NCERT Exemplar for Class 11 Biology Chapter-12 (Book Solutions)

Multiple Choice Questions(MCQs)

1. Which one of the following roles is not characteristic of an essential element?

(a) being a component of biomolecules

(b) changing the chemistry of soil

(c) being a structural component of energy-related chemical compounds

(d) activation or inhibition of enzymes 

Ans: (b) changing the chemistry of soil

Explanation: Soil is not a living thing, and hence essential elements have no role to play in soil chemistry.

2. Which one of the following statements can best explain the term critical concentration of an essential element?

(a) essential element concentration below which plant growth is retarded.

(b) essential element concentration below which plant growth becomes enhanced.

(c) essential element concentration below which plant remains in the vegetative phase.

(d) none of the above

Ans:  (a) essential element concentration below which plant growth becomes retarded.

Explanation: Critical concentration is the minimum threshold concentration required for proper growth and development. If the concentration of essential elements falls below this level, growth will be compromised.

3. Deficiency symptoms of an element tend to appear first in young leaves. It indicates that the element is relatively immobile. Which one of the following elemental deficiencies would show such symptoms?

(a) Sulphur

(b) Magnesium

(c) Nitrogen

(d) Potassium

Ans:  (a) Sulphur

4. Which one of the following symptoms is not due to manganese toxicity in plants?

(a) Calcium translocation in shoot apex is inhibited

(b) Deficiency in both Iron and Nitrogen is induced

(c) Appearance of brown spot surrounded by chlorotic veins

(d) None of the above

Ans: (b) Deficiency in both Iron and Nitrogen is induced

Explanation: The prominent symptom of manganese toxicity is the appearance of brown spots surrounded by chlorotic veins. It is essential to know that manganese competes with iron and magnesium for uptake and with magnesium for binding with enzymes. Manganese also inhibits calcium translocation in the shoot apex. Therefore, excess manganese may induce deficiencies of iron, magnesium, and calcium.

5. Reaction carried out by N2 fixing microbes include

(a) \[{\mathbf{2N}}{{\mathbf{H}}_{\mathbf{3}}} + {\text{ }}{\mathbf{3}}{{\mathbf{O}}_{\mathbf{2}}} \to {\mathbf{2N}}{{\mathbf{O}}^ - }_{\mathbf{2}} + {\mathbf{2}}{{\mathbf{H}}^ + } + {\text{ }}{\mathbf{2}}{{\mathbf{H}}_{\mathbf{2}}}{\mathbf{O}}\,\, \cdot  \cdot  \cdot (i)\]

(b) \[{\mathbf{2N}}{{\mathbf{O}}^ - }_{\mathbf{2}} + {\text{ }}{{\mathbf{O}}_{\mathbf{2}}} \to {\mathbf{2N}}{{\mathbf{O}}^ - }_{\mathbf{3}}\, \cdot  \cdot  \cdot \left( {{\mathbf{ii}}} \right)\]

Which of the following statements about these equations is not true

(a) step (i) is carried out by Nitrosomonas or Nitrococcus

(b) step (ii) is carried out by Nitrobacter

(c) both steps (i) and (ii) can be called nitrification

(d) bacteria carrying out these steps are usually photoautotrophs

Ans: (d) bacteria carrying out these steps are usually photoautotrophs

Explanation: Bacteria that assist in nitrogen fixation are heterotrophs, and that is why they enter into the symbiotic association.

6. With regard to the Biological Nitrogen Fixation by Rhizobium in association with soybean, Which one of the following statements/ statements does not hold true.

(a) Nitrogenase may require oxygen for its functioning.

(b) Nitrogenase is Mo- Fe protein

(c) Leg-hemoglobin is a pink-colored pigment.

(d) Nitrogenase helps to convert N2 gas into two molecules of ammonia. 

Ans: (a) Nitrogenase may require oxygen for its functioning

Explanation: Nitrogenase does not require oxygen for its functioning.

7. Match the element with its associated functions/roles and choose the correct option among given below.

(a) A-(i), B-(ii), C-(iii), D.(iv), E-(v)

(b) A-(iv), B-(i), C-(iii), D-(ii), E-(v)

(c) A-(iii), B-(ii), C-(iv), D-(v), E-(i)

(d) A-(ii), B-(iii), C-(v), D-(i), E-(iv)

Ans: (b) A-(iv), B-(i), C-(iii), D-(ii), E-(v)

8. Plants can be grown in (Tick the incorrect option)

(a) soil with essential nutrients.

(b) water with essential nutrients.

(c) either water or soil with essential nutrients.

(d) water or soil without essential nutrients.

Ans: (d) water or soil without essential nutrients.

