{"id":30,"date":"2017-08-16T07:18:51","date_gmt":"2017-08-16T07:18:51","guid":{"rendered":"http:\/\/americanboard.org\/Subjects\/biology\/?page_id=30"},"modified":"2017-10-02T17:06:28","modified_gmt":"2017-10-02T17:06:28","slug":"reproduction","status":"publish","type":"page","link":"https:\/\/americanboard.org\/Subjects\/biology\/reproduction\/","title":{"rendered":"Reproduction"},"content":{"rendered":"<div class=\"twelve columns\" style=\"margin-top: 10%;\">\n<div class=\"advance\"><a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/biology\/biology-basics\">\u2b05 Previous Lesson<\/a>\u00a0<a class=\"button\" href=\"http:\/\/americanboard.org\/Subjects\/biology\/basic-science-core\">Workshop Index<\/a>\u00a0<a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/biology\/mendelian-genetics\">Next Lesson \u27a1<\/a><\/div>\n<p><!-- CONTENT BEGINS HERE --><\/p>\n<h1 id=\"title\">Reproduction<\/h1>\n<h4>Objective<\/h4>\n<p>In this lesson, you will learn about asexual and sexual reproduction. Scientists, regardless of their specialization, need to possess a basic level of science literacy across all disciplines. This lesson provides an overview of the major concepts pertaining to reproduction that all students of the sciences should know. The chapters that follow will focus in greater detail on these ideas.<\/p>\n<h4>Previously Covered:<\/h4>\n<ul>\n<li>All living things are composed of cells that contain DNA.<\/li>\n<li>DNA carries all of the information necessary for the construction and functioning of living things.<\/li>\n<li>DNA carries the genetic information that is passed from parents to offspring.<\/li>\n<\/ul>\n<section>Among the characteristics shared by all living things, from single cells to whales, is that they reproduce and pass genetic information in the form of DNA. Cells within complex, multicellular organisms, eukaryotes such as humans, divide a limited number of times via <abbr title=\"\">mitosis<\/abbr> and <abbr title=\"\">cytokinesis<\/abbr> to create clones\u2014genetically identical copies. Cell division allows growth. Simple <abbr title=\"\">prokaryotic<\/abbr> organisms reproduce exclusively asexually, usually via <abbr title=\"\">binary fission<\/abbr>. Most animals reproduce sexually, but there are exceptions. Among <abbr title=\"\">eukaryotes<\/abbr>, there are many modes of reproduction, both asexual and sexual. Asexual reproduction usually involves production of a genetically identical offspring from a single parent. For example, taking a cutting from a plant and rooting it is a form of asexual reproduction; a clonal plant is produced from a single parent. Forms of asexual reproduction include:<\/p>\n<h4>Mitosis and Cytokinesis<\/h4>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/biology\/wp-content\/uploads\/sites\/2\/2017\/08\/mod3slide1.jpg\" alt=\"Mitosis diagram\" \/><\/center><\/p>\n<h4>Binary Fission<\/h4>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/biology\/wp-content\/uploads\/sites\/2\/2017\/08\/mod3slide2.jpg\" alt=\"Binary fission diagram\" \/><\/center><\/p>\n<h4>Budding<\/h4>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/biology\/wp-content\/uploads\/sites\/2\/2017\/08\/mod3slide3.jpg\" alt=\"Budding in eukaryotes\" \/><\/center><\/p>\n<h4>Regeneration and Fragmentation<\/h4>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/biology\/wp-content\/uploads\/sites\/2\/2017\/08\/mod3slide4.jpg\" alt=\"Regeneration and fragmentation in eukaryotes\" \/><\/center><\/p>\n<h4>Parthenogenesis<\/h4>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/biology\/wp-content\/uploads\/sites\/2\/2017\/08\/mod3slide5.jpg\" alt=\"Parthenocarpy diagram\" \/><\/center><\/p>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p>Simple prokaryotic organisms reproduce asexually, usually via which mode?<\/p>\n<ol>\n<li>Budding<\/li>\n<li>Parthenogenesis<\/li>\n<li>Cytokinesis<\/li>\n<li>Binary fission<\/li>\n<\/ol>\n<p><a class=\"q-answer button button-primary\">Reveal Answer<\/a><\/p>\n<p class=\"q-reveal\">Hope you chose D. While choices A, B, and C are asexual modes of reproduction, binary fission is the most common.<\/p>\n<\/section>\n<p><abbr title=\"the production of a new living thing by two parent organisms, with each parent contributing half the material in the DNA of the offspring\">Sexual reproduction<\/abbr> is characterized by <abbr title=\"cell division process, associated with sexual reproduction, that reduces chromosome numbers from diploid to haploid; produces gametes in animals and spores in plants\">meiosis<\/abbr> and fusion of two genetically unique <abbr title=\"a reproductive cell containing a haploid chromosome or half of the genetic material needed for the formation of a new organism through fusion with another gamete cell\">gametes<\/abbr> to form a unique offspring. Self pollination of a flower is a form of sexual reproduction, because the flower has both male and female reproductive structures that produce unique gametes.