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Plants: Evolving to occupy land

The first land available for colonization was inhospitable due to the considerable amounts of volcanic action. Consequently as volcanoes erupted on land, life in the oceans multiplied with a diversity of species with different structures and adaptations, but the land remained unconquered. Marine algae may have secured an existence on the littoral zones of the ocean in the same way they do today. Around 420 million years ago the first waxy layers developed in plants to prevent desiccation, but this did not totally free such plants from an aquatic environment since they required an aquatic medium for reproduction. Algae reproduce through both asexual division and sexual methods. Sexual reproduction involves the production of sex cells which require locomotion in water for the fusion of the cells to take place.