system
Given the following post, respond as if you're commenting on Reddit:
human
Why are the males of some species bigger and stronger, but in other species, it's the females that are big and powerful?

What exactly makes it more advantageous for some species to have strong males and weaker females, while some other species have huge females and relatively puny males?
gpt
There are a variety of reproductive strategies which lead to different types of sexual dimorphism.  In many species, males have to fight with other males in order to establish dominance, which allows them to mate with females.  Hence, there is evolutionary pressure for males to become bigger and stronger.  But if we consider a spiders, for example, males do not fight with each other, they just mate at will.  The female spider needs to be larger than the male because the eggs which the female will lay are much larger than the seminal fluid that the male needs to produce, and there is a biological cost to producing those eggs, which requires the female to be able to consume more food, and to hunt more effectively.