NCERT Solutions for Class 11 Biology Chapter 20

Chapter 20 Biology Class 11 – Locomotion and Movement introduces students to new concepts of Human Physiology, and that is why many students find it to be a difficult chapter. The practise questions at the end of the chapter can help students get a better understanding of the concepts. But, how will students get to know if they have answered a question correctly?

The NCERT Solutions for Class 11 Biology Chapter 20 by Extramarks help students by providing the correct and reliable answers to the questions. The solutions are prepared by the subject matter experts, so students can rely on them for accuracy. 

NCERT Solutions for Class 11 Biology Chapter 20 – Locomotion and Movement 

Access NCERT Solutions for Class 11 Biology Chapter 20 – Locomotion and Movement

The NCERT Solutions for Class 11 Biology Chapter 20 are excellent reference material for students who are preparing for their Class 11 examinations and have doubts that come up, particularly in Chapter 20. 

Since all the NCERT textbook questions are answered in Chapter 20 Biology Class 11 NCERT Solutions by Extramarks, students do not have to look out for other solutions to prepare for their exams.

NCERT Solutions of Locomotion and Movement Class 11 

Chapter 20 Biology Class 11 – Locomotion and Movement is a chapter from the Human Physiology Unit (Unit V). Occurrences of various forms of locomotion in unicellular organisms and in human bodies are discussed in this chapter along with the different types of muscle movements, skeletal structure, and joint movement of the human body. Disorders of the muscle and skeleton system are covered in this chapter as well. Colourful diagrams are bound to incite student’s interest.

This chapter imparts information about voluntary and involuntary action of muscles, and disorders like arthritis. It gives in-depth explanations of the functions of joints and bones.

When solving questions given at the end of the chapter, students can refer to NCERT Solutions for Class 11 Biology Chapter 20 by Extramarks.

NCERT Solutions of Chapter 20 Biology Class 11- Marks Distribution

Chapter 20 – Locomotion and Movement is one of the seven chapters in Unit V of CBSE Biology Class 11. Unit V has a weightage of 18 marks in the final examinations. A 20% weightage is given to this unit in NEET.

Benefits of NCERT Solutions for Class 11 Biology Locomotion and Movement 

NCERT Solutions Class 11 Biology Chapter 20 provided by Extramarks comprise all the questions that are a part of the Chapter 20 Biology Class 11 – Locomotion and Movement. Here is how these solutions will aid students in scoring better in their exams. 

  • All the questions from the textbook are answered and all answers are framed in a way that is simple and understandable.
  • Students can access the solutions online and offline.
  • The solutions are curated by subject matter experts, which ensures 100 per cent accuracy.
  • Diagrams and examples are given in the answers to explain them in a better way to students.

Related Questions

Question: Which statement is correct for muscle contraction?

  1. Length of two Z-line increases
  2. Length of H-zone decreases
  3. Length of the A-band remains constant
  4. Length of A- band decreases

Answer: 4. Length of the A-band remains constant.

Explanation: During muscle contraction, thick filaments have thin filaments dropping over them. Muscular contraction is initiated due to a signal sent by the central nervous system through the motor neuron. The combining of calcium ions with troponin results in muscle contraction. During this contraction, the Z-lines draw closer together and the sarcomere shortens. A-band’s length remains constant while the H-zone narrows and I-bands shorten. Muscle contraction is terminated by muscle relaxation. Muscle relaxation is basically the muscle fibres’ restoration to their low tension-producing rate. 

Question: The dark colour of the breast muscles of a bird of flight is due to the high concentration of

  1. Mitochondria
  2. Myoglobin
  3. Haemoglobin
  4. Both myoglobin and mitochondria

Answer: 2) Myoglobin

Explanation: Oxygen-carrying protein called myoglobin is incorporated in the muscle fibres of the breasts of birds. Oxygen received from red blood cells is transported by the myoglobin to the muscle cells’ mitochondria. Here this oxygen is utilised in cellular respiration for producing energy. A high concentration of myoglobin in the breast muscles of birds is what causes these muscles to be a dark colour. 

Question: The smallest functional unit of the striated muscle is called as

  1. Myosin
  2. Fibril
  3. Sarcomere
  4. Sarcoplasm

Answer: 3) Sarcomere

Explanation: The smallest or basic unit of striated muscle tissue is Sarcomere. Sarcomeres can only be found in striated muscles. Striated muscles consist of skeletal muscles and cardiac muscle cells. Striated muscles are different as compared to smooth muscles with sarcomeres. While striated muscles are repeating units between two Z-lines, sarcomeres enable them to contract. The creation of force and contraction are the functions of these muscles.

Question: Which of the following is a locomotory organ in the snail?

