Predation

Predation is a biological interaction in which one organism, the predator, kills and eats another, its prey, a relationship distinguished from parasitism and scavenging even though predators sometimes scavenge as well. Predators hunt through several distinct strategies: pursuit predation, in which animals such as wolves, dolphins, and dragonflies actively chase fleeing prey; ambush predation, in which animals such as trapdoor spiders and many frogs wait concealed before striking; and ballistic interception, in which animals such as chameleons and archerfish calculate and intercept a prey's path. Predators shape ecosystems by regulating prey populations, preserving biodiversity by preventing any one competitor from dominating, and acting as keystone species whose removal can cascade through an entire food web, as seen when the loss and later reintroduction of wolves in Yellowstone altered vegetation and habitat structure well beyond the predator-prey relationship itself. Predation has also driven major evolutionary innovations over Earth's history, shaping the evolution of shells, mobility, and the complexity of organisms generally.