Opinions on the human perception of the value of life, explained through veganism

Now before I get into what I want to say, I need to mention that I have nothing against veganism or vegans. It's none of my business how you live your life, and veganism stems from feelings of sympathy and justice so by no means do I think it is a wrong practice. I'm just using it as an example to go off of.

I believe we tend to think of lives as more "valuable" the closer they are to us biologically. A human life is the most valuable, then comes mammals and birds and fish and such, then comes insects, and the last on our list are plants and fungi. Even veganism, which stems from the thought that all lives should be valuable and we shouldn't kill or farm other species since their lives are just as important, completely invalidates plants and fungi as living organisms of a different species. The assumption that plants cannot feel or perceive their environments and so cannot go through pain for being farmed or killed or harvested honestly has no real basis. When eyes aren't the only way of seeing and echolocation exists, what makes us assume that nervous systems are the only way of feeling? A nervous system is made up of neurons transmitting electrochemical signals, and though plants do not have neurons they still transmit electrical signals to and from different parts of their bodies in response to environmental stimuli. When we can barely even understand a portion of the functioning of our brains, how do we expect to know that these electrical signals are not signaling stress or fear? Just because they do not feel the same way does not mean they do not feel, and just because they do not live the same way does not mean they do not live. So how can we say that their lives are any less valuable, that their dignity deserves any less protection than those of animals?

Then again, another topic I want to discuss is how we think of ourselves as separate from "nature". We are animals, we are a part of nature. We might be an invasive species, but so are common carps and I don't see them worrying about the lives of different species. We might be "more intelligent" than other species (which I think is a wrong description in and of itself but I will leave that alone for now), but we aren't exempt from the cycle of life and neither are we exempt from the necessity to consume other living organisms for survival that any species except for primary producers have. 

In the end, what I am saying is not that animals deserve torture and not that vegans shouldn't eat plants. It is simply that all living organisms should be respected to a degree, however we must also recognize that we are one of those organisms and, while torture or excessive pain infliction is unnecessary, consumption of other living organisms is our only method of acquiring the energy we need to live. At least until we learn how to photosynthesize, which I doubt the plants which we disrespect the lives of would be willing to teach us anytime soon lol