What makes animal to continually reproduce?

Question

I was reading about Trypophobia and reached to Surinam Toad's reproduction methods. Then I had this doubt- Why would animals want to reproduce so much? In case of humans we mostly have the offsprings nearby for entire life, so some of them may take care of us. But in case of many other animals after birth they have no connection with their parents. So why do they always try to reproduce in large quantities in entire life time? What they achieve in this?

Answer 1

There is also another angle to look at this, to consider live bearing species, such as rodents and rabbits, that also breed relatively often and at high rates, but do not lay eggs, and to explain why other egg laying species, such as some reptiles, put a great deal of parental care into their offspring.

Very generally, you can think of two ways to make sure your genes make it to the next generation: have one or a few offspring, and take care of them till old enough to reproduce (humans) or have a hundred offspring each year, and hope that at least a few of them make it (frogs, mice, insects). Both strategies are effective, and different environments can lend evolutionary pressures to result in one or the other being the most optimal for a species.

Answer 2

So I am going to skip past the trypophobia idea because thats just disturbing and go straight into the science-y stuff. I am going to start off by saying that the mass-breeding species generally follow a completely different reproductive cycle than humans. Mass breeding species tend to be egg-laying. This means that they don't have to wait huge length of time for younglings to fully form in the womb before giving birth. This permits them to reproduce more often.

Think about it like this. Egg-laying species tend to be animals would be detrimentally influenced if they had to carry round around with them for long periods of time. For example: imagine a tiny sparrow trying to fly with several babies in its womb. Or a frog trying to hop away from a predator with several fully formed frog babies in its womb. Its not possible. Or a snake trying to slither with a bunch of babies. Not a pretty picture. Laying eggs became an evolutionary thing to allow the parent to survive through child-birth. However, eggs are helpless. So to increase the likelihood a single offspring is going to survive through hatchery, the animal produce a huge amount of offspring.

Meanwhile other such as sharks found it easier to develop a live-birth method because sharks aren't exactly physically able to sit in one place and watch over a underwater net of eggs. However, some fish have developed an egg-laying technique. An example of this is the clown fish. While it cannot sit still, it puts its eggs in sea anemones witch protect the eggs.

I hope this amply answers your question!!