The Ordovician Period saw the rapid evolution and diversification of many new types of invertebrate animals, including trilobites, brachiopods, and bryozoans. Primitive plants began to colonize land for the first time, while fungi formed mutualistic relationships with plant roots. The period ended in a major extinction event.

3. Primitive vascular plants appeared the land, until then almost totally barren.

4. The supercontinent of Gondwana drifted over the south pole, initiating a great Ice Age that gripped the earth at this time. The end of the period is marked by a major extinction event.

10. The trilobites were among the most successful of all early animals, roaming the oceans for over 270 million years.