why do fish and frog lay more number of eggs where cows and humans usually give birth to only one at a time
Answers
Answer:
It’s all about employing different reproductive strategies.
Different organisms have different priorities when it comes to the means used in propagating their species. In the case of animals like fishes and frogs - animals that have evolved within environments with low survival rates - they mate a single time and produce a high number of offspring, thereby granting them a higher chance of allowing at some of the offspring to not only survive the path to adulthood, but also live long enough to reproduce themselves and propagate their genes.
This strategy extended to animals such as sauropod dinosaurs as well. At the time of their hatching, the largest species of sauropod dinosaurs were about the size of a house cat; by the time they’d reached adulthood however, they were the largest terrestrial vertebrates in existence, enough so that their size itself was their defense against predators.
In the case of mammals however, reproductive strategies become more complex. Mammals and birds are endothermic organisms, meaning that, unlike reptiles, amphibians and fishes who are poikilothermic organisms, they require a greater degree of energy in order to maintain their biological functions.
In addition, cows and humans are placental mammals, meaning that the embryonic development is undergone within the mother’s uterus with a chorioallantoic placenta to provide nourishment; which is a huge investment in terms of energy and resources. Humans in particular, require a significant amount of time to transition from infancy all the way to adulthood.
Usually larger mammals have longer gestation periods and fewer offspring, while smaller mammals have shorter gestation periods and a higher number of offspring, though this isn’t always an absolute rule