{"id":49,"date":"2019-01-10T22:50:57","date_gmt":"2019-01-10T22:50:57","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-rockland-biology\/chapter\/reconnection-and-rates-of-speciation\/"},"modified":"2019-04-15T17:36:39","modified_gmt":"2019-04-15T17:36:39","slug":"reconnection-and-rates-of-speciation","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-ecology\/chapter\/reconnection-and-rates-of-speciation\/","title":{"raw":"Reconnection and Rates of Speciation","rendered":"Reconnection and Rates of Speciation"},"content":{"raw":"<div class=\"textbox learning-objectives\">\r\n<h3>Learning Objectives<\/h3>\r\nBy the end of this section, you will be able to:\r\n<ul>\r\n \t<li>Describe pathways of species evolution in hybrid zones<\/li>\r\n \t<li>Explain the two major theories on rates of speciation<\/li>\r\n<\/ul>\r\n<\/div>\r\n<p id=\"fs-idp80045424\">Speciation occurs over a span of evolutionary time, so when a new species arises, there is a transition period during which the closely related species continue to interact.<\/p>\r\n\r\n<section id=\"fs-idp108462176\">\r\n<h2>Reconnection<\/h2>\r\n<p id=\"fs-idm66830160\">After speciation, two species may recombine or even continue interacting indefinitely. Individual organisms will mate with any nearby individual who they are capable of breeding with. An area where two closely related species continue to interact and reproduce, forming hybrids, is called a <span>hybrid zone<\/span>. Over time, the hybrid zone may change depending on the fitness of the hybrids and the reproductive barriers (<a class=\"autogenerated-content\" href=\"#fig-ch18_03_01\">[Figure 1]<\/a>). If the hybrids are less fit than the parents, reinforcement of speciation occurs, and the species continue to diverge until they can no longer mate and produce viable offspring. If reproductive barriers weaken, fusion occurs and the two species become one. Barriers remain the same if hybrids are fit and reproductive: stability may occur and hybridization continues.<\/p>\r\n\r\n<div id=\"fs-idm1826256\" class=\"note art-connection\">\r\n<div class=\"title\">\r\n<div class=\"textbox exercises\">\r\n<h3>Art Connection<\/h3>\r\n<div id=\"fs-idm1826256\" class=\"note art-connection\">\r\n<figure id=\"fig-ch18_03_01\"><figcaption><\/figcaption>\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"472\"]<img class=\"\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3943\/2019\/01\/10225052\/Figure_18_03_01.png\" alt=\" Three different possible changes in the hybrid zone may occur over time. The first possible change, reinforcement, results when hybrids are less fit than either purebred species. Like a fork in the road, the species continue to diverge until hybridization no longer occurs. The second possible change, fusion, results when reproductive barriers weaken until two species become one. In this scenario species initially diverge, but then join together. In the third scenario, stability, fit hybrids continue to be produced at a steady rate.\" width=\"472\" height=\"283\" \/> Figure 1: After speciation has occurred, the two separate but closely related species may continue to produce offspring in an area called the hybrid zone. Reinforcement, fusion, or stability may result, depending on reproductive barriers and the relative fitness of the hybrids.[\/caption]<\/figure>\r\n<p id=\"fs-idp149787056\">If two species eat a different diet but one of the food sources is eliminated and both species are forced to eat the same foods, what change in the hybrid zone is most likely to occur?<\/p>\r\n[reveal-answer q=\"921722\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"921722\"]Fusion is most likely to occur because the two species will interact more and similar traits in food acquisition will be selected.[\/hidden-answer]\r\n\r\n&lt;!-- \t \t \t \t \t \tFusion is most likely to occur because the two species will interact more and similar traits in food acquisition will be selected.