Cause and effect, sometimes called causal analysis, explores the cause-and-effect relationship between two (or more) subjects or items.When you discuss the reasons producing something, you are analyzing the cause；when you discuss the results produced by something, you are analyzing the effect.A causal analysis essay usually focuses on either the causes or the effects of a situation or an event.Now read the following two model essays below, and identify which essay focuses on causes and which essay focuses on effects.
Model Essay One
The Extinction of Dinosaurs
For almost 140 million years, dinosaurs and other large reptiles ruled the land, sky and sea.Dinosaurs came in sizes and shapes suited to every corner of the world.Then approximately 65 million years ago, these huge reptiles died out and mammals took over the Earth.Few mysteries have ever excited the imaginations of scientists as much as this great extinction that killed off all the dinosaurs.Over the years, scientists have developed numerous theories to explain the causes of the disappearance of the dinosaurs and other great reptiles.Three possible causes are a change in the Earth's climate, disease, and the Earth's collision with a large asteroid (小行星).
Some scientists believe that the number of dinosaurs declined and eventually disappeared due to a change in the Earth's climate.During the Cretaceous (白垩纪的) period, the climate was tropical.Research indicates that at the end of the Cretaceous period, the temperature dropped and the climate became much colder.For this reason, many of the plants that the plant-eating dinosaurs ate died.The death of the plants would cause many of the plant-eaters to die, too.As the plant-eating dinosaurs died off, so did the meat-eaters who fed on them.The colder climate may have caused problems for the dinosaurs in other ways, too.Because of their size, many dinosaurs were too big to hibernate in dens (洞穴). They also lacked fur or feathers for protection against the cold.As a result, the dinosaurs were unable to adapt to the new cold conditions.