Warm-Blooded vs. Cold-Blooded: How Animals Generate Heat

They taught us that animals can be divided into warm-blooded or cold-blooded categories, depending on whether they generate their own heat or depend on the sun to provide it. But it turns out that the divide is not so clear, and that different species have varying methods for staying warm enough to thrive. While many animals can be described as one or another, there are also many species that fall somewhere between, which tells us that heat-generating strategies are really a spectrum. Or maybe not, because the word "spectrum" suggests a straight line of gradients, while animal species are really all over the chart.   

This video is only 2:40 in length. The rest is an ad. -via Geeks Are Sexy