As body size increases in animals, . Select one: a. the surface-area-to-volume ratio decreases b. reproduction becomes limited to terrestrial environments c. there is greater variability in metabolic rate d. migration to tropical areas becomes necessary for thermoregulation e. it becomes more difficult to conserve body warmth in cold environments

: a. the surface-area-to-volume ratio decreases

Explanation:

This is the normal physiological relationship of organisms.Small animals have large surface area to volume ratio, because of limited area exposed to the surrounding environment. However, larger animals with complex body structure have small area to volume ratio. This explains the reasons why larger animals needed to develop efficient body organs and mechanism for osmoregulatory functions for survival.  microvilli in the intestine,convoluted walls of the capillaries, formation of root hairs and capillaries,  the nepron tubules etc.

For example  when exposed to cold environments the low surface area to volume ratio is an adaptation to conserve warmth,  in large animals as limited heat is lost to the surrounding environment via evaporation from the body  surfaces. Conversely this is at disadvantage to lower size animals with large surface area to volume ratio, because,heat is evaporated through the large surface area exposed.They are therefore very active to generate large amount of heat energy to make up for this.