Why are the offsprings of some animals large but some small?

[UGG]

A human has relatively large offspring compared to a panda, who usually have two very small offspring. Why is this? What are you thoughts?

[mith]

development time

[futurezoologist]

It is beneficial to certain animals to have different portions of the development of their offspring inside or outside of their body, it depends on many factors including whether it is a predator or prey, its environmental conditions etc. (sorry cant think of an example at the moment)

[2009queenb]

I didn't exactly get your question. But the smallest chameleon in the world is the Brookesia Minima. Adults are about the size of your pinky nail. And the babies are wayyy smaller. So there you do. And its a reptile! Not an insect!!

[MJD]

Resource allocation. A balance of the costs of producing an offspring, caring for an offspring, and the chance that it will survive in the environment. Cost to Benefit Ratio. For instance, some animals produce many offspring at once, which increases the probability that at least or two will survive. This increases the probability that the parental genes will be passed on to the next generation. On the other hand, offspring that are larger may need to compete for resources sooner. Humans aren't a good example. Think about whales. The calf has to be able to escape predators, even if the mother or the group provides some degree of protection. Simple, yet complex.

[Chroma]

With many herd animals like deer they have to be able to move soon after they are born so that would definitely favor a larger more developed size.

With pandas I'm not really sure. Though, one could imagine the lack of natural predators and low nutrient bamboo diet would be significant factors.

[jwalin]

its the selection pressure that must be working in both the cases. in the pandas may be the smaller ones may be favoured more. by the nature and perhaps its surrounding the human activities nowadays.

[andra]

Well,i absolutely agree with mith's opinion,
Enviromental factor,genetic factor,and its evolution path can cause developemental differences between one creature to another

[TheVirus]

I also agree that the best answer is the development time. Maybe the sizes of the offsprings are proportional to their potential size (the maximum size they will get in their lives), which is determined by their genes. For example, a whale's offspring is bigger than a human's just because an adult whale is also bigger than an adult human being.

[carter]

we can deal with this problem in many kinds of perspective.Ecology,genetics,evolution are all workable.The answers of the former are all reasonable in different angles.