A model organism is a species that has been widely studied to understand a particular biological phenomena, normally used because they are easy to breed and maintain in a laboratory setting and has certain experimental advantage.
The criteria that Thomas hunt Morgan was looking for include; the model organism should be small in size, easy to keep in the laboratory and also able to produce large number of off springs in a short time.
Answer:
Diffusion is powerful over a particular distance and bounds the size that a character cellular can gain.
Explanation: If cellular is an unmarried-celled microorganism, consisting of an amoeba, it is able to satisfy all of its nutrient and waste needs via diffusion. If the mobile is too massive, then diffusion is useless at finishing all of these responsibilities.