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Originally posted by drivers1492
reply to post by ShortMemory
Yes I understand how the seed seems to benefit dispersion. My questioning is why or how would these changes take place to make said seed. It may actually come down to the driving force of evolution and how exactly these changes are spawned or the reasoning behind them. That would be what I am looking to understand.
or 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 (and would have colonised the freshwater habitat before making the move to terrestrial existence). They would also be exposed to an alternating wet and desiccating environment. Adaptations to survive drying out would have had strong survival value, and it is important to note that seaweeds are poikilohydric and able to withstand periods of desiccation.
The earliest evidence for the appearance of land plants, in the form of fossilised spores, comes from the Ordovician period (510 - 439 million years ago), a time when the global climate was mild and extensive shallow seas surrounded the low-lying continental masses. (These spores were probably produced by submerged plants that raised their sporangia above the water - wind dispersal would offer a means of colonising other bodies of water.) However, DNA-derived dates suggest an even earlier colonisation of the land, around 700 million years ago.
reply to post by drivers1492
I understand what your saying and thats not really something I had considered really. Like I said I had always factored in a mind as part of the driving force which is/was wrong but it never hit me I suppose. So subtracting that from the equation the driving force would be either simple chance or something that is not known as of yet. The sheer overwhelming diversity of plant and animal life throughout the history of earth makes me lean toward something were not understanding yet. Although I could be very wrong.