Explanation: Plants can be grown in either soil or water or in both with essential nutrients. But it cannot grow in water or soil deficient in nutrients.

9. What is common to Nepenthes, Utricularia, and Drosera with regard to the mode of nutrition?

Ans:  All of them are insectivorous plants.

10. Plants with zinc deficiency show reduced biosynthesis of.

Ans: Auxin 

11. Yellowish edges appear in leaves deficient in               .

Ans: Nitrogen

 12. Name the macronutrient which is a component of all organic compounds but is not obtained from the soil.

Ans: Carbon

13. Name one non-symbiotic nitrogen-fixing prokaryote.

Ans: Azotobacter

 14. Rice fields produce important greenhouse gas. Name it.

Ans: Methane CH₄

15. Complete the equation for reductive amination____?

 \[\underline {\,\,\,\,\,\,?\,\,\,\,\,\,\,\,\,} + {\text{ }}{\mathbf{N}}{{\mathbf{H}}_4}^ + \;\; + \;\;\;{\mathbf{NADPH}}\;\xrightarrow{?}{\mathbf{Glutamate}}\,{\text{ + }}\,{{\mathbf{H}}_{\mathbf{2}}}{\mathbf{O}}{\text{ }} + {\text{ }}{\mathbf{NADP}}\]

Ans:  The equation for reductive amination is given by

- ketoglutaric acid + NH₄++ NADPH        Glutamate            Dehydrogenase Glutamate + H₂O + NADP 

16. Excess of Mn in the soil leads to deficiency of Ca, Mg, and Fe. Justify.

Ans: Manganese competes with iron and magnesium for uptake and magnesium for binding to specific enzymes. It also inhibits calcium translocation in the shoot apex. Hence, excess magnesium may induce Ca, Mg, and Fe deficiency.

SHORT ANSWER TYPE QUESTIONS

 1. How is sulphur important for plants? Name the amino acids in which it is present.

Ans: Sulphurs are the main constituent of several coenzymes, vitamins, and ferredoxin. It is present in two amino acids; cysteine and methionine

2. How are organisms like Pseudomonas and Thiobacillus of great significance in the nitrogen cycle?

Ans: Nitrates present in soil are reduced to nitrogen through a process called denitrification. Denitrification is carried out by Pseudomonas and Thiobacillus. Thus, Pseudomonas and Thiobacillus have great importance in the nitrogen cycle.

3. Carefully observe the following figure:

(a) Name the technique shown in the figure and the scientist who demonstrated this technique for the first time.

Ans:  This figure shows the technique of hydroponics. Julius von Sachs first demonstrated this in 1860.

(b) Name at least three plants for which this technique can be employed for their commercial production.

Ans:  This technique can be commercially applied to many plants. Three of them are as follows: Tomato, seedless cucumber, and lettuce.

(c) What is the significance of aerating tube and feeding funnel in this setup?

Ans:  The aerating tube supplies oxygen to the roots. A feeding funnel is used to add water and nutrients as per requirement.

4. Name the most crucial enzyme found in root nodules for N2 fixation? Does it require a special pink coloured pigment for its functioning? Elaborate.

Ans: Nitrogenase is the essential enzyme found in root nodules for nitrogen fixation. It requires a pink-colored pigment called leghaemoglobin. Leghaemoglobin works as an oxygen scavenger and thus creates anaerobic conditions in the root nodule of a legume. Nitrogenase is highly sensitive to oxygen and needs anaerobic conditions to maintain its existence.

5. How are the terms ‘critical concentration’ and ‘deficient’ different from each other in terms of the concentration of an essential element in plants? Can you find the values of ‘critical concentration’ and ‘deficient’ for minerals — Fe & Zn.

Ans: The concentration below which plant growth is retarded is critical for an essential element. Any concentration below the critical concentration is called a deficiency.

6. Carnivorous plants exhibit nutritional adaptation: Citing an example explain this fact.

Ans: Plants that grow in marshes and swamps cannot get nitrogenous nutrients from the soil. So, these plants feed on insects to fulfill their need for nitrogen. Venus flytrap and Pitcher plant are examples of insectivorous plants. These plants show various adaptations to trap insects. For example, the leaf of a pitcher plant can be modified into a pitcher with a lid. The inner wall of the pitcher has suckers to absorb body fluid from insects.

7. A farmer adds/ supplies Na, Ca, Mg and Fe regularly to his field, and yet he observes that the plants show deficiency of Ca, Mg, and Fe. Give a valid reason and suggest a way to help the farmer improve the growth of plants.

