This is the part in Call of the Wild where Spitz kept stealing Buck's sleeping spot, which led them to their first fight. this has t o do with survival of the fittest because that was Buck's sleeping spot and Spitz stole it from him, so Buck has to get mean and take it back from him.
This is when they had to cut off Polly's. This has to do with survival of the fittest because if the didn't kill Polly then Polly could have killed or infected other dogs or people with her rabies. So they are better off without her.
This is the part in the Call of the Wild where they had to kill Dave because he was dying and kept wanting to work which made it worse, so they shot him. This has something to do with survival of the fittest because Dave would not have survived very much longer, so they put him out of his pain, and he wasn't much help to anyone anymore so there was really no point in keeping him.
This is the part in the book were Buck goes after the Indians Because he believes that they kidnapped John Thorton. So he goes and rips out all of their throats'. This has to do with survival of the fittest because Buck is trying to let John Thorton survive by killing all of the indians, or just by avenging John Thorton.
This is the part in the book where Buck is ripping all of the other wolves throat's out. This has to do with survival of the fittest because Buck is killing all of them to show all of his strength to prove he is the strongest.
This is the part in the book where Mercedes was sitting or resting on the sleigh, while everyone else is walking. This has to do with survival of the fittest because Mercedes couldn't even walk, she had to sit on the sleigh, so she was not fit to survive in that area, or in the wild for that matter.