Category: Class 11 Biology

NCERT Exemplar Class 11 Biology Chapter 15 Plant Growth and Development are part of NCERT Exemplar Class 11 Biology. Here we have given NCERT Exemplar Class 11 Biology Chapter 15 Plant Growth and Development.

NCERT Exemplar Class 11 Biology Chapter 15 Plant Growth and Development

Multiple Choice Questions

Q1. Ethylene is used for
(a) Retarding ripening of tomatoes
(b) Hastening of ripening of fruits
(c) Slowing down ripening of apples
(d) Both (b) and (c)
Ans: (b) Ethylene is used for hastening of ripening of fruits.

Q2. Coconut water contains
(a) ABA
(b) auxin
(c) cytokinin
(d) gibberellin
Ans: (c) Coconut water contains cytokinin.

Q3. The effect of apical dominance can be overcome by which of the following hormone?
(a) IAA
(b) Ethylene
(c) Gibberellin
(d) Cytokinin
Ans: (d) The effect of apical dominance can be overcome by cytokinin hormone.

Q4. Match the following:

A.	IAA	(0	Herring sperm DNA
B.	ABA	(ii)	Bolting
C.	Ethylene	(iii)	Stomatal closure
D.	GA	(iv)	Weed-free lawns
E.	Cytokinins	(v)	Ripening of fruits

Ans: (a)

A.	IAA	(iv)	Weed-free lawns
B.	ABA	(iii)	Stomatal closure
C.	Ethylene	(v)	Ripening of fruits
D.	GA	(ii)	Bolting
E.	Cytokinins	(i)	Herring sperm DNA

 

Q5. Apples are generally wrapped in waxed paper to
(a) prevent sunlight for changing its colour
(b) prevent aerobic respiration by checking the entry of 02
(c) prevent ethylene formation due to injury
(d) make the apples look attractive
Ans: (b) Apples are generally wrapped in waxed paper to prevent aerobic respiration by checking the entry of 02.

Q6. Growth can be measured in various ways. Which of these can be used as parameters to measure growth?
(a) Increase in cell number
(b) Increase in cell size
(c) Increase in length and weight
(d) All the above
Ans: (d) Growth can be measured in various ways. Increase in cell number, increase in cell size and increase in length and weight are used as parameters to measure growth.

Q7. The term synergistic action of hormones refers to
(a) when two hormones act together but bring about opposite effects
(b) when two hormones act together and contribute to the same function
(c) when one hormone affects more than one function
(d) when many hormones bring about any one function
Ans: (b) The term synergistic action of hormones refers to when two hormones act together and contribute to the same function.

Q8. Plasticity in plant growth means that
(a) plant roots are extensible
(b) plant development is dependent on the environment
(c) stems can extend
(d) none of the above
Ans: (b) Plasticity in plant growth means that plant development is dependent on the environment.

Q9. To increase sugar production in sugarcanes, they are sprayed with
(a) IAA
(b) cytokinin
(c) gibberellin
(d) ethylene
Ans: (c) To increase sugar production in sugarcanes, they are sprayed with gibberellin.

Q10. ABA acts antagonistic to
(a) ethylene
(b) cytokinin
(c) gibberellic acid
(d) IAA
Ans: (c) ABA acts antagonistic to gibberellic acid.

Q11. Monocarpic plants are those which
(a) bear flowers with one ovary
(b) flower once and die
(c) bear only one flower
(d) all of the above
Ans: (b) Monocarpic plants are flower once and die.

Q12. The photoperiod in plants is perceived at
(a) meristem
(b) flower
(c) floral buds
(d) leaves
Ans: (d) The photoperiod in plants is perceived at leaves.

Very Short Answer type Questions
Q1. Fill in the places with appropriate word/words.
a. A phase of growth which is maximum and fastest is .
b. Apical dominance as expressed in dicotyledonous plants is due to the
presence of more _____ in the apical bud than in the lateral ones.
c. In addition to auxin, a ________ must be supplied to culture medium to
obtain a good callus in plant tissue culture.
d. _________of a vegetative plants are the sites of photoperiodic perception.
Ans: a. Exponential/log phase of an S-curve.
b. Auxin/IAA
c. CytokininlKinetinl6 BAP/Zeatinletc.
d. Leaves

Q2. PJ.ant growth substances (PGS) have innumerable practical applications. Name the PGS you should use to
a. increase yield of sugar cane b. promote lateral shoot growth
c. cause sprouting of potato tuber d. inhibit seed germination
Ans: a. GA3/gibberellinlgibberellic acid
b. CytokininlzeatinlkinetinJKn
c. C2H4/Ethylene
d. ABA/Abscisic acid

Q3. A primary root grows from 5 cm to 19 cm in a week. Calculate the growth rate and relative growth rate over the period.

Q4. Gibberellins were first discovered in Japan when rice plants were suffering from bakane (the foolish seedling disease) caused by a fungus Gibberella fujikuroi.
a. Give two functions of this priytohormone.
b. Which property of Gibberellin caused foolish seedling disease in rice?
Ans: a. GA3 is used to speed up the malting process in brewing industry. Gibberellins also promote bolting (internode elongation just prior to flowering) in beet, cabbages and many plants with rosette habit.
b. Gibberellin causes foolish seedling disease in rice because it has the property of internode elongation.

Q5. Gibberellins promote the formation of _________ flowers on genetically _________ plants in Cannabis whereas ethylene promotes formation of _______ flowers
on genetically ____ plants.
Ans: Gibberellins promote the formation of male flowers on genetically female plants in Cannabis whereas ethylene promotes formation of female flowers on genetically male plants.

Q6. Classify the following plants into Long-Day Plants (LDP), Short-Day Plants (SDP) and Day-Neutral Plants (DNP) Xanthium, Henbane (Hyoscyamus niger), Spinach, Rice, Strawberry, Bryophyllum, Sunflower, Tomato, Maize.
Ans: Xanthium: (SDP)
Henbane (Hyoscyamus niger): (LDP)
Spinach: (LDP)
Rice: (SDP)
Strawberry: (SDP)
Bryophyllum: LSDP (Long short day plants)
Sunflower: (DNP)
Tomato: (DNP)
Maize: (DNP)

Q7. A farmer grows cucumber plants in his field. He wants to increase the number of female flowers in them. Which can plant growth regulator be applied to achieve this?
Ans: Ethylene (C2H4)

Q8. Where are the following hormones synthesised in plants?
a. IAA
b. Gibberellins
c. Cytokinins
Ans: a. IAA: Shoot tips and apical bud
b. Gibberellins: Root tips and young leaves
c. Cytokinins: Meristematic zones like root tips

Q9. In botanical gardens and tea gardens, gardeners trim the plants regularly so that they remain bushy. Does this practice have any scientific explanation?
Ans: Mostly in higher plants, the growing apical bud inhibits the growth of the lateral (axillary) buds, a phenomenon called apical dominance. Removal of shoot tips (decapitation) usually results in the growth of lateral buds. Hence, in botanical gardens and tea gardens, gardeners trim the plants regularly so that they remain bushy.

Q10. Light plays an important role ‘in the life of all organisms. Name any three physiological processes in plants which are affected by light.
Ans: Photoperiodism, phototropism and photosynthesis.

Q11. In the figure of Sigmoid growth curve given below, label segments 1,2 and 3

Q12. Growth is one of the characteristics of all living organisms. Do unicellular organism also grow? If so, what are the parameters?
Ans: Increase in mass and increase in number of individuals are twin characteristics of growth. A multicellular organism grows by cell division. Unicellular organisms grow by cell division. One can easily observe this in in vitro cultures by simply counting the number of cells under the microscope.

Q13. The rice seedlings infected with fungus Gibberella fujikuroi is called foolish seedlings? What was the reason behind it?
Ans: The rice seedling infected with fungus Gibberella fujikuroi is called foolish seedlings because the fungus secreted a hormone gibberellin and causes excessive growth of rice plants. Plants become tall but unable to produce seeds so they are called foolish.

Short Answer Type Questions

Q1. Nicotiana tobacum, a short-day plant, when exposed to more than critical period of light fails to flower. Explain.
Ans: a. Some plants require a periodic exposure to alternate light and dark for its flowering response. This phenomenon is termed photoperiodism.
b. The requirement of light exposure is critical. The SDP plants, when exposed to light period in excess of critical period fail to flower,
c. Those plants which require exposure to light period at critical or more than critical period for its flowering response are called long-dayplant.
d. Nicotiana tabacum fails to flower if exposed to more than critical period of light because it is an SDP.

Q2. What are the structural characteristics of
a. Meristematic cells near root tip
b. The cells in the elongation zone of the root
Ans: a. The meristematic cells near root tip are characterised by
• rich protoplasm
• large conspicuous nucleus
• thin and cellulosic cell wall -primary in nature
• fewer vacuoles
• greater number of mitochondria
• numerous (abundant) plasmodesmata
b. The cells in the elongation zone of a root are characterized by
• increased vacuolation
• enlarged size/dimension
• deposition of new cellulosic cell walls

Q3. Does the growth pattern in plants differ from that in animals? Do all the parts of plant grow indefinitely? If not, name the regions of plant, which can grow indefinitely.
Ans: Yes, the growth pattern in plants differ from that in animals. Plant growth is unique because plants retain the capacity for unlimited growth throughout their life. This ability of the plants is due to the presence of meristems at certain locations in their body. The cells of such meristems have the capacity to divide and self-perpetuate. The product, however, soon loses the capacity to divide and such cells make up the plant body. This form of growth wherein new cells are always being added to the plant body by the activity of the meristem is called the open form of growth.

Q4. Explain in 2-3 lines each of the following terms with the help of examples taken from different plant tissues.
a. Differentiation
b. De-differentiation
c. Re-differentiation
Ans: a. Differentiation: The cells derived from root apical and shoot-apical meristems and cambium differentiate and mature to perform specific functions. This act leading to maturation is termed as differentiation. During differentiation, cells undergo few to major structural changes both in their cell walls and protoplasm. For example, to form a tracheary element, the cells would lose their protoplasm. They also develop a very strong, elastic, lignocellulosic secondary cell walls, to carry water to long distances even under extreme tension.
b. De-differentiation: The living differentiated cells that by now have lost the capacity to divide can regain the capacity of division under certain conditions. This phenomenon is termed as de-differentiation. For example, formation of meristems – interfascicular cambium and cork cambium from fully differentiated parenchyma cells.
c. Re-differentiation: While doing de-differentiation, such meristems/ tissues are able to divide and produce cells that once again lose the capacity to divide but mature to perform specific functions, i.e., get re-differentiated, e.g., secondary xylem and secondary cortex.

Q5. Auxins are growth hormones capable of promoting cell elongation. They have been used in horticulture to promote growth, flowering and rooting. Write a line to explain the meaning of the following terms related to auxins.
a. Auxin precursors
b. Anti-auxins
c. Synthetic auxins
Ans: a. Auxin precursors: The substances that produce the auxin are called auxin precursors. For example, tryptophan is the auxin precursor.
b. Anti-auxins: The substances which inhibit the synthesis or transport of auxin are called anti-auxins. For example, TIBA (Triiodobenzoic acid) is anti-auxin compound.
c. Synthetic auxins: The artificially synthesised chemicals having auxin-like property are called synthetic auxins. For example, NAA
– (Naphthalene acetic acid) and 2, 4-D (2, 4-Dichloro phenoxyacetic acid).

