Evolve

They are one of evolution's most useful and prevalent inventions. Ninety five percent of living species are equipped with eyes and they exist in many different forms.

It doesn't just take willpower to survive. It takes guts--in the form of a digestive system that turns food into fuel. Look closely at the role guts have played in shaping some of Earth's most successful animals.

It's one of the most important developments in the history of life. An adaptation that lets animals kill, butcher, and devour. There is perhaps no instrument more important to survival than a strong set of jaws.

In the history of life on earth, sex may be the ultimate survival skill, because the bottom line is: reproduce or die. This episode looks at sex in its many forms.

It makes up 16% of your body weight, is the largest organ in the human body, allows birds to fly, mammals to nurse their young, and provides a lifelong defense against predators and parasites alike. What is it? Skin.

Humans have always been fascinated with the one part of the world that we could not conquer--the sky. How did the earth's first flying creatures come to be?

How has our ability to communicate defined us as a species? Sharing information with each other has allowed humans to rise to the top of the food chain and dominate our environments. But humans aren't the only species that can communicate.

Life has evolved into a multitude of sizes. Over the course of three billion years, life has taken on many forms--from an .02-micrometer-long bacteria to the 110-foot-long blue whale.

The ability to react and move can often mean the difference between life and death in the animal kingdom. Some animals have evolved into championship fliers, swimmers, and runners.

The deadliest natural weapon employed in the animal kingdom, venom has independently evolved in creatures as diverse as jellyfish, insects, snakes, and even mammals.

Living organisms have entered into a battle for survival for hundreds of millions of years and the pressure to survive has resulted in ever changing shapes.