Pearls are harvested from
- A.Prawn
- B.Pila
- C.Tuna
- D.Oyster
Correct answer
Explanation
The correct answer is D, Oyster. Pearls are harvested from pearl oysters, which are bivalve molluscs. When a foreign particle, such as a grain of sand or a parasite, gets inside the shell, the oyster's mantle covers it layer after layer with nacre, the shiny material also called mother of pearl. Over months and years these layers build up into a pearl. In pearl culture, workers place a small bead or a piece of mantle tissue inside the oyster on purpose and then rear the oysters in the sea or in ponds. The marine pearl oyster Pinctada is the main source, and the Gulf of Mannar has long been known for pearl fishing in India. Option A is wrong because the prawn is a crustacean caught for food and does not make pearls. Option B is wrong because Pila, the apple snail, is a freshwater gastropod that produces no pearls. Option C is wrong because the tuna is a fish, valued as food, with no link to pearls. Exam tip: pearl comes from the oyster's nacre; Pinctada, Gulf of Mannar.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
Read the full explanation →Which one of the following statements is correct?
- A.Urea is produced in liver.
- B.Urea is produced in blood.
- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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Liver cells turn the toxic ammonia released from the breakdown of amino acids into urea through the ornithine cycle, also called the urea cycle.
Read the full explanation →Which one of the following is the correct sequence of passage of light in a compound microscope?
- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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Light passes through the condenser to the specimen, is picked up by the objective lens, travels up the body tube and reaches the eye through the eyepiece.
Read the full explanation →Which one of the following statements regarding haemoglobin is correct?
- A.Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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It binds oxygen at its iron-containing haem groups and carries some carbon dioxide on its protein chains. Each haemoglobin molecule has four polypeptide chains and four haem groups, and each haem iron can hold one oxygen molecule, forming oxyhaemoglobin in the lungs.
Read the full explanation →Which one of the following statements regarding histone proteins is correct?
- A.Histones are proteins that are present in mitochondrial membrane.
- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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They are the proteins around which DNA winds to form chromatin in the nucleus of eukaryotic cells. Histones are small basic proteins, rich in the positively charged amino acids lysine and arginine, which attract the negatively charged phosphate groups of DNA.
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