The Cambrian Period marks an important point in the history of life on Earth; it is the time when most of the major groups of animals first appear in the fossil record. This event is sometimes called the "Cambrian Explosion," because of the relatively short time over which this diversity of forms appears
Because their jobs required them to set all day.
- helps protect internal organs and fragile body tissues eg. : the cranium protects your brain and eyes and the ribs protect your heart and lungs.
Calcium deficiency disease (hypocalcemia) --- like osteoporosis, osteopenia !!
