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Biology Questions and Answers

641.

Which of the following represent maximum number of species among global biodiversity?

Answer: C

Fungi account for the largest number of species among these.

About 100,000 have been described and the true number is estimated in the millions, against perhaps 40,000 algae, 20,000 lichens and 25,000 mosses and ferns. Fungi are second only to insects among all groups of organisms.

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Answer: C

In science either deductive or inductive reasoning, or both, may be used.

Induction generalises from observations into a hypothesis; deduction then draws from that hypothesis a prediction which can be tested. The two work together in the cycle of hypothesis and test.

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643.

One day you wake with a sore throat and a runny nose. Your doctor takes a swab from your throat, sends it to a lab, and telephones you the next day to say that antibiotic will not help you get better.

Answer: D

The antibiotic will not help because you are infected by a virus.

Antibiotics work on structures and processes peculiar to bacteria - the cell wall, bacterial ribosomes, bacterial enzymes. A virus has none of these and replicates inside your own cells, so an antibiotic has nothing to act on. Most sore throats and colds are viral.

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644.

The flavour of apples is mainly due to which one of the following?

Answer: C

The flavour of apples is chiefly due to ethanal (acetaldehyde).

It is one of the volatile compounds released as the fruit ripens, along with esters such as ethyl butanoate. Formalin and benzaldehyde are quite different: benzaldehyde gives almonds their smell.

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645.

Palaeobotany is the branch of botany in which we study

Answer: B

Palaeobotany is the study of plant fossils.

It reconstructs past vegetation and climates from fossil wood, leaves, pollen and spores, and provides much of the evidence for continental drift - the same fossil flora appearing on continents now far apart.

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646.

Which among the following statements concerning platelets is INCORRECT. Platelets:

Answer: A

The incorrect statement is that platelets contain DNA.

They have no nucleus, being fragments budded off from megakaryocytes in the marrow. The rest is true: they are roughly disc-shaped, about 2 to 3 micrometres across against the red cell's 7, and synthesise very little protein.

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647.

Bone deformities occur due to the excess intake of

Answer: D

Excess fluorine causes bone deformity.

Skeletal fluorosis follows years of drinking water with more than about 1.5 mg of fluoride per litre: the bones thicken, the ligaments calcify and the spine and limbs bend. It is endemic in parts of Rajasthan, Andhra Pradesh and Gujarat.

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648.

What is pH value of human blood ?

Answer: A

Human blood has a pH of about 7.4 - slightly alkaline.

It is held within 7.35 to 7.45 by the bicarbonate buffer system, by the lungs regulating carbon dioxide and by the kidneys excreting acid. Outside about 6.8 to 7.8 life cannot continue.

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Answer: B

Respiration proceeds glycolysis → Krebs cycle → electron transport chain.

Glycolysis splits glucose into pyruvate in the cytoplasm; the Krebs cycle oxidises it fully in the mitochondrial matrix, releasing carbon dioxide and reduced coenzymes; and the electron transport chain uses those to make most of the ATP.

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650.

The inflorescence of wheat is-

Answer: C

The inflorescence of wheat is a spike.

Its flowers are borne in spikelets attached directly to the main axis without stalks, which is what defines a spike. A raceme has stalked flowers, a panicle is a branched raceme, and a catkin is a pendulous spike of unisexual flowers.

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