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 all that effort when they could just lounge at the sea's edge? Some algal colonies take to the land in response to 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.