Complex Organization Examples?

Question

I still am not entirely sure of what a complex organization is, but I think knowing a few examples of some would help my understanding.

Answer 1

Compare between a bacterium and an Amoeba. Being single- celled, yet their internal organizations are different. Amoeba is far more complex as it has a membrane system in th cytoplasm and has several proteins to impart movement. Amoeba has nucleus and chromosomes are complexed with proteins(histones etc.).
At tissue level, take the case of a sponge and compare it with that of a flatworm.
At organ level, take the case of heart of a fish, which has only two chambers and compare it with that of a man which has four chambers.