{"id":292,"date":"2018-01-18T18:32:59","date_gmt":"2018-01-18T18:32:59","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/wm-nmbiology2\/chapter\/life-cycles-and-habitats\/"},"modified":"2018-07-02T20:16:27","modified_gmt":"2018-07-02T20:16:27","slug":"life-cycles-and-habitats","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/atd-herkimer-biologyfundamentals1\/chapter\/life-cycles-and-habitats\/","title":{"raw":"Life Cycles and Habitats","rendered":"Life Cycles and Habitats"},"content":{"raw":"<div class=\"textbox learning-objectives\">\r\n<h3>Learning Outcomes<\/h3>\r\n<ul>\r\n \t<li>Describe the life cycle and habitat diversity of protists<\/li>\r\n<\/ul>\r\n<\/div>\r\n<h2>Life Cycles<\/h2>\r\nProtists reproduce by a variety of mechanisms. Most undergo some form of asexual reproduction, such as binary fission, to produce two daughter cells. In protists, binary fission can be divided into transverse or longitudinal, depending on the axis of orientation; sometimes <em>Paramecium<\/em> exhibit this method. Some protists such as the true slime molds exhibit multiple fission and simultaneously divide into many daughter cells. Others produce tiny buds that go on to divide and grow to the size of the parental protist. Sexual reproduction, involving meiosis and fertilization, is common among protists, and many protist species can switch from asexual to sexual reproduction when necessary. Sexual reproduction is often associated with periods when nutrients are depleted or environmental changes occur. Sexual reproduction may allow protists to recombine genes and produce new variations of progeny that may be better suited to surviving in the new environment. However, sexual reproduction is often associated with resistant cysts that are a protective, resting stage. Depending on their habitat, the cysts may be particularly resistant to temperature extremes, desiccation, or low pH. This strategy also allows certain protists to \u201cwait out\u201d stressors until their environment becomes more favorable for survival or until they are carried (such as by wind, water, or transport on a larger organism) to a different environment, because cysts exhibit virtually no cellular metabolism.\r\n\r\nProtist life cycles range from simple to extremely elaborate. Certain parasitic protists have complicated life cycles and must infect different host species at different developmental stages to complete their life cycle. Some protists are unicellular in the haploid form and multicellular in the diploid form, a strategy employed by animals. Other protists have multicellular stages in both haploid and diploid forms, a strategy called alternation of generations that is also used by plants.\r\n<h2>Habitats<\/h2>\r\nNearly all protists exist in some type of aquatic environment, including freshwater and marine environments, damp soil, and even snow. Several protist species are parasites that infect animals or plants. A few protist species live on dead organisms or their wastes, and contribute to their decay.\r\n<div class=\"textbox exercises\">\r\n<h3>Practice Questions<\/h3>\r\nExplain in your own words why sexual reproduction can be useful if a protist\u2019s environment changes.\r\n\r\n[practice-area rows=\"2\"][\/practice-area]\r\n[reveal-answer q=\"347707\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"347707\"]The ability to perform sexual reproduction allows protists to recombine their genes and produce new variations of progeny that may be better suited to the new environment. In contrast, asexual reproduction generates progeny that are clones of the parent.\r\n\r\n[\/hidden-answer]\r\n\r\n<em>Giardia lamblia<\/em> is a cyst-forming protist parasite that causes diarrhea if ingested. Given this information, against what type(s) of environments might <em>G. lamblia<\/em> cysts be particularly resistant?\r\n\r\n[practice-area rows=\"2\"][\/practice-area]\r\n[reveal-answer q=\"155458\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"155458\"]As an intestinal parasite, <em>Giardia<\/em> cysts would be exposed to low pH in the stomach acids of its host. To survive this environment and reach the intestine, the cysts would have to be resistant to acidic conditions.[\/hidden-answer]\r\n\r\n<\/div>","rendered":"<div class=\"textbox learning-objectives\">\n<h3>Learning Outcomes<\/h3>\n<ul>\n<li>Describe the life cycle and habitat diversity of protists<\/li>\n<\/ul>\n<\/div>\n<h2>Life Cycles<\/h2>\n<p>Protists reproduce by a variety of mechanisms. Most undergo some form of asexual reproduction, such as binary fission, to produce two daughter cells. In protists, binary fission can be divided into transverse or longitudinal, depending on the axis of orientation; sometimes <em>Paramecium<\/em> exhibit this method. Some protists such as the true slime molds exhibit multiple fission and simultaneously divide into many daughter cells. Others produce tiny buds that go on to divide and grow to the size of the parental protist. Sexual reproduction, involving meiosis and fertilization, is common among protists, and many protist species can switch from asexual to sexual reproduction when necessary. Sexual reproduction is often associated with periods when nutrients are depleted or environmental changes occur. Sexual reproduction may allow protists to recombine genes and produce new variations of progeny that may be better suited to surviving in the new environment. However, sexual reproduction is often associated with resistant cysts that are a protective, resting stage. Depending on their habitat, the cysts may be particularly resistant to temperature extremes, desiccation, or low pH. This strategy also allows certain protists to \u201cwait out\u201d stressors until their environment becomes more favorable for survival or until they are carried (such as by wind, water, or transport on a larger organism) to a different environment, because cysts exhibit virtually no cellular metabolism.