Everyone is familiar with porcupines, beavers, rats, squirrels, and, of course, mice—common representatives of the order Rodentia or the rodents. They are defined by zoologists as having a single pair of constantly growing upper and lower jaw incisors. Over 40 percent (about 1,700) of mammal species are rodents.

Being called a "bird brain" implies that an individual is scatterbrained and flighty. Through the decades, however, ornithologists have grown to appreciate the amazing design and abilities of these feathered creatures. From their respiratory system to intricate vocalization patterns, birds reveal profound sophistication.

Most people have a passing knowledge of the food they eat, and perhaps how it gets digested. As with all human body systems, however, details of the digestive or gastrointestinal (GI) tract—including the incredibly rich microbial flora found at the last portion of the small intestine and the entire large intestine—are an amazing testimony to creation.

Scientists recently studied laughter in different animals, such as rats and primates, by tickling them. One study compared the sounds made by humans and great apes: