Why do school bags have broad shoulder traps ?

Why do the veins have valves?

Why do some plants have both chasmogamous and cleistogamous flowers?

Why do molluscs have shells?

Why do molluscs have shells?

Why do animals in cold regions have a layer of fat below their skin.

Why do some people have earache when they travel by an aeroplane ?

Why do we see moonlight ?

Why do noble gases have comparatively large atomic size ?

Since your earlier school days you have been solving mysteries/puzzles labelled as use your brain power . Did you ever wonder why human brain has such a capacity ? Why and how we evolved along these lines ? What is the extent of similarity between are humans , chimpanzees and monkeys ?

Why do we call as plants producers on land?