--&gt;\r\n\r\n<\/div>\r\n<p id=\"fs-idp8416320\">Hybrids can be either less fit than the parents, more fit, or about the same. Usually hybrids tend to be less fit; therefore, such reproduction diminishes over time, nudging the two species to diverge further in a process called <span>reinforcement<\/span>. This term is used because the low success of the hybrids reinforces the original speciation. If the hybrids are as fit or more fit than the parents, the two species may fuse back into one species (<a class=\"autogenerated-content\" href=\"#fig-ch18_03_02\">[Figure 2]<\/a>). Scientists have also observed that sometimes two species will remain separate but also continue to interact to produce some hybrid individuals; this is classified as stability because no real net change is taking place.<\/p>\r\n\r\n<\/div>\r\n<h2>Varying Rates of Speciation<\/h2>\r\n<\/div>\r\n<\/div>\r\n<\/section><section id=\"fs-idp497664\">\r\n<p id=\"fs-idm7342480\">Scientists around the world study speciation, documenting observations both of living organisms and those found in the fossil record. As their ideas take shape and as research reveals new details about how life evolves, they develop models to help explain rates of speciation. In terms of how quickly speciation occurs, two patterns are currently observed: gradual speciation model and punctuated equilibrium model.<\/p>\r\n<p id=\"fs-idp24246288\">In the <span>gradual speciation model<\/span>, species diverge gradually over time in small steps. In the <span>punctuated equilibrium<\/span> model, a new species undergoes changes quickly from the parent species, and then remains largely unchanged for long periods of time afterward (<a class=\"autogenerated-content\" href=\"#fig-ch18_03_02\">[Figure 2]<\/a>). This early change model is called punctuated equilibrium, because it begins with a punctuated or periodic change and then remains in balance afterward. While punctuated equilibrium suggests a faster tempo, it does not necessarily exclude gradualism.<\/p>\r\n\r\n<div id=\"fs-idp167977744\" class=\"note art-connection\">\r\n<div class=\"title\">\r\n<div class=\"textbox exercises\">\r\n<h3>Art Connection<\/h3>\r\n<div id=\"fs-idp167977744\" class=\"note art-connection\">\r\n<figure id=\"fig-ch18_03_02\"><figcaption><\/figcaption>\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"525\"]<img src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3943\/2019\/01\/10225055\/Figure_18_03_02.png\" alt=\" In the gradual speciation example, a founder species of bird diverges into one species with a hooked beak, and another with strait beak. Over time, the hooked beak gets longer and thinner, and the straight beak gets shorter and fatter. In the punctuated equilibrium example, as in the graduated speciation example, the founder species diverges into one species with a hooked break and another with a straight beak. However, in this case the hooked and straight beaks gives rise immediately to long, thin and short, fat beaks.\" width=\"525\" height=\"750\" \/> Figure 2: In (a) gradual speciation, species diverge at a slow, steady pace as traits change incrementally. In (b) punctuated equilibrium, species diverge quickly and then remain unchanged for long periods of time.[\/caption]\r\n\r\n<span id=\"fs-idp57861136\">\u00a0<\/span><\/figure>\r\n<p id=\"fs-idp101273328\">Which of the following statements is false?<\/p>\r\n\r\n<ol id=\"fs-idm9622240\">\r\n \t<li>Punctuated equilibrium is most likely to occur in a small population that experiences a rapid change in its environment.<\/li>\r\n \t<li>Punctuated equilibrium is most likely to occur in a large population that lives in a stable climate.<\/li>\r\n \t<li>Gradual speciation is most likely to occur in species that live in a stable climate.<\/li>\r\n \t<li>Gradual speciation and punctuated equilibrium both result in the divergence of species.\r\n[reveal-answer q=\"711032\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"711032\"]Answer 2[\/hidden-answer]<\/li>\r\n<\/ol>\r\n&lt;!