What are the advantages (and disadvantages) of oviparity, ovoviparity and viviparity?
Oviparous animals undergo all embryotic development outside of their parent’s body. The female lays her eggs with exposure to the external environment instead of retaining them internally. This method of reproduction requires less energy, as the developing embryo depends completely on a concentration of nutrients within the egg called the yolk. This allows more eggs to be produced in some cases, but this lack of parental investment also reduces the offspring’s likelihood of survival.
Viviparous animals develop embryonically within the body of their mother. All nutrients are received from the mother by diffusion from her circulatory system. After development, live birth takes place. This process is much more energy-expensive than oviparity. Although this often leads to a lower number of offspring produced, higher parental investment allows them to have higher survival rates.
Animals that are ovoviparous undergo embryotic development within their mother’s body, but do not have access to her circulatory system. Instead, the embryo develops within an independent egg and feeds off of an independent yolk. The egg hatches while the offspring is still within the mother and the young animal then makes its way out into the open environment, giving the appearance of live birth. This process uses an intermediate amount of energy, and therefore also produces an intermediate amount of offspring with an intermediate survival probability on average.