  1. Outer shell
  2. Muscular foot
  3. Muscular rings
  4. All of the above

Answer: 2) Muscular foot

Explanation: Utilising muscle contractions in their foot muscles, snails deform a layer of mucus beneath them in order to propel themselves. This type of unique locomotion enables snails to move through obstacles (including being able to climb steep inclines). A snail’s locomotory organ is its muscular foot. 

Question: An example of amoeboid movement is

  1. Limbs
  2. Leucocytes
  3. Trachea
  4. None of the above

Answer: 2) Leucocytes

Explanation: A characteristic feature of every living organism is movement. Cells in the human body display different types of movement which are as follows:

Ciliary Movement: This movement is exhibited by reproductive cells like sperms and ova. 

Amoeboid movement: Amoeboid movement is exhibited by the leukocytes or leucocytes in the human blood.

Muscular movement: Muscle tissues present inside digestive organs, heart, and blood vessels aid in the movement of substances throughout the body. Therefore, leukocytes are an example of amoeboid movement.

Question: The main advantage of bipedal locomotion is:

  1. Availability of hands for other uses
  2. Increased speed
  3. Better body balance
  4. Reduced weight

Answer: 1) Availability of hands for other uses

Explanations: A terrestrial locomotion that has an organism moving about on its legs or two rear limbs is called bipedal locomotion. This form of locomotion leaves the forelimbs free for other tasks and purposes. 

Question: The movement of the whole animal from one place to another place is called

  1. Skeletal movement
  2. Non-skeletal movement
  3. Movement
  4. Locomotion

Answer: 4) Locomotion

Explanation: The movement of a part of the body resulting in a change in location and position of the organism is called locomotion. Jumping, running, walking, crawling, flying, slithering, climbing, etc. are movements carried out by multicellular organisms. Therefore, a whole animal’s movement from one place to another is known as locomotion. 

Q.1 Draw the diagram of a sarcomere of skeletal muscle showing different regions.

Ans-

The diagram of a sarcomere of skeletal muscle showing different regions:

Q.2 Define sliding filament theory of muscle contraction.

Ans-

According to the sliding filament theory of muscle contraction, contraction of muscle fibres to produce contractile force takes place by the sliding of the thin filaments (actin fibres) over the thick filaments (myosin) found in the sarcomere of the muscle cell.

[Explanation: Sliding filament theory best describes the molecular basis of muscle contraction. It explains how myofibrils (actin and myosin) interact to produce contractile force. In sarcomere, actin forms thin filaments and myosin forms thick filaments. Sarcomere consists of two bands- A-band (Dark band) and I-band (Light band). A-band is the region of myosin thick filaments while I-band is the region of actin filaments which are not superimposed with myosin filaments. Actin filaments of I-band are connected to an elastic fibre called Z-line. There is a region in the central part of sarcomere that does not overlap with actin fibres is called H-zone. During the process of muscle contraction, thick filaments (myosin fibres, A-band) remains constant while thin filaments (actin fibres, I-band) change their length and slide over the myosin filaments. Actin filaments interact with the myosin head that results in pulling the actin filaments towards the centre of the sarcomere. In this process, length of sarcomere decreases and Z-lines of sarcomere come closer.]

Q.3 Describe the important steps in muscle contraction.

Ans-

Muscle contraction is explained by sliding filament theory. According to sliding filament theory, contraction of muscle fibers to produce contractile force takes place by the sliding of the thin filament (actin fibers) over the thick filaments (myosin) found in the sarcomere of the muscle cell. Important steps in muscle contraction are as follows:

1. Central nervous system sends signal for initiation of muscle contraction via a motor neuron.

2. Neural signal reaches motor end plate (the junction between a motor neuron and sarcolemma of the muscle fiber) and releases a neurotransmitter (acetylcholine) which generates an action potential in the sarcolemma that spreads through the muscle fiber and causes the release of calcium ions into the sarcoplasm.

3. Calcium ions bind to troponin that removes tropomyosin from the active sites of actin. These exposed active actin sites are now available to interact with myosin.

5. Heads of myosins form cross bridges by interacting with active sites on actin filaments and pull them towards the center of A-band by utilising the energy from ATP hydrolysis. Z line which is attached to actin filaments are also pulled inwards that shortens the sarcomere resulting in contraction. In this process, I-bands get shortened while the lengths of A-bands remain the same.

6. Myosin goes into relaxed state by releasing ADP and Pi. Cross bridge is broken. A new ATP binds to myosin and upon ATP hydrolysis next cycle of cross-bridge formation starts. This process continues till the calcium ions are sent back into sarcoplasmic cisternae that results into masking of active sites on actin filaments.

Q.4 Write true or false. If false, change the statement so that it is true.
(a) Actin is present in thin filament
(b) H-zone of striated muscle fibre represents both thick and thin filaments.
(c) Human skeleton has 206 bones.
(d) There are 11 pairs of ribs in man.
(e) Sternum is present on the ventral side of the body.

