There are many events which can be used for discovery science like (1)Ozone : the destroyer: The temperature decreases with increasing altitude in the troposphere (8 to 16 km from earth surface), while it increases with increasing altitude in the stratosphere. This rise in temperature in stratosphere is caused by ozone layer. (2) Acid rains: an invisible threat Acid rains create complex problems and their impacts are far reaching. They increase soil acidity, this affecting land flora and fauna. (3) Dinosaurs: they appeared during Triassic period, 231millions years ago (4) Insects: have a chitinous exoskeleton.