During the distributed classroom sessions (November-December 2011) we got a lot of interesting questions from students attending the sessions. We would like to share a few of these questions with more elaborate answers with you.
A student from IMSCCR asked-
How can classification demonstrate evolutionary relationship?
Answer:
The individuals having characters best adapted to the surroundings are able to survive. Their characters, that is, the genes present in them, pass on to the further generations. Biological evolution is basically, change in living organisms over a long period of time. Evolutionary theory states that different types of living organisms originate from common ancestor due to modifications in successive generations.
All living organisms show variation in characters. Biological classification is arrangement of living organisms into groups based on similarities and differences observed among them. The smallest group or taxon is species which consists of individuals which can successfully reproduce with each other. It is observed that, generally, the organisms having close evolutionary relationship are placed together in a smaller taxon. As we go to higher taxon, the relatedness decreases. This is consistent with the evolutionary theory. Therefore classification helps to establish evolutionary relationship.
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I will clarify what taxon means. Taxon is nothing but UNIT used in classification. A better word to describe taxon is rank. You must have learnt that all animals together are classified under animal kingdom. Within that, humans belong to phylum Vertebrata i.e. all animals having a vertebral column and other similar characters. And more specifically, we are Homo sapiens where ‘Homo’ is a genus and ‘sapiens’ is species. These ranks or units are called taxon.
In descending order, the main taxa are as follows-
Kingdom, Phylum, Class, Order, Family, Genus, Species
So the species are the smallest taxon in biological classification system.
* Please note that in binomial nomenclature, scientific name is always printed in italics or underlined while writing.Therefore, although it is not possible here, Homo sapiens should be in italics.