Body Movements – Class 6 Science (Notes + Questions & Answers)
This chapter explains how our body moves, the role of different kinds of joints, the human skeleton, and how animals like earthworms, snails, fish, birds, and cockroaches move. Below you’ll find crisp, exam-friendly notes and a complete practice set: 7 MCQs, 7 Very Short, 7 Short, and 7 Long answers. Use the jump buttons above to quickly reach the section you need during revision.
📘 Easy Notes: Body Movements (Class 6 Science)
1) What is Movement and Locomotion?
Movement means a change in the position of any body part (like bending your elbow or blinking). Locomotion is movement from one place to another (like walking or running). All locomotion includes movement, but not all movement is locomotion. In daily life, writing, nodding, chewing, or standing up involve coordinated movements of bones, muscles, and joints.
2) Skeletal System: Our Framework
The skeleton is the hard, bony framework that gives shape to the body, supports soft organs, protects delicate parts (like the brain inside the skull, heart and lungs inside the rib cage), and helps in movement. Major parts include:
- Skull: Protects the brain; has immovable (fixed) joints between skull bones.
- Backbone (vertebral column): Made of many small bones called vertebrae; flexible and allows bending; protects the spinal cord.
- Rib cage: Curved bones (ribs) attached to the backbone and the breastbone; protects heart and lungs. We typically have 12 pairs of ribs.
- Shoulder and hip girdles: Girdles attach limbs to the skeleton.
- Limbs: Two forelimbs (arms) and two hind limbs (legs), each with several bones connected by joints.
3) Types of Joints and Their Movements
- Fixed Joints (Immovable): No movement; bones are tightly fused. Example: joints in the skull.
- Hinge Joint: Allows bending and straightening in one plane (like a door hinge). Examples: elbow, knee, fingers and toes.
- Ball-and-Socket Joint: The rounded head of one bone fits into the cup-like socket of another, allowing movement in many directions (rotation, swinging). Examples: shoulder, hip.
- Pivot Joint: Allows rotation around a central axis. Example: joint between skull and the top vertebra; you can turn your head left-right, up-down.
- Gliding/Sliding (concept link): Some bones slide over each other for limited movement (e.g., small bones in the wrist/ankle). Though not always highlighted at length in Class 6, it helps explain wrist flexibility.
4) Muscles and How They Work
Muscles are attached to bones by strong tissues called tendons. Muscles work in pairs—when one muscle of the pair contracts (shortens), the opposite partner relaxes (lengthens). To bend the elbow, the biceps contracts while the triceps relaxes; to straighten it, the triceps contracts and the biceps relaxes. Muscles cannot push bones; they only pull.
5) Movement in Animals (Structure Suits Function)
Earthworm
The earthworm has a soft, segmented body with tiny bristles called setae that grip the ground. It moves by alternately contracting and expanding its muscles, making the body long and thin, then short and thick. A slimy coating reduces friction. This wave-like motion is called peristaltic movement.
Snail
A snail carries a hard protective shell. It moves using a muscular foot beneath its body, which produces slimy mucus to reduce friction. The shell itself does not help in movement and is not involved in bending; it mainly protects.
Fish
Fish have a streamlined body that reduces water resistance. Strong muscles and a flexible backbone help create side-to-side waves that push water backward, propelling the fish forward. Fins help in steering, balancing, and changing direction; the tail fin provides most thrust.
Bird
Birds typically have light, hollow bones, a streamlined body, and powerful chest muscles attached to the breastbone. Wings act like aerofoils. During flight, the upstroke and downstroke, along with tail feathers, provide lift and control. Many birds can also walk, hop, or swim.
Cockroach
A cockroach has a tough outer skeleton called an exoskeleton. It moves with jointed legs for walking and can fly short distances with wings. The legs have muscles that help push against the ground, creating forward motion.
6) Fun Facts That Clarify Doubts
- You can’t bend your forearm backward at the elbow because a hinge joint allows movement in only one plane.
- We are taller in the morning than at night by a tiny amount because spinal discs (cartilage) decompress during rest.
- Ribs are attached to the backbone; most ribs join the breastbone forming the rib cage.
📝 Questions & Answers: Body Movements
Practice set: 7 MCQs + 7 Very Short + 7 Short + 7 Long answers. Use these for class tests and quick revision.
A) Multiple Choice Questions (Choose the correct option)
1. The joint that allows movement in many directions is the:
(A) Hinge joint (B) Pivot joint (C) Ball-and-socket joint (D) Fixed joint
2. Bending and straightening your knee uses a:
(A) Ball-and-socket joint (B) Hinge joint (C) Pivot joint (D) Gliding joint
3. The joint between the skull and the top vertebra mainly allows you to:
(A) Jump (B) Rotate your head (C) Grip objects (D) Stand straight
4. Fish move efficiently in water primarily because of their:
(A) Hollow bones (B) Exoskeleton (C) Streamlined body (D) Sticky foot
5. Which structure protects the heart and lungs?
(A) Skull (B) Rib cage (C) Backbone (D) Hip girdle
6. The soft tissue that cushions bones at joints is:
(A) Tendon (B) Ligament (C) Cartilage (D) Muscle
7. Earthworm moves with the help of:
(A) Wings (B) Setae and body muscles (C) Fins (D) Jointed legs
B) Very Short Answer Questions (1–2 lines)
1. Define locomotion.
Ans: Movement of an organism from one place to another, e.g., walking or swimming.