-- \t \t \t \t \t \t B--&gt;\r\n\r\n<\/div>\r\n<p id=\"fs-idp32765200\">The primary influencing factor on changes in speciation rate is environmental conditions. Under some conditions, selection occurs quickly or radically. Consider a species of snails that had been living with the same basic form for many thousands of years. Layers of their fossils would appear similar for a long time. When a change in the environment takes place\u2014such as a drop in the water level\u2014a small number of organisms are separated from the rest in a brief period of time, essentially forming one large and one tiny population. The tiny population faces new environmental conditions. Because its gene pool quickly became so small, any variation that surfaces and that aids in surviving the new conditions becomes the predominant form.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm96226288\" class=\"note interactive\">\r\n<div class=\"textbox shaded\"><section id=\"fs-idp497664\">\r\n<div id=\"fs-idm96226288\" class=\"note interactive\">\r\n<p id=\"fs-idp193909168\">Visit <a href=\"http:\/\/openstaxcollege.org\/l\/snails\" target=\"_window\">this website<\/a> to continue the speciation story of the snails.<\/p>\r\n\r\n<\/div>\r\n<\/section><\/div>\r\n<\/div>\r\n<\/section><section id=\"fs-idp94757088\" class=\"summary\">\r\n<h2>Section Summary<\/h2>\r\n<p id=\"fs-idp22539712\">Speciation is not a precise division: overlap between closely related species can occur in areas called hybrid zones. Organisms reproduce with other similar organisms. The fitness of these hybrid offspring can affect the evolutionary path of the two species. Scientists propose two models for the rate of speciation: one model illustrates how a species can change slowly over time; the other model demonstrates how change can occur quickly from a parent generation to a new species. Both models continue to follow the patterns of natural selection.<\/p>\r\n\r\n<\/section><section id=\"fs-idm45978368\" class=\"art-exercise\"><\/section><section id=\"fs-idp175082320\" class=\"multiple-choice\">\r\n<h2>Review Questions<\/h2>\r\n<div id=\"fs-idp101132192\" class=\"exercise textbox\">\r\n<div id=\"fs-idm45131920\" class=\"problem\">\r\n<p id=\"fs-idp79685440\">Which term is used to describe the continued divergence of species based on the low fitness of hybrid offspring?<\/p>\r\n\r\n<ol id=\"fs-idp152407824\">\r\n \t<li>reinforcement<\/li>\r\n \t<li>fusion<\/li>\r\n \t<li>stability<\/li>\r\n \t<li>punctuated equilibrium<\/li>\r\n<\/ol>\r\n<\/div>\r\n<div id=\"fs-idp11219344\" class=\"solution\">\r\n<p id=\"fs-idp75843488\">[reveal-answer q=\"143575\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"143575\"]1[\/hidden-answer]<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idp10501840\" class=\"exercise textbox\">\r\n<div id=\"fs-idm20775936\" class=\"problem\">\r\n<p id=\"fs-idp147559024\">Which components of speciation would be least likely to be a part of punctuated equilibrium?<\/p>\r\n\r\n<ol id=\"fs-idm2737504\">\r\n \t<li>a division of populations<\/li>\r\n \t<li>a change in environmental conditions<\/li>\r\n \t<li>ongoing gene flow among all individuals<\/li>\r\n \t<li>a large number of mutations taking place at once<\/li>\r\n<\/ol>\r\n<\/div>\r\n<div id=\"fs-idp109485056\" class=\"solution\">\r\n<p id=\"fs-idm42452864\">[reveal-answer q=\"624509\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"624509\"]3[\/hidden-answer]<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/section><section id=\"fs-idm46257824\" class=\"free-response\">\r\n<h1>Free Response<\/h1>\r\n<div id=\"fs-idm23889104\" class=\"exercise textbox\">\r\n<div id=\"fs-idm5690640\" class=\"problem\">\r\n<p id=\"fs-idp110912\">What do both rate of speciation models have in common?<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idp18326400\" class=\"solution\">\r\n<p id=\"fs-idm64665072\">[practice-area rows=\"8\"][\/practice-area]\r\n[reveal-answer q=\"543482\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"543482\"]Both models continue to conform to the rules of natural selection, and the influences of gene flow, genetic drift, and mutation.