Q6. The role of ethylene and abscisic acid is both positive and negative. Justify the statement.
Ans: Positive roles of ethylene: Influences of ethylene on plants include horizontal growth of seedlings, swelling of the axis and apical hook formation in dicot seedlings. Ethylene breaks seed and bud dormancy, initiates germination in peanut seeds, sprouting of potato tubers.
• Negative roles of ethylene: Ethylene promotes senescence and abscission of plant organs especially of leaves and flowers.
• Positive roles of abscisic acid: ABA plays an important role in seed development and maturation.
• Negative roles of abscisic acid: It acts as a general plant growth inhibitor and an inhibitor of plant metabolism. ABA inhibits seed germination. ABA stimulates the closure of stomata in the epidermis and increases the tolerance of plants to various kinds of stresses.

Q7. While experimentation, why do you think it is difficult to assign any effect seen to any single hormone?
Ans: Many hormones have synergistic and antagonistic effect with each other. So, while experimentation, it is difficult to assign any effect seen to any single hormone.

Q8. What is the mechanism underlying the phenomenon by which the terminal/ apical bud suppresses the growth of lateral buds? Suggest measures to overcome this phenomenon.
Ans: The phenomenon by which the terminal/apical bud suppresses the growth of lateral buds is called apical dominance. Apical dominance is due to auxin hormone secreted by apical buds. This can be overcome by decapitation (removal of apical buds) or the application of cytokinin.

Q9. In animals there are special glands secreting hormones, whereas there are no glands in plants. Where are plant hormones formed? How are the hormones translocated to the site of activity?
Ans: In plants, the hormones are formed by different tissues like shoot tips, root tips, meristematic tissues, leaves and apical buds, etc.
Hormones are translocated to the site of activity by vascular tissues (xylem and phloem)

Q10. Many discoveries in science have been accidental. This is true for plant hormones also. Can you justify this statement by giving an example? Also what term is used for such accidental findings?
Ans: The discovery of each of the five major groups of PGRs have been accidental. All this started with the observation of Charles Darwin and his son Francis Darwin when they observed that the coleoptiles of canary grass responded to unilateral illumination by growing towards the light source (phototropism). After a series of experiments, it was concluded that the tip of coleoptile was the site of transmittable influence that caused the bending of the entire coleoptile. Auxin was isolated by F.W. Went from tips of coleoptiles of oat seedlings. Such accidental findings or discoveries are known as serendipity.

Q11. To get carpet-like grass lawn are mowed regularly. Is there any scientific explanation for this?
Ans: To get a carpet-like grass lawns are mowed regularly because mowing causes decapitation which promotes the growth of lateral buds.

Q12. In a slide showing different types of cells, can you identify which type of the cell may be meristematic and the one which is incapable of dividing and how?
Ans: The meristematic cells are rich in protoplasm, possess large conspicuous nuclei. Their cell walls are primary in nature, thin and cellulosic with abundant plasmodesmatal connections. Cells incapable of dividing attain their maximal size in terms of wall thickening and protoplasmic modifications.

Q13. A rubber band stretches and reverts back to its original position. Bubble gum stretches, but it would not return to its original position. Is there any difference between the two processes? Discuss it with respect to plant growth (Hint: Elasticity (reversible), Plasticity (irreversible))
Ans: A rubber band stretches and reverts back to its original position, it is due to elasticity. Bubble gum stretches, but it would not return to its original position, this is due to plasticity.
• The meristematic cells are rich in protoplasm, possess large conspicuous nuclei. Their cell walls are primary in nature, thin, cellulosic and elastic with abundant plasmodesmatal connections.
• Plants follow different pathways in response to environment or phases of life to form different kinds of structures. This ability is called plasticity,
e. g., heterophylly in cotton, coriander and larkspur. In such plants, the leaves of the juvenile plant are different in shape from those in mature plants.

Q14. Label the diagram
a. This is which part of a dicotyledonous plant?
b. If we remove part 1 from the plant, what will happen?

Q15. Both animals and plants grow. Why do we say that growth and differentiation in plants is open and not so in animals? Does this statement hold true for sponges also?
Ans: Plant growth is unique because plants retain the capacity for unlimited growth throughout their life. This ability of the plants is due to the presence of meristems at certain locations in their body. The cells of such meristems have the capacity to divide and self-perpetuate. The product, however, soon loses the capacity to divide and such cells make up the plant body. This form of growth wherein new cells are always being added to the plant body by the
Plant Growtli and Development 167
activity of the meristem is called the open form of growth. Yes, this statement hold true for sponges also.

Q16. Define parthenocarpy. Name the plant hormone used to induce parthenocarpy.
Ans: Most fruits however develop only from the ovary and are called true fruits.
Although in most of the species, fruits are the results of fertilisation, there are a few species in which fruits develop without fertilisation. Such fruits are called parthenocarpic fruits. Banana is one such example. Parthenocarpy can be induced through the application of growth hormones (like gibberellin and auxin) and such fruits are seedless. Auxins induce parthenocarpy in tomatoes.

Q17. While eating watermelons, all of us wish it was seedless. As a plant physiologist can you suggest any method by which this can be achieved.
Ans: This can be achieved through parthenocarpy. Parthenocarpy can be induced through the application of growth hormones (like gibberellin and auxin) and such fruits are seedless.

Q18. A gardener finds some broad-leaved dicot weeds growing in his lawns. What can be done to get rid of the weeds efficiently?
Ans: The dicotyledonous plants grow by their apical shoot meristems while grasses (which make lawns) possess intercalary meristem. Certain auxins, such as synthetic 2, 4-Dichlorophenoxyacetic acid (2,4-D) when applied in excess can damage the shoot apical meristems but they do not cause any damage to the- intercalary meristems. Thus, when 2, 4-D is sprayed on lawns, only the dicots get killed and the lawns become free of weeds.

Q19. On germination a seed first produces shoots with leaves, flowers appear later,
a. Why do you think this happens?
b. How is this advantageous to the plant?
Ans: a. All organisms have to reach a certain stage of growth and maturity in their life, before they can reproduce sexually. That period of growth is called the juvenile phase. It is known as vegetative phase in plants. This phase is of variable durations in different organisms. The end of juvenile/ vegetative phase which marks the beginning of the reproductive phase can be seen easily in the higher plants when they come to flower.
b. This enables the plant to have sufficient time to reach maturity.

Q20. Fill in the blanks:
a. Maximum growth is observed in phase.
b. Apical dominance is due to .
c. initiate rooting. .
d. Pigment involved in Photoperception in flowering plants is .
Ans: a. Maximum growth is observed in log/exponential phase.
b. Apical dominance is due to auxin.
c. Auxins initiate rooting.
d. Pigment involved in Photoperception in flowering plants is
phytochrome.

Long Answer Type Questions ‘
Q1. Some varieties of wheat are known as spring wheat while others are called winter wheat. Former variety is sown, and planted in spring and is harvested by the end of the same season. However, winter varieties, if planted in spring, fail to flower or produce mature grains within a span of a flowering season. Explain, why?
Ans: There are plants for which flowering is either quantitatively or qualitatively dependent on exposure to low temperature. This phenomenon is termed vernalisation. It prevents precocious reproductive development late in the growing season, and enables the plant to have sufficient time to reach maturity. Vernalisation refers specially to the promotion of flowering by a period of low temperature. Some important food plants, wheat, barley, rye have two kinds of varieties: winter and spring varieties. The ‘spring’ variety are normally planted in the spring and come to flower and produce grain before the end of the growing season. Winter varieties, however, if planted in spring would normally fail to flower or produce mature grain within a span of a flowering season. Hence, they are planted in autumn. They germinate, and over winter come out as small seedlings, resume growth in the spring, and are harvested usually around mid-summer.

Q2. It is known that some varieties of wheat are sown in autumn but are harvested around next mid-summer.
a. ■ What could be the probable reason for this?
b. What term is used for this promotion of flowering under low temperature?
c. Which plant hormone can replace the cold treatment?
Ans: a. Winter varieties, if planted in spring would normally fail to flower or produce mature grain within a span of a flowering season. Hence, they are planted in autumn. They germinate, and over winter come out as small seedlings, resume growth in the spring, and are harvested usually around mid-summer.
b. Vernalisation
c. Gibberellin

Q3. Name a hormone which
a. is gaseous in nature
b. is responsible for phototropism
c. induces femaleness in flowers of cucumber
d. is used for killing weeds (dicots)
e. induces flowering in long day plants
Ans: a. Gaseous in nature: Ethylene (C2H4)
b. Responsible for phototropism: Auxin
c. Induces femaleness in flowers of cucumber: Ethylene (C2H4)
d. Used for killing weeds (dicots): Auxin
e. Induces flowering in long day plants: Gibberellin

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NCERT Exemplar Class 11 Biology Chapter 4 Animal Kingdom are part of NCERT Exemplar Class 11 Biology. Here we have given NCERT Exemplar Class 11 Biology Chapter 4 Animal Kingdom.

NCERT Exemplar Class 11 Biology Chapter 4 Animal Kingdom

Multiple Choice Questions

Q1. In some animal groups, the body is found divided into compartments with serial repetition of at least some organs. This characteristic feature is called
(a) Segmentation (b) Metamerism
(c) Metagenesis (d) Metamorphosis
Ans: (b) Metamerism: In some animals, the body is externally and internally divided into segments with a serial repetition of at least some organs. For example, in earthworm, the body shows this pattern called metameric segmentation and the phenomenon is known as metamerism or true segmentation. Metamerism is found in 3 animal phylums—Annelida, Arthropoda and Chordata.

Q2. Given below are the types of cells present in some animals. Which of the following cells can differentiate to perform different functions?
(a) Choanocytes (b) Interstitial cells
(c) Gastrodermal cells (d) Nematocytes
Ans: (b) Interstitial cells can differentiate to perform different functions. Choanocytes is the characteristics cells of porifera.
Gastrodermal cells and Nematocytes are found in Hydra.

Q3. Which one of the following sets of animals share a four chambered heart?
(a) Amphibian, Reptiles, Birds (b) Crocodiles, Birds, Mammals
(c) Crocodiles, Lizards, Turtles (d) Lizards, Mammals, Birds
Ans: (b) Crocodiles, Birds, Mammals are the set of animals that share a four chambered heart
• Amphibian—two chambered heart
• Reptiles and lizards—three chambered heart except crocodiles

Q4. Which of the following pairs of animals has non-glandular skin?
(a) Snake and Frog (b) Chameleon and Turtle
(c) Frog and Pigeon (d) Crocodile and Tiger
Ans: (b) Chameleon and Turtle has non-glandular skin.

Q5. Birds and mammals share one of the following characteristics as a common feature.
(a) Pigmented skin (b) Pneumatic bones
(c) Viviparity (d) Warm blooded nature
Ans: (d) Birds and mammals both are warm blooded.

