Ecology, the study of the interactions of organisms with their physical environment as well as each other, has struck biologists as the focus of study for decades. Within these interactions lies a concept of evolution know as the "arms race". In a never ending arms race, the battle between the species proves to be one that is nothing of a simple kind, but one that entails an immense amount of adaptation and change. There is a constant need to keep up with the pace of the enemy, which is why species must cope with this by arming themselves with different methods of defense. Some of these challenges force them to adapt or die out.
Predators-prey interactions are frequently marked by an ever-increasing arms race. The seeds of legumes are the frequent prey of bruchid weevils, a kind of beetle. The adult lays its eggs, and the larvae when they hatch, burrow into seeds. Each larva occupies one seed. Some legumes have evolved seeds so tiny that one will not sufficiently nourish a larva to pupatation and thus creating a successful defense against the bruchid weevils. In this particular arms race, the legumes adapted themselves to face the challenges posed by the bruchid weevils. Other legumes produce a chemical that inhibits the protein-digesting enzymes. These defenses are still successful against most insects but bruchid weevils have created a stronger weapon and have evolved metabolic pathways that bypass the enzyme block. Soybeans appear to be a momentary victor as bruchid larvae laid in soybeans die out. In this arms race, the challenges force the bruchid larvae to die out.
One of the most prevalent ecological interactions is competition for limited resources. Paramecium is a single-celled, ciliated protozoan that feeds on bacteria. It can be raised in a test-tube, in a broth of bacteria, which is its food supply. In fact, there are a number of species of paramecium, which can be raised in this fashion.