After a scary biking accident, Alex extinguished his conditioned fear of bikes by cycling on a safe biking trail every day for a week. Alex now feels safe riding his bike. Two weeks later, he suddenly feels afraid again while riding his bike. The reappearance of his previously extinguished fear when he rode a bike on the same trail two weeks later best illustrates

In some zoos, rare crosses between a male lion and a female tiger have produced hybrid offspring called "ligers." male ligers are sterile but some female ligers are fertile. in the wild, lion and tiger ranges do not naturally overlap, making such a cross unlikely. furthermore, the solitary behavior of tigers and the social organizations of lions create behavioral differences. the production of sterile male ligers is an example of read the following scenario to answer the following question. in some zoos, rare crosses between a male lion and a female tiger have produced hybrid offspring called "ligers." male ligers are sterile but some female ligers are fertile. in the wild, lion and tiger ranges do not naturally overlap, making such a cross unlikely. furthermore, the solitary behavior of tigers and the social organizations of lions create behavioral differences. the production of sterile male ligers is an example of a postzygotic barrier the founder effect sympatric speciation a prezygotic barrier

What was the social class pyramid during the civil war?

There are 25 elements found in living things. how many of these elements are found in some organisms but not all? 1 , 6 , 19 , 25