[\/hidden-answer]<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm59561840\" class=\"exercise textbox\">\r\n<div id=\"fs-idp72466256\" class=\"problem\">\r\n<p id=\"fs-idp122441904\">Describe a situation where hybrid reproduction would cause two species to fuse into one.<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idm7267248\" class=\"solution\">\r\n<p id=\"fs-idp14118736\">[practice-area rows=\"8\"][\/practice-area]\r\n[reveal-answer q=\"778387\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"778387\"]If the hybrid offspring are as fit or more fit than the parents, reproduction would likely continue between both species and the hybrids, eventually bringing all organisms under the umbrella of one species.[\/hidden-answer]<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/section>\r\n<div>\r\n<h2>Glossary<\/h2>\r\n<dl id=\"fs-idp72882880\" class=\"definition\">\r\n \t<dt><strong>gradual speciation model<\/strong><\/dt>\r\n \t<dd id=\"fs-idp96205920\">model that shows how species diverge gradually over time in small steps<\/dd>\r\n<\/dl>\r\n<dl id=\"fs-idm96811840\" class=\"definition\">\r\n \t<dt><strong>hybrid zone<\/strong><\/dt>\r\n \t<dd id=\"fs-idm46445328\">area where two closely related species continue to interact and reproduce, forming hybrids<\/dd>\r\n<\/dl>\r\n<dl id=\"fs-idm64914688\" class=\"definition\">\r\n \t<dt><strong>punctuated equilibrium<\/strong><\/dt>\r\n \t<dd id=\"fs-idm199868352\">model for rapid speciation that can occur when an event causes a small portion of a population to be cut off from the rest of the population<\/dd>\r\n<\/dl>\r\n<dl id=\"fs-idm58480288\" class=\"definition\">\r\n \t<dt><strong>reinforcement<\/strong><\/dt>\r\n \t<dd id=\"fs-idp68355936\">continued speciation divergence between two related species due to low fitness of hybrids between them<\/dd>\r\n<\/dl>\r\n<\/div>","rendered":"<div class=\"textbox learning-objectives\">\n<h3>Learning Objectives<\/h3>\n<p>By the end of this section, you will be able to:<\/p>\n<ul>\n<li>Describe pathways of species evolution in hybrid zones<\/li>\n<li>Explain the two major theories on rates of speciation<\/li>\n<\/ul>\n<\/div>\n<p id=\"fs-idp80045424\">Speciation occurs over a span of evolutionary time, so when a new species arises, there is a transition period during which the closely related species continue to interact.<\/p>\n<section id=\"fs-idp108462176\">\n<h2>Reconnection<\/h2>\n<p id=\"fs-idm66830160\">After speciation, two species may recombine or even continue interacting indefinitely. Individual organisms will mate with any nearby individual who they are capable of breeding with. An area where two closely related species continue to interact and reproduce, forming hybrids, is called a <span>hybrid zone<\/span>. Over time, the hybrid zone may change depending on the fitness of the hybrids and the reproductive barriers (<a class=\"autogenerated-content\" href=\"#fig-ch18_03_01\">[Figure 1]<\/a>). If the hybrids are less fit than the parents, reinforcement of speciation occurs, and the species continue to diverge until they can no longer mate and produce viable offspring. If reproductive barriers weaken, fusion occurs and the two species become one. Barriers remain the same if hybrids are fit and reproductive: stability may occur and hybridization continues.<\/p>\n<div id=\"fs-idm1826256\" class=\"note art-connection\">\n<div class=\"title\">\n<div class=\"textbox exercises\">\n<h3>Art Connection<\/h3>\n<div id=\"fs-idm1826256\" class=\"note art-connection\">\n<figure id=\"fig-ch18_03_01\"><figcaption><\/figcaption><div style=\"width: 482px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3943\/2019\/01\/10225052\/Figure_18_03_01.png\" alt=\"Three different possible changes in the hybrid zone may occur over time. The first possible change, reinforcement, results when hybrids are less fit than either purebred species. Like a fork in the road, the species continue to diverge until hybridization no longer occurs. The second possible change, fusion, results when reproductive barriers weaken until two species become one. In this scenario species initially diverge, but then join together. In the third scenario, stability, fit hybrids continue to be produced at a steady rate.