Ans: Plants require micronutrients in deficient amounts. Any increase in this limit may result in toxicity because of the high level of a particular nutrient. In this case, the plants may be suffering from manganese toxicity. Most of the farmers use broad-spectrum fertilizer. Most broad-spectrum fertilizers contain manganese. Manganese competes with iron and magnesium for uptake and with magnesium for binding. It also inhibits calcium translocation shoot apex. Hence, excess manganese may induce Ca, Mg, and Fe deficiency.

Cure for manganese toxicity in plants:

1. Manage water efficiently. Mn absorption may be accelerated under the condition of surface drainage.

2. Balance the use of fertilizers (NPK or NPK + lime) to avoid nutrient stress as a source of Mn toxicity. Apply lime on acid soils to reduce the concentration of active Mn.

3. Do not apply excessive amounts of organic matter (Manure, straw) on soils containing large Mn and organic matter concentrations and poorly drained soils.

LONG ANSWER TYPE QUESTIONS 

1. It is observed that deficiency of a particular element showed its symptoms initially in older leaves and then in younger leaves.

(a) Does it indicate that the element is actively mobilized or relatively immobile?

Ans: This indicates that the element is actively mobilized. Elements actively mobilized show deficiency symptoms first in older parts of a plant.

(b) Name two elements which are highly mobile and two which are relatively immobile.

Ans: Nitrogen and potassium are highly mobile, while calcium and potassium are relatively immobile.

(c) How is the aspect of mobility of elements important to horticulture and agriculture?

Ans: The mobility of elements is essential to horticulture and agriculture. By observing the prevalence of deficiency symptoms in older or younger parts, a farmer or agriculture scientist can analyze whether the deficiency is due to relatively mobile elements or immobile elements. Further plans for treating the plants can be made on the basis of this observation.

2. We find that Rhizobium forms nodules on the roots of leguminous plants. Also, Frankia, another microbe, forms nitrogen-fixing nodules on the roots of the non-leguminous plant Alnus.

(a) Can we artificially induce the property of nitrogen fixation in a plant-leguminous or non–leguminous?

Ans: Scientists have attempted to induce the property of nitrogen fixation in plants artificially. But these experiments have shown very low success rates. So, no viable alternative to natural nitrogen fixation is available to date.

(b) What kind of relationship is observed between mycorrhiza and pine trees?

Ans: This is a symbiotic relationship.

(c) Is it necessary for a microbe to be in close association with a plant to provide mineral nutrition? Explain with the help of one example.

Ans: It is indeed necessary for a microbe to be closely associated with a plant to provide mineral nutrition. This can be illustrated by the example of Rhizobium and leguminous plants. Rhizobium is a bacterium that lives in the root nodules of leguminous plants. The bacteria get shelter and food in the root nodules. Instead of that, these bacteria help in nitrogen fixation in soil.

3. What are essential elements for plants? Give the criteria of essentiality? How are minerals classified depending upon the amount in which they are needed by the plants?

Ans: An element that fulfills the essentiality criteria is called an essential element for plants. Following are the various criteria for essentiality.

(a) The element must be essential for supporting average growth and reproduction in plants.

(b) The element requirement must be specific and not replaceable by any other element.

(c) The element must be directly involved in metabolism in the plant.

On the basis of the amount in which plants need minerals, they are divided into two categories, viz. macronutrients, and micronutrients.

Macronutrients: Elements present in large amounts, i.e. more than 10 moles per kg of dry matter, are called macronutrients—examples: carbon, hydrogen, oxygen, nitrogen, etc.

Micronutrients: Elements present in small amounts, i.e. less than 10 moles per kg of dry matter, are called micronutrients—examples: iron, calcium, magnesium, etc.

4. With the help of examples describe the classification of essential elements based on the function they perform.

Ans: Based on function, essential elements can be classified into four categories which are as follows:

(a) Components of Biomolecules: These are also called structural elements of cells, e.g. carbon, hydrogen, oxygen, and nitrogen.

(b) Components of Energy-Related Compounds: Examples: magnesium in chlorophyll and phosphorus in ATP.

(c) Elements that activate or inhibit enzymes: Examples: magnesium and zinc.

(d) Elements that can alter the osmotic potential of cells, such as potassium.

5. We know that plants require nutrients. If we supply these in excess, will it be beneficial to the plants? If yes, how/ If no, why?

Ans: Essential elements are required in low quantities by plants, especially for micronutrients. Even a slight deviation from this quantity can be detrimental to the plant. If micronutrients increase even by 10%, this can produce toxicity in plants.

Let us take an example of manganese which is an essential micronutrient for plants. Manganese shows the following properties:

(a) It competes with iron and magnesium for uptake.

(b) It competes with magnesium for binding to specific enzymes.

(c) It inhibits translocation of calcium to shoot apex.

