It appears to be determined by the wielder
On Titan when Thanos uses the Reality Stone to flashback, he says that his solution to the over population of Titan was a random culling of half the population. A truly random one that would effect rich and poor alike without bias malice.
Later, after his fight with Iron Man, he promises Doctor Strange that:
TL;DR: It would appear as if Thanos killed all animal life with the snap, which would include sentient and non-sentient creatures.
The line in the comics is:
My love bade me to extinguish the light of half the universe's populace.
Populace would imply every living creature rather than just sentient beings.
This can be seen in the page below from ...
In Earth-616 and the comic New Avengers Volume 3 Issue 3 the stones are placed into the Infinity Gauntlet in the following order:
In the Infinity Gauntlet comic arc which Avengers: Infinity War is somewhat based off of the Infinity Gems are placed in the following order:
As mentioned here:
Thanos possesses the superhuman physiology of all Eternals, granting him superhuman strength, endurance, reflexes, and agility. His skin in nearly invulnerable, particularly against heat, cold, electricity, radiation, toxins, ageing, and disease.
My initial guess is his invulnerability against radiation. This could be one reason how/...
I'm going to try to flesh this out into a full answer. Lots of speculation ahead.
As I stated in the comments, "Thanos Wrecks the MCU" makes for a boring, repetitive movie. No one is going to want to see that (okay, maybe some people, but not enough to get green-lit by the likes of Disney). A good movie needs to get audiences emotionally ...
Thanos himself says his selection process is passionless and (IIRC) random. Not based on wealth, power, or any subjective parameter. So presumably it's the same during the Snap as it was when he was doing it manually.
He may have made the one choice about saving Tony at that point, but he could just as easily have decided he only meant that he would ...
I'm primarily interested in named characters that exist and are seen or referenced in both the comics and the films.
There are significant differences in the comic and movie. The snap is the instigating factor in the comic run and the snap happens almost at the end of Issue #1 when Thanos already has the fully-loaded gauntlet. There's no fight to stop him ...
The power of the Infinity Gauntlet doesn't seem to worry The Living Tribunal
TLT has shown no worry over the power of the Infinity Gauntlet. As you noted he was not worried about Thanos taking control of it and challenging Eternity and in the aftermath of that event he made Adam Warlock split them.
That seems logical if we consider that while the Infinity ...
The Infinity Gauntlet grants omnipotence, more than enough power to overcome any enchantment of Odin.
From the Wikipedia article on the Infinity Gauntlet series, the comic story that the MCU is drawing from:
Each Gem grants its bearer complete mastery over one aspect of the multiverse: Time, Space, Mind, Soul, Reality, and Power. Combined on the ...
Thanos is laid low by Adam Warlock and converted into granite by an unexplained power of the green Soul Gem. The mechanics of his petrification are unexplained since neither the Soul Gem nor Adam Warlock possessed such powers until that point.
Thanos manipulates Adam Warlock into killing himself and eliminating a future threat (The Strange Death of Adam ...
He wasn't exactly dead, but Thanos' previous semi-permanent defeat came in Marvel Two-In-One Annual #2.
Marvel Wikia explains what happened:
Over powered, the heroes prove unable to defeat Thanos until Spider-Man manages to free the Soul Gem, causing the soul of Adam Warlock to appear from it and turn Thanos into stone. After rejoicing over their victory,...
He can certainly use the Space Stone, as that’s how he got to the hut in the first place.
As for all the other stones individually, or collectively for finger-snap purposes, we don’t know yet. There’s no obvious reason for the other stones not to work individually, and we’ve seen them wielded without the gauntlet in other movies.
Story-telling-wise, it ...
Earlier in the series, you find out Thanos has a large array of powers acquired through many means, science, genetics, bionics etc. Shortly before that he demonstrates teleporting away from a large battle.
So, he simply outsmarted the heroes by faking his death and teleporting away at the last moment.
Furthermore, others have correctly pointed out that ...
Thanos's death occurred in a story titled "Death Watch" that spanned Avenger Annual #7 and Marvel Two-in-One Annual #2. Specifically he was turned to stone in Marvel Two-in-One Annual #2 by the disembodied soul of Adam Warlock.
He was returned to life by Mistress Death in Silver Surfer #34. That story then led directly into Thanos Quest where Thanos ...
As seen in Warlock and the Infinity watch , and Infinity War, when the living tribunal so wishes, he can stop the full infinity Gauntlet from working. So for a time, the gems would not work in unison because of his ruling. So, yes.