Ans-

(a) True

(b) False. H-zone of striated muscle fibre represents only thick filaments.

(c) True

(d) False. There are 12 pairs of ribs in man.

(e) True

Q.5 Write the difference between:
(a) Actin and Myosin
(b) Red and White muscles
(c) Pectoral and Pelvic girdle

Ans-

  1. Actin and Myosin

  1. Red and White muscles
  1. Pectoral and Pelvic girdle

Q.6 Match Column I with Column II:

Column I Column II
(a) Smooth muscle (i) Myoglobin
(b) Tropomyosin (ii) Thin filament
(c) Red muscle (iii) Sutures
(d) Skull (iv) Involuntary

Ans-

Column I Column II
(a) Smooth muscle (iv) Involuntary
(b) Tropomyosin (ii) Thin filament
(c) Red muscle (i) Myoglobin
(d) Skull (iii) Sutures

Q.7 What are the different types of movements exhibited by the cells of human body?

Ans-

Four different types of movements are exhibited by the cells of human body:

1. Amoeboid movement: This kind of movement is shown by specialised cells like macrophages and leukocytes in the blood which migrate from bloodstream to the site of injury to perform their function. These cells move by the formation of pseudopodia (streaming of cytoplasm) in the direction of movement. Microfilaments of the cytoskeleton are involved in this kind of movement.

2. Ciliary movement: Ciliary movement is shown by cells of the ciliated epithelium lining internal tubular organs. Cells present in the lining of trachea perform ciliary movement to sweep the dirt and mucus out of the lung. In females, the ciliary movement shown by the cells lining the fallopian tubes helps in moving ova from ovary to uterus. Cilia are also found in the cochlear cells of the ear.

3. Muscular movement: Muscle cells exhibit contraction and relaxation movement. This kind of movement is involved in moving our limbs, jaws, tongue, etc.

4. Flagellar movement: Sperms swim by means of flagellum which shows flagellar movement.

Q.8 How do you distinguish between a skeletal muscle and a cardiac muscle?

Ans-

Name the type of joint between the following:-
(a) atlas/axis
(b) carpal/metacarpal of thumb
(c) between phalanges
(d) femur/acetabulum
(e) between cranial bones
(f) between pubic bones in the pelvic girdle

Bone Type of Joint
(a) atlas/axis Pivotal Joint
(b) carpal/metacarpal of thumb Saddle Joint
(c) between phalanges Hinge Joint
(d) femur/acetabulum Ball and socket Joint
(e) between cranial bones Fibrous joint
(f) between pubic bones in the pelvic girdle Cartilaginous joint (Pubic Symphysis)

Q.9 Fill in the blank spaces:
(a) All mammals (except a few) have __________ cervical vertebra.
(b) The number of phalanges in each limb of human is __________.
(c) Thin filament of myofibril contains 2 ‘F’ actins and two other proteins namely __________ and __________.
(d) In a muscle fibre Ca++ is stored in __________.
(e) __________ and __________ pairs of ribs are called floating ribs.
(f) The human cranium is made of __________ bones.

Ans-

(a) All mammals (except a few) have seven cervical vertebra.

(b) The number of phalanges in each limb of human is 14.

(c) Thin filament of myofibril contains 2 ‘F’ actins and two other proteins namely troponin and tropomyosin.

(d) In a muscle fibre Ca++ is stored in sarcoplasmic reticulum.

(e) 11th and 12th pairs of ribs are called floating ribs.

(f) The human cranium is made of eight bones.

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FAQs (Frequently Asked Questions)

  • A red muscle fibre is smaller and thinner than a white muscle fibre. 
  • Red muscle fibre contains more mitochondria than white muscle fibre. 
  • The amount of myoglobin in red muscle fibre is more than that of white muscle fibre. This comparatively more quantity of myoglobin in red muscle fibre is what gives it red colour while the less quantity in white muscle fibre is the reason for its white colour. 
  • Energy is provided by white muscle fibre through anaerobic respiration while red muscle fibre does so by aerobic respiration. 

The different types of muscles in existence are as follows:

Visceral muscles

The inner walls of hollow visceral organs in the human body see the presence of visceral muscles. These muscles look smoother than skeletal muscles which is why they are called non-striated muscles or smooth muscles. These are also called involuntary muscles. Examples of these types of muscles include reproductive tracts, alimentary canal, etc. 

Skeletal muscles 

The primary functions of skeletal muscles involve changes in posture and locomotory actions. These muscles are linked with the human body’s skeletal attributes. Their appearance is stripped when one views them under a microscope which is why they are called striated muscles. These muscles are generally under the nervous system’s control so they are called voluntary muscles. 

Cardiac muscles

Cardiac muscles are involuntary in function. These muscles are present in the heart and striated in appearance.