Q6. Which one of the following sets of animals belong to a single taxonomic group?
(a) Cuttlefish, Jellyfish, Silverfish, Dogfish, Starfish
(b) Bat, Pigeon, Butterfly
(c) Monkey, Chimpanzee, Man
(d) Silkworm, Tapeworm, Earthworm
Ans: (c) Monkey, Chimpanzee and Man belong to a single taxonomic group mammalia (class).

Q7. Which one of the following statements is incorrect? ,
(a) Mesoglea is present in between ectoderm and endoderm in Obelia
(b) Asterias exhibits radial symmetry
(c) Fasciola is a pseudocoelomate animal
(d) Taenia is a triploblastic animal
Ans: (c) Fasciola is an acoelomate animal.

Q8. Which one of the following statements is incorrect?
(a) In cockroaches and prawns excretion of waste material occurs through Malpighian tubules.
(b) In ctenophore, locomotion is mediated by comb plates.
(c) In Fasciola flame cells take part in excretion.
(d) Earthworms are hermaphrodites and yet cross fertilization take place among them.
Ans: (a)
• In cockroaches excretion of waste material occurs through Malpighian tubules.
• In prawns excretion of waste material occurs through green glands or antennal glands.

Q9. Which one of the following is oviparous?
(a) Platypus (b) Flying fox (Bat)
(c) Elephant (d) Whale
Ans: (a) Prototherians have evolved from reptiles. Mammary gland lacks nipples or teats.Corpus callosum is absent. Prototherians are oviparous/egg laying mammals. E.g.: Omithorynchus (Duck-billed platypus) is monotreme mammal.

Q10. Which one of the following is not a poisonous snake?
(a) Cobra (b) Viper (c) Python (d) Krait
Ans: (c) Python (Ajgar) is a non-poisonous snake. Poisonous snakes: Naja (Cobra), Bangarus coeruleus (Krait), Vipera (Viper), Hydrophis (Sea snake)
Najahaunaha: King Cobra. King Cobra is only snake which builds its nest. Nest forming snake is terrestrial and poisonous.

Q11. Match the following list of animals with their level of organization.

Division of Labour		Animal
A.	Organ level	(i)	Pheretima
B.	Cellular aggregate level	(ii)	Fasciola
C.	Tissue level	(iii)	Spongilla
D.	Organ system level	(iv)	Obelia

Choose the correct match showing division of labour with animal example.

• B—(i), C—(ii), D—(iii), A—(iv)
• B—(i), D—(ii), C—(iii), A—(iv)
• D—(i), A—(ii), B—(iii), C—(iv)
• A—(i), D—(ii), C—(iii), B—(iv)

Ans. (c)

A.	Organ level	(ii)	Fasciola
B.	Cellular aggregate level	(iii)	Spongilla
C.	Tissue level	(iv)	Obelia
D.	Organ system level	(i)	Pheretima

Q12. Body cavity is the cavity present between body wall and gut wall. In some animals the body cavity is not lined by mesoderm. Such animals are called (a) Acoelomate (b) Pseudocoelomate .
(c) Coelomate (d) Haemocoelomate
Ans: (b)
(i) Acoelomate: The animals in which the body cavity is absent are
called acoelomates, e.g.: Porifers, Coelentrates, Ctenophores and Platyhelminthes. .
(ii) Pseudocoelomate: In some animals, the body cavity is not lined by mesoderm, instead,the mesoderm is present as scattered pouches in between the ectoderm and endoderm. Here body cavity is directly connected to archenteron. Such a body cavity is called pseudocoelom and the animals possessing them are called pseudocoelomates. E.g.: Aschelminthes (Ascaris). Pseudocoelom is derived from blastocoel.
(iii) Coelomate: The body cavity, which is lined by mesoderm (on both sides) is called coelom. Animals possessing coelom are called coelomates, or coelom is cavity between alimentary canal and body wall enclosed by mesoderm on both sides. E.g.: Annelids, Arthropods, Molluscs, Echinoderms, Hemichordates and Chordates.
Depending upon its origin, true coelom or eucoelom is of two types:
(a) Schizocoelous: The coelom is formed by splitting of mesoderm. E.g.: Annelida, Arthropoda and Mollusca.
Note: The cavity filled with blood is called haemocoel. It is found in Arthropods (cockroach) and Molluscs (Pila).
(b) Enterocoelom: The coelom develops as an outgrowth of the enteron or embryonic gut. E.g.: Deuterostomia (Echinodermata and Chordata). Echinodermata is an enterocoelomate invertebrate.

Q13. Match the column A with column B and choose the correct option.

Column A		Column B
A.	Porifera	(i)	Canal system
B.	Aschelminthes	(ii)	Water-vascular system
C.	Annelida	(iii)	Muscular Pharynx
D.	Arthropoda	(iv)	Jointed appendages
E.	Echinodermata	(v)	Metamers

• A—(ii), B—(iii), C—(v), D—(iv), E—(i)
• A—(ii), B—(v), C—(iii), D—(iv), E—(i)
• A—(i), B—(iii), C—(v), D—(iv), E—(ii)
• A—(i), B—(v), C—(iii), D—(iv), E—(ii)

Ans: (c)

A.	Porifera	(i)	Canal system                             .
B.	Aschelminthes	(iii)	Muscular Pharynx
C.	Annelida	(v)	Metamers
D.	Arthropoda	(iv)	Jointed appendages
E.	Echinodermata	(ii)	Water-vascular system

Very Short Answer Type Questions

Q1. Identify the phylum in which adults exhibit radial symmetry and larva exhibit bilateral symmetry.
Ans: In phylum echinodermata, adults show radial symmetry whereas larva show bilateral symmetry.

Q2. What is the importance of pneumatic’ bOnes and air sacs in Aves?
Ans: Pneumatic bones in Aves keep the body light and thus help in flight. Air sacs help in respiration and buoyancy.

Q3. What is metagenesis? Mention an example which exhibits this phenomenon.
Ans: Alteration of generation is known as metagenesis. Obelia exhibits this phenomenon.

Q4. What is the role of feathers?
Ans: Feathers keep the body light and thus help in flight.

Q5. Which group of chordates possess sucking and circular mouth without jaws?
Ans: Cyclostomes have a sucking and circular mouth without jaws.

Q6. Give one example each for an animal possessing placoid scales and that with cycloid scales.
Ans: Placoid scales—Pristis, Trygon, Torpedo. Cycloid scales—Labeo Catla, Clarias

Q7.Mention two modifications in reptiles required for terrestrial mode of life.
Ans: 1. Their body is covered by dry and comified skin, epidermal scales or scutes.
2. Cleidoic eggs

Q8. Mention one example each for animals with chitinous exoskeleton and those covered by a calcareous shell.
Ans: The body of arthropods (like cockroach) is covered by chitinous exoskeleton and molluscan (like Pila) body is covered by a calcareous shell.

Q9. What is the role of radula in molluscs?
Ans: Radula is a file-like rasping organ help in feeding.

Q10. Name the animal, which exhibits the phenomenon of bioluminescence. Mention the phylum to which it belongs.
Ans: Bioluminescence (the property of a living organism to emit light) is well- marked in ctenophores.
Examples: Pleurobrachia, Ctenoplana, Beroe, Coeloplana and Velamen.

Q11. Write one example each of the following in the space provided.
a. Cold blooded animal
b. Warm blooded animal
c. Animal possessing dry and comified skin
d. Dioecious animal
Ans: Examples:
a. Cold blooded animal: amphibians (Frog)
b. Warm blooded animal: mammals (Human)
c. Animal possessing dry and comified skin: reptiles (Lizard)
d. Dioecious animal: aschelminthes (Ascaris)

Q12. Differentiate between a diploblastic and a triploblastic animal.
Ans: (i) Diploblastic: Animals in which the cells are arranged in two embryonic layers, an external ectoderm and an internal endoderm, are called diploblastic animals, e.g. Porifers, coelenterates and ctenophores.
(ii) Triploblastic: Those animals in which the developing embryo has a third germinal layer, mesoderm, in between the ectoderm and endoderm, are called triploblastic animals. E.g.: Platyhelminthes to Chordates.

Q13. Give an example for the following:
a. Roundworm
b. Fish possessing poison sting
c. A limbless reptile/amphibian .
d. An oviparous mammal
Ans: Examples:
a. Roundworm: Ascaris
b. Fish possessing poison sting: Trygon
c. A limbless reptile/ amphibian: Snakelfcthyophis
d. An oviparous mammal: Ornithorynchus (Duck-billed platypus)

Q14. Provide appropriate technical term in the space provided.
a. Blood-filled cavity in arthropods _________
b. Free-floating form of cnidaria _________
c. Stinging organ of jelly fishes _________
d. Lateral appendages in aquatic annelids _________
Ans: Provide appropriate technical term in the space provided.
a. Blood-filled cavity in arthropods: Haemocoel
b. Free-floating form of cnidaria: Medusa
c. Stinging organ of jelly fishes: Nematocyst
d. Lateral appendages in aquatic annelids: Parapodia
Q15. Match the following:

Animals		Locomotory organ
a.	Octopus              –	(i)	Limbs
b.	Crocodile	(ii)	Comb plates
c.	Catla	(iii)	Tentacles
d.	Ctenoplana	(iv)	Fins

Ans:

Animals		Locomotory organ
a.’	Octopus	(iii)	Tentacles
b.	Crocodile	(i)	Limbs
c.	Catla	(iv)	Fins
d.	Ctenoplana	(ii)	Comb plates

Short Answer Type Questions
Q1. Differentiate between:
a. Open circulatory system and closed circulatory system
b. Oviparous and viviparous characteristic
c. Direct development and Indirect development
Ans: a. Open Circulatory System and Closed Circulatory System:

Open Circulatory System	Closed Circulatory System
The blood is pumped out of the heart into sinuses and the cells and tissues are directly bathed in it.	The blood is circulated within a network of vessels.

b. Oviparous and Viviparous:

Oviparous	Viviparous
Animals which lay eggs are called oviparous.	Animals which give birth to their young ones are called viviparous.

C. Direct Development and Indirect Development:

Direct Development	Indirect Development
Animals which do not have a larval stage in their development are said to exhibit direct development.	Animals which have a larval stage, which do not resemble the adult in their development are said to exhibit indirect development

Q2. Sort out the animals on the basis of their symmetry (radial or bilateral) coelenterates, ctenophores, annelids, arthropods, and echinoderms.
Ans: Coelenterates: Radial Ctenophores: Radial Annelids: Bilateral Arthropods: Bilateral Echinoderms: Radial

Q3. There has been an increase in the number of chambers in heart during evolution of vertebrates. Give the names of the class of vertebrates having two, three or four-chambered heart.
Ans: Two chambered heart: chondrichthyes and osteichthyes
Three chambered heart: Amphibia and Reptilia
Four chambered heart: Aves and mammalia

Q4. Fill up the blank spaces appropriately.

