Bumper sticker of the day: "Smile, it's the second best thing you can do with your lips."
2. Fossil record spans billions of years. We conceptualize vast periods of times into Eras.
3. Precambriam represents the era before multicellular animals appear in the fossil record. This is where the first life forms are recorded: prokaryotic and eukaryotic cells.
4. Paleozoic starts with the Cambrian period about 570 MYA. Multicellular animals and algae appear on earth for the first time. During the Silurian period (starting 438 MYA), plants colonized the land (bryophytes and fern allies such as Psilotum). During the Devonian period (408 MYA) ferns and progymnosperms are recorded for the first time in the fossil record. Conifers also appear for the first time here. Other gymnosperms arose in the Carboniferous (360 MYA) and Permian (286 MYA) periods.
5. Mesozoic era includes the Triassic (248 MYA), Jurassic (213 MYA), and Cretaceous (144 MYA). This was the time of the great dinosaurs, which had a mass extinction at the end of the Cretaceous. Angiosperms are first recorded in the Cretaceous period, but probably originated before then.
6. There is an active debate about what the earliest angiosperms were like -- trees similar to Magnolia, or diminuative herbaceous plants -- the Paleoherbs.
7. The Cenozoic era includes the Tertiary (65 MYA to 5 MYA) and the Quaternary (2 MYA to recent) periods. In the Tertiary, mammals diversified as did the angiosperms. This period has had major climatic changes, including a drying trend and major epochs of glaciation. Vegetation across the planet changed drastically.
8. The fossil record is most complete for the Cenozoic -- especially for transitional forms that are critical for elucidating evolution of major lineages.