\" width=\"472\" height=\"283\" \/><\/p>\n<p class=\"wp-caption-text\">Figure 1: After speciation has occurred, the two separate but closely related species may continue to produce offspring in an area called the hybrid zone. Reinforcement, fusion, or stability may result, depending on reproductive barriers and the relative fitness of the hybrids.<\/p>\n<\/div>\n<\/figure>\n<p id=\"fs-idp149787056\">If two species eat a different diet but one of the food sources is eliminated and both species are forced to eat the same foods, what change in the hybrid zone is most likely to occur?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q921722\">Show Answer<\/span><\/p>\n<div id=\"q921722\" class=\"hidden-answer\" style=\"display: none\">Fusion is most likely to occur because the two species will interact more and similar traits in food acquisition will be selected.<\/div>\n<\/div>\n<p>&lt;!&#8211; \t \t \t \t \t \tFusion is most likely to occur because the two species will interact more and similar traits in food acquisition will be selected.&#8211;&gt;<\/p>\n<\/div>\n<p id=\"fs-idp8416320\">Hybrids can be either less fit than the parents, more fit, or about the same. Usually hybrids tend to be less fit; therefore, such reproduction diminishes over time, nudging the two species to diverge further in a process called <span>reinforcement<\/span>. This term is used because the low success of the hybrids reinforces the original speciation. If the hybrids are as fit or more fit than the parents, the two species may fuse back into one species (<a class=\"autogenerated-content\" href=\"#fig-ch18_03_02\">[Figure 2]<\/a>). Scientists have also observed that sometimes two species will remain separate but also continue to interact to produce some hybrid individuals; this is classified as stability because no real net change is taking place.<\/p>\n<\/div>\n<h2>Varying Rates of Speciation<\/h2>\n<\/div>\n<\/div>\n<\/section>\n<section id=\"fs-idp497664\">\n<p id=\"fs-idm7342480\">Scientists around the world study speciation, documenting observations both of living organisms and those found in the fossil record. As their ideas take shape and as research reveals new details about how life evolves, they develop models to help explain rates of speciation. In terms of how quickly speciation occurs, two patterns are currently observed: gradual speciation model and punctuated equilibrium model.<\/p>\n<p id=\"fs-idp24246288\">In the <span>gradual speciation model<\/span>, species diverge gradually over time in small steps. In the <span>punctuated equilibrium<\/span> model, a new species undergoes changes quickly from the parent species, and then remains largely unchanged for long periods of time afterward (<a class=\"autogenerated-content\" href=\"#fig-ch18_03_02\">[Figure 2]<\/a>). This early change model is called punctuated equilibrium, because it begins with a punctuated or periodic change and then remains in balance afterward. While punctuated equilibrium suggests a faster tempo, it does not necessarily exclude gradualism.<\/p>\n<div id=\"fs-idp167977744\" class=\"note art-connection\">\n<div class=\"title\">\n<div class=\"textbox exercises\">\n<h3>Art Connection<\/h3>\n<div id=\"fs-idp167977744\" class=\"note art-connection\">\n<figure id=\"fig-ch18_03_02\"><figcaption><\/figcaption><div style=\"width: 535px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3943\/2019\/01\/10225055\/Figure_18_03_02.png\" alt=\"In the gradual speciation example, a founder species of bird diverges into one species with a hooked beak, and another with strait beak. Over time, the hooked beak gets longer and thinner, and the straight beak gets shorter and fatter. In the punctuated equilibrium example, as in the graduated speciation example, the founder species diverges into one species with a hooked break and another with a straight beak. However, in this case the hooked and straight beaks gives rise immediately to long, thin and short, fat beaks.