It's difficult to definitively say which life function is *more* essential to the species than the individual, as they are all interconnected and crucial for survival. However, reproduction stands out as a life function that is inherently focused on the continuation of the species, rather than the individual's own survival.

Here's why:

* Species survival: Reproduction is the only way for a species to persist. Without it, the population would dwindle and eventually cease to exist.

* Individual sacrifice: Reproduction often involves risks and sacrifices for the individual. Parents may expend significant energy and resources caring for offspring, potentially putting themselves at risk. Some organisms even die after reproducing.

* Evolutionary advantage: Successful reproduction, the ability to pass on genes, is the ultimate measure of evolutionary success.

While other functions like nutrition, respiration, and excretion are essential for individual survival, they are not directly tied to the continuation of the species in the same way that reproduction is.

It's important to note that while reproduction is crucial for species survival, individuals are still essential for carrying out the necessary functions that allow for successful reproduction. The interplay between individual and species survival is complex and multifaceted.