2. Name the tissue that connects muscles to bones.
Ans: Tendon.
3. Which joint is present at the shoulder?
Ans: Ball-and-socket joint.
4. What protects the brain?
Ans: Skull (cranium).
5. Name the long, flexible column of small bones in our back.
Ans: Backbone or vertebral column.
6. What helps a fish move forward in water?
Ans: Tail fin with side-to-side body movement (streamlined body helps too).
7. Which animal uses a muscular foot for movement?
Ans: Snail.
C) Short Answer Questions (2–4 sentences)
1. Differentiate between movement and locomotion.
Ans: Movement is change in position of a body part (e.g., blinking). Locomotion is movement that takes the whole body from one place to another (e.g., walking). All locomotion involves movement; not all movement is locomotion.
2. State two functions of the skeleton.
Ans: It provides shape and support to the body, and it protects delicate organs (e.g., skull protects brain, rib cage protects heart and lungs). It also helps in movement with muscles and joints.
3. Why can you not bend your elbow backwards?
Ans: The elbow is a hinge joint that allows movement in one plane only—bending and straightening. Hence, it cannot bend backwards.
4. What is a pivot joint? Give one example.
Ans: A pivot joint allows rotation around a center or axis. Example: joint between skull and first vertebra that lets us turn the head.
5. How does an earthworm move?
Ans: It alternately contracts and relaxes its body muscles, using setae to grip the ground. The body becomes long and thin, then short and thick, producing forward motion.
6. Mention any two features that help birds fly.
Ans: Light, hollow bones and a streamlined body reduce weight and air resistance; strong chest muscles power the wings.
7. What is the role of cartilage in joints?
Ans: Cartilage cushions the ends of bones, reduces friction, and prevents wear during movement.
D) Long Answer Questions (explain in detail)
1. Describe the major parts of the human skeleton and their functions.
Ans: The skeleton includes the skull, vertebral column, rib cage, girdles, and limbs. The skull surrounds the brain and has fixed joints that prevent movement to protect it. The vertebral column is a chain of many vertebrae with cushioning tissue; it supports body weight, allows bending and twisting, and protects the spinal cord. The rib cage forms a protective box around the heart and lungs, assisting breathing as it moves up and down. Shoulder and hip girdles attach limbs to the trunk, transferring forces during movement. Limbs consist of several bones joined at movable joints, enabling complex actions like grasping and walking. Together, bones, joints, and muscles coordinate to produce movement while maintaining shape and protection.
2. Explain four types of joints with everyday examples of their movements.
Ans: Fixed joints (e.g., skull bones) allow no movement, ensuring protection. Hinge joints (e.g., elbow, knee) permit bending and straightening in one plane, like opening a door. Ball-and-socket joints (e.g., shoulder, hip) allow movement in many directions including rotation—useful for throwing or swinging. Pivot joint (between skull and first vertebra) allows rotational movements; we turn our head left-right and nod partly due to this joint. Understanding the joint type predicts the kind of motion possible at that body part.
3. How do muscles work in pairs to move bones? Use the elbow as an example.
Ans: Muscles can only pull; they cannot push. Therefore, they are arranged in antagonistic pairs. At the elbow, the biceps muscle on the front of the upper arm contracts to pull the forearm up (flexion) while the triceps on the back relaxes. To straighten the elbow (extension), the triceps contracts to pull the forearm down while the biceps relaxes. This coordinated alternation enables smooth, controlled movement without damaging the joint.
4. Compare the movement in earthworm, snail, fish, bird, and cockroach, relating structure to function.
Ans: The earthworm uses body segments and setae to grip soil; muscular waves push it forward—ideal for underground life. The snail has a muscular foot that glides on mucus, reducing friction; the shell protects but does not aid movement. The fish has a streamlined body and flexible spine; side-to-side waves and tail fin generate thrust for efficient swimming. The bird has hollow bones, streamlined shape, broad wings, and strong breast muscles for powered flight; tail feathers stabilize and steer. The cockroach has an exoskeleton, jointed legs for fast running, and wings for short flights. Each movement method suits its environment.
5. What safety and health practices keep our joints and muscles healthy?
Ans: Regular moderate exercise strengthens muscles that support joints, improving stability and posture. Warm-up and cool-down reduce injury risk by preparing muscles and tendons. A balanced diet with adequate protein, calcium, and vitamin D supports muscle and bone health. Maintaining healthy body weight reduces stress on knees, hips, and spine. Proper ergonomics (correct backpack use, lifting with knees not back, maintaining neutral spine while studying) prevents strain. Adequate rest allows tissue repair, and avoiding sudden, jerky movements protects ligaments and cartilage.
6. Why do we need both rigid bones and