Many groups of animals have defensive spines. Examples include porcupines, sea urchins, and hedgehogs. What information do you need in order to determine whether or not spines are the result of homology or homoplasy?

The correct answer would be - Classification of the organism and characteristics of the spines.

Explanation:

Homology is the term that used to describe the similarities in between biological structures or the organs in 2 or more distinct organism that comes from a common ancestors.

Homoplasy in other hand does not share a common lineage and evolve over the period in different organism, most likely in response of natural selection.

Information one will need to determine whether these spines are result of homoplasy or homology would be the characteristics of spines if they are thorns or spikes and other characters. The second most important information is the classification to know the place on the cladogram.

Thus, the correct answer would be - Classification of the organism and characteristics of the spines.