<Table> <Tr> <Td> </Td> <Td> This article needs more links to other articles to help integrate it into the encyclopedia . Please help improve this article by adding links that are relevant to the context within the existing text . (December 2016) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs more links to other articles to help integrate it into the encyclopedia . Please help improve this article by adding links that are relevant to the context within the existing text . (December 2016) (Learn how and when to remove this template message) </Td> </Tr> <P> External fertilization is a male organism's sperm fertilizing a female organism's egg outside of the female's body . Internal fertilization, on the other hand, is the occurrence of internal insemination as the mode of combining sperm and egg . External fertilization occurs in water or a moist area because it gives the sperm external mobility to get to the egg . While in the water, the sperm and ova can shed simultaneously to fertilize the egg . The release of eggs and sperm into the water is known as spawning . When females spawn, they release a batch of eggs into a spot of their choice or just into the water, as in bottom dwelling or sessile species and all of the males start to release sperm that are in close proximity . Within vertebrates, it is the amphibians and fish that use external fertilization . When it comes to invertebrates, most are benthic, sessile, or benthic sessile combined animals such as coral, sea anemones, and tube dwelling polychaetes . The benthic zone is the lowest level of the ocean where organisms called benthos reside . An organism that is sessile does not have the ability to move or be mobile . Benthic marine plants such as algae also go through external fertilization to reproduce . Overall, environmental factors and the timing have a heavy influence over the success of external fertilization.In external fertilization some of the eggs laid by the animals gets wasted due to huge rainfall, floods etc . </P> <P> Sexual selection may not seem to occur during external fertilization, but there are ways it actually can . The two types of external fertilizers are nest builders and broadcast spawners . For female nest builders, the main choice is the location of where to lay her eggs . A female can choose a nest close to the male she wants to fertilize her eggs, but there is no guarantee that the preferred male will fertilize any of the eggs . Broadcast spawners have a very weak selection, due to the randomness of releasing gametes . To look into the effect of female choice on external fertilization, an in vitro sperm competition experiment was performed . The results concluded that there was a decreased importance of sperm number, but increased the importance of the sperm velocity, thus changing the outcome of sperm competition . The ovarian fluid also increased the paternity for the preferred male because they release fewer and faster sperm . The success of a male fertilizing an egg relies on the ability of a male's sperm to outcompete other sperm that is looking to fertilize the same egg . Sperm chemotaxis is the use of chemical signals to give sperm the ability to navigate an egg and is a huge contributor to reproductive success . </P>

Among members of kingdom animalia external fertilization is commonly observed in
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