"spiders have evolved to produce webs. evolutionary pressures have favored species which produce webs that are safe for the organism and effective at trapping enough prey to maintain the life and reproductive cycles of the organism."
I don’t really think “milk customized for a calf” makes much of a difference for the point OP was making. Sorry, if this was kind of a waste of time, I just love that milk changes composition based on the baby’s situation and then got really interested in the linguistic limits of “design.”