The Innate Superiority of Full Sentients

All animal life (essentially) subsists on plant life or other animals that do. What makes animal life superior? The absence of pain in plants or lack of some form of consciousness? But animals subsist, at least, by taking the lives of plants, the right to life being the ultimate right of any living thing that is said to have rights. The only distinguishing characteristic of many forms of lower animal life from plants is the ability to move around. Does that make them morally superior?

Morality is what we're talking about here. When does it become immoral to take the life of another living thing? Is it anything but a grey area?

As we move up the food chain, intelligence increases, particularly with mammals, some displaying primitive forms of self-awareness in higher primates, cetaceans, elephants, maybe dogs, and cats--well, dogs anyway--and maybe even some birds. Many cultures bestow informal rights on these higher animals to better treatment, especially to those most valued in this category, our children, who do not achieve full self-awareness for several years.

So what is full self-awareness, and does it give those who have it, or the potential for it, superior rights over the rest? Even animals who have learned a language, such as Koko the gorilla, and who recognize themselves in mirrors, struggle with the concept of "I", "me", "mine", "them" and "theirs". And while they may grieve the death of a "loved" one, we are apparently the only ones that understand the universality and inevitability of mortality--and that's what makes us fully aware. That and self-awareness itself enable us to understand what it means to kill another, giving birth to innate morality.

I think some take that too far and attempt to give equal rights to (some/all?) animals. Does our superior self-awareness make us immoral if we eat other animals, but not the many predators in the animal kingdom lower down on the food/intelligence/self-awareness chain that do? Why?