Curly has been killed. I feel like this shows survival of the fittest because Curly didn´t adapt quickly and she thought that they might be nice but they were not so they ganged up on Curly and killed her.
Buck kills Spitz.
Spitz took Buck's food. This represents survival of the fittest because Buck had to learn to eat his food fast before it gets taken.
Dave gets killed.
Spitz took Buck´s spot. This represents survival of the fittest because Buck learned that you got to protect whatever is belongs to you.
Dolly gets killed.
Buck killed Spitz. This shows survival of the fittest because Spitz did not adapt as quickly as Buck so they got into a fight and since Spitz did not adapt quickly, Buck killed him.
Dave gets killed. This represents survival of the fittest because Dave was holding up the team because he was hurt and not adapting just getting weaker and weaker. So they decided to shoot him instead of letting him die on his own.
Dolly got hit in the head with an axe. This represents survival of the fittest because Dolly was adapting it's just that she had gone mad and went on a rampage and tried attacking everyone so they decided to kill her.