Final answer:
Increasing the proportion of 16-carbon fatty acids relative to 18-carbon fatty acids in the membranes will increase fluidity in both poikilotherms and homeotherms. Both types of organisms adapt their membrane lipid composition for optimal fluidity, but they have different strategies due to their distinct thermoregulatory needs, with cholesterol also playing a significant role in maintaining membrane fluidity.
Step-by-step explanation:
In comparing the membranes of poikilotherms (cold-blooded organisms) and homeotherms (warm-blooded organisms), it can be said that increasing the proportion of 16-carbon relative to 18-carbon fatty acids in their membranes will increase fluidity in both organisms. Poikilotherms and homeotherms both engage in adjusting the fatty acid composition of their cell membranes to regulate fluidity in response to environmental temperatures, though the specific strategies and needs differ due to their thermoregulation mechanisms.
Poikilotherms primarily adapt to environmental temperature changes by altering the degree of unsaturation of fatty acids in their cell membranes. In response to cold, they increase unsaturated fatty acids to maintain membrane fluidity. Conversely, homeotherms tend to have a stable membrane composition that supports their constant body temperature and higher metabolic rate.
Cholesterol also plays a role in membrane fluidity, especially for homeotherms, by buffering temperature effects and providing a suitable fluidity range for cell membrane function across various temperatures.