Final answer:
Karl von Frisch shared the Nobel Prize for Medicine and Physiology in 1973 with Niko Tinbergen.
Step-by-step explanation:
The ethologist who shared the Nobel Prize for Medicine and Physiology in 1973 with Niko Tinbergen was Karl von Frisch. Frisch was awarded for his discoveries in the field of animal behavior, particularly his research on the communication and navigation abilities of honeybees. His findings enhanced our understanding of animal behavior and the ways in which animals interact with their environment.