The system that circulates blood through the body, consisting of the heart and blood vessels. In all vertebrates and certain invertebrates, the circulatory system is completely contained within a network of vessels. In vertebrates, the lymphatic system is also considered part of the circulatory system.
While a squirrel isnât going to pen the next bestseller or ace a calculus class, the squirrel is smart in his own way. When looking at animal intelligence, humans shouldnât judge animals by human standards.
Top 10 Smartest Animals. No. 10 in our countdown of smartest animals is the rat, a highly intelligent yet much-maligned animal in Western cultures. Widely used in research, the lab rat has been known to find shortcuts, loopholes and escape routes in the laboratory experiments designed by the top scientific minds of our time. In Chinese culture, the rat is revered for its cunning and resourcefulness.