wp-json\/wp\/v2\/media?parent=214"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-bio2labs\/wp-json\/pressbooks\/v2\/chapter-type?post=214"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-bio2labs\/wp-json\/wp\/v2\/contributor?post=214"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-bio2labs\/wp-json\/wp\/v2\/license?post=214"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}