Chapter 5 (Variety of Life) F.Sc 1st Year Biology Short Questions

What is phylogenetic system of classification?

It is the system of classification that names groups of organisms according to their evolutionary history. Like Linnaean classification, phylogenetic classification produces a nested hierarchy where an organism is assigned a series of names that more and more specifically locate it within the hierarchy. However, unlike Linnaean classification, phylogenetic classification only names clades and does not assign ranks to hierarchical levels.

What are oncoviruses or retroviruses? Give examples.

These are single stranded RNA tumour viruses which are spherical in form, about 100nm in diameter and enveloped by host membrane. The most familiar of these viruses is the human immunodeficiecncy virus (HIV).

Write a short note on AIDS.

The AIDS was reported in early 1980’s. In 1986 the virus was named as human immunodeficiency virus (HIV). The major cell infected by HIV is the helper T-lymphocyte. Symptoms include severe pneumonia, rare vascular cancer, sudden weight loss, swollen lymph nodes and general loss of immune functions. The HIV is transmitted by intimate sexual contact, blood transfusion and breast feeding. Prevention of intravenous drugs with common syringe and use of sterile needles /syringes and utensils is important.

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Differentiate between Retroviruses and Bacteriophage.

Retroviruses are single stranded RNA tumour viruses which are spherical in form, about 100nm in diameter and enveloped by host membrane. On the other hand bacteriophages are viruses that infect bacteria.

How has small pox been eliminated from world?

Smallpox has been eliminated from the world by immunization and other control measures. Credit goes to Jenner who first used,vaccine against this disease.

What do you know about the capsid of a virus?

The genome is surrounded by a protein coat, the capsid. Capsid gives definite shape to virion. Capsid is made up of protein subunits known as capsomeres. 162 capsomeres are present in the capsid of herpes virus and 252 in the capsid of adenovirus which cause some common colds.

Why some biologists found two kingdom system of classification unworkable?

Many unicellular organisms like Euglena have both plant like (presence of chlorophyll) and animal like (lack of cell wall) characters. This system ignores the differences between prokaryotic and eukaryotic cells.

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