Answer No 1)
<em>The correct option is D) The two species have a common ancestor</em>
Homologous structures can be described as organs or other structures which are similar in different organisms. These structures might not perform the same function, but are similar in their making. This similarity of structures between organisms of different species suggests that there might be a common ancestor for these organisms.
Answer No 2)
<em>The correct option is B) Y, Z, X</em>
The organism Y is the most similar to the worm because it has all the amino acid sequence similar to the portion shown for the worm, except for a single amino acid which is S. The sequence Z has more similarities with the amino acid sequence for the enzyme from a worm than the sequence of the organism X. Hence, the correct option is B.
Answer No 3)
<em>The correct option is A) Sequence the same gene in both species to compare their similarity.</em>
The process of DNA sequencing has now made it possible to determine the evolutionary histories among organism by comparing the DNA sequence of one organism to the DNA sequence of another organism. The organisms having similarities in the DNA sequence clearly determine the evolutionary relationship between any organisms.
Answer No 4)
<em>The correct option is C) Vestigial</em>
Vestigial structures can simple be described as structures which had some function to perform in the ancestors but are not known to perform any function in organisms known today. These structures show that evolution might have caused these structures to non- performing structures as they were of less benefit to the organisms present now on Earth.
