My assumptions, true or false, of what kills an animal is a bullet or arrow making a hole in the heart which damages a vital organ resulting in death. A bullet or arrow slicing through the lungs filling them with blood resulting in suffocation/death.

That being said, there is obviously an amount of energy needed to allow the bullet or arrow to pierce the skin, the muscle and ultimately the vital organ that will eventually result in the death of the animal.

I'm just not sure what that amount of energy is, I don't claim to understand alot about KE or exactly what it is. However, I began hunting 5 years ago. Right away i heard about this 1,000lb number that is supposed to be a minimum standard. I've always just used it and accepted it a a minimum especially when i was trying to choose a particular cartridge for my first gun for me and my daughter (thank you Rebel Hog)
Now, I'm trying to understand that number and why it is set at that particular figure. There is a lot of experience on these forums. Zrex and Eldeguello have always had great info. In fact Zrex is probably responsible for my 243 purchase (although he doesn't know it). And since i just bought a reloader kit i'm sure i will be watching Eldeguello's posts more often

Thanks lots for the responses so far