Answer:
Neuron - Gangalion - Brain - Central nervous system.
Step-by-step explanation:
The structural organisation of living tissues starts from cell. A group of cell forms tissues. This group in turn leads to the formation of organs. The group of organs collectively makes up the organs system. The entire organ system makes the body of the organism.
The order of degree of level of organisation can be shown as:
Cell-tissue-organ-organ system-Organism.
In case of the image given in the question, the lowest degree of internal organisation is neuron (cell), which is followed by gangalion (tissue), followed by brain (organ) and finally the highest degree of internal organisation whcih is central nervous system (Organ system).