What fundamental principle states that total functional information in living systems must decrease over time?

The principle that states the total functional information in living systems must decrease over time is known as genetic entropy. This concept is rooted in the idea that as biological organisms reproduce, mutations can occur, leading to a gradual accumulation of genetic errors or deleterious changes. Over generations, this accumulation can result in a decline of the overall biological information and functional capacity of a population or species.

Genetic entropy emphasizes that while natural selection might eliminate some harmful mutations, it is not always capable of preventing the overall decline of genetic information due to the inherent nature of mutation processes. The idea suggests that this loss of information contributes to eventual challenges in survival and adaptation over long timescales.

The other options, such as information theory, nucleotide degradation, and systematic decline, do not specifically encapsulate this principle regarding the decrease of functional information in living systems over time. Information theory generally deals with the quantification of information in various contexts, nucleotide degradation refers to the breakdown of nucleotides and is a biochemical process, and systematic decline is too vague and does not specifically address genetic principles.