Learn about the first animal in this video. The ancient sponge appeared about 2.5 billion years ago coming in many sizes and shapes, sponge bodies are a loose assemblage of cells held together by a special protein called collagen which...

This video covers the origins and functions of cartilage and collagen. [3:38]

This lesson will look at how the human body changes over time as a person ages as well as identify factors that can affect the aging process. It is 2 of 5 in the series titled "Effects of Aging on Your Body."