how about chicken or cow. are they got life purpose?  

Does universe has a purpose? Does Sun has a purpose, will things that doesn't serve any purpose exists?

We are like an ant in an ant colony, non of us carry a conception of the grand design of the colonial home, but with the division of labour and collective responsibility, a highly organized social structure emerged. In isolated view, an ant with only limited intelligent and ability, but in a holistic view, the colony as a whole display a level of purpose and sophisticated link society.

Asking the purpose of life in isolated view is less meaningful as just like asking what is the purpose of a "single" shoe? It needs to be a pair in order to serve a purpose.

We exhale CO2 which is needed be the tree, we inhale O2 which is produced by the tree as a result of photosynthesis using Sun energy. If Sun one day says that its life is purposeless, do you agree with this?

Oneness is truth, and truth is oneness. Everything comes forth from oneness ---- Zen

Why not. There is one branch of philosophy stating that if we could understand the origin of the universe one day, the purpose would be able to be explained then. Origin <----- Purpose

It was a metaphor. If Sun has a mind, it may asks the purpose of continuous explosion of helium and hydrogen. But when we look at the holistic view, it has it's purpose to the universe.

purpose of life is to eat sleep and reproduce and die.