Why are viruses considered as being at the 'borderline' between living and non-living things?

Viruses are considered at the borderline of living and non-living because they show both the characteristics of living and a non-living. As they react like non-living in the free atmosphere but when they enter the body of a living organism then they show the features of a living organism and start reproduction.

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.

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