{"id":4478,"date":"2017-03-29T17:01:04","date_gmt":"2017-03-29T17:01:04","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/wm-biology2\/?post_type=chapter&#038;p=4478"},"modified":"2024-04-26T01:43:07","modified_gmt":"2024-04-26T01:43:07","slug":"external-and-internal-fertilization","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/wm-biology2\/chapter\/external-and-internal-fertilization\/","title":{"raw":"External and Internal Fertilization","rendered":"External and Internal Fertilization"},"content":{"raw":"<div class=\"textbox learning-objectives\">\r\n<h3>Learning Outcomes<\/h3>\r\n<ul>\r\n \t<li>Discuss external methods of fertilization<\/li>\r\n \t<li>Discuss internal methods of fertilization<\/li>\r\n<\/ul>\r\n<\/div>\r\n<h2>External Fertilization<\/h2>\r\nExternal fertilization usually occurs in aquatic environments where both eggs and sperm are released into the water. After the sperm reaches the egg, fertilization takes place. Most external fertilization happens during the process of spawning where one or several females release their eggs and the male(s) release sperm in the same area, at the same time. The release of the reproductive material may be triggered by water temperature or the length of daylight. Nearly all fish spawn, as do crustaceans (such as crabs and shrimp), mollusks (such as oysters), squid, and echinoderms (such as sea urchins and sea cucumbers). Figure 1a\u00a0shows salmon spawning in a shallow stream. Frogs, like those shown in Figure 1b, corals, mayflies, and mosquitoes also spawn.\r\n\r\n[caption id=\"attachment_3066\" align=\"aligncenter\" width=\"818\"]<img class=\"size-full wp-image-3066\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/02\/09211704\/Figure_43_02_01ab.jpg\" alt=\"Photo A shows many salmon swimming up a shallow creek. Photo B shows mating toads.\" width=\"818\" height=\"404\" \/> Figure 1.\u00a0(a) Salmon reproduce through spawning. (b) During sexual reproduction in toads, the male grasps the female from behind and externally fertilizes the eggs as they are deposited. (credit a: Dan Bennett; credit b: \"OakleyOriginals\"\/Flickr)[\/caption]\r\n\r\nPairs of fish that are not broadcast spawners may exhibit courtship behavior. This allows the female to select a particular male. The trigger for egg and sperm release (spawning) causes the egg and sperm to be placed in a small area, enhancing the possibility of fertilization.\r\n\r\nExternal fertilization in an aquatic environment protects the eggs from drying out. Broadcast spawning can result in a greater mixture of the genes within a group, leading to higher genetic diversity and a greater chance of species survival in a hostile environment. For sessile aquatic organisms like sponges, broadcast spawning is the only mechanism for fertilization and colonization of new environments. The presence of the fertilized eggs and developing young in the water provides opportunities for predation resulting in a loss of offspring. Therefore, millions of eggs must be produced by individuals, and the offspring produced through this method must mature rapidly. The survival rate of eggs produced through broadcast spawning is low.\r\n<h2>Internal Fertilization<\/h2>\r\nInternal fertilization occurs most often in land-based animals, although some aquatic animals also use this method. There are three ways that offspring are produced following internal fertilization. In <b>oviparity<\/b>, fertilized eggs are laid outside the female\u2019s body and develop there, receiving nourishment from the yolk that is a part of the egg. This occurs in most bony fish, many reptiles, some cartilaginous fish, most amphibians, two mammals, and all birds. Reptiles and insects produce leathery eggs, while birds and turtles produce eggs with high concentrations of calcium carbonate in the shell, making them hard. Chicken eggs are an example of this second type.\r\n\r\nIn <b>ovoviparity<\/b>, fertilized eggs are retained in the female, but the embryo obtains its nourishment from the egg\u2019s yolk and the young are fully developed when they are hatched. This occurs in some bony fish (like the guppy <em>Lebistes reticulatus<\/em>), some sharks, some lizards, some snakes (such as the garter snake <em>Thamnophis sirtalis<\/em>), some vipers, and some invertebrate animals (like the Madagascar hissing cockroach <em>Gromphadorhina portentosa<\/em>).\r\n\r\nIn <b>viviparity<\/b> the young develop within the female, receiving nourishment from the mother\u2019s blood through a placenta. The offspring develops in the female and is born alive. This occurs in most mammals, some cartilaginous fish, and a few reptiles.\r\n\r\nInternal fertilization has the advantage of protecting the fertilized egg from dehydration on land. The embryo is isolated within the female, which limits predation on the young. Internal fertilization enhances the fertilization of eggs by a specific male. Fewer offspring are produced through this method, but their survival rate is higher than that for external fertilization.\r\n<div class=\"textbox tryit\">\r\n<h3>Try It<\/h3>\r\nhttps:\/\/assess.lumenlearning.com\/practice\/eb1aea5f-1865-494e-b507-a94b7f5eda15\r\nhttps:\/\/assess.lumenlearning.com\/practice\/ce18c0d8-4d60-4781-9e06-3ae7f7581e87\r\n\r\n<\/div>","rendered":"<div class=\"textbox learning-objectives\">\n<h3>Learning Outcomes<\/h3>\n<ul>\n<li>Discuss external methods of fertilization<\/li>\n<li>Discuss internal methods of fertilization<\/li>\n<\/ul>\n<\/div>\n<h2>External Fertilization<\/h2>\n<p>External fertilization usually occurs in aquatic environments where both eggs and sperm are released into the water. After the sperm reaches the egg, fertilization takes place. Most external fertilization happens during the process of spawning where one or several females release their eggs and the male(s) release sperm in the same area, at the same time. The release of the reproductive material may be triggered by water temperature or the length of daylight. Nearly all fish spawn, as do crustaceans (such as crabs and shrimp), mollusks (such as oysters), squid, and echinoderms (such as sea urchins and sea cucumbers). Figure 1a\u00a0shows salmon spawning in a shallow stream. Frogs, like those shown in Figure 1b, corals, mayflies, and mosquitoes also spawn.