NCERT-Based Explanation
Uncontrolled, irregular and excessive muscle contractions may occur due to abnormal nerve impulses reaching the muscles. Dysfunction of a neuron can lead to such abnormal muscle contractions. Therefore, both the assertion and the reason are true, and the reason correctly explains the assertion.

Pedagogical Value
NCERT does not discuss the term “wild contractions”. This question encourages students to relate their understanding of the neuromuscular system to abnormal muscle activity and explore how neuronal dysfunction can affect muscle contraction.

NCERT-Based Explanation
NCERT states that leucocytes exhibit amoeboid movement. Amoeboid movement does not involve coordinated muscular activity. Therefore, not all movements require coordinated muscular activities. Hence, both the assertion and the reason are true, and the reason correctly explains the assertion.

Pedagogical Value
This question encourages students to connect concepts from multiple NCERT chapters. In Locomotion and Movement, leucocytes are described as exhibiting amoeboid movement. In Structural Organisation in Animals, connective tissue contains WBCs, and in Human Health and Disease, lymphoid organs contain B and T lymphocytes. Integrating these facts helps students appreciate that different types of WBCs are capable of migration and that amoeboid movement is a general property of leucocytes, even though the extent of movement may vary among different cell types. It reinforces that movement is not always dependent on coordinated muscular activity.

NCERT-Based Explanation
NCERT describes different types of movements, including amoeboid, ciliary, flagellar and muscular movements. Amoeboid movement of leucocytes occurs without joints. Therefore, joints are not essential for all types of movements, making the assertion false. Locomotory movements involve the movement of bony parts and require joints. Hence, the reason is true.

Pedagogical Value
This question helps students distinguish between movement and locomotion. Although locomotory movements require joints, not all movements involve joints. It prevents students from overgeneralising the role of joints in all forms of movement.

NCERT-Based Explanation
Movement includes both locomotion and non-locomotory movements. Walking is a movement as well as a locomotion and requires coordinated muscular activities. Blinking of the eyes is a movement but not a locomotion, and it also requires coordinated muscular activities. In contrast, amoeboid movement of WBCs is a movement that does not require coordinated muscular activities. Therefore, only some movements require coordinated muscular activities. Although locomotion is a subset of movement, this does not explain the assertion. Hence, both the assertion and the reason are true, but the reason is not the correct explanation.

Pedagogical Value
This question distinguishes classification from function. Students should recognise that locomotion is a subset of movement, but this fact does not explain the involvement of coordinated muscular activities. It prevents students from assuming that every true statement related to the assertion is necessarily its explanation.

NCERT-Based Explanation
NCERT states that fibrous joints do not allow any movement. However, not all movements are because of joints. Movements such as amoeboid, ciliary and flagellar movements occur without the involvement of joints. Therefore, the assertion is false. The second part of the reason is also false because joints are not essential for all types of movements.

Pedagogical Value
This question distinguishes between movement and movement involving the skeletal system. It also reinforces that while some joints are immovable, joints are not responsible for every type of movement occurring in living organisms.

NCERT-Based Explanation
NCERT states that muscles possess the property of elasticity. Elasticity enables muscles to return to their original resting length after contraction or stretching. Therefore, both the assertion and the reason are true, and the reason correctly explains the assertion.

Pedagogical Value
This question helps students relate the definition of elasticity to its functional significance. Instead of memorising elasticity as one of the properties of muscles, students understand that it enables muscles to regain their original resting length after contraction or stretching.

NCERT-Based Explanation
A muscle spasm is a sudden, involuntary contraction of a muscle or group of muscles. Such contractions may be brief or prolonged and can cause pain or discomfort. Therefore, both the assertion and the reason are true, and the reason correctly explains the nature of a muscle spasm.

Pedagogical Value
This question helps students understand the definition of a muscle spasm and its clinical presentation. It reinforces that spasms vary in duration and may be associated with pain, preventing students from assuming that all spasms are identical.

NCERT-Based Explanation
NCERT states that muscular dystrophy is the progressive degeneration of skeletal muscles due to a genetic disorder. Mutation in the dystrophin gene, the largest known gene in humans, causes Duchenne muscular dystrophy. Therefore, both the assertion and the reason are true, and the reason correctly explains the assertion.

Pedagogical Value
The assertion is based on Class 11 NCERT (Locomotion and Movement), whereas the reason relates to the Human Genome Project subsection of Class 12 NCERT (Molecular Basis of Inheritance), where the dystrophin gene is mentioned as the largest known human gene. This question encourages students to integrate concepts across NCERT lessons and appreciate that understanding Biology often requires connecting information from different chapters rather than studying them in isolation.

NCERT-Based Explanation
NCERT states that muscles possess the property of extensibility. Because muscles can be stretched, a sarcomere need not always show actin–myosin overlap. Therefore, the assertion is false, whereas the reason is true.

Pedagogical Value
This question encourages students to connect the property of extensibility with the structure of the sarcomere. Instead of memorising the arrangement of actin and myosin filaments, students are prompted to think about how stretching can alter their overlap.

NCERT-Based Explanation
NCERT states that joints act as a fulcrum in the body. The reason correctly explains this statement by relating the musculoskeletal system to a lever system, where bones act as levers, joints as fulcrums, and muscles provide the force for movement. Hence, both the assertion and the reason are true, and the reason correctly explains the assertion.