Thus, excess manganese can hamper the uptake of iron and magnesium, and plants may begin to suffer from iron and magnesium deficiency. Excess of manganese can prevent magnesium from binding with certain enzymes. This can hamper many metabolic activities. Inhibition of translocation of calcium to shoot apex can result in stunted growth. 

Thus, excess of any micronutrient can never be beneficial for the plant; rather, it would be detrimental.

6. Trace the events starting from the coming in contact of Rhizobium to a leguminous root till nodule formation. Add a note on importance of leg-hemoglobin.

Ans: Nodule Formation:

(a) Rhizobium bacteria contact a susceptible root hair and begin to divide near it.

(b) After successful infection, the root hair curls.

(c) The infected thread of the root carries the bacteria to the inner cortex. The bacteria get modified into rod-shaped bacteroids. This causes the inner cortical and pericycle cells to divide.

(d) Division and growth of cortical and pericycle cells result in nodule formation.

(e) A mature nodule is complete with vascular tissues, which are continuous with the vascular tissues of the root.

Importance of Leghaemoglobin: Leghaemoglobin works as an oxygen scavenger and thus creates anaerobic conditions in the root nodule of a legume. Nitrogenase is highly sensitive to oxygen and needs an anaerobic condition to maintain its existence.

7. Give the biochemical events occurring in the root nodule of a pulse plant. What is the end product? What is its fate?

Ans: The root nodule contains all the necessary biochemical components required for nitrogen fixation. For example, it has the enzyme nitrogenase and a pigment leghaemoglobin. Nitrogenase is Mo-Fe protein. It catalyzes the conversion of atmospheric nitrogen into ammonia. Ammonia is the first stable product of nitrogen fixation. The following equation can show the conversion of atmospheric nitrogen into ammonia:

\[{N_2} + {\text{ }}8{e^ - } + {\text{ }}8{H^ - } + {\text{ }}16ATP{\text{ }} \to 2N{H_3} + {\text{ }}{H_2} + {\text{ }}16{\text{ }}ADP{\text{ }} + {\text{ }}16Pi\]

The following figure shows the conversion of nitrogen into ammonia:

The fate of Ammonia: Ammonia gets converted into ammonium ions. Most of the plants can assimilate nitrate and ammonium ions. But ammonium ions are quite toxic and cannot accumulate in plants. Hence, ammonium ion is converted into amino acids; through transamination and reductive amination.

8. Hydroponics have been shown to be a successful technique for growing plants. Yet most of the crops are still grown on land. Why?

Ans: Hydroponics appears to be a successful technique for the commercial production of plants. Many plants have been grown using this technique. But crops are still grown on land because of certain limitations of hydroponics.

(a) Hydroponics is still at the experimental stage, and more developments need to happen before being used on a mass scale.

(b) The initial setup cost is very high, and thus growing plants through technique cannot be commercially viable.

(c) There is a frequent problem of maintaining a high level of sterilization while growing plants through this technique.

(d) Plants grown through this method need frequent input of nutrients and air, which is highly cumbersome.

(e)Plants can be highly susceptible to environmental conditions because they are grown in laboratory conditions.

The students of Class 11 CBSE need not worry about finding the right course material for studying the biology of Class 11 NCERT. At Vedantu, we have everything available for CBSE Class 11 including the NCERT Exemplar Biology Chapter-12 book solutions which are curated at your convenience to make studying fun. These book solutions are very beneficial for the students of Class 11 as they are detailed without being too complex which makes them easy to understand and remember. 

These solutions make sure that you ace your Class 11 exams and understand the biology basics of this Class in such a way that for higher Classes and competitive exams, there is no problem in your path to progress. You can also download the NCERT Exemplars of various other subjects for Class 11 CBSE to help you with your studies and find the right study material to make your basics for Class 12 better.

About Class 11 Chapter 12: Mineral Nutritions 

A student of Class 11 will study terms like Mineral nutrition and how they are divided into two different types. Macronutrients and Micronutrients. They will also learn the importance of nutrition in plants and how much a plant needs specific nutrients in order to survive and to get benefit from it. 

You will also learn about their deficiencies and how it affects the plants and processes like the Nitrogen cycle, biological nitrogen fixation among many other new processes and definitions such as flux, translocation of solutes, etc. In a way, the students need to clear their basics of biology of Class 9 and 10 of botany or plant physiology so they can understand the Class 11 Biology Chapter-12, Mineral nutrition with ease. 

To understand these diverse concepts related to mineral nutrition, you need the ideal solution formulated by the top subject matter experts of Vedantu. Download the solution file from here and add it to your study material. Find out how efficiently the questions have been answered and how you can utilize them to score better in the board exams. Refer to the solution whenever you have a doubt and want to resolve it faster to complete preparing this chapter.