Plant evolution
Plant evolution
For 1500 million years photosynthetic
organisms remained in the sea. This is because, in the absence of a protective
ozone layer, the land was bathed in lethal levels of UV radiation. Once
atmospheric oxygen levels were high enough the ozone layer formed, meaning that
it was possible for living things to venture onto the land.
The seashore would have been enormously
important in the colonisation of
land. In this zone algae would have been exposed to fresh water running off the
land. They would also be exposed to an alternating wet and desiccating
environment. Adaptations to survive drying out would have had strong survival value.
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