Prior to the ability to decipher and compare DNA, comparing anatomy and behavior

Question

Prior to the ability to decipher and compare DNA, comparing anatomy and behavior of organisms was the only way to group them. Why is it important to look at the comparisons between anatomy and behavior as well as many genes when determining the relationship between two species? Give examples of organisms that may seem related based on anatomy but are dissimilar when the DNA is investigated.

http://science.nbcnews.com/_news/2013/03/26/17472795-tiny-lookalike-lemurs-are-actually-two-new-species?lite

Explanation / Answer

By comparing the anatomy and behavior of organisms one can know about the similarity and dissmilarity between the species in terms physical appearance and adaptation to a particular location or environment etc. It also gives an idea about whether the different species have been evolved from the common ancestor or not.

However, comparing the two species only based on anatomy and behavior can be misleading as many species of organisms can anatomically evolve in a similar manner but their evolution could be a response to totally different triggers. For example limbs on aquatic animals and land animals although look similar anatomically but they have been the adaptative response of these animals to totally different environmental challenges. Therefore, it is important to compare the species on genetic level along with anatomical and behavioral levels. This way one could know if the similarity or dissimilarity in the species are actually due to the genetic makeup or the species just happen to look similar based on their similarity in anatomy or behavior.

An example where comparison made just on the anatomy could be misleading is that of a bat, a crow, and a squirrel. Since both the bat and the crow have wings but the squirrel does not, one may think that a bat is more closely related to a crow than a squirrel. However, when DNA of these species are compared it was easy to be found that the bat is closely related to the squirrel and is a distance apart from the crow.

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