Question

What are primitive organisms and how are they different from advanced organisms?

Answer 1

A primitive organism is the lower organism which exhibits simple body structure and simple organization. An advanced organism exhibits little complexity in the body structure and organization. Complexity of the organism is prone to changes. The changes in the body structure and design may result from adaptations developed by the organism to the environment.
Primitive organisms do not change their body design so easily as advanced organisms do.

Prokaryotes are considered to be primitive forms and eukaryotes are the advanced organisms. In prokaryotes all the bodily activities are performed by a single cell whereas in advanced organisms there are different organs to perform different metabolic functions.