What are the characteristics of mammals, their similarities, and biological differences? In a recent TED-Ed video, the lesson covers placenta mammals, marsupial mammals, and monotremes.
From the description:
All mammals share certain characteristics, like warm blood and backbones. But despite their similarities, these creatures also have many biological differences — and one of the most remarkable differences is how they give birth. Kate Slabosky details the placental, marsupial, and monotreme methods of giving birth.