\" width=\"525\" height=\"750\" \/><\/p>\n<p class=\"wp-caption-text\">Figure 2: In (a) gradual speciation, species diverge at a slow, steady pace as traits change incrementally. In (b) punctuated equilibrium, species diverge quickly and then remain unchanged for long periods of time.<\/p>\n<\/div>\n<p><span id=\"fs-idp57861136\">\u00a0<\/span><\/figure>\n<p id=\"fs-idp101273328\">Which of the following statements is false?<\/p>\n<ol id=\"fs-idm9622240\">\n<li>Punctuated equilibrium is most likely to occur in a small population that experiences a rapid change in its environment.<\/li>\n<li>Punctuated equilibrium is most likely to occur in a large population that lives in a stable climate.<\/li>\n<li>Gradual speciation is most likely to occur in species that live in a stable climate.<\/li>\n<li>Gradual speciation and punctuated equilibrium both result in the divergence of species.\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q711032\">Show Answer<\/span><\/p>\n<div id=\"q711032\" class=\"hidden-answer\" style=\"display: none\">Answer 2<\/div>\n<\/div>\n<\/li>\n<\/ol>\n<p>&lt;!&#8211; \t \t \t \t \t \t B&#8211;&gt;<\/p>\n<\/div>\n<p id=\"fs-idp32765200\">The primary influencing factor on changes in speciation rate is environmental conditions. Under some conditions, selection occurs quickly or radically. Consider a species of snails that had been living with the same basic form for many thousands of years. Layers of their fossils would appear similar for a long time. When a change in the environment takes place\u2014such as a drop in the water level\u2014a small number of organisms are separated from the rest in a brief period of time, essentially forming one large and one tiny population. The tiny population faces new environmental conditions. Because its gene pool quickly became so small, any variation that surfaces and that aids in surviving the new conditions becomes the predominant form.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-idm96226288\" class=\"note interactive\">\n<div class=\"textbox shaded\">\n<section id=\"fs-idp497664\">\n<div id=\"fs-idm96226288\" class=\"note interactive\">\n<p id=\"fs-idp193909168\">Visit <a href=\"http:\/\/openstaxcollege.org\/l\/snails\" target=\"_window\">this website<\/a> to continue the speciation story of the snails.<\/p>\n<\/div>\n<\/section>\n<\/div>\n<\/div>\n<\/section>\n<section id=\"fs-idp94757088\" class=\"summary\">\n<h2>Section Summary<\/h2>\n<p id=\"fs-idp22539712\">Speciation is not a precise division: overlap between closely related species can occur in areas called hybrid zones. Organisms reproduce with other similar organisms. The fitness of these hybrid offspring can affect the evolutionary path of the two species. Scientists propose two models for the rate of speciation: one model illustrates how a species can change slowly over time; the other model demonstrates how change can occur quickly from a parent generation to a new species. Both models continue to follow the patterns of natural selection.<\/p>\n<\/section>\n<section id=\"fs-idm45978368\" class=\"art-exercise\"><\/section>\n<section id=\"fs-idp175082320\" class=\"multiple-choice\">\n<h2>Review Questions<\/h2>\n<div id=\"fs-idp101132192\" class=\"exercise textbox\">\n<div id=\"fs-idm45131920\" class=\"problem\">\n<p id=\"fs-idp79685440\">Which term is used to describe the continued divergence of species based on the low fitness of hybrid offspring?<\/p>\n<ol id=\"fs-idp152407824\">\n<li>reinforcement<\/li>\n<li>fusion<\/li>\n<li>stability<\/li>\n<li>punctuated equilibrium<\/li>\n<\/ol>\n<\/div>\n<div id=\"fs-idp11219344\" class=\"solution\">\n<p id=\"fs-idp75843488\">\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q143575\">Show Answer<\/span><\/p>\n<div id=\"q143575\" class=\"hidden-answer\" style=\"display: none\">1<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-idp10501840\" class=\"exercise textbox\">\n<div id=\"fs-idm20775936\" class=\"problem\">\n<p id=\"fs-idp147559024\">Which components of speciation would be least likely to be a part of punctuated equilibrium?