Many scientists think that the most important function in the study of ecosystems is to prevent their collapse. Populations of different species are the building blocks of ecosystems. So the question becomes, why would the failure of an ecosystem be so significant?
The first rule of species survival in an ecosystem is that the population must be large enough to withstand disease, shortages of food and water, predators, and the other hazards of living.
Food Webs: The Ties that Bind
In nature, however, cheetahs feed on a variety of prey, not just gazelles. This means that cheetahs, like other organisms in an ecosystem, are members of many different food chains. All of these interrelated food chains create a food web. Relationships among members of a food chain must be in balance. Otherwise, individual populations could become too large or small and fracture the delicate connections that hold the ecosystem together.
Why should you care about populations and relationships between populations and the ecosystem? To answer this question, it is useful to begin by thinking about sex.