How far does Selaginella one of the few living members of lycopodiales (pteridophytes) fall short of seed habit.

Each plant or group of plants has some phylogenetic significance in relation to evolution. Cycas, one of the few living members of gymonsperms is called as the 'relic of past'. Can you establish a phylogenetic relationship of Cycas with any other group of plants that justifies the above statement?

What is nuclear fall out ? How does it reach living organisms ?

Figure shows how fish react when the glass on one side of an aquarium tank is tapped with a finger. What characteristics of living organisms does the demonstrate?