All living organisms are linked to one another because

1. they have common genetic material of the same type
2. they share common genetic material but to varying degrees
3. all have common cellular organisation
4. All of the above

(b) All living organisms share common genetic material, ie., DNA but with variations, e.g., bacteria have single stranded circular DNA while in highly evolved eukaryotic cells of plants and animals DNA is a long double stranded helix.