<\/p>\n<p>Organisms that reproduce sexually must reduce their number of chromosomes by half via meiosis at some point during their life cycle. Sexual reproducers have one of three distinct life cycles:<\/p>\n<h4>Zygotic Life Cycle:<\/h4>\n<p>The zygote is the only diploid form of the organism. It quickly undergoes meiosis to produce the dominant haploid form. All sexually reproducing fungi and some algae have zygotic life cycles.<\/p>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/biology\/wp-content\/uploads\/sites\/2\/2017\/08\/thumb6.jpg\" alt=\"Zygotic Life Cycle diagram\" \/><\/center><\/p>\n<h4>Sporic Life Cycle:<\/h4>\n<p>There is a true alternation of generations, such that both the diploid and haploid forms undergo mitosis to produce multicellular forms. Some algae and all plants have sporic life cycles. In primitive nonvascular plants, such as mosses, the haploid form is dominant. In seed plants, the diploid form is dominant.<\/p>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/biology\/wp-content\/uploads\/sites\/2\/2017\/08\/thumb7.jpg\" alt=\"Sporic Life Cycle diagram\" \/><\/center><\/p>\n<h4>Gametic Life Cycle:<\/h4>\n<p>The gamete is the only haploid form of the organism, and it is always unicellular. Most animals, including humans, have gametic life cycles.<\/p>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/biology\/wp-content\/uploads\/sites\/2\/2017\/08\/thumb8.jpg\" alt=\"Gametic Life Cycle diagram\" \/><\/center>Genetic variation is the result of any change, or mutation, in the genetic code of an organism. In prokaryotes, all genetic variation is the result of mutation, <abbr title=\"as a result of DNA transfer from one bacterial cell to another there is a resulting alteration of the bacterial cell particularly with pathogen cells\">transformation<\/abbr>, <abbr title=\"transfer of genetic material or characteristics from one bacterium to another via a bacteriophage or plasmid\">transduction<\/abbr>, or <abbr title=\"a sexual reproduction method that involves a temporary union for the purpose of genetic material exchange; commonly observed in bacteria, ciliate protozoans, and certain algae and fungi\">conjugation<\/abbr>.<\/p>\n<ul>\n<li>Mutation is the ultimate source of genetic variation in all living things. The diversity of life is the result of billions of years of change in the genetic code of organisms via mutation acted on by natural selection.<\/li>\n<li>Transformation is a process by which bacteria can take up fragments of DNA from a surrounding medium during cell division. Since many species of bacteria usually coexist, exchange of genetic information via transformation is thought to be significant.<\/li>\n<li>Transduction occurs when a viral <abbr title=\"a type of virus that only targets certain bacteria\">bacteriophage<\/abbr> incorporates its DNA into a bacterial cell.<\/li>\n<li>Conjugation occurs when bacteria transfer plasmids, small rings of DNA distinct from the bacterial chromosome. Bacteria resistance to antibiotics may be transferred via conjugation.<\/li>\n<\/ul>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p>What is transduction?<\/p>\n<ol>\n<li>It is the ultimate source of genetic variation in all living things.<\/li>\n<li>It is the transfer of plasmids by bacteria.<\/li>\n<li>It is the incorporation of viral DNA into a bacterial cell.<\/li>\n<li>It is the taking up of DNA fragments by bacteria.<\/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. Choice A defines mutation, choice B defines conjugation, and choice D defines transformation.<\/p>\n<\/section>\n<p>When gametes are produced via meiosis in sexually reproducing organisms, genetic variation is introduced in several ways.<\/p>\n<p><abbr title=\"fusion of two gametes via fertilization\">Syngamy<\/abbr> produces a unique diploid zygote.<\/p>\n<p><strong>Crossing-over<\/strong> of homologous chromosomes during prophase 1 leads to genetic recombination and formation of unique chromosomes.<\/p>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/biology\/wp-content\/uploads\/sites\/2\/2017\/08\/thumb10.jpg\" alt=\"Crossing-over of chromosomes\" \/><\/center><strong>Independent assortment<\/strong> of homologous chromosomes during anaphase 1 produces unique haploid gametes.