1.2. Concept and use of a classification system

 

Organisms can be classified into groups based on the features they share.

Shared features suggest that organisms are related to each other, and so have evolutionary relationships.

Swedish botanist Carolus Linnaeus is the Father of Systematic Biology. 

He believed he could:

• Put every organism into a group  (the science of TAXONOMY)
• Give every organism a name (the science of NOMENCLATURE).

In his BINOMIAL SYSTEM, every living organism has a unique, scientific two-part name:

• The first name is Genus, the second name is species. 

• Names are written in Latin, printed in italics. 

• The genus always has a capital letter, and the species always has a small letter.

*this system is now internationally agreed upon

For example:

All life forms are categorized into a scheme that had 7 categorical terms. The biggest group that we need to know about is Kingdom, the smallest one is Species. Species are:

• a group of organisms

• can reproduce --> fertile* offspring

• *fertile = can continue to reproduce.

Each kingdom is divided into smaller groups, which include genus and species. Organisms can exist in only one group at each level of classification. For example, an organism can only belong to one kingdom or one genus.

Classification is traditionally based on studies of:

• morphology: form, the outward appearance of organisms
• anatomy: internal structure, when organism is dissected

That said, a more accurate way of classification is by looking at the organism at its core material, which are its sequences of bases DNA and amino acids in proteins. The closer related the organisms (with more recent ancestor), the more similar their DNA base sequences will be.

Practice questions

[source: textbook]

1. Yaks have the scientific name Bos grunniens. Explain what this tells us about the groups into which yaks are classified.
2. A yakolo is the offspring of a yak and a buffalo. Yakolos are unable to reproduce. Explain how this suggests that yaks and buffalo belong to different species.

[source: workbook]

Tigers, Panthera tigris, and lions, Panthera leo, sometimes mate with each other if they are kept together in a zoo. The offspring are called ligers. Ligers are perfectly healthy, but are unable to reproduce. Use this information to write down:

1. one piece of evidence that lions and tigers are closely related
2. two pieces of evidence that lions and tigers belong to different species.

Original post: Classification of living organisms
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