Question

Match the following and find correct combination

(a)	Obligate anaerobe	(i)	Fasciola hepatica
(b)	Facultative anaerobe	(ii)	Antelope
(c)	Polyembryony	(iii)	Ascaris lumbricoides
(d)	Reservoir host	(iv)	Female culex mosquito
(e)	Biological vector	(v)	Entamoeba histolytica

A. a – v, b – ii, c – i, d – iii, e – iv
B. a – v, b – iii, c – i, d – ii, e – iv
C. a – iv, b – ii, c – i, d – iii, e – v
D. a – iv, b – iii, c – i, d – ii, e – v

Answer 1

Hint: Obligate anaerobe or completely anaerobes can live only in the absence of oxygen, whereas, facultative anaerobe can live in absence as well as in presence of oxygen. Polyembryony is an asexual method of reproduction found in both plants and animals. Reservoir host means the host that contains the pathogen for further spread of infection. Biological vector is an organism that acts as a carrier for a pathogen.

Complete answer:
- Obligate anaerobes are the microorganisms that cannot survive in the normal atmospheric concentrations of oxygen. Entamoeba histolytica is an obligate anaerobe which infects human beings and other primates and causes a disease called Amoebiasis.

- A facultative anaerobe is an organism which can survive in the presence of oxygen, using oxygen for aerobic respiration, but is also able to survive without oxygen by doing fermentation or anaerobic respiration. In other words they can metabolize energy aerobically or anaerobically. Ascaris lumbricoides is a good example of facultative anaerobe because it is capable of taking up oxygen when incubated in air, on the other hand, it normally resides in the intestinal lumen where the conditions are essentially anaerobic.

- Fasciola hepatica, commonly known as liver fluke, is an important parasite of sheep and cattle. Its life cycle is completed in two hosts – the primary host is sheep or cattle and the secondary host is a gastropod mollusc. The life history of liver fluke includes a number of larval stages which propagate asexually through polyembryony. Polyembryony is also known as embryo cloning. It refers to the splitting of one sexually produced embryo into two or more embryos. Such embryos are genetically identical to one another but are genetically diverse from their parents.

- A disease called Trypanosomiasis (sleeping sickness) is caused by protozoan parasite Trypanosoma. The reservoir hosts for Trypanosoma are humans, domestic cattle and wild animals like antelopes. Reservoir host is either the population of organisms or the specific environment in which a transmittable pathogen lives naturally and reproduces, and upon which the pathogen mostly depends for its survival. The pathogen survives inside the body of the reservoir, usually (though not always) without causing disease for the reservoir itself.

- Biological vector is an organism that carries the pathogen and transfers the infection from one host to the other, however, it itself does not cause the disease. Before being transmitted to the next host the pathogenic organism develops and multiplies inside the body of the biological vector. For example female culex mosquito is a biological vector that carries the pathogen for lymphatic filariasis and transmits the pathogen to the human being by biting.

Thus, the correct answer is ‘B’.

Note: A reservoir host may be a living host, such as an animal or a plant, or it may also be an environment external to an organism, for example contaminated water body or air. Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense are the two species that cause sleeping sickness. Humans are the reservoir host for T. b. gambiense whereas domestic cattle and wild animals, including antelopes are the reservoirs of T. b. rhodesiense.