According to Darwinism,in brief SURVIVAL OF THE FITTEST, one niche (such as grassland) may have organism depending upon that niche(for ex zebra and wildebeast dominates grasslands of Africa).Each species want to dominate over other so that they can enjoy more amount of resources and other prospects. So each organism want to reproduce more and more so that their population can dominate over other. So we can say that resources are limited, but organism depended on that resources are more, so each species want to get complete control over common resources, so they reproduce more and more and dont want to control their population.