<\/p>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/biology\/wp-content\/uploads\/sites\/2\/2017\/08\/thumb11.jpg\" alt=\"Independent assortment of chromosomes\" \/><\/center><\/p>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p>Which is the source of genetic variation in organisms that reproduce asexually?<\/p>\n<ol>\n<li>Syngamy<\/li>\n<li>Crossing over<\/li>\n<li>Independent Assortment<\/li>\n<li>Mutation<\/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. Choices A-C all reflect processes that occur only in sexually reproducing organisms. Mutation is the ultimate source of all genetic variation of all living things.<\/p>\n<\/section>\n<p>Asexual reproduction is advantageous in several ways. It allows very fast, energetically inexpensive production of many genetically identical offspring in organisms, such as bacteria and simple eukaryotes. If the organisms in question are well-adapted to a relatively stable environment, production of many clonal offspring is advantageous. Asexual reproduction is also favored by some plants and animals under stressful conditions, when mates or pollinators may be scarce.<\/p>\n<p>Sexual reproduction introduces genetic diversity, which is generally advantageous. Genetically diverse populations are better able to tolerate environmental changes and are less susceptible to catastrophic losses when changes do occur. Genetic variation is the core of evolution by <abbr title=\"the process of organisms best adapted to their environment are the most likely to survive and transmit their hereditary characteristics to subsequent generations\">natural selection<\/abbr>, and has produced the marvelously adapted organisms on Earth today.<\/p>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p>Why is sexual reproduction advantageous?<\/p>\n<ol>\n<li>Because it is very fast and energetically inexpensive.<\/li>\n<li>Because it is a response to stressful environmental conditions.<\/li>\n<li>Because it produces many genetically identical offspring.<\/li>\n<li>Because it produces populations that are less susceptible to catastrophic changes.<\/li>\n<\/ol>\n<p><a class=\"q-answer button button-primary\">Reveal Answer<\/a><\/p>\n<p class=\"q-reveal\">D is the correct answer. Choices A, B, and C all refer to asexual reproduction.<\/p>\n<\/section>\n<h3>Summary<\/h3>\n<ul>\n<li>Mitosis followed by cytokinesis is the process by which eukaryotic cells reproduce themselves to create genetically identical copies.<\/li>\n<li>Asexual reproduction involves production of a genetically identical offspring from a single parent.<\/li>\n<li>Sexual reproduction is characterized by meiosis and fusion of two genetically unique gametes to form a unique offspring.<\/li>\n<li>Sexual reproduction introduces genetic variation via recombination, independent assortment, and syngamy. Genetic variation is usually evolutionarily advantageous.<\/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\/biology\/biology-basics\">\u2b05 Previous Lesson<\/a>\u00a0<a class=\"button\" href=\"http:\/\/americanboard.org\/Subjects\/biology\/basic-science-core\">Workshop Index<\/a>\u00a0<a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/biology\/mendelian-genetics\">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 Reproduction Objective In this lesson, you will learn about asexual and sexual reproduction. Scientists, regardless of their specialization, need to possess a basic level of science literacy across all disciplines. This lesson provides an overview of the major concepts pertaining to reproduction that all students of the sciences should [&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-30","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/americanboard.org\/Subjects\/biology\/wp-json\/wp\/v2\/pages\/30","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/americanboard.org\/Subjects\/biology\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/americanboard.org\/Subjects\/biology\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/americanboard.org\/Subjects\/biology\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/americanboard.org\/Subjects\/biology\/wp-json\/wp\/v2\/comments?post=30"}],"version-history":[{"count":14,"href":"https:\/\/americanboard.org\/Subjects\/biology\/wp-json\/wp\/v2\/pages\/30\/revisions"}],"predecessor-version":[{"id":1241,"href":"https:\/\/americanboard.org\/Subjects\/biology\/wp-json\/wp\/v2\/pages\/30\/revisions\/1241"}],"wp:attachment":[{"href":"https:\/\/americanboard.org\/Subjects\/biology\/wp-json\/wp\/v2\/media?parent=30"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}