Subject

Biology

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

21.

Assertion: The nymph of a cockroach undergoes moulting several times.

Reason: There is gradual metamorphosis in cockroach.

  • If both assertion and reason are true and reason is the correct explanation of assertion. 

  • If both assertion and reason are true but reason is not the correct explanation of assertion. 

  • If assertion is true but reason is false. 

  • If both assertion and reason are false.


A.

If both assertion and reason are true and reason is the correct explanation of assertion. 

Gradual metamorphosis occurs in many insects such as cockroaches. In gradual metamorphosis, there are three stages: egg, nymph and adult. As nymphs, they moult several times (13 times in cockroach), but once they become adults they do not moult again. Nymphs are similar in shape to the adults, but smaller in size and without wings.


22.

Assertion: Cephalisation is advantageous to an animal.

Reason: It improves the appearance of the animal.

  • If both assertion and reason are true and reason is the correct explanation of assertion. 

  • If both assertion and reason are true but reason is not the correct explanation of assertion. 

  • If assertion is true but reason is false. 

  • If both assertion and reason are false.


C.

If assertion is true but reason is false. 

Cephalisation is the concentration of nervous tissues and sense organs in or towards the anterior end forming a distinct head. It provides greater prominence and domination of the head over the rest of the body. It does not improve the appearance of the animal.


23.

Assertion: Secondary metabolites are produced in small quantities and their extraction from the plant is difficult and expensive.

Reason: Secondary metabolites can be commercially produced by using tissue culture technique.

  • If both assertion and reason are true and reason is the correct explanation of assertion. 

  • If both assertion and reason are true but reason is not the correct explanation of assertion. 

  • If assertion is true but reason is false. 

  • If both assertion and reason are false.


B.

If both assertion and reason are true but reason is not the correct explanation of assertion. 

Secondary metabolites are biosynthetically derived from primary metabolites but more limited in distribution in plant kingdom, being restricted to a particular taxonomic group. Secondary metabolites are accumulated by plants in smaller quantities than are primary metabolites. Also, they are synthesised in specialised cell types and at distinct developmental stages, making their extraction and purification difficult and expensive. By the culture media using tissue culture techniques, secondary metabolites can be produced on a large scale.


24.

Assertion: Branchiostoma and Balanoglossus are bilaterally symmetrical and triploblastic animals.

Reason: They are exclusively marine and possess notochord.

  • If both assertion and reason are true and reason is the correct explanation of assertion. 

  • If both assertion and reason are true but reason is not the correct explanation of assertion. 

  • If assertion is true but reason is false. 

  • If both assertion and reason are false.


C.

If assertion is true but reason is false. 

Balanoglossus (Phylum-Hemichordata) and Branchiostoma (= Amphioxus, Subphylum - Cephalochordata) both are bilaterally symmetrical and triploblastic animals. Both are marine animals. Balanoglossus does not possess a notochord whereas Branchiostoma being a chordate possesses notochord that persists throughout life.


25.

Assertion: Nitrogen is one of the most essential elements of human body.

Reason: All types of prokaryotic organisms are able to fix nitrogen.

  • If both assertion and reason are true and reason is the correct explanation of assertion. 

  • If both assertion and reason are true but reason is not the correct explanation of assertion. 

  • If assertion is true but reason is false. 

  • If both assertion and reason are false.


C.

If assertion is true but reason is false. 

Nitrogen is one of the most essential elements of human body. It is a constituent of a number of organic compounds like amino acids, proteins, nucleotides, nucleic acids, many vitamins, hormones etc. Biological N2 fixation is a very important natural process which is performed by two types of prokaryotes - bacteria and cyanobacteria. They include both free living and symbiotic forms.


26.

Assertion: Plant growth regulators (PGRs) are very important for plant growth and development.

Reason: Auxins do not induce flowering in gymnosperms

  • If both assertion and reason are true and reason is the correct explanation of assertion. 

  • If both assertion and reason are true but reason is not the correct explanation of assertion. 

  • If assertion is true but reason is false. 

  • If both assertion and reason are false.


B.

If both assertion and reason are true but reason is not the correct explanation of assertion. 

Plant growth regulators (PGRs) are small, simple molecules of diverse chemical composition, which in low concentration regulate growth, differentiation and development by promoting or inhibiting the same. One type of plant growth regulators are plant hormones or phytohormones. Auxins are the phytohormones. They do not induce flowering in gymnosperms.


