Why do organisms have to compete for resources

Idon’t know the answer and i’ve been stuck on it for a while now skskskskks

Zoo geographic regions are characterized by the presence of specific groups of animals these regions are determined by the taxonomic or phylogenetic relationships of animals. the map shows the zoogeographic regions proposed by the naturalist alfred russel wallace in 1876. the similarities of organisms in which two areas numbered above provide the best evidence for common ancestry between the organisms in both locations ?

A(n) is a molecule influences the way that a molecule reacts.