In the past week I observed three peculiar biological phenomena. I wonder why these were evolved. The observations:
1. I have a money plant at my place. I observed that only alternate leaves on a stem dry up. Why?
2. The bananas start ripening from bottom to up. Why not top to bottom? Or, all at once?
3. Crying is very contagious. When someone cries, you get an urge to cry even though you have no particular emotion or desire for crying. Why this?
Nature is perfect designer. Nothing is evolved per se. Everything has a reason. So, these must have perfectly valid advantages for the organism. What are these?