Phylum/ Class	Excretory Organ	Circulatory Organ	Respiratory Organ
Arthropoda	A	B .	Lungs/Gills/ Tracheal System
C	Nephridia	Closed	Skin/Parapodia
D	Metanephridia	Open	E
Amphibia	F	Closed	Lung

Ans.
A = Malpighian Tubule/ coxal glands/
antemary glands/ green glands
B = Open
C = Annelida
D = Mollusca
E = Feather like gills
F = Kidney

Q5. Match the following:

a.	Amphibia	(i)	Air bladder
b.	Mammals	(ii)	Cartilagenous notochord
c.	Chondrichthyes	(hi)	Mammary glands
d.	Osteichthyes	(iv)	Pneumatic bones
e.	Cyclostomata	(v)	Dual habitat
f.	Aves	(vi)	Sucking and circular mouth without jaws

 Ans:

a.	Amphibia	(v)	Dual habitat
b.	Mammals	(iii)	Mammary glands
c.	Chondrichthyes	(ii)	Cartilagenous notochord
d.	Osteichthyes	(i)	Air bladder
e.	Cyclostomata	(vi)	Sucking and circular mouth without jaws
f.	Aves	(iv)	Pneumatic bones

Q6. Endoparasites are found inside the host body. Mention the special structure, possessed by these and which enables them to survive in those conditions.
Ans: The life cycles of endoparasities are more complex because of their extreme specialisation. Their morphological and anatomical features are greatly simplified while emphasizing their reproductive potential.
In accordance with their life style parasites evolve special adaptations such as:
1. Loss of unnecessary sense organs.
2. Loss of digestive system.
3. High reproductive capacity.
4. Presence of adhesive organs or suckers to cling on to the host.

Q7. Match the following and write correct choice in space provided.

Animal		Characteristics
a.	Pila	(i)	Jointed appendages
b.	Cockroach	(ii)	Perching
c.	Asterias	. (iii)	Water vascular system
d.	Torpedo	(iv)	Electric organ
e.	Parrot	(v)	Presence of shell
f.	Dog fish	(vi)	Placoid scales

Ans.

Animal		. Characteristics
a.	Pila	(v)	Presence of shell
b.	Cockroach	(i)	Jointed appendages
c.	Asterias	(iii)	Water vascular system
d.	Torpedo	(iv)	Electric organ
e.	Parrot	(ii)	Perching
f.	Dog fish	(vi)	Placoid scales

Q8. Differentiate between:
a. Open and closed circulatory system .
b. Oviparity and viviparity
c. Direct and indirect development
d. Aceolomate and pseudocoelomate
e. Notochord and nerve cord
f. Polyp and medusa
Ans: a. The circulatory system may be of two types:
1. Open type in which the blood is pumped out of the heart and the cells and tissues are directly bathed in it. E.g.: Arthropoda, Mollusca and Hemichordata.
2. Closed type in which the blood is circulated through a series of vessels of varying diameters (arteries, veins and capillaries). E.g.: Annelida and Chordata.
b. Oviparous animals give birth to an egg while viviparous animals are those that give birth to the live young ones.
c. Direct development: It is a type of development in which an embryo develops into a mature individual without involving a larval stage. Indirect development: It is a type of development that involves a sexually-immature larval stage.
d. Acoelomate: The animals in which the body cavity is absent are •called acoelomates, e.g.: Porifers, Coelentrates, Ctenophores and Platyhelminthes. ,
Pseudocoelomate: In some animals, the body cavity is not lined by mesoderm, instead, the mesoderm is present as scattered pouches in between the ectodenp and endoderm. E.g., aschelminthes
e. Notochord is a mesodermally derived rod-like-structure formed on the
dorsal side during embryonic development in some animals and it is the part of skeletal system. .
Nerve cord is the part of nervous system.
f. The polyp is a sessile and cylindrical fonn like Hydra, Adamsia, etc., whereas, the medusa is umbrella-shaped and free-swimming like Aurelia or jelly fish.

Q9. Give the characteristic features of the following citing one example of each:
a. Chondrichthyes and osteichthyes
b. Urochordata and cephalochordata
Ans: a. Chondrichthyes-. They are marine animals with streamlined body and have cartilaginous endoskeleton. Mouth is located ventrally. Notochord is persistent throughout life. Gill slits are separate and without operculum (gill cover). The skin is tough, containing minute placoid scales. Teeth are modified placoid scales which are backwardly directed. Their jaws are very powerful. These animals are predaceous. Due to the absence of air bladder, they have to swim constantly to avoid sinking. Scoliodon (Dog fish), Pristis (Saw fish), Carcharodon (Great white shark), Trygon (Sting ray).
Osteichthyes: It includes both marine and fresh water fishes with bony endoskeleton. Their body is streamlined. Mouth is mostly terminal. They have four pairs of gills which are covered by an operculum on each side. Skin is covered with cycloid/ctenoid scales. Air bladder is present which regulates buoyancy.
Examples: Marine—Exocoetus (Flying fish), Hippocampus (Sea horse); Freshwater—Labeo (Rohu), Catla (Katla), Clarias (Magur); Aquarium—Betta (Fighting fish), Pterophyllum (Angel fish),
b. Subphyla Urochordata and Cephalochordata are often referred to as protochordates and are exclusively marine. In Urochordata, notochord is present only in larval tail, while in Cephalochordata, it extends from head to tail region and is persistent throughout their life.
Examples: Urochordata—Ascidia, Salpa, Doliolum; Cephalochordata— Branchiostoma (Amphioxus or Lancelet).

Q10. Mention two similarities between:
Aves and mammals
A frog and crocodile ‘
A turtle and pila
Ans: Similarities between aves and mammalian

(i) Both are homeothermic animals (warm blooded)
(ii) Both have four chambered heart
b. Similarities between frog and crocodile
(i) Both are poikilothermic animals (cold blooded)
(ii) Both are oviparous animals
c. Similarities between turtle and Pila
(i) Both are poikilothermic animals (cold blooded)
(ii) Both are oviparous animals

Q11. Name
a. A limbless animal ‘
b. A cold blooded animal
c. A warm blooded animal
d. An animal possessing dry and comified skin
e. An animal having canal system and spicules
f. An animal with cnidoblasts

Ans: a. A limbless animal: Icthyophis
b. A cold blooded animal: Trygon (sting ray)
c. A warm blooded animal: Macaca (monkey)
d. An animal possessing dry and comifiedskin: Naja (Cobra)
e. An animal having canal system and spicules: Euspongia (bath sponge)
f. An animal with cnidoblasts: Hydra.
Q12. Give an example for each of the following:
a. A viviparous animal
b. A fish possessing a poison sting
c. A fish possessing an electric organ
d. An organ, which regulates buoyancy
e. Animal, which exhibits alternation of generation
f. Oviparous animal with mammary gland.
Ans: a. A viviparous animal: Panthera leo (lion)
b. A fish possessing a poison sting: Trygon (sting ray)
c. A fish possessing an electric organ: Torpedo
d. An organ, which regulates buoyancy: Air bladder
e. Animal, which exhibits alternation of generation: Obelia (Sea-fur)
f. Oviparous animal with mammary gland: Echidna (Platypus).

Q13. Excretory organs of different animals are given below. Choose correctly and write in the space provided.

Animal		Excetory Organ/Unit
a.	Balanoglossus	(i)	Metanephridia
b.	Leech	(ii)	Nephridia
c.	Locust	(iii)	Flame cells
d.	Liver fluke	(iv)	Absent
e.	Sea urchin	(v)	Malpighian tubule
f.	Pila	(vi)	Proboscis gland

Ans.

a.	Balanoglossus	(vi)	Proboscis gland
b.	Leech	(ii)	Nephridia
c.	Locust	(v)	Malpighian tubule
d.	Liver fluke	(iii)	Flame cells
e.	Sea urchin	(iv)	Absent
f.	Pila	(0	Metanephridia

Long Answer Type Questions
Q1. Give three major differences between chordates and non-chordates and draw a schematic sketch of a chordate showing those features.
Ans: Animals belonging to phylum Chordata are fundamentally characterised by the presence of a notochord, a dorsal hollow nerve cord and paired
pharyngeal gill slits. These are bilaterally symmetrical, triploblastic, coelomate with organ-system level of organisation. They possess a post anal tail and a closed circulatory system.

S. No.	Chordates	Non-chordates
1.	Notochord present.	Notochord absent.
2.	Central nervous system is dorsal, hollow and single.	Central nervous system is ventral, solid and double.
3.	Pharynx perforated by gill slits.	Gill slits are absent.
4.	Heart is ventral.	Heart is dorsal (if present).
5.	A post-anal part (tail) is present.	Post-anal tail is absent.

Q2. What is the relationship between germinal layers and the formation of body cavity in case of coelomate, acoelomates and pseudocoetomates?
Ans: Presence or absence of a cavity between the body wall and the gut wall is very important in classification. The body cavity, which is lined by mesoderm is called coelom. Animals possessing coelom are called coelomates, e.g., annelids, molluscs, arthropods, echinoderms, hemichordates and chordates. In some animals, the body cavity is not lined by mesoderm, instead, the mesoderm is present as scattered pouches in between the ectoderm and endoderm. Such a body cavity is called pseudocoelom and the animals possessing them are called pseudocoelomates, e.g., aschelminthes. The animals in which the body cavity is absent are called acoelomates, e.g., platyhelminthes

Q3. Comment upon the habitats and external features of animals belonging to class, amphibia and reptilia.
Ans: Class—Amphibia As the name indicates (Gr., Amphi: dual, bios, life), amphibians can live in aquatic as well as terrestrial habitats. Most of them have two pairs of limbs. Body is divisible into head and trunk. Tail may be present in some. The amphibian skin is moist (without scales). The eyes have eyelids. A tympanum represents the ear.
Examples: Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), Ichthyophis (Limbless amphibia).
Class-Reptilia :The class name refers to their creeping or crawling mode of locomotion (Latin, repere or reptum, to creep or crawl). They are mostly terrestrial animals and their body is covered by dry and comified skin, epidermal scales or scutes. They do not have external ear openings. Tympanum represents ear. Limbs, when present, are two pairs.
Examples: Chelone (Turtle), Testudo (Tortoise), Chameleon (Tree lizard), Calotes (Garden lizard), Crocodilus (Crocodile), Alligator (Alligator). Hemidactylus (Wall lizard), Poisonous snakes – Naja (Cobra), Bangarus (Krait), Vipera (Viper).

Q4. Mammals are most adapted among the vertebrates. Elaborate.
Ans: Mammals are most adapted among the vertebrates as they are found in a variety of habitats – polar ice caps, deserts, mountains, forests, grasslands and*dark caves. Some of them have adapted to fly or live in water.
They have two pairs of limbs, adapted for walking, running, climbing,. burrowing, swimming or flying. The skin of mammals is unique in possessing hair. External ears or pinnae are present. Different types of teeth are present in the jaw. Heart is four chambered.
They are ‘homoiot’hermous. Respiration is by lungs. Sexes are separate and fertilisation is internal. They are viviparous with few exceotions and development is direct.

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NCERT Exemplar Class 11 Biology Chapter 20 Locomotion and Movement are part of NCERT Exemplar Class 11 Biology. Here we have given NCERT Exemplar Class 11 Biology Chapter 20 Locomotion and Movement.

NCERT Exemplar Class 11 Biology Chapter 20 Locomotion and Movement

Multiple Choice Questions

Q1. Match the following and mark the correct option.

