Why is there constant competition for limited resources in each generation?

The reason why there is a constant competition for limited resources in each generation is the competitive exclusion principle. According the competitive exclusion principle  two species with similar ecological niches can not exist sympatrically (in the same environment). This means that one will always "win" and these more competitive species that  will stay. The other will either adapt or be excluded.

Zodiac signs help determine and explain your birthdate but not you as a human you could be a Aquarius but “act” like a Scorpio
I’m a Scorpio