<\/p>\n<ol id=\"fs-idm2737504\">\n<li>a division of populations<\/li>\n<li>a change in environmental conditions<\/li>\n<li>ongoing gene flow among all individuals<\/li>\n<li>a large number of mutations taking place at once<\/li>\n<\/ol>\n<\/div>\n<div id=\"fs-idp109485056\" class=\"solution\">\n<p id=\"fs-idm42452864\">\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q624509\">Show Answer<\/span><\/p>\n<div id=\"q624509\" class=\"hidden-answer\" style=\"display: none\">3<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n<section id=\"fs-idm46257824\" class=\"free-response\">\n<h1>Free Response<\/h1>\n<div id=\"fs-idm23889104\" class=\"exercise textbox\">\n<div id=\"fs-idm5690640\" class=\"problem\">\n<p id=\"fs-idp110912\">What do both rate of speciation models have in common?<\/p>\n<\/div>\n<div id=\"fs-idp18326400\" class=\"solution\">\n<p id=\"fs-idm64665072\"><textarea aria-label=\"Your Answer\" rows=\"8\"><\/textarea><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q543482\">Show Answer<\/span><\/p>\n<div id=\"q543482\" class=\"hidden-answer\" style=\"display: none\">Both models continue to conform to the rules of natural selection, and the influences of gene flow, genetic drift, and mutation.<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-idm59561840\" class=\"exercise textbox\">\n<div id=\"fs-idp72466256\" class=\"problem\">\n<p id=\"fs-idp122441904\">Describe a situation where hybrid reproduction would cause two species to fuse into one.<\/p>\n<\/div>\n<div id=\"fs-idm7267248\" class=\"solution\">\n<p id=\"fs-idp14118736\"><textarea aria-label=\"Your Answer\" rows=\"8\"><\/textarea><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q778387\">Show Answer<\/span><\/p>\n<div id=\"q778387\" class=\"hidden-answer\" style=\"display: none\">If the hybrid offspring are as fit or more fit than the parents, reproduction would likely continue between both species and the hybrids, eventually bringing all organisms under the umbrella of one species.<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n<div>\n<h2>Glossary<\/h2>\n<dl id=\"fs-idp72882880\" class=\"definition\">\n<dt><strong>gradual speciation model<\/strong><\/dt>\n<dd id=\"fs-idp96205920\">model that shows how species diverge gradually over time in small steps<\/dd>\n<\/dl>\n<dl id=\"fs-idm96811840\" class=\"definition\">\n<dt><strong>hybrid zone<\/strong><\/dt>\n<dd id=\"fs-idm46445328\">area where two closely related species continue to interact and reproduce, forming hybrids<\/dd>\n<\/dl>\n<dl id=\"fs-idm64914688\" class=\"definition\">\n<dt><strong>punctuated equilibrium<\/strong><\/dt>\n<dd id=\"fs-idm199868352\">model for rapid speciation that can occur when an event causes a small portion of a population to be cut off from the rest of the population<\/dd>\n<\/dl>\n<dl id=\"fs-idm58480288\" class=\"definition\">\n<dt><strong>reinforcement<\/strong><\/dt>\n<dd id=\"fs-idp68355936\">continued speciation divergence between two related species due to low fitness of hybrids between them<\/dd>\n<\/dl>\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-49\">\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><li>Introduction to Ecology &amp; Evolutionary Biology, Derived from Biology by OpenStax. <strong>Authored by<\/strong>: Adrienne Correa. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/cnx.org\/contents\/25adc78c-f54a-4ef4-a081-ebe711c480ed@3.19\">http:\/\/cnx.org\/contents\/25adc78c-f54a-4ef4-a081-ebe711c480ed@3.19<\/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\/25adc78c-f54a-4ef4-a081-ebe711c480ed@3.19<\/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":141992,"menu_order":4,"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\"},{\"type\":\"cc\",\"description\":\"Introduction to Ecology & Evolutionary Biology, Derived from Biology by OpenStax\",\"author\":\"Adrienne Correa\",\"organization\":\"\",\"url\":\"http:\/\/cnx.org\/contents\/25adc78c-f54a-4ef4-a081-ebe711c480ed@3.19\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"Download for free at 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