Pedagogical Value
NCERT states that joints act as a fulcrum in the body but does not explain the mechanics of a fulcrum. This question encourages students to explore the concept of a lever system learned earlier and connect it with biomechanics. It helps them understand why joints are called fulcrums by relating the roles of bones, joints and muscles in producing movement, thereby integrating prior knowledge with the NCERT concept.

NCERT-Based Explanation
NCERT mentions muscular dystrophy as an example of a genetic disorder affecting skeletal muscles. Hence, the assertion is true. The reason is false because muscular dystrophy is not an autoimmune disease.

Pedagogical Value
This question reminds students that NCERT often presents representative examples rather than an exhaustive classification of diseases. Students should recognise what NCERT explicitly states while avoiding the assumption that every disease not discussed in detail must belong to the same category. It also encourages them to distinguish genetic disorders from autoimmune disorders without overgeneralising from limited textbook descriptions.

NCERT-Based Explanation
NCERT states that the pectoral girdle attaches the upper limbs to the axial skeleton. Since each girdle is formed of two halves, the right half of the pectoral girdle attaches the right upper limb to the axial skeleton. Therefore, both the assertion and the reason are true, and the reason correctly explains the assertion.

Pedagogical Value
This question encourages students to visualise the bilateral organisation of the pectoral girdle. Instead of viewing the girdle as a single unit, students infer that each half is associated with the corresponding upper limb, thereby strengthening their understanding of skeletal organisation.

NCERT-Based Explanation
Joints enable the movement of bony parts. Without joints, bones would remain rigid, making movement involving the skeleton impossible. Therefore, both the assertion and the reason are true, and the reason correctly explains the assertion.

Pedagogical Value
This question distinguishes movement involving the bony parts from movement in general. It reinforces the role of joints in skeletal movement and prevents students from overgeneralising the concept of movement.

NCERT-Based Explanation
NCERT states that humans exhibit different types of movements. Walking, crawling, running and swimming are examples of locomotion, which is only one type of movement. Hence, both the assertion and the reason are true, but the reason does not correctly explain the assertion.

Pedagogical Value
This question distinguishes movement from locomotion. It helps students recognise that locomotion is only one category of movement and should not be considered synonymous with movement in general.

NCERT-Based Explanation
NCERT states that muscles possess the property of extensibility. Extensibility enables a muscle to be stretched beyond its normal length. As the muscle stretches, the sarcomeres also lengthen. Therefore, a muscle exhibiting extensibility can attain a maximum sarcomere length. Hence, both the assertion and the reason are true, and the reason correctly explains the assertion.

Pedagogical Value
NCERT introduces extensibility as a property of muscles but does not explicitly relate it to sarcomere length. This question encourages students to connect a physiological property of muscle with the structural changes occurring within the sarcomere, helping them understand the consequence of extensibility rather than merely memorising its definition.

NCERT-Based Explanation
NCERT states that the globular head of myosin is an active ATPase and has ATP-binding sites and active sites for actin. ATP binds to the ATP-binding site, where it is hydrolysed to provide the energy required for muscle contraction. Therefore, both the assertion and the reason are true, and the reason correctly explains the assertion.

Pedagogical Value
NCERT simplifies many concepts to make them suitable for school-level learning. Occasionally, such simplifications may create ambiguity when highly specific scientific questions are asked. This question encourages students to recognise that simplified terminology should not always be interpreted as precise scientific terminology. When a concept requires deeper mechanistic understanding, students should verify the terminology using standard physiology or biochemistry references. Developing this habit helps prevent misconceptions arising from over-interpreting simplified textbook statements.

NCERT-Based Explanation
NCERT states that joints are points of contact between bones or between bones and cartilages. The first sternocostal joint is an example of a joint between the sternum (bone) and the first costal cartilage. Therefore, both the assertion and the reason are true, and the reason correctly explains the assertion.

Pedagogical Value
Students often memorise that joints may occur between a bone and a cartilage without visualising an actual example. This question reinforces the NCERT statement by connecting it with a standard anatomical example, helping students translate a general definition into a concrete structure.

NCERT-Based Explanation
NCERT states that movement is one of the significant features of living beings, including plants. It also describes locomotion in many unicellular organisms. Therefore, plants and some unicellular organisms cannot be excluded from the characteristic of movement, making the assertion false. The reason is true because plants do not possess locomotory structures, and some unicellular organisms also lack locomotory structures.

Pedagogical Value
This question distinguishes movement from locomotion and tests careful reading of qualifying words such as “some”. It also reinforces that the absence of locomotory structures does not imply the absence of movement.

NCERT-Based Explanation
NCERT states that synovial joints are characterised by the presence of a fluid-filled synovial cavity between the articulating surfaces of the two bones. The reason is true, as the term “synovial” is derived from the egg-white-like (viscous) nature of the synovial fluid. However, this does not explain why synovial joints are characterised by the presence of synovial fluid. Therefore, both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.

Pedagogical Value
NCERT introduces the term synovial joint but does not explain the origin of the word “synovial”. This question encourages students to explore the terminology and appreciate the etymology of scientific terms while distinguishing between an interesting fact and a causal explanation.

NCERT-Based Explanation
NCERT classifies the saddle joint as a type of synovial joint. The saddle-shaped articulating surfaces, being both concave and convex, permit movement in more than one plane while maintaining stability. Therefore, both the assertion and the reason are true, and the reason correctly explains the assertion.

Pedagogical Value
This question helps students relate the structure of a saddle joint to its function. It reinforces that the shape of the articulating surfaces determines the type and range of movement allowed at a joint.