Philosophy of social attitudes. By a child.

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 . PPT Download http://www.4shared.com/file/0J2fjEhFba/Plant_evolution.html?