An excerpt from chapter 7 on The Good from Objectivism: The Philosophy of Ayn Rand by Leonard Peikoff.
Now let us see how the principle of life as the standard of value applies to specific kinds of organisms—above all, to man.
Plants and animals initiate automatically the actions their life requires. Such entities may encounter adverse conditions beyond their capacity to cope with, such as drought, temperature extremes, or an absence of food. In addition, an animal’s knowledge may prove inadequate (a large-scale example would be the lemmings that unwittingly swim out too far and perish). But whatever the conditions they encounter and whatever an animal’s knowledge, there is no alternative in the functioning of these organisms …
Read the rest in Objectivism: The Philosophy of Ayn Rand.