humans
Very hard to say, but I suspect the archaebacteria are the least related to all other organisms (not just humans) as their common ancestor with other organisms is only shortly after the origin of life on earth. They are so distant that they even use a few amino acids in some of their proteins that no other organism today uses!
legs
Thesus monkey is the most closely related to Humans because it has the least number of differences in cytochrome c.
An organism must be composed of at least one cell.
An organism
The organism that would probably be least abundant in a community would be Keystone predators.
What is the least favorite animal??
living things as different a single celled amoebas and multivalued humans both considered are both living and an organism must contain at least some Tye of living things.
If they are humans, yes they are of the same species (homo sapiens).
Humans and only humans, at least to my current knowledge.
A silent mutation, where a change in the DNA sequence does not result in a change to the amino acid sequence of the protein, is likely to have the least effect on an organism. This is because the protein produced is unaffected, and therefore the organism's functioning remains unchanged.