Why was the discovery of lucy so important?

What does it mean for a cell membrane to be selectively permable

Amale bird-of-paradise uses a dance to attract mates in which it flaps its tail feathers on the ground and jumps around a potential female mate. a different male bird-of-paradise does a similar dance but it jumps around the female in the opposite direction. the female bird is only attracted to one style of dance, in one direction.

Explain the process that creates the heat of the sun?