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
Answer:
carbon-to-carbon double bond
Bees can get in and out, carrying pollen with them from flower to flower pollinating as they go. On the the other hand, Gymnosperms have to let their seeds somehow travel away and plant itself, or with the help of nature, they plant themselfs
But it is easier for those flowering plants to pollinate.
=)
