CBSE Class 11 Biology Chapter 20: Locomotion and Movement NCERT Solutions
This chapter delves into the fundamental biological processes of locomotion and movement, crucial for understanding how organisms interact with their environment. The NCERT Solutions for Class 11 Biology, Chapter 20, provide comprehensive explanations for key concepts. This includes detailed breakdowns of Multiple Choice Questions (MCQs) that test understanding of muscle fiber types, skeletal structures like ribs and sternum, and the different types of joints. The solutions clarify the characteristics of fast and slow muscle fibers, the attachment points of ribs, and the specific types of movable joints such as pivot and saddle joints, explaining their structure and function. These solutions are designed to aid students in grasping the intricacies of the musculoskeletal system, preparing them effectively for their examinations by offering clear, step-by-step problem-solving approaches.
Quick info
| Board | CBSE |
|---|---|
| Class | Class 11 |
| Subject | Biology Exemplar |
| Session | 2026 |
| Language | English |
| Type | NCERT Solutions |
| Chapter | Chapter 20 |
Chapter summary
Chapter 20 of the Class 11 Biology NCERT Solutions focuses on Locomotion and Movement. It covers essential topics like the classification and characteristics of muscle fibers (fast and slow), the skeletal components involved in support and movement such as ribs and sternum, and the various types of joints (pivot, saddle, hinge, gliding) with examples. The provided solutions offer detailed explanations for MCQs, helping students understand the underlying principles of musculoskeletal function and joint mechanics.
Learning outcomes
- Understand the differences between fast and slow muscle fibers.
- Identify the skeletal structures involved in forming the thoracic cage.
- Differentiate between various types of movable joints.
- Explain the function and location of pivot and saddle joints.
- Solve MCQs related to muscle and skeletal anatomy.
Topics covered
Paper topics
- Locomotion and Movement
- Muscle Fibers
- Fast Muscle Fibers
- Slow Muscle Fibers
- Skeletal System
- Ribs
- Sternum
- Joints
- Movable Joints
- Pivot Joint
- Saddle Joint
- Atlas and Axis
Important topics
- Muscle Fiber Types and Characteristics
- Skeletal Attachments (Ribs and Sternum)
- Types of Movable Joints
- Pivot and Saddle Joint Mechanics
PDF preview
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Questions and Solutions
Q. 1
Column I | Column II
A. Fast muscle fibres | 1. Myoglobin
B. Slow muscle fibres | 2. Lactic acid
C. Actin filament | 3. Contractile unit
D. Sarcomere | 4. I-band
CodesA B C D
(a) 1 2 4 3
(b) 2 1 3 4
(c) 2 1 4 3
(d) 3 2 4 1
The correct matching is A-2, B-1, C-4, D-3.
Explanation:
- Fast muscle fibres (A) are characterized by their rapid contraction and reliance on anaerobic respiration, which leads to the accumulation of lactic acid (2) in shorter periods.
- Slow muscle fibres (B) possess a higher concentration of myoglobin (1), which aids in oxygen storage and aerobic respiration, making them more resistant to fatigue and capable of sustained, slow contractions.
- Actin filaments (C) are the thin filaments that constitute the I-band (4) (Isotropic band) of the sarcomere.
- Sarcomere (D) is the fundamental contractile unit (3) of a muscle fibre, extending between two Z-lines.
Therefore, the correct code is (c) 2 1 4 3.
Q. 2
(a) scapula
(b) sternum
(c) clavicle
(d) ilium
The correct answer is (b) sternum.
Explanation:
The thoracic cage is formed by the ribs, sternum, and thoracic vertebrae. There are typically 12 pairs of ribs. The true ribs, which are the first seven pairs, are directly attached to the sternum via costal cartilages. The sternum is a flat bone located in the midline of the chest. The scapula and clavicle together form the pectoral girdle, which supports the forelimbs. The ilium is a major bone of the pelvic girdle, which supports the hindlimbs.
Q. 3
(a) Pivot
(b) Saddle
(c) Hinge
(d) Gliding
The correct answer is (a) Pivot.
Explanation:
The joint between the atlas (the first cervical vertebra, C1) and the axis (the second cervical vertebra, C2) is a type of pivot joint. This joint allows for the rotational movement of the head, enabling us to turn our head from side to side. In a pivot joint, a rounded or pointed projection of one bone fits into a ring or socket formed by another bone or ligament, allowing rotation around a central axis.
Other types of joints mentioned:
- Saddle joint: Allows movement in two planes (biaxial). An example is the joint between the carpal and metacarpal of the thumb.
- Hinge joint: Allows movement in only one plane (uniaxial), like the elbow or knee joint.
- Gliding joint: Allows slight gliding or sliding movements between flat surfaces of bones, such as those between the carpal bones in the wrist.
Common mistakes
- Confusing the characteristics of fast and slow muscle fibers.
- Incorrectly identifying the bones to which ribs are attached.
- Misclassifying different types of joints based on their structure and movement.
- Difficulty in matching components in complex MCQs.
Revision tips
- Create flashcards comparing fast and slow muscle fibers.
- Draw diagrams of different joint types and label their key features.
- Practice the MCQs multiple times to reinforce understanding of concepts.
- Review the attachment points of ribs to the sternum and vertebrae.
Practice MCQs
Q1. Match the following columns and choose the correct code.
Explanation: Fast muscle fibers accumulate lactic acid faster due to anaerobic conditions, while slow muscle fibers have more myoglobin and are fatigue-resistant. Actin filaments form the I-band, and the sarcomere is the contractile unit.
Q2. Ribs are attached to which of the following bones?
Explanation: The true ribs (7 pairs) are directly attached to the sternum, which is located in the middle of the chest. Scapula and clavicle form the pectoral girdle, and ilium is part of the pelvic girdle.
Q3. What type of movable joint is present between the atlas and axis vertebrae?
Explanation: The joint between the atlas (first cervical vertebra) and the axis (second cervical vertebra) is a pivot joint, allowing rotational movement of the head. This type of joint involves a rounded bone fitting into a shallow depression.
Frequently asked questions
What are the key differences between fast and slow muscle fibers?
Fast muscle fibers contract rapidly and rely on anaerobic respiration, leading to quicker fatigue and lactic acid accumulation. Slow muscle fibers have a higher myoglobin content, enabling sustained, slow contractions and greater resistance to fatigue.
Which bone do the ribs attach to?
The true ribs (the first seven pairs) are attached to the sternum, a flat bone located in the middle of the chest. The other pairs are indirectly attached or not attached to the sternum.
What is a pivot joint and where is it found?
A pivot joint allows for rotational movement. It is formed when a rounded or pointed bone fits into a shallow depression of another bone. Examples include the joint between the atlas and axis vertebrae in the neck and the joint between the radius and ulna near the elbow.
How do these NCERT solutions help in exam preparation?
These solutions provide clear, step-by-step explanations for MCQs and concepts related to locomotion and movement, helping students understand the underlying principles and practice problem-solving for their exams.
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