Column I		Column II
A.	Fast muscle fibres	(i)	Myoglobin
B.	Slow muscle fibres	(ii)	Lactic acid
C.	Actin filament	(iii)	Contractile unit
D.	Sarcomere	(iv)	I-band

Options:
(a) A—(i), B—(ii), C—(iv), D—(iii)
(b) A—(ii), B—(i), C—(iii), D—(iv)
(c) A—(ii), B—(i), C—(iv), D—(iii)
(d) A—(iii), B—(ii), C—(iv), D—(i)

Ans. (c)

A.	Fast muscle fibres	(ii)	Lactic acid
B.	Slow muscle fibres	(i)	Myoglobin
C.	Actin filament	(iv)	I-band
D.	Sarcomere	(iii)	Contractile unit

Q2. Ribs are attached to
(a) Scapula (b) Sternum (c) Clavicle (d) Ilium
Ans: (b) Ribs are attached to sternum.

Q3. What is the type of movable joint present between the atlas and axis?
(a) Pivot (b) Saddle (c) Hinge (d) Gliding
Ans: (a) Pivot joint: Between atlas and axis called atlanto-axial joint.

Q4. ATPase of the muscle is located in
(a) Actinin (b) Troponin (c) Myosin (d) Actin
Ans: (c) ATPase of the muscle is located in head of myosin.

Q5. Intervertebral disc is found in the vertebral column of
(a) Birds (b) Reptiles (c) Mammals (d) Amphibians
Ans: (c) Intervertebral disc is found in the vertebral column of mammals.

Q6. Which one of the following is showing the correct sequential order of vertebrae in the vertebral column of human beings? ‘
(a) Cervical — lumbar — thoracic — sacral — coccygeal
(b) Cervical — thoracic — sacral — lumbar — coccygeal
(c) Cervical — sacral — thoracic — lumbar — coccygeal
(d) Cervical — thoracic — lumbar — sacral — coccygeal
Ans: (d) Cervical—thoracic—lumbar—sacral—coccygeal is the correct sequential order of vertebrae in the vertebral column of human beings.

Q7. Which one of the following options is incorrect?
(a) Hinge joint—between humerus and pectoral girdle
(b) Pivot joint—between atlas, axis and occipital condyle
(c) Gliding joint—between the carpals
(d) Saddle joint—between carpel and metacarpals of thumb
Ans: (a) Hinge joint—Knee joint and elbow joint

Q8. Knee joint and elbow joints are examples of
(a) Saddle joint (b) Ball and socket joint
(c) Pivot joint (d) Hinge joint
Ans: (d) Knee joint and elbow joints are examples of hinge joint.

Q9. Macrophages and leucocytes exhibit
(a) Ciliary movement
(b) Flagellar movement
(c) Amoeboid movement
(d) Gliding movement
Ans: (c) Amoeboid movements: Some specialised cells in our body like macrophages and leucocytes in blood exhibit amoeboid movement. It is effected by pseudopodia formed by the streaming of protoplasm (as in Amoeba). Cytoskeletal elements like microfilaments are also involved in amoeboid movement.

Q10. Which one of the following is not a disorder of bone?
(a) Arthritis
(b) Osteoporosis
(c) Rickets
(d) Atherosclerosis
Ans: (d) Atherosclerosis is a disorder of circulatory system.

Q11. Which one of the following statement is incorrect?
(a) Heart muscles are striated and involuntary
(b) The muscles of hands and legs are striated and voluntary
(c) The muscles located in the inner walls of alimentary canal are striated and involuntary
(d) Muscles located in the reproductive tracts are unstriated and involuntary
Ans:(c) The muscles located in the inner walls of alimentary canal are non- striated and involuntary.

Q12. Which one of the following statements is-true?
(a) Head of humerus bone articulates with acetabulum of pectoral girdle
(b) Head of humerus bone articulates with glenoid cavity of pectoral girdle
(c) Head of humerus bone articulates with a cavity called acetabulum of pelvic girdle
(d) Head of humerus bone articulates with a glenoid cavity of pelvic girdle
Ans: (b) Below the acromion is a depression called the glenoid cavity which articulates with the head of the humerus to form the shoulder joint.

Q13. Muscles with characteristic striations and involuntary are
(a) Muscles in the wall of alimentary canal
(b) Muscles of the heart
(c) Muscles assisting locomotion
(d) Muscles of the eyelids
Ans: (b) Muscles with characteristic striations and involuntary are muscles of the heart (Cardiac muscles).

Q14. Match the followings and mark the correct option.

Column I		.                  Column II
A.	Sternum	(i)	Synovial fluid
B.	Glenoid cavity	(ii)	Vertebrae
C.	Freely movable joint	(iii)	Pectoral girdle
D.	Cartilaginous joint	(iv)	Flat bones

Options:

(a) A—(ii), B—(i), C—{iii), D—(iv)
(b) A—(iv), B—(iii), C—(i), D—(ii)
(c) A—(ii), B—(i), C—(iv), D—(iii)
(d) A—(iii), B—(i), C—(ii), D—(iv)

Ans. (b)

A.	Sternum	(iv)	Flat bones
B.	Glenoid cavity	(iii)	Synovial fluid
C.	Freely movable joint	(i)	Pectoral girdle
D.	Cartilaginous joint	(ii)	Yertebrae

 

Very Short Answer Type Questions
Q1. Name the cells/tissues in human body which
a. exhibit amoeboid movement
b. exhibit ciliary movement
Ans: a. Macrophages and leucocytes
b. Trachea, fallopian tube and bronchiole

Q2. Locomotion requires a perfect‘coordinated activity of muscular _____________, _______ , systems.
Ans: Skeletal and Neural

Q3. Sarcolemma, sarcoplasm and sarcoplasmic reticulum refer to a particular type of cell in our body. Which is this cell and to what parts of that cell do these names refer to?
Ans: Each muscle fibre or muscle cell is lined by the plasma membrane called sarcolemma enclosing the sarcoplasm. A muscle fibre is a syncytium as the sarcoplasm (cytoplasm) contains many nuclei. The endoplasmic reticulum, i. e., sarcoplasmic reticulum of the muscle fibres is the store house of calcium ions.

Q4 .Label the different components of actin filament in the diagram given

Q5. The. three tiny bones present in middle ear are called ear ossicles. Write them in correct sequence beginning from eardrum.
Ans: Malleus, incus and stapes.

Q6. What is the difference between the matrix of bones and cartilage?
Ans: Bones have a hard and non-pliable ground substance rich in calcium salts and collagen fibres which give bone its strength.
The inter-cellular material of cartilage is solid and pliable which resists compression. Cell of cartilage are called chondrocytes which are enclosed in a small cavities (lacunae) within the matrix secreted by them.

Q7. Which tissue is afflicted by Myasthenia gravis? What is the underlying cause?
Ans: Myasthenia gravis: Auto-immune disorder affecting neuromuscular junction leading to fatigue, weakening and paralysis of skeletal muscle.

Q8. How do our bone joints function without grinding noise and pain?
Ans: Our bone joints function without grinding noise and pain due to the presence of synovial fluid between bones.

Q9. Give the location of a ball and socket joint in a human body.
Ans: Ball and socket joint: Between humerus and pectoral girdle (shoulder joint). Between femur and acetabulum of pelvic girdle (hip joint). Total 4 ball and socket joints present in human body -2 shoulder joint and 2 hip joint.

Q10. Our forearm is made of three different bones. Comment.
Ans: The bones of the forearm are humerus, radius and ulna.

Q1. With respect to rib cage, explain the following:
a. Bicephalic ribs
b. True ribs
c. Floating ribs
Ans: a. Bicephalic ribs: Each rib is a thin flat bone connected dorsally to the vertebral column and ventrally to the sternum. It has two articulation surfaces on its dorsal end and is hence called bicephalic.
b. True ribs: First seven pairs of ribs are called true ribs. Dorsally, they are attached to the thoracic vertebrae and ventrally connected to the sternum with the help of hyaline cartilage.
c. Floating ribs: Last 2 pairs (11th and 12th) of ribs are not connected ventrally and are therefore, called floating ribs.

Q2. In old age, people often suffer from stiff and inflamed joints. What is this condition called? What are the possible reasons for these symptoms?
Ans: In old age, people suffer from stiff and inflamed joints, it is due to rheumatoid arthritis (autoimmune disorder)
Causes: (i) Inflammation of synovial membrane
(ii) Genetic factors (50% cases) .
(iii) Smoking
(iv) Vitamin-D deficiency

Q3. Exchange of calcium between bone and extracellular fluid takes place under the influence of certain hormones.

1. What will happen if more of Ca ⁺ is in extracellular fluid?
2. What will happen if very less amount of Ca⁺⁺ is in the extracellular fluid?

Ans: a. If more of Ca⁺⁺ is in extracellular fluid then it will be accumulated on the bones under the influence of thyrocalcitonin (TCT).
b. If very less amount of Ca⁺⁺ is in the extracellular fluid then parathyroid hormone (PTFI) acts on bones and stimulates the process of bone resorption (dissolution/demineralisation). PTH also stimulates reabsorption of Ca²⁺ by the renal tubules and increases Ca²⁺ absorption from the digested food.

Q4. Name at least two hormones which result in fluctuation of Ca⁺⁺

Ans: Thyrocalcitonin (TCT) and Parathyroid Hormone (PTH).

Q5. Rahul exercises regularly by visiting a gymnasium. Of late he is gaining weight. What could be the reason? Choose the correct answer and elaborate.
a. Rahul has gained weight due to accumulation of fats in body.
b. Rahul has gained weight due to increased muscle and less of fat.
c. Rahul has gained weight because his muscle shape has improved.
d. Rahul has gained weight bdcause he is accumulating water in the body.
Ans: Rahul has gained weight due to increased muscle and less of fat.

Q6. Radha was running on a treadmill at a great speed for 15 minutes continuously. She stopped the treadmill and abruptly came out. For the next few minutes, she was breathing heavily/fast. Answer the following questions:
a. What happened to her muscles when she did strenuously exercise?
b. How did her breathing rate change?
Ans: a. Repeated activation of the muscles can lead to the accumulation of lactic acid due to anaerobic breakdown of glycogen in them, causing fatigue.
b. During strenuous exercise demand of oxygen also increases so breathing rate has been changed.

Q7. Write a few lines about Gout.
Ans: When metabolic waste-uric acid crystals are accumulated in bones, then it results into inflammation of bone and joints thereby causing pain. This disorder of skeletal system is called gout.

Q8. What is the source of energy for muscle contraction?
Ans: ATP (Adenosine Triphosphate)

Q9. What are the points for articulation of pelvic and pectoral girdles?
Ans: The components of pelvic girdle are ilium, ischium and pubis. It articulates with, femur through acetabulum. The components of pectoral girdle are scapula and clavicle. It is the glenoid cavity of pectoral girdle in which head . of humerus articulates.

