Difference Between Viviparous, Oviparous and Ovoviviparous Animals
Viviparous Animals |
Oviparous Animals |
Ovoviviparous Animals |
|
Reproductive Strategy |
Young individuals are born alive. No eggs are hatched in this process. |
Such animals produce eggs which attain maturity after being expelled from the body. |
The eggs are generally hatched inside the mothers body; |
Fertilization |
Internal fertilization; The development of the zygote occurs inside the females body. |
May undergo either internal or external fertilization; The development of the zygote happens outside the females body. |
Undergoes internal fertilization; until fully matured the newborns are not given birth. |
Embryo Nourishment |
The egg receives all its nutrition from the mother (matrotrophic) |
The embryo receives all its nutrition from the egg yolk. (lecithotrophic). |
The embryo receives all its nutrition from the yolk content of the egg sacs. |
Examples |
Human beings and mostly mammals. |
Birds, reptiles, amphibians, etc. |
Sharks, rays, snakes, and other aquatic species. |
Modes of reproduction editMain article:
The two traditional methods of reproduction are oviparity, which is thought to be the ancestral condition and is traditionally defined as the situation in which either fertilized eggs or unfertilized oocytes spawn, and viviparity, which is traditionally defined as any mechanism in which the young are born alive or in which one or both parents support the development of the young in any part of their body. [1].
But the traditional category of oviparous reproduction has recently been split into two modes by the biologist Thierry Lodé, which are distinguished by the nature of the relationship between the zygote (fertilized egg) and the parents:[1][2].
- Generally speaking, ovuliparityin which fertilization occurs externallyis considered the ancestral state. Unfertilized oocytes are contained in the eggs that the female releases into the environment, and the male fertilizes them by releasing sperms close to the eggs. Most ovuliparous species’ eggs, in whatever form they are laid, contain a significant amount of yolk to support the embryo’s growth and activity following fertilization and, occasionally, for a short while after hatching. [1] Fish and the majority of amphibians are common examples of ovuliparity among vertebrates. Along with molluscs, echinoderms, cnidarians, and several other aquatic animal phyla, it is also found in these organisms. [1].
- Whether the male injects the sperm into the female intermittently or she actively or passively picks it up, it is assumed that (true) oviparity, in which fertilization is internal, is the derived condition. The female lays eggs containing zygotes with a substantial quantity of yolk to feed the embryo while it is in the egg and, in many species, to feed it for some time afterwards. The primary difference between oviparity and ovoviviparity is that the egg is not retained in the body for the majority of the embryo’s development inside the egg. [1] All birds, the majority of reptiles, certain fish, and most arthropods are oviparous. Monotremes, which include the platypus and four species of echidna, are the only oviparous mammals.
With the exception of rare instances of both ovuliparity and oviparity, the yolkwhich the mother’s reproductive system pre-deposited in the eggprovides the majority of the embryo’s nutrition (the process known as vitellogenesis). Lecithotrophic, which literally translates to “feeding on yolk,” refers to offspring that rely on yolk in this way as opposed to matrotrophy, which occurs when the mother’s circulation meets the needs of the offspring. By eliminating the ovuliparous species, which include the majority of fish, frogs, and invertebrates, the number of species with oviparous modes of reproduction is inevitably reduced when the distinction between oviparity and ovuliparity is made. These divisions are mostly made for practical reasons, and as such, they can be significant in real-world situations. However, in general, when discussing situations where the distinction is irrelevant, it is customary to combine the two groups under the heading “oviparous.”
The Process of Metamorphosis in Viviparous Animals
All living things mature into adults after their young are born. This process of growth is subjected to different stages. In most instances, such as with frogs, silkworms, butterflies, etc., the progeny may have an entirely distinct appearance from the adults.
For instance, frogs develop from eggs, tadpoles, and adulthood.
As they mature, these organisms go through distinct changes, from caterpillar to pupa to adult silkworms. “Metamorphosis” is the term for this process by which children become adults through a series of progressive changes, or rather, a development. .
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