The event, called Evolution Sunday, is an outgrowth of the Clergy Letter Project, started by academics and ministers in Wisconsin in early 2005 as a response to efforts, most notably in Dover, Pa., to discredit the teaching of evolutionary theory in public schools.

"There was a growing need to demonstrate that the loud, shrill voices of fundamentalists claiming that Christians had to choose between modern science and religion were presenting a false dichotomy," said Michael Zimmerman, dean of the College of Letters and Sciences at the University of Wisconsin Oshkosh and the major organizer of the letter project.

Mr. Zimmerman said more than 10,000 ministers had signed the letter, which states, in part, that the theory of evolution is "a foundational scientific truth." To reject it, the letter continues, "is to deliberately embrace scientific ignorance and transmit such ignorance to our children."

"We believe that among God's good gifts are human minds capable of critical thought and that the failure to fully employ this gift is a rejection of the will of our Creator," the letter says.

A majority of members on the Board of Education of Ohio, the first state to single out evolution for "critical analysis" in science classes more than three years ago, are expected on Tuesday to challenge a model biology lesson plan they consider an excuse to teach the tenets of the disputed theory of intelligent design.

A reversal in Ohio would be the most significant in a series of developments signaling a sea change across the country against intelligent design — which posits that life is too complex to be explained by evolution alone — since a federal judge's ruling in December that teaching the theory in the public schools of Dover, Pa., was unconstitutional.

A small rural school district in California last month quickly scuttled plans for a philosophy elective on intelligent design after being challenged by lawyers involved in the Pennsylvania case. Also last month, an Indiana lawmaker who said in November that he would introduce legislation to mandate teaching of intelligent design instead offered a watered-down bill requiring only "accuracy in textbooks." And just last week, two Democrats in Wisconsin proposed a ban on schools' teaching intelligent design as science, the first such proposal in the country.