27.

Assertion: A correct concentration of auxin and cytokinin is required for the development of root and shoot in a callus.

Reason: When the ratio of kinetin to auxin is high, then only shoots develop. But when the ratio is low then only roots develop.

  • If both assertion and reason are true and reason is the correct explanation of assertion. 

  • If both assertion and reason are true but reason is not the correct explanation of assertion. 

  • If assertion is true but reason is false. 

  • If both assertion and reason are false.


A.

If both assertion and reason are true and reason is the correct explanation of assertion. 

The ratio of cytokinin (kinetin) to auxin (IAA) is important in determining the nature of organogenesis in tissue culture. High level of kinetin results in bud initiation, while high concentration of auxin favours rooting.


28.

Assertion: In light reaction of photosynthesis, light is required for the functioning of PS I and PS II, and production of NADPH and ATP.

Reason: Dark reaction does not occur in light.

  • If both assertion and reason are true and reason is the correct explanation of assertion. 

  • If both assertion and reason are true but reason is not the correct explanation of assertion. 

  • If assertion is true but reason is false. 

  • If both assertion and reason are false.


C.

If assertion is true but reason is false. 

Light reactions of photosynthesis take place in the presence of light. These involve photolysis of water and production of assimilatory power (NADPH + ATP) through PS I and PS II.

Dark reactions of photosynthesis catalyse assimilation of CO2 to carbohydrates. Dark reactions are light independent reactions, hence can take place both in the light as well as in the dark


29.

Assertion: Blood in cockroach is colourless haemolymph with no respiratory pigment.

Reason: Respiration in cockroach occurs through diffusion in haemolymph.

  • If both assertion and reason are true and reason is the correct explanation of assertion. 

  • If both assertion and reason are true but reason is not the correct explanation of assertion. 

  • If assertion is true but reason is false. 

  • If both assertion and reason are false.


C.

If assertion is true but reason is false. 

The colourless blood or haemolymph of cockroach has a clear plasma and numerous white corpuscles called haemocytes. Being devoid of any respiratory pigment, it does not serve for gaseous exchange. Its plasma contains about 70% water. Rest of it is composed of amino acids, uric acid, proteins, sugars, fats, and salts of sodium, potassium, calcium and magnesium. Transportation of these materials between different parts of body is the main function of haemolymph.

In all terrestrial insects, like cockroach, every tissue of body is in direct contact with atmospheric air for gaseous exchange. A complicated system of numerous shiny, transparent and branched air tubes or tracheae is found for this purpose in the haemocoel cavity. Atmospheric air enters into and escapes out from this system through ten pairs of slit-like apertures called stigmata or spiracles, located on lateral sides of body


30.

Assertion: ADH and RAAS work in response to low blood volume and blood pressure.

Reason: ANF works in response to high blood volume and blood pressure.

  • If both assertion and reason are true and reason is the correct explanation of assertion. 

  • If both assertion and reason are true but reason is not the correct explanation of assertion. 

  • If assertion is true but reason is false. 

  • If both assertion and reason are false.


B.

If both assertion and reason are true but reason is not the correct explanation of assertion. 

ADH (Antidiuretic hormone) and RAAS (Renin Angiotensin Aldosterone System) work in response to low blood volume and low blood pressure.

ADH increases the reabsorption of water in the distal convoluted tubule and collecting duct, and thus results in an increase in blood volume and blood pressure.

RAAS is operated by JGA (Juxtaglomerular apparatus). It increases blood volume and blood pressure by two ways: Firstly, it induces the proximal convoluted tubules to reabsorb more NaCl and water and secondly, it stimulates the adrenal gland to release a hormone, called aldosterone that induces the distal convoluted tubule to absorb more Na' and water.

ANF (Atrial Natriuretic Factor) works in response to high blood volume and high blood pressure. It opposes the regulation by RAAS. The walls of the atria of the heart release ANF in response to an increase in blood volume and blood pressure. ANF inhibits release of renin from the JGA and thereby inhibits NaCl reabsorption by the collecting duct and reduces aldosterone release from the adrenal gland.

Thus ADH, RAAS and ANF regulate the functions of kidneys and control body fluid osmolarity, salt concentration, blood pressure and blood volume.