Long Answer Type Questions

Q1. Calcium ion concentration in blood affects muscle contraction. Does it lead to tetany in certain cases? How will you correlate fluctuation in blood calcium with tetany?
Ans: Muscle contraction is initiated by a signal sent by the central nervous system (CNS) via a motor neuron. A neural signal reaching this junction releases a neurotransmitter (acetyl choline) which generates an action potential in the sarcolemma. This spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm. Increase in Ca⁺⁺ level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby remove the masking of active sites for myosin. Utilising the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross-bridge. This pulls the attached actin filaments towards the centre of ‘A’ band. The ‘Z’ line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e., contraction. The process continues till the Ca⁺⁺ ions are pumped back to the sarcoplasmic cisternae resulting in the masking of actin filaments.

Tetany: Rapid spasms (wild contractions) in muscle due to low Ca in body fluid.

Q2. An elderly woman slipped in th£ bathroom and had severe pain in her lower back. After X-ray examination doctors told her it is due to a slipped disc. What does that mean? How does it affect our health?
Ans: Displacement of intervertebral disc from’ their normal position is called slipped disc.
Effects:
i. Neck or lower back pain
ii. Muscular weakness
iii. Paralysis
iv. Sciatica

Q3. Explain sliding filament theory of muscle contraction with neat sketches.
Ans. Mechanism of muscle contraction: Mechanism of muscle contraction is best explained by the sliding filament theory which states that contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments. Muscle contraction is initiated by a signal sent by the Central Nervous System (CNS) via a motor neuron. A motor neuron alongwith the muscle fibres connected to it constitute a motor unit. The junction between a motor neuron and the sarcolemma of the muscle fibre is called the neuromuscular junction or motor-end plate. A neural signal reaching this junction releases a neurotransmitter (acetyl choline) which generates an action potential in the sarcolemma. This spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm. Increase in Ca⁺⁺ level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby remove the masking of active sites for myosin.Utilising the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross-bridge. This pulls the attached

actin filaments towards the centre of ‘A’ band. The ‘Z’ line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e., contraction. It is clear from the above steps, that during shortening of the muscle, i.e., contraction, the ‘I’ bands get reduced, whereas the ‘A’ bands retain the length. The myosin, releasing the ADP and P, goes back to its relaxed state. A new ATP binds and the cross-bridge is broken. The ATP is again hydrolysed by the myosin head and the cycle of cross-bridge formation and breakage is repeated causing further sliding. The process continues till the Ca⁺⁺ ions are pumped back to the sarcoplasmic cistemae resulting in the masking of actin filaments. This causes the return of ‘Z’ lines back to their original position, i.e., relaxation.

Q5. Discuss the role of Ca²⁺ ions in muscle contraction. Draw neat sketches to illustrate your answer.
Ans: Muscle contraction is initiated by a neural signal, which after reaching neuromuscular junction or motor end plate releases a neurotransmitter, as a result an action potential in the sarcolemma is generated. Action potential spreads through muscle fibre and causes the release of calcium ions into the sarcoplasm. Increase in Ca²⁺ level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby removes the masking of active sites for myosin. Utilising the energy from ATP hydrolysis, the myosin head now binds to the exposed active site on actin to form a cross-bridge. This pulls the attached actin filaments towards the centre of ‘A’ band. The ‘Z’ line attached to these actins are also pulled inwards thereby causing shortening of the sarcomere, i.e., contraction.

A new ATP binds to myosin head and the cross-bridge is broken. The ATP is again hydrolysed by the myosin head and the cycle of cross-bridge formation and breakage is repeated causing further sliding. The process continues till the Ca⁺⁺ ions are pumped back to the sarcoplasmic cistemae resulting in masking of actin filaments and breakage of all cross-bridges. This cause the return of ‘Z’ lines along with filaments back to their original position, i.e., relaxation.

Q6. Differentiate between pectoral and pelvic girdle.
Ans: Pectoral and pelvic girdle help in the articulation of upper and lower limbs respectively. Each girdle is made of two equal halves. Each half of a pectoral girdle consists of clavicle and scapula. Scapula is a large triangular flat bone. There is glenoid cavity at the joint of scapula, clavicle and acromian process, which articulates with the head of humerus to form the shoulder joint. Each half of pelvic girdle is formed by three bones—ilium, ischium and pubis. At the point of their fusion; there is a cavity called acetabulum to which the head of femur articulates.

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We hope the NCERT Exemplar Class 11 Biology Chapter 20 Locomotion and Movement help you. If you have any query regarding NCERT Exemplar Class 11 Biology Chapter 20 Locomotion and Movement, drop a comment below and we will get back to you at the earliest.

NCERT Exemplar Class 11 Biology Chapter 17 Breathing and Exchange of Gases are part of NCERT Exemplar Class 11 Biology. Here we have given NCERT Exemplar Class 11 Biology Chapter 17 Breathing and Exchange of Gases.

NCERT Exemplar Class 11 Biology Chapter 17 Breathing and Exchange of Gases

Multiple Choice Questions

Q1. Respiration in insects is called direct because ‘

(a) The cells exchange 0₂/C0₂ directly with the air in the tubes
(b) The tissues exchange 0₂/C0₂ directly with coelomic fluid
(c) The tissues exchange 0₂/C0₂ directly with the air outside through body surface
(d) “ Tracheal tubes exchange 0₂/C0₂ directly with the haemocoel which then exchange with tissues
Ans: (d) Respiration in insects is called direct because tracheal tubes exchange 0₂/C0₂ directly with the haemocoel which then exchange with tissues.

Q2.A person suffers punctures in his chest cavity in an accident, without any damage to the lungs, its effect could be
(a) Reduced breathing rate
(b) Rapid increase in breathing rate
(c) No change in respiration                 
(d) Cessation of breathing
Ans: (d)A person suffers punctures in his chest cavity in an accident, without any damage to the lungs, its effect could be cessation of breathing.

Q3. It is known that exposure to carbon monoxide is harmful to animals because
(a) It reduces C0₂ transport
(b) It reduces 0₂ transport
(c) It increases C0₂ transport               
(d) It increases 0₂ transport
Ans: (b) CO is a poisonous gas which binds with Hb more rapidly than 0₂ to form carboxyhaemoglobin. CO makes .the most stable combination with the Hb of blood. CO has 200-250 times more affinity for Hb as compared to 0₂. When the inhaled air contains CO gas then a person suffers from suffocation because product cannot dissociate so decreases free oxygen. So it reduces 0₂ transport.

Q4. Mark the true statement among the following with reference to normal breathing.
(a) Inspiration is a passive process whereas expiration is active
(b) Inspiration is an active process whereas expiration is passive
(c) Inspiration and expiration are active processes
(d) Inspiration and expiration are passive processes
Ans: (b) Inspiration is an active process whereas expiration is passive.

Q5. Mark the incorrect statement in context to 0₂ binding to Hb.
(a) Lower pH
(b) Lower temperature
(c) Lower pC0₂                                       
(d) Higher p0₂
Ans: (a) 0₂ binding to Hb occurs in the following conditions: lower temperature, lower pC0₂ and higher p0₂.

Q6.Mark the correct pair of muscles involved in the normal breathing in humans
(a)External and internal intercostal muscles
(b)Diaphragm and abdominal muscles
(c)Diaphragm and external intercostal muscles
(d) Diaphragm and intercostal muscles
Ans: (d) Diaphragm and intercostal muscles involved in the normal breathing in humans. ,

Q7. Incidence of Emphysema—a respiratory disorder is high in cigarette smokers. In such cases
(a) The bronchioles are found damaged
(b) The alveolar walls are found damaged
(c) The plasma membrane is found damaged
(d) The respiratory muscles are found damaged
Ans: (b) Emphysema is a chronic disorderin which alveolar walls are damaged due to which respiratory surface is decreased.

Q8. Respiratory process is regulated by certain specialised centres in the brain. One of the following listed centres can reduce the inspiratory duration upon stimulation
(a) Medullary inspiratory centre (b) Pneumotaxic centre
(c) Apneustic centre (d) Chemosensitive centre
Ans: (b) Pneumotaxic centre can reduce the inspiratory duration upon stimulation.

Q9. C0₂ dissociates from carbaminohaemoglobin when
(a)    pC0₂ is high and p0₂ is low           
(b)     p0₂ is high and pC0₂ is low
(c)     pC0₂ and p0₂ are equal                 
(d)     None of the above
Ans: (b) C0₂ dissociates from carbaminohaemoglobin when p0₂ is high and pC0₂ is low,

Q10. In breathing movements, air volume can be estimated by .
(a)    Stethoscope                                     
(b)     Hygrometer
(c)    Sphygmomanometer                    
(d)     Spirometer
Ans: (d) In breathing movements, air volume can be estimated by spirometer.

Q11.From the following relationships between respiratory volumes and capacities, mark the correct option.

i. Inspiratory Capacity (IC) = Tidal Volume + Inspiratory Residual Volume (IRV) ,
iii. Residual Volume (RV) = TLC – VC

Q12. The oxygen-haemoglobin dissociation curve will show a right shift in case of
(a) High pC0₂                                          
(b) Highp0₂
(c) Low pC0₂                                           
(d) Less H⁺ concentration
Ans: (a) Curve shift is right in following conditions: (1) Decrease in p0₂, (2) Increase in pC0₂ (Bohr effect), (3) Increase in body temperature, (4) Increase in H⁺ ion concentration, (5) Decrease in pH, (6) Increase in 2, 3 diphosphoglycerate.

Q13. Match the following and mark the correct options

Animal		Respiratory organ
A.	Earthworm	(0	Moist cuticle
B.	Aquatic Arthropods	(ii)	Gills
C.	Fishes	(iii)	Lungs
D.	Birds/Reptiles	(iv)	Trachea

(a) A—(ii), B—(i), C—(iv), D—(iii)
(b) A—(i), B—(iv), C—(ii), D—(iii)
(c) A—(i), B—(iii), C—(ii), D—(iv)
(d) A—(i), B—(iv), C—(ii), D—(iii)

Ans: (d)

Animal		Respiratory organ
A.	Earthworm	0)	Moist cuticle
B.	Aquatic Arthropods	(iv)	Trachea
C.	Fishes	(ii)	Gills
D.	Birds/Reptiles	(iii)	Lungs

 

Very Short Answer Type Questions
Q1. Define the following terms
a. Tidal volume
b. Residual volume
c. Asthma
Ans: a. Tidal volume: Volume of air inspired or expired during a normal respiration. It is approx. 500 mL, i.e., a healthy man can inspire or expire approximately 6000 to 8000 mL of air per minute.
b. Residual volume: Volume of air remaining in the lungs even after a forcible expiration. This averages 1100 mL to 1200 mL. Residual air mainly occurs in alveoli.
c. Asthma: Asthma is a difficulty in breathing causing wheezing due to inflammation of bronchi and bronchioles. In asthma, due to flattening of
tracheal vessels, alveoli are deprived of oxygen. Asthma is characterised by spasm in bronchial muscle.

Q2. A fluid-filled double membranous layer surrounds the lungs. Name it and mention its important function.
Ans: Pleural fluid is found in between the two membranes of lung and it reduces the friction on the lung surface.

Q3. Name the primary site of exchange of gases in our body?
Ans: Alveoli

Q4. Cigarette smoking causes emphysema. Give reason.
Ans: Cigarette smoking causes damage of the alveolar walls leading to decreased respiratory surfaces for exchange of gases.

