Charles Darwin understood that evolution was a slow and gradual process. By gradual, Darwin inferred a "stepwise" process with a species evolving and accumulating small variations over long periods of time until a new species was born. If evolution is gradual, there should be a fossilized record of small, incremental changes on the way to a new species. But in many cases, scientists were unable to find these intermediate forms. In 1972, evolutionary scientists Stephen Jay Gould and Niles Eldredge proposed another idea of evolution. They suggested that species are generally stable, changing little for millions of years. This stable species becomes the victim of a rapid burst of change that results in a new species and that leaves few fossils behind. Gould and Eldredge proposed this new theory called A) gradualism. B) catastrophism. C) adaptive radiation. D) punctuated equilibrium.

• bridgetspeare: D) punctuated equilibrium.
  
• TheBrokenMarionette:

   D)  punctuated equilibrium.

  punctuated equilibrium The steady, stable state is punctuated by rapid change, thus the phrase punctuated equilibrium.

  ~From USATestprep~