<\/p>\n<div id=\"attachment_3066\" style=\"width: 828px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-3066\" class=\"size-full wp-image-3066\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/02\/09211704\/Figure_43_02_01ab.jpg\" alt=\"Photo A shows many salmon swimming up a shallow creek. Photo B shows mating toads.\" width=\"818\" height=\"404\" \/><\/p>\n<p id=\"caption-attachment-3066\" class=\"wp-caption-text\">Figure 1.\u00a0(a) Salmon reproduce through spawning. (b) During sexual reproduction in toads, the male grasps the female from behind and externally fertilizes the eggs as they are deposited. (credit a: Dan Bennett; credit b: &#8220;OakleyOriginals&#8221;\/Flickr)<\/p>\n<\/div>\n<p>Pairs of fish that are not broadcast spawners may exhibit courtship behavior. This allows the female to select a particular male. The trigger for egg and sperm release (spawning) causes the egg and sperm to be placed in a small area, enhancing the possibility of fertilization.<\/p>\n<p>External fertilization in an aquatic environment protects the eggs from drying out. Broadcast spawning can result in a greater mixture of the genes within a group, leading to higher genetic diversity and a greater chance of species survival in a hostile environment. For sessile aquatic organisms like sponges, broadcast spawning is the only mechanism for fertilization and colonization of new environments. The presence of the fertilized eggs and developing young in the water provides opportunities for predation resulting in a loss of offspring. Therefore, millions of eggs must be produced by individuals, and the offspring produced through this method must mature rapidly. The survival rate of eggs produced through broadcast spawning is low.<\/p>\n<h2>Internal Fertilization<\/h2>\n<p>Internal fertilization occurs most often in land-based animals, although some aquatic animals also use this method. There are three ways that offspring are produced following internal fertilization. In <b>oviparity<\/b>, fertilized eggs are laid outside the female\u2019s body and develop there, receiving nourishment from the yolk that is a part of the egg. This occurs in most bony fish, many reptiles, some cartilaginous fish, most amphibians, two mammals, and all birds. Reptiles and insects produce leathery eggs, while birds and turtles produce eggs with high concentrations of calcium carbonate in the shell, making them hard. Chicken eggs are an example of this second type.<\/p>\n<p>In <b>ovoviparity<\/b>, fertilized eggs are retained in the female, but the embryo obtains its nourishment from the egg\u2019s yolk and the young are fully developed when they are hatched. This occurs in some bony fish (like the guppy <em>Lebistes reticulatus<\/em>), some sharks, some lizards, some snakes (such as the garter snake <em>Thamnophis sirtalis<\/em>), some vipers, and some invertebrate animals (like the Madagascar hissing cockroach <em>Gromphadorhina portentosa<\/em>).<\/p>\n<p>In <b>viviparity<\/b> the young develop within the female, receiving nourishment from the mother\u2019s blood through a placenta. The offspring develops in the female and is born alive. This occurs in most mammals, some cartilaginous fish, and a few reptiles.<\/p>\n<p>Internal fertilization has the advantage of protecting the fertilized egg from dehydration on land. The embryo is isolated within the female, which limits predation on the young. Internal fertilization enhances the fertilization of eggs by a specific male. Fewer offspring are produced through this method, but their survival rate is higher than that for external fertilization.<\/p>\n<div class=\"textbox tryit\">\n<h3>Try It<\/h3>\n<p>\t<iframe id=\"assessment_practice_eb1aea5f-1865-494e-b507-a94b7f5eda15\" class=\"resizable\" src=\"https:\/\/assess.lumenlearning.com\/practice\/eb1aea5f-1865-494e-b507-a94b7f5eda15?iframe_resize_id=assessment_practice_id_eb1aea5f-1865-494e-b507-a94b7f5eda15\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:300px;\"><br \/>\n\t<\/iframe><br \/>\n\t<iframe id=\"assessment_practice_ce18c0d8-4d60-4781-9e06-3ae7f7581e87\" class=\"resizable\" src=\"https:\/\/assess.lumenlearning.com\/practice\/ce18c0d8-4d60-4781-9e06-3ae7f7581e87?iframe_resize_id=assessment_practice_id_ce18c0d8-4d60-4781-9e06-3ae7f7581e87\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:300px;\"><br \/>\n\t<\/iframe><\/p>\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-4478\">\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 2e. <strong>Provided by<\/strong>: OpenStax. <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>: Access for free at https:\/\/openstax.org\/books\/biology-2e\/pages\/1-introduction<\/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":15,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Biology 2e\",\"author\":\"\",\"organization\":\"OpenStax\",\"url\":\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"Access for free at https:\/\/openstax.org\/books\/biology-2e\/pages\/1-introduction\"}]","CANDELA_OUTCOMES_GUID":"9003cbd2-a1af-47a3-b4d5-2c10007bbaa3, 2eb59e7b-b1af-4981-9c23-df998ee5ea35, 0a0b0163-7e9a-438a-8b2d-e7fc3c5b48db","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-4478","chapter","type-chapter","status-publish","hentry"],"part":3801,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters\/4478","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/users\/17"}],"version-history":[{"count":8,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters\/4478\/revisions"}],"predecessor-version":[{"id":8562,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters\/4478\/revisions\/8562"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/parts\/3801"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters\/4478\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/media?parent=4478"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapter-type?post=4478"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/contributor?post=4478"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/license?post=4478"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}