What was a prerequisite for the survival of life on land?

Answer 1

An ozone layer.

Early Earth was anaerobic ; there was no free atmospheric oxygen and thus no ozone layer (#O_3#) to shield the Earth from harmful UV rays. Earth was thus subjected to intense UV radiation , which was somewhat negated in an aquatic environment. On land however, this was not the case and UV was extremely harmful, making it impossible to live on. When the ozone layer eventually formed due to a rise in photosynthetic activity, life could colonise land without intense UV rays.

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Answer 2

Nicholas Ahn

The evolution of structures and adaptations that allowed organisms to take in oxygen from the air and avoid becoming dehydrated was one of the requirements for life on land. These included the development of respiratory and circulatory systems, as well as mechanisms to stop water loss, like the creation of waterproof skin or exoskeletons.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.