Zoology MCQs for NEET — Practice Questions with Answers

Allergy is the hypersensitiveness of a person to some foreign substances coming in contact with or entering the body. The common allergens are dust, pollen mould, spores, fabricates, bacteria, etc. During allergic reaction, there is increased release of histamine from mast cells. Use of anti-histamines and steroids give a quick relief from allergy.

Thymus is haemopoietic as well as an endocrine gland. Thymus is the ‘seedbed' of thymic lymphocytes (T-lymphocytes). Certain stem cells, originating in yolk sac and liver in early embryo, but only in bone marrow in late embryo, migrate into the thymus and proliferate to form a large number of lymphocytes. 

Thyroid is an endocrine gland.

Thalamus is the part of forebrain in vertebrate lies above the hypdthalamus.

Tonsil is a mass of lymphoid tissue, several of which are situated at the back of the mouth and throat in higher vertebrates.

(d) Neutrophils and monocytes are phagocytic white blood cells. Monocytes are largest of all leucocytes and generally change into macrophages after entering tissue spaces Neutrophils are most numerous of all leucocytes, and have many lobed nucleus.

Eosinophils are granular white blood cells. Their number increases in people with allergic conditions such as asthma or hay fever. They are non-phagocytic and seem to play part in immune system.

Lymphocytes are non-motile and non-phagocytic in nature. They produce antibodies to destroy microbes. These are found as B and T-lymphocytes. T-lymphocytes either directly attack the antigens or stimulate B-lymphocytes to produce antibodies.

Asthma is a respiratory disorder. It is caused by foreign allergens and dust particles present in the air passing through it, the pollen grains present in air can cause asthmatic attacks in certain seasons.

Histamine is a protein, acting as a vasodilator (widening of blood vessels) in inflammatory and allergic reactions and also increases the permeability of small vessels. It is secreted from the mast cells which widely occur in the areolar connective tissue.
Two other active substances secreted by mast cells are Heparin, a proteoglycan, which prevent coagulation of blood vessels and Serotonin,  a protein, which acts as vasoconstrictor to stop bleeding and to increase blood pressure.

Antibodies are the protein (glycoproteins) called immunoglobulins, These are produced by the lymphocytes in response to entry of a foreign substance or antigen into the body. Lipoproteins are the micellar complex of protein and lipids.
Steroids are a group of lipids derived from a saturated compound cyclopentano perhydrophenanthrene which has a nucleus of four rings.
Prostaglandin is a group of organic compounds derived from essential fatty acids and causing a range of physiological effects in animals.

(d): Histiocyte are phagocyte found mainly in connective tissue. Although normally non-motile, it can become converted into a mobile, amoeboid macrophage. Histiocytes are large, irregularly shaped cells with granular, vacuolated cytoplasm. They are associated with inflammatory conditions, and are especially found near tissue haemorrhages. Mast cells are the connective tissue cells that contain heparin and histamine in their granules. Important in cellular defence mechanisms including blood coagulation needed during injury or infection. Plasma cells are leucocyte formed from an antigen- stimulated B-lymphocytes.

The so called tertain periodicity of Plasmodium vivax refers to the erythrocytic phase.

(b): Hybridoma is a cell produced by the fusion of an antigen-producing cell and a multiple myeloma cell. This hybrid cell is capable of producing a continuous supply of antibody.

Myelomas are B lymphocyte tumors that readily fuse with plasma cells to form antibody- producing hybridomas.

(d): Communicable diseases are infectious diseases which are caused by pathogens and spread from infected person to healthy person. These are of two types- contagious diseases (which are transmitted from infected person to healthy person through contact e.g., syphilis, chickenpox, etc.) and non-contagious diseases (which are transmitted from infected person to healthy persons through an agency of water, food or air or by some carrier or vector, e.g., ascariasis, cholera, filariasis, plague etc).