Zoology MCQs for NEET — Practice Questions with Answers

(d)

(a) In Entamoeba histolytica, the precystic or minute forms encyst only in the lumen of the intestine. In precystic stage, the chromatid bodies are found which disappear as the cysts mature.

(d): Wuchereria bancrofti is a dreaded human parasite. It is digenetic parasite completing its life cycle in two hosts, the final host is man harbouring the adult worm. The adult worms live coiled up in the gland and lymph vessels of man.  

Electron beam therapy or radiation therapy involves the use of radioactive waves to treat certain types of cancer. The therapy can be given with external beams of radiation. Electron beams are of low energy. They are often used in skin conditions and cancers. The procedure to deliver external beam radiation is somewhat similar to giving an X-ray. The person is put into position, and the machine delivers the radiation to the desired area. This beam therapy involves iodine, cobalt, protons and electrons. This therapy is used in cancer of cervix, cancer of larynx, germ cell cancer, hodgkin's lymphoma, prostate cancer, breast cancer, lung cancer etc.

(b) : Passive immunity may be artifically acquired, particularly when antiserum or antibodies produced by one individual are transfused into a second individual. In all cases, passive immunity represents the passive acquisition of an immune response that was actively acquired by another individual. Passive immunity can last for at most months since antibodies have a finite life span within the body.

Inflammation is common to almost all diseases that involve microbiologic, chemical or physical injury to living tissues. Acute inflammation may be defined as the microcirculation response to injury; the cardinal signs are heat, redness, pain, swelling, and loss of function. The accompanying microcirculatory changes comprise arteriolar vasodilation, increased small vein permeability, formation of edema fluid, and WBC migration to the site of injury. Histamine is stored in mast cell granules and basophils and is released by inflammatory and immunologic stimuli. It plays an important role in acute inflammation, exerting a dilator action on arterioles, increasing the permeability of small venules to plasma proteins and causing pain by stimulating nociceptors. However, the generally poor clinical efficacy of anthihistamines suggests that their role in nonimmune inflammation is limited. Plasma kinins such as bradykinin are not stored but are released by the action of kininogenase on plasma a2 globulin. Bradykinin is a potent vasodilator, increasing small vein permeability and causing pain by stimulating peripheral nociceptors, but it has a short half-life.

(d): Valium (diazepam) is in a class of drugs called benzodiazepines. Valium (diazepam) affects chemicals in the brain that may become unbalanced and cause anxiety, seizures, and muscle spasms. Valium (diazepam) is used to relieve anxiety, nervousness, and tension associated with anxiety disorders. It is also used to treat certain types of seizure disorders and muscle spasms.

(c) : Glaucoma is a condition which loss of vision occurs because of an abnormally high pressure in the eye. In most cases there is no other ocular disease. This is known as primary glaucoma and there are two pathologically distinct types- acute and chronic simple. In acute (or angle-closure) glaucoma, there is an abrupt rise in pressure due to sudden closure of the angle between the cornea and iris where aqueous humour usually drains from the eye. This is accompanied by pain and marked blurring of vision associated with inflammation of the anterior segment. In the more common chronic simple (or open-angle) glaucoma, the pressure increases gradually, usually without producing, pain, and the visual loss is insidious. The same type of visual loss may rarel occur in eyes with a normal pressure, this is called low-tension glaucoma.

Hepatitis is an inflammation of the liver caused by viruses, toxic substances or immunological abnormalities. Measles (Rubeola disease) is an acute infectious eruptive viral disease of childhood (3-5 years old) caused by specific virus of the group myxoviruses. Basically it is caused by an RNA containing Rubeola virus/Polynesia morbillorum. Measles is the infection of respiratory tract and conjunctiva which is transmitted by contact, fomite and droplet methods. Bronchitis is the inflammation of the bronchi.

(c): Cancer is caused by cells dividing repeatedly out of control. They cease to respond to the normal signals around them and form unspecialised masses of cells called tumours. Lung cancer usually starts in the epithelium of the bronchioles, so-called bronchial carcinoma. It usually spreads throughout the lungs. It is caused almost exclusively by smoking. Tobacco smoke contains chemicals responsible for lung cancer. The most important of these are polycyclic hydrocarbons which are converted in the body to carcinogens. 
Besides, carbon monoxide combines with haemoglobin and reduces oxygen transport by about 15% in smokers and nicotine increases blood pressure, heart rate and constriciton of blood vessels.

(d) : A major problem in the treatment of bacterial mediated diseases is that many bacteria have been found to show resistance to antibiotics. The emergence of antibiotic-resistant bacteria is closely linked to the extent that antibiotics are used in humans and item of human diet. Resistant strains may appear rapidly or slowly, according to the amount or type of antibiotic used. Bacteria occur in such large number that there is a high chance of mutant individual eventually appearing in the population. As soon as it does, use of the antibiotic to which it is resistant will give it a selective advantage over non-resistant types and it will multiply and eventually become the dominant type.
Antibiotics may also be destroyed by enzymes inside the cells being targetted. A well-known and important example is the group of enzymes known as penicillinases which hydrolyses and destroys penicillins and cephalosporins.