Q5. What is the amount of 0₂ supplied to tissues through every 100 mL of oxygenated blood under normal physiological conditions?
Ans: 5 mL of oxygen/100 mL of oxygenated blood.

Q6. A major percentage (97%) of 0₂ is transported by RBCs in the blood. How does the remaining percentage (3%) of 0₂ transported?
Ans: Through Plasma

 

Q7. Arrange the following terms based on their volumes in an ascending order
a. Tidal Volume (TV)
b. Residual Volume (RV)
c. Inspiratory Reserve Volume (IRV)
d. Expiratory Capacity (EC)
Ans: a. Tidal Volume (TV): 500 mL
b. Residual Volume (RV): 1100 mL-200 mL
c. Inspiratory Reserve Volume (IRV): 2500 mL-3000 mL
d. Expiratory Capacity (EC): 1500 mL-1600 mL

Q8. Complete the missing terms
a. Inspiratory Capacity (IC) = _____+ IRV
b. _____ = TV + ERV
c. Functional Residual Capacity (FRC) = ERV + _____
Ans. a. Inspiratory Capacity (IC) = TV + IRV
b. EC = TV + ERV
c. Functional Residual Capacity (FRC) = ERV + RV

Q9. Name the organs of respiration in the following organisms:
a. Flatworm
b.Birds
c. Frog
d. Cockroach
Ans: a. Flatworm—Entire body surface
b. Birds—Lung
c. Frog—Lung and moist skin
d. Cockroach—Tracheal tubes

Short Answer Type Questions

Q1. State the different modes of C0₂ transport in blood.
Ans: Nearly 20-25% of C0₂ by RBCs
Nearly 70% of C0₂ as bicarbonates Nearly 7% of C0₂ as dissolved state in plasma

Q2. Compared to 0₂, the diffusion rate of C0₂ through the diffusion membrane per unit difference in partial pressure is much higher. Explain.
Ans: Solubility is an important factor deciding diffusion rate. As the solubility of C0₂ is 20-25 times higher than 0₂, diffusion of C0₂ through the diffusion membrane per unit difference in partial pressure is much higher.

Q3. For completion of respiration process, write the given steps in sequential manner.                                                                        .

1. Diffusion of gases (0₂ and C0₂) across alveolar membrane.
2. Transport of gases by blood.
3. Utilisation of 0₂ by the cells for catabolic reactions and resultant release of C0₂.
4. Pulmonary ventilation by which atmospheric air is drawn in and C0₂ rich alveolar air is released out.
5. Diffusion of 0₂ and C0₂ between blood and tissues.

Ans: Respiration involves the following steps:

1. Breathing or pulmonary ventilation by which atmospheric air is drawn in and C0₂ rich alveolar air is released out.
2. Diffusion of gases (0₂ and C0₂) across alveolar membrane.
3. Transport of gases by the blood.
4. Diffusion of 0₂ and C0₂ between blood and tissues.
5. Utilisation of 0₂ by the cells for catabolic reactions and resultant release of C0₂.

Long Answer Type Questions

Q1. Explain the transport of 0₂ and C0₂ between alveoli and tissue with a diagram.
Ans:

• Transport of gases: Blood is the medium of transport for 0₂ and C0₂. About 97% of 0₂ is transported by RBCs in the blood. The remaining 3% of 0₂ is carried in a dissolved state through the plasma. Nearly 20-25% of C0₂ is transported by RBCs whereas 70% of it is carried as bicarbonate. About 7% of C0₂ is carried in a dissolved state through plasma.
• Transport of oxygen: Haemoglobin is a red coloured iron containing pigment present in the RBCs. 0₂ can bind with haemoglobin in a reversible manner to form oxyhaemoglobin. Each haemoglobin molecule can carry a maximum of four molecules of 0₂. Binding of oxygen with haemoglobin is primarily related to partial pressure of 0₂. Partial pressure of C0₂, hydrogen ion concentration and temperature are the other factors which can interfere with this binding. A sigmoid curve is obtained when percentage saturation of haemoglobin with 0₂ is plotted against the p0₂. This curve is called the Oxygen dissociation curve and is highly useful in studying the effect of factors like pC0₂, H⁺ concentration, etc., on binding of 0₂ with haemoglobin. In the alveoli, where there is high p0₂, low pC0₂, lesser H⁺ concentration and lower temperature, the factors are all favourable for the formation of oxyhaemoglobin, whereas in the tissues, where low p0₂, high pC0₂, high H⁺ concentration and higher temperature exist, the conditions are favourable for dissociation of oxygen from the oxyhaemoglobin. This clearly indicates that 0₂ gets bound to haemoglobin in the lung surface and gets dissociated at the tissues. Every 100 mL of oxygenated blood can deliver around 5 mL of 0₂ to the tissues under normal physiological conditions.
• Transport of carbon dioxide: C0₂ is carried by haemoglobin as carbamino-haemoglobin (about 20-25%). This binding is related to the partial pressure of C0₂. p0₂ is a major factor which could affect this binding. When pC0₂ is high and p0₂ is low as in the tissues, more binding of carbon dioxide occurs whereas, when the pC0₂ is low and p0₂ is high as in the alveoli, dissociation of C0₂ from carbamino-haemoglobin takes place, i.e., C0₂ which is bound to haemoglobin from the tissues is delivered at the alveoli. RBCs contain a very high concentration of the enzyme, carbonic anhydrase and minute quantities of the same is present in the plasma too. This enzyme facilitates the following reaction in both directions

At the tissue site where partial pressure of C0₂ is high due to catabolism, C0₂ diffuses into blood (RBCs and plasma) and forms HC0₂ and H⁺. At the alveolar site where pC0₂ is low, the reaction proceeds in the oppositedirection leading to the formation of C0₂ and H₂0. Thus, C0₂ trapped as bicarbonate at the tissue level and transported to the alveoli is released out as C0₂. Every 100 mL of deoxygenated blood delivers approximately 4 mL of C0₂ to the alveoli.

Q2. Explain the mechanism of breathing with neat labelled sketches.
Ans: Breathing involves two stages:
a. Inspiration: Inspiration is initiated by the contraction of diaphragm, which increases the volume of thoracic chamber in the anteroposterior axis. The contraction of external inter-costal muscles lifts up the ribs and the sternum causing an increase in the volume of thoracic chamber in the dorso-ventral axis also. Such an increase in thoracic volume leads to a similar increase in pulmonary volume resulting in decreased intra- pulmonary pressure to less than atmospheric pressure. This causes the movement of external air into the lungs, i.e., inspiration.
b. Expiration: The inter-costal muscles return the diaphragm and sternum to their normal positions with relaxation of the diaphragm. This reduces the thoracic volume and thereby the pulmonary volume. As a result an increase in intra-pulmonary pressure to slightly above the atmospheric pressure causes the expulsion of air from the lungs i.e., expiration.

Q3. Explain the role of neural system in regulation of respiration.
Ans: Human beings have a significant ability to maintain and moderate the respiratory rhythm to suit the demands of the body tissues. This is done by the neural system. A specialised centre present in the medulla region of the brain called respiratory rhythm centre is primarily responsible for this regulation. Another centre present in the pons region of the brain called pneumotaxic centre can moderate the functions of the respiratory rhythm centre. Neural signal from this centre “can reduce the duration of inspiration and thereby alter the respiratory rate. A chemosensitive area is situated adjacent to the rhythm centre which is highly sensitive to C02 and hydrogen ions. Increase in these substances can activate this centre, which in turn can signal the rhythm centre to make necessary adjustments in the respiratory process by which these substances can be eliminated. Receptors associated with aortic arch and carotid artery also can recognise changes in C02 and H+ concentration and send necessary’ signals to the rhythm centre for remedial actions. The role of oxygen in the regulation of respiratory rhythm is quite insignificant.

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We hope the NCERT Exemplar Class 11 Biology Chapter 17 Breathing and Exchange of Gases help you. If you have any query regarding NCERT Exemplar Class 11 Biology Chapter 17 Breathing and Exchange of Gases, drop a comment below and we will get back to you at the earliest.

NCERT Exemplar Class 11 Biology Chapter 21 Neural Control and Coordination are part of NCERT Exemplar Class 11 Biology. Here we have given NCERT Exemplar Class 11 Biology Chapter 21 Neural Control and Coordination.

NCERT Exemplar Class 11 Biology Chapter 21 Neural Control and Coordination

Multiple Choice Questions

Q1. Chemicals which are released at the synaptic junction are called
(a) Hormones
(b) Neurotransmitters
(c) Cerebrospinal fluid
(d) Lymph
Ans: (b) Chemicals released at the synaptic junction are called neurotransmitters.

Q2. Potential difference across resting membrane is negatively charged. This is due to differential distribution of the following ions
(a)Na⁺ and K⁺ ions
(b) C0³⁺⁺and Cl“ ions
(c) Ca*⁺ and Mg⁺⁺ ions                         
(d) Ca⁺⁴ and CL ions
Ans: (a) Potential difference across resting membrane is negatively charged. This is due to differential distribution of Na⁺ and K⁺ ions.

Q3. Resting membrane potential is maintained by
(a) Hormones (b) Neurotransmitters
(c) Ion pumps (d) None of the above
Ans: (c) Resting membrane potential is maintained by ion pumps.

Q4. The function of our visceral organs is controlled by
(a) Sympathetic and somatic neural system
(b) Sympathetic and parasympathetic neural system
(c) Central and somatic neural system.
(d) None of the above
Ans: (b) The function of our visceral organs is controlled by sympathetic and parasympathetic neural systems.

Q5. Which of the following is not involved in knee-jerk reflex?
(a) Muscle spindle (b) Motor neuron
(c) Brain (d) Intemeurons
Ans: (c) Brain is not involved in knee-jerk reflex.

Q6. An area in the brain which is associated with strong emotions is
(a) Cerebral cortex (b) Cerebellum
(c) Limbic system (d) Medulla
Ans: (c) An area in the brain is associated with strong emotions is limbic system.

Q7. Mark the vitamin present in rhodopsin.
(a) VitA (b) Vit B (c) VitC (d) VitD
Ans: (a) Vit A is present in rhodopsin.

Q8. Human eyeball consists of three layers and it encloses
(a) Lens, iris, optic nerve
(b) Lens, aqueous humor and vitreous humor
(c) Cornea, lens, iris
(d) Cornea, lens, optic nerve
Ans: (b) Human eyeball consists of three layers and it encloses lens, aqueous humor and vitreous humor.

Q9. Wax gland present in the ear canal is called
(a) Sweat gland
(b) Prostate gland
(c) Cowper’s gland –
(d) Sebaceous gland/ceruminous gland
Ans: (d) Wax gland present in the ear canal is called sebaceous gland/ceruminous gland.

Q10. The “part of internal ear responsible for hearing is
(a) Cochlea (b) Semicircular canal
(c) Utriculus (d) Sacculus
Ans: (a) The part of internal ear responsible for hearing is cochlea.

Q11. The organ of Corti is a structure present in
(a) External ear (b) Middle ear
(c) Semicircular canal (d) Cochlea
Ans: (d) The organ of Corti is a structure present in cochlea.

