The correct answer is the organ.
The multicellular species are formed of various parts, which are required for survival. These parts are differentiated into the levels of the organization. There are five different levels, which are named as cells, tissue, organs, organ systems, and organisms.
When two or more layers of tissue function together, they produce an organ. All the animals comprise vital organs, without which they cannot survive. These include the kidneys, liver, lungs, brain, and heart.
There are basically three types of evolution divergent, convergent and parallel evolution.
a) Divergent Evolution – As the name depicts the species in this form of evolution becomes divergent i.e they evolve to become different from each other. This form of evolution is responsible for the current diversity of organisms existing on planet earth. For example human and apes evolved from a common primate ancestor.