Not sure if this comment was directed at me, but my response is still the same regardless. Of course you should know the biology, but you should also know which shots are high risk (of missing because it's a small target) and avoid them. High angle (ie. straight down) shots are high risk because of this...yeah, you if you nail it you're a hero and drop the deer on the spot. You miss it by an inch or two, however, and you have a wounded, possibly non-recoverable deer.