Q12. While travelling to higher altitudes, people can feel pain in the ear and dizziness. Which part, among the following is involved?
(a) Cochlea, ear ossicles
(b) Tympanic membrane
(c) Eustachian tube, utricle, saccule and semicircular canals
(d) None of the above
Ans: (c)

Very Short Answer Type Questions
Q1. Rearrange the following in the correct order of involvement in electrical impulse movement: Synaptic knob, dendrites, cell body, Axon terminal, Axon
Ans: Dendrites—Cell body—Axon—Axon terminal—Synaptic knob.

Q2. Comment upon the role of ear in maintaining the balance of the body and posture.
Ans: The crista and macula are the specific receptors of the vestibular apparatus responsible for maintenance of balance of the body and posture.

Q3. Which cells of the retina enable us to see coloured objects around us?
Ans: Cone cells of the retina enable us to see the coloured objects around us.

Q4. Arrange the following in the order of reception and transmission of sound wave from the ear drum:
Cochlear nerve, external auditory canal, ear drum, stapes, incus, malleus, cochlea.
Ans: Ear drum, malleus, incus, stapes, cochlea, chochlear nerve.

Q5. During resting potential, the axonal membrane is polarised, indicate the movement of +ve and -ve ions leading to polarisation diagrammatically.
Ans: Neurons are excitable cells because their membranes are in a polarised state. Different types of ion channels are present on the neural membrane. These ion channels are selectively permeable to different ions. When a neuron is not conducting any impulse, i.e., resting, the axonal membrane is comparatively more permeable to potassium ions (K⁺) and nearly impermeable to sodium ions (Na⁺). Similarly, the membrane is impermeable to negatively charged proteins present in the axoplasm. Consequently, the axoplasm inside the axon contains high concentration of K⁺ and negatively charged proteins and low concentration of Na⁺. In contrast, the fluid outside the axon contains a “low concentration of K⁺, a high concentration of Na⁺ and thus form a concentration gradient. These ionic gradients across the resting membrane are maintained by the active transport of ions by the sodium-potassium pump which transports 3 Na⁺ outwards for 2 K⁺ into the cell. As a result, the outer surface of the axonal membrane possesses a positive charge while its inner surface becomes negatively charged and therefore is polarised. The electrical potential difference across the resting plasma membrane is called as the resting potential.

Q6. Name the structures involved in fhe protection of the brain.
Ans: The human brain is well protected by the skull. Inside the skull, the brain is covered by cranial meninges consisting of an outer layer called dura mater, a very thin middle layer called arachnoid and an inner layer (which is in contact with the brain tissue) called pia mater. Piamater is a vascular membrane which is richly supplied with blood capillaries. Space between the duramater and arachnoid is called subdural space. Space between the arachnoid and pia mater is called subarachnoid space. Subarachnoid space is filled with the cerebrospinal fluid (CSF) which acts as a cushion for CNS from shocks.

Q7. Our reactions like aggressive behaviour, use of abusive words, restlessness etc. are regulated by brain, name the parts involved.
Ans: Limbic system and hypothalamus

Q8. What do grey and white matter in the brain represent?
Ans: The layer of cells which covers the cerebral hemisphere is called cerebral cortex and is thrown into prominent folds. The cerebral cortex is referred to as the grey matter due to its greyish appearance. The neuron cell bodies are concentrated here giving the colour. Fibres of the tracts are covered with the myelin sheath, which constitute the inner part of cerebral hemisphere. They give an opaque white appearance to the layer and, hence, is called the white matter.

Q9. Where is the hunger centre located in human brain?
Ans: Hypothalamus

Q10. Which sensory organ is involved in vertigo (sensation of oneself or objects spinning around)?
Ans: Vestibular apparatus of inner ear

Q11. While travelling at a higher altitude, a person complains of dizziness and vomiting sensation. Which part of the inner ear is disturbed during the journey?
Ans: Vestibular apparatus (saccule, utricle and semicircular canals)

Q12. Complete the statement by choosing appropriate match among the following:

(a)	Resting potential	(i)	Chemicals involved in the transmission of impulses at synapses.
(b)	Nerve impulse	(«)	Gap between the presynaptic and postsynaptic neurons.
(c)	Synaptic cleft	(iii)	Electrical potential difference across the resting neural membrane.
(d)	N euro transmitters	(iv)	An electrical wave-like response of a neuron to a stimulation.

Ans:

(a)	Resting potential	(iii)	Electrical potential difference across the resting neural membrane.
(b)	Nerve impulse	(iv)	An electrical wave-like response of a neuron to a stimulation.
(c)	Synaptic cleft	(ii)	Gap between the presynaptic and postsynaptic neurons.
(d)	N euro transmitters	(i)	Chemicals involved in the transmission of impulses at synapses.

Short Answer Type Questions
Q1. The major parts of the human neural system is depicted below. Fill in the empty boxes with appropriate words.

Q2. What is the difference between electrical transmission and chemical transmission?
Ans:

	Electrical transmission		Chemical transmission
1.	Mediated by electrical synapses.	1.	Mediated through neuro transmitters.
2.	The membranes of pre- and post-synaptic neurons are in very close proximity.	2.	The membranes of pre- and post- synaptic neurons are separated by synaptic cleft.
3.	Electrical current can flow directly from one neuron into the other across the synapses.	3.	Neurotransmitters are involved in the transmission of impulses at the synapses.
4.	This transmission is faster.	4.	This transmission is slower.
5.	These are rare in our system.	5.	These are common in our system.

 

Q3. Neural system and computers share certain common features. Comment in five lines. (Hint: CPU, input-output devices).
Ans: Neural system and computers share certain common features. The neural system has brain as command and control centre similar to the computer that has CPU (Central processing unit). Sensory organs are input devices of neural system like the mouse and keyboard of the computer. Responses of the body are the output of the neural system.like the data analysis and typed material of the computer. Nerves are comparable to the wires of the computers.

Q4. If someone receives a blow on the back of neck, what would be the effect on the person’s CNS?
Ans: If someone receives a blow on the back of neck, it may result in the dislocation of the cervical vertebrae that may lead to the injury of the spinal cord passes through neural canal. Injury of spinal cord may lead to paralysis.

Q5. What is the function ascribed to Eustachian tube?
Ans: A Eustachian tube connects the middle ear cavity with the pharynx. The Eustachian tube helps in equalising the pressures on either sides of the ear drum.

Q6. Label the following parts in the given diagram using arrow.

a. Aqueous chamber
b. Cornea
c. Lens
d. Retina
e. Vitreous chamber
f. Blind spot

Long Answer Type Questions
Q1. Explain the process of the transport and release of a neurotransmitter with the help of a labelled diagram showing a complete neuron, axon terminal and synapse.
Ans: A nerve impulse is transmitted from one neuron to another through junctions called synapses. A synapse is formed by the membranes of a presynaptic neuron and a postsynaptic neuron, which may or may not be separated by a gap called synaptic cleft. At a chemical synapse, the membranes of the pre- and post-synaptic neurons are separated by a fluid-filled space called synaptic cleft. Chemicals called neurotransmitters are involved in the transmission of impulses at these synapses. The axon terminals contain vesicles filled with these neurotransmitters. When an impulse (action potential) arrives at the axon terminal, it stimulates the movement of the synaptic vesicles towards the membrane where they fuse with the plasma membrane and release their neurotransmitters in the synaptic cleft. The released neurotransmitters bind to their specific receptors, present on the postsynaptic membrane. This binding opens ion channels allowing the entry of ions which can generate a new potential in the postsynaptic neuron. The new potential developed may be either excitatory or inhibitory.

Q2. Name the parts of human forebrain indicating their respective functions.
Ans: Forebrain:
The forebrain consists of cerebrum, thalamus and hypothalamus. Cerebrum forms_ the major part of the human brain. A deep cleft divides the cerebrum longitudinally into two halves, which are termed as the left and right cerebral hemispheres. The hemispheres are connected by a tract of nerve fibres called corpus callosum. The layer of cells which covers the cerebral hemisphere is called cerebral cortex and is thrown into prominent folds. The cerebral cortex is referred to as the grey matter due to its greyish appearance. The neuron cell bodies are concentrated here giving the colour. The cerebral cortex contains motor areas, sensory areas and large regions that are neither clearly sensory nor motor in function. These regions called as the association areas are responsible for complex functions like intersensory associations, memory and communication. Fibres of the tracts are covered with the myelin sheath, which constitute the inner part of cerebral hemisphere. They give an opaque white appearance to the layer and, hence, is called the white matter. The cerebrum wraps around a structure called thalamus, which is a major coordinating centre for sensory and motor signaling. Another very important part of the brain called hypothalamus lies at the base of the thalamus. The hypothalamus contains a number of centres which control body temperature, urge for eating and drinking. It also contains several groups of neurosecretory cells, which secrete hormones called hypothalamic hormones. The inner parts of cerebral hemispheres and a group of associated deep structures like amygdala, hippocampus, etc., form a complex structure called the limbic lobe or limbic system. Along with the hypothalamus, it is involved in the regulation of sexual behaviour, expression of emotional reactions (e.g., excitement, pleasure, rage and fear), and motivation.

Q3. Explain the structure of middle and internal ear with the help of diagram.
Ans: The middle ear contains three ossicles called malleus, incus and stapes which are attached to one another in a chainlike fashion. The malleus is attached to the tympanic membrane and the stapes is attached to the oval window of the cochlea. The ear ossicles increase the efficiency of transmission of sound waves to the inner ear. A Eustachian tube connects the middle ear cavity with the pharynx. The Eustachian tube helps in equalising the pressures on either sides of the ear drum.

• The fluid-filled inner ear called labyrinth consists of two parts, the bony and the membranous labyrinths. The bony labyrinth is a series of channels. Inside these channels lies the membranous labyrinth, which is surrounded by a fluid called perilymph. The membranous labyrinth is filled with a fluid called endolymph. The coiled portion of the labyrinth is called cochlea. The membranes constituting cochlea, the Reissner’s and basilar, divide the surrounding perilymph filled bony labyrinth into an upper scala vestibuli and a lower scala tympani. The space within cochlea called scala media is filled with endolymph. At the base of the cochlea, the scala vestibuli ends at the oval window, while the scala tympani terminates at the round window which opens to the middle ear. The organ of Corti is a structure located on the basilar membrane which contains hair cells that act as auditory receptors. The hair cells are present in rows on the internal side of the organ of Corti. The basal end of the hair cell is in close contact with the afferent nerve fibres. A large number of processes called stereo cilia are projected from the apical part of each hair cell. Above the rows of the hair cells is a thin elastic membrane called tectorial membrane.
• The inner ear also contains a complex system called vestibular apparatus, located above the cochlea. The vestibular apparatus is composed of three semi-circular canals and the otolith (macula is the sensory part of saccule and utricle). Each semi-circular canal lies in a different plane at right angles to each other. The membranous canals are suspended in the perilymph of the bony canals. The base of canals is swollen and is called ampulla, which contains a projecting ridge called crista ampullaris which has hair cells. The saccule and utricle contain a projecting ridge called macula. The crista and macula are the specific receptors of the vestibular apparatus responsible for maintenance of balance of the body and posture.

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