<\/p>\n<p>Protist life cycles range from simple to extremely elaborate. Certain parasitic protists have complicated life cycles and must infect different host species at different developmental stages to complete their life cycle. Some protists are unicellular in the haploid form and multicellular in the diploid form, a strategy employed by animals. Other protists have multicellular stages in both haploid and diploid forms, a strategy called alternation of generations that is also used by plants.<\/p>\n<h2>Habitats<\/h2>\n<p>Nearly all protists exist in some type of aquatic environment, including freshwater and marine environments, damp soil, and even snow. Several protist species are parasites that infect animals or plants. A few protist species live on dead organisms or their wastes, and contribute to their decay.<\/p>\n<div class=\"textbox exercises\">\n<h3>Practice Questions<\/h3>\n<p>Explain in your own words why sexual reproduction can be useful if a protist\u2019s environment changes.<\/p>\n<p><textarea aria-label=\"Your Answer\" rows=\"2\"><\/textarea><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q347707\">Show Answer<\/span><\/p>\n<div id=\"q347707\" class=\"hidden-answer\" style=\"display: none\">The ability to perform sexual reproduction allows protists to recombine their genes and produce new variations of progeny that may be better suited to the new environment. In contrast, asexual reproduction generates progeny that are clones of the parent.<\/p>\n<\/div>\n<\/div>\n<p><em>Giardia lamblia<\/em> is a cyst-forming protist parasite that causes diarrhea if ingested. Given this information, against what type(s) of environments might <em>G. lamblia<\/em> cysts be particularly resistant?<\/p>\n<p><textarea aria-label=\"Your Answer\" rows=\"2\"><\/textarea><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q155458\">Show Answer<\/span><\/p>\n<div id=\"q155458\" class=\"hidden-answer\" style=\"display: none\">As an intestinal parasite, <em>Giardia<\/em> cysts would be exposed to low pH in the stomach acids of its host. To survive this environment and reach the intestine, the cysts would have to be resistant to acidic conditions.<\/div>\n<\/div>\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-292\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Biology. <strong>Provided by<\/strong>: OpenStax CNX. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\">http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em>. <strong>License Terms<\/strong>: Download for free at http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8<\/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":17,"menu_order":5,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Biology\",\"author\":\"\",\"organization\":\"OpenStax CNX\",\"url\":\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"Download for free at http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\"}]","CANDELA_OUTCOMES_GUID":"07062720-ea9c-437a-862a-4529952a356c, 90c4bfb7-d6c0-4c1b-a56c-375ff1d2f1de","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-292","chapter","type-chapter","status-publish","hentry"],"part":285,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/atd-herkimer-biologyfundamentals1\/wp-json\/pressbooks\/v2\/chapters\/292","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/atd-herkimer-biologyfundamentals1\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/atd-herkimer-biologyfundamentals1\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/atd-herkimer-biologyfundamentals1\/wp-json\/wp\/v2\/users\/17"}],"version-history":[{"count":5,"href":"https:\/\/courses.lumenlearning.com\/atd-herkimer-biologyfundamentals1\/wp-json\/pressbooks\/v2\/chapters\/292\/revisions"}],"predecessor-version":[{"id":1907,"href":"https:\/\/courses.lumenlearning.com\/atd-herkimer-biologyfundamentals1\/wp-json\/pressbooks\/v2\/chapters\/292\/revisions\/1907"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/atd-herkimer-biologyfundamentals1\/wp-json\/pressbooks\/v2\/parts\/285"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/atd-herkimer-biologyfundamentals1\/wp-json\/pressbooks\/v2\/chapters\/292\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/atd-herkimer-biologyfundamentals1\/wp-json\/wp\/v2\/media?parent=292"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/atd-herkimer-biologyfundamentals1\/wp-json\/pressbooks\/v2\/chapter-type?post=292"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/atd-herkimer-biologyfundamentals1\/wp-json\/wp\/v2\/contributor?post=292"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/atd-herkimer-biologyfundamentals1\/wp-json\/wp\/v2\/license?post=292"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}