Robert Full is interested in the biomechanics of arthropod movement. Arthropods move low to the ground using their legs in a tripod fashion, which is inherently stable. Their skeleton provides local control over movement. But the secret to their success is their jointed legs, which act as struts and shock absorbers. [7:15]

If you draw a line down the middle of the body, both sides are mirror images of each other. With a head and stereo senses leading the way, this body plan is ideal for active hunters. [2:49]

Des Collins studies the fossils of the Burgess Shale that represent the Cambrian Explosion of animal life. An animation of this event shows the transition from the simple animals that existed before the explosion to the many complex, weird forms that evolved in a geological blink of the eye. Rudy Raff presents several theories to explain what caused the explosion. By the end of the explosion, all 35 of the present groups or phyla of animals existed and no new ones have evolved since. Nature had evolved life's essential designs in a single evolutionary leap. Every new shape of life that has followed has been a variation on one of these themes or phyla. [13:07]

The Monterey Bay Aquarium Research Institute launches an expedition to explore the depths of the ocean in search of cnidarians. Scientists find that jellyfish and other cnidarians are dominant in both moderate depths and the deep parts of the ocean. [8:39]

Follow Des Collins, a paleontologist, as he looks back into deep time to study the Cambrian explosion in this video. He studies fossils from the Burgess Shale in Canada. He describes the excitement and difficulty of putting together an entire fossil Anomalacaris. [6:12]

The five-part symmetry of echinoderms is demonstrated, as the five-armed starfish is morphed into an urchin that is then morphed into a sea cucumber. [1:42]

The flatworm's bilateral body plan has a head with a brain and stereo eyes that enable it to actively hunt. Its mouth and pharynx are in the center of its underside. With no circulatory system, the gut distributes food to all parts of the body. [2:49]

Flatworms are hermaphroditic with both male and female reproductive organs. They also have internal fertilization. See Penis Fencing (Behavior Sequences) to learn how the sperm gets delivered. [0:48]

A video exploring the reproduction of flatworms. See how the two marine flatworms jab each other to inject sperm. The one that gets injected becomes the female and nourishes the developing fertilized eggs. [1:44]

Mitch Sogin analyses the genes of a sponge in his search for the origin of animals. In order to sequence the genes, he extracts them from the cells. We see the threads of DNA in a test tube. He compares a similar gene found in all the sequences in the animals he tested. Over time small mutations occur in all genes. The more closely related the animals are, the more similar is the code in a shared gene. He created a family tree by comparing the number of changes in the code. The sponge was at the bottom because its gene had the fewest changes. [8:09]

All the cells in all animals have a complete set of genes with the instructions for building an organism. Working with mutations in fruit flies, scientists have found a group of regulatory genes called Hox genes that signal other genes in sequence to build the body of an animal. All animals except sponges have Hox genes. [6:04]

The human body plan is bilateral with symmetrical sense organs, a fast responding brain, half the body weight in muscles, a powerful heart, and miles of arteries and veins and a brain that coordinates it all. All large active animals have this same body plan. [2:28]

The scientific fields of paleontology, embryology, anatomy, and genetics have all contributed to a new view of the evolution of the animal kingdom. [3:42]

The squid's body plan has developed for fast action. The shell is reduced to a thin "pen." The mantle wall has elastic fibers that intensify the jet propulsion. Giant nerves allow a fast reflex and three hearts pump oxygen to the gills. [1:34]

It sometimes takes years and many mistakes to piece together an entire animal. Collins uses Anomalocaris as an example of the long complicated process. Several fossil pieces of Anomalocaris were originally identified as entirely different animals. Finally Collins finds a complete fossil and solves the mystery. We see both a model and animation of the animal. [4:09]

A single location, the Burgess Shale, in the Canadian Rockies has revealed thousands of fossils that tell a story of an ancient explosion of animal life, called the Cambrian Explosion. [5:05]

Taxonomists organize the diversity of life. Aristotle was the first to attempt to do this. Then in the 1700s Linnaeus introduced the idea of genus and species. Later Darwin revolutionized science with the idea that species can change over time and that all animals may have a common ancestor. For centuries taxonomists have been organizing the diversity of life. Classification of the human species is used as an example. [2:52]

A video exploring arthropods which were the first animals to venture onto land and spread over the earth. Their body plan allowed them to diversify and adapt to every environment, including the air, inventing new ways to extract oxygen from air rather than water. Some arthropods, like dragonfly larvae, live in freshwater, and then through metamorphosis, develop wings and take to the air. Flight was a major adaptation for arthropods opening up new realms: three-fourths of all the animals on earth are flying insects. And spiders evolved an ingenious method for catching the flying insects. Understand how arthropods provide essential services to ecosystems and humans both as recyclers and pollinators. [13:41]

We think that humans are at the top of the evolutionary ladder. But is being big, brainy, and fast the best design? Evolution has produced many animals with different approaches to life. Every animal is uniquely adapted to win at the game of survival. [3:50]