Final answer:
The primary benefit of circulatory systems is overcoming the slow rate of diffusion across cells, providing rapid transport of oxygen, nutrients, and waste products. Evolution from simple diffusion to complex circulatory systems enables larger multicellular organisms to efficiently maintain homeostasis, including body temperature regulation.
Step-by-step explanation:
Circulatory systems have the primary benefit of overcoming the shortcomings of B) the slow rate at which diffusion occurs across cells. The evolution of circulatory systems in organisms, particularly those with specialized respiratory organs such as lungs and gills, is a response to the need for efficient transportation of oxygen and nutrients to body tissues, and the removal of carbon dioxide and waste products.
As organisms evolved from simple, single-celled life forms to complex multicellular animals, diffusion alone became insufficient for transporting essential substances across the increasingly larger distances within their bodies. This led to the development of open and closed circulatory systems, equipped with organs like the heart and a network of blood vessels to facilitate rapid transport and maintain homeostasis, including regulation of body temperature through mechanisms like vasodilation and vasoconstriction.
Among the various benefits, closed circulatory systems are particularly efficient in endotherms for maintaining optimal body temperature using adaptations such as countercurrent heat exchange. Found in diverse creatures such as dolphins and hummingbirds, this adaptation allows for the transfer of heat between blood vessels carrying blood toward and away from the heart, helping to regulate core temperature. By doing this, the circulatory system supports not just nutrient and waste exchange, but also thermoregulation.