Zoology MCQs for NEET — Practice Questions with Answers

(c) : Attenuation is the lessining or reduction of virulence of a pathogenic bacterium or virus. The phenomenon was first noticed by Louis Pasteur (1822-95), who developed it as a means of producing strains of bacteria suitable for vaccination. Attenuated strains of bacteria are obtained by successive subculturing in controlled conditions, whereas attenuated virus may be obtained by ultraviolet irradiation. Such strains of bacteria or viruses are used to induce active immunity by inoculation.

(d) : Anthrax is an acute infectious disease caused by the spore forming bacterium Bacillus anthracis. The long-lived spores of this organism can also be found in soil and their stability makes them an ideal bioweapon.

It most commonly occurs in wild and domestic lower vertebrates (cattle, sheep, goats camels etc) but it can also occur in humans when they are exposed to infected animals or tissue from infected animals. Anthrax infections can occur in three forms - cutaneous, inhalation and gastrointestinal

(c) : Opium is a narcotic drug that is obtained from the unripe seedpods of the opium poppy (Papaver somniferum), a plant of the family papaveraceae. Opim is obtained by slightly incising the seed capsules of the poppy after the plant's flower petals have fallen. The slit seedpods exude a milky latex that coagulates and changes colour, turning into a gum like brown mass upon exposure to air. This raw opium may be ground into a powder, sold as lumps, cakes, or bricks, or treated further to obtain such derivatives as morphine, codeine, and heroin. Opium and the drugs obtained from it are called opiates.

People get malaria by being bitten by an infective female Anopheles mosquito. Only Anopheles mosquitoes can transmit malaria and they must have been infected through a previous blood meal taken from an infected person.

Because the malaria parasite is found in red blood cells of an infected person, malaria can also be transmitted through blood transfusion, organ transplant, or the shared use of needles or syringes contaminated with blood. Malaria may also be transmitted from a mother to her unborn infant before or during delivery(vertical transmission through placental defect).

(c): Memory cells refer to memory B cells. It is a B cell sub-type that are formed following primary infection. When a B cell is activated, by recognising a specific antigen, it proliferates to form antibody producing plasma cells and long-lived memory cells. The memory B cells are specisics or the antigen that first stimulated their production. If this antigen is encountered again, memory B cells can recognise it and quickly proliferate. This forms a new generation of antibody-producing plasma cells. This means that the antibody response is much more rapid and specific in subsequent infections than in primary infection, reducing the chance of symptom development. This is the principle behind vaccination.

158.(d) : Influenza A virus subtype H5N1, also known as A (H5N1) or H5N1, is a subtype of the influenza A virus that can cause illness in humans and many other animal species. A bird-adapted strain of H5N1, called HPAI A(H5N1) for "highly pathogenic avian influenza virus of type A of subtype H5N1", is the causative agent of H5N1 flu, commonly known as "avian influenza" or "bird flu". It is endemic in many bird populations, especially in Southeast Asia. One strain of HPAI A(H5N1) is spreading globally after first appearing in Asia. It is epizootic (an epidemic in nonhumans) and panzootic (affecting animals of many species, specially over a wide area), killing tens of millions of birds and spurring the culling of hundreds of millions of others to stem its spread. HPA1A(H5N1) is an avian disease. H5N1 is mainly spread by domestic poultry, both through the movements of infected birds and poultry product and through the use of infected poultry manure as fertiliser or feed. Humans with H5N1 have typically caught it from chickens, which were in turn infected by other poultry or waterfowl. Migrating waterfowl (wild ducks, geese and swans) carry H5N1, often without themselves becoming sick. Many species of birds and mammals can be infected with HPAI A (H5N1), but the role of animals other than poultry and waterfowl as disease-spreading hosts is unknown.

(a) : The degree of pathogenicity of a microorganism is called virulence. This is indicated by case fatality rates and/or its ability to invade the tissues of the host; the competence of any infectious agent to produce pathological effects.

(a) : Hepatitis A caused by picornavirus a positive stranded RNA virus Hepatitis B - caused by partially double stranded, and partially single stranded DNA virus called Hydra virus.

(b): Cocaine is a natural alkaloid obtained from leaves of Erthyroxylon coca. Its chemical formula is C₁₇H₂₁ NO₄. It is a powerful CNS stimulant. It causes lack of sleep and loss of appetite.

Escherichia coli is the non-pathogenic bacteria of colon. One of the characteristics of Escherichia coli is the production of bacteriocins (colerains), a specific type of metabolite which is not only lethal to the organism of the same species but also to related organisms. Balantidium coli results in inflammation of alimentary tract. Entamoeba coli causes amoebic dysentery. Enterobius vermicularis infection is known as oxyuriasis or enterobiosis.