Question

Why do some organisms reproduce many young ones and some only one ?

Answer 1

All animals want to make sure that at least some of their young ones reach adulthood and reproduce themselves. 

2. Some animals do this by looking after a few young ones until they can fend for themselves. 

3. Other animals produce hundreds of eggs which they leave to develop by themselves. Most of them will die, but a few will survive.

Answer 2

All animals want to make sure that at least some of their young ones reach adulthood and reproduce themselves.  Some animals do this by looking after a few young ones until they can fend for themselves.  Other animals produce hundreds of eggs which they leave to develop by themselves. Most of them will die, but a few will survive.