Question

BIO REVIEW SHEET 4

1. Define “taxonomy”.
2. Define “binomial nomenclature” and know how to properly write an organism’s scientific name.
3. List the major taxonomic categories or the current hierarchical classification system, from the most to least inclusive.
4. Describe Linnaeus’ original two kingdom classification and name two shortcomings of this scheme.
5. List three Domains
6. State the guidelines/rules for properly building a dichotomous key and/or identify errors in an example a dichotomous key and/or build a dichotomous key using a given set of specimens

Answer 1

1. Taxonomy is the branch of Biology which deals with naming, defining and classifying groups of organisms on the basis of shared characteristics. It came from the Greek words taxis, meaning 'arrangement', and nomia, meaning 'method'.

2. Binomial nomenclature is a formal system of’ 'two-term naming' of organisms, which gives all species their unique scientific names. The first part of a binomial name is the genus of the organism. The second part specifies the species. While writing scientific names, the entire two-part name must be written in italics. If italicization is not possible, genus and species epithet can be under lined. The genus name is always written first with first letter capitalized. The specific epithet is never capitalized. E.g.: Homo sapiens

3. Taxonomy uses different ranks in order from most inclusive to least inclusive as Domain, Kingdom, Phylum or division, Class, Order, Family, Genus, Species, and Strain.

4. Karl Linnaeus grouped organisms based on gross morphology and functions into two groups or kingdoms as plants and animals. Some of the shortcomings of his classifications are

• Both Eukaryotes and prokaryotes were placed together. He could not discriminate them.
• Linnaeus could not place all the organisms properly in the groups. Some exhibited properties of both groups. E.g. Euglena.
• He placed both photosynthetic and non-photosynthetic species together in the group of plants.

5. The three domains are the Archaea, the Bacteria, and the Eukarya. Archaea include ancient forms of bacteria. Bacteria include true bacterial species. Eukarya includes all the organisms that are eukaryotic.

6. Dichotomous keys are used to identify and classify organisms into smaller groups based on their similarities. The steps in building dichotomous key are:

• List down the characteristics of organisms under study.
• Organize the characteristics in order in a way that the most general characteristics listed first, before moving to the more specific ones.
• Divide the specimens based on one characteristic into two groups. (Eg: Has it a dry skin?)
• Subdivide the specimen further based on the next contrasting characteristic. (Eg: The organism with dry skin can be subdivided based on presence or absence of hair)
• Draw a dichotomous key diagram for graphically representing the data either as a tree or a flow chart.  
• Test it out to see if it works for the given organism.