A Walk Through Time

Happy Landings

The Original Green Movement

500 Million Years Ago

Green algae (ancestors to plants) living in sunlit shallows and tide pools start a "green" revolution. They invent ways to stay wet on the inside while drying up on the outside. Algae become plants by carrying the ocean inside themselves as they move ashore.

Why go to the effort when they could just lounge at the sea's edge? Some algal colonies take to the land to avoid a disturbing increase in marine predators. Once ashore, the spirit of life drives them to expand across this huge new frontier. The insects, which are both predators and pals to algae, follow with dispatch.

Top: These green and brown algal protoctists are thready chains of cells full of plastids. (Photoograph by Lois Brynes)

Bottom: The amazing arthropods, which constitute over 80% of the species in the animal kingdom, are the first to follow algae inland. No doubt their hard-shelled, lobsterlike legs helped. (Photograph courtesy JASON Foundation for Education)


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