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External fertilization is a mode of reproduction in which a male organism's sperm fertilizes a female organism's egg outside of the female's body. [1] It is contrasted with internal fertilization, in which sperm are introduced via insemination and then combine with an egg inside the body of a female organism.
This is an accepted version of this page This is the latest accepted revision, reviewed on 22 January 2025. Union of gametes of opposite sexes during the process of sexual reproduction to form a zygote This article is about fertilisation in animals and plants. For fertilisation in humans specifically, see Human fertilization. For soil improvement, see Fertilizer. "Conceive" redirects here. For ...
A pair of clicking stream frogs (Strongylopus grayii) in amplexus Orange-thighed frogs (Litoria xanthomera) in amplexusAmplexus (Latin "embrace") is a type of mating behavior exhibited by some externally fertilizing species (chiefly amphibians and horseshoe crabs) in which a male grasps a female with his front legs as part of the mating process, and at the same time or with some time delay, he ...
Most fish species spawn eggs that are fertilized externally, typically with the male inseminating the eggs after the female lays them. These eggs do not have a shell and would dry out in the air. Even air-breathing amphibians lay their eggs in water, or in protective foam as with the Coast foam-nest treefrog, Chiromantis xerampelina .
Oviparous animals are animals that reproduce by depositing fertilized zygotes outside the body (known as laying or spawning) in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings known as hatchlings with little or no embryonic development within the mother.
The biologist Thierry Lodé proposed (2001, 2012) five modes of reproduction based on the relationship between the zygote (fertilised egg) and the parents: [1] [2]. Ovuliparity: fertilisation is external, the oocytes being released into the environment and fertilised outside the body by the male. [1]
In sea urchins, fertilization occurs externally in the ocean, such that hundreds of sperm can encounter the egg within several seconds. In mammals it occurs 2-3 seconds after the first sperm enters the egg, it is a chemical process which involves changing the potential of egg from a resting potential of -70 mv to 10 mv.
The majority of gastropods have internal fertilization, but there are some prosobranch species that have external fertilization. [4] Gastropods are capable of being either male or female, or hermaphrodites, and this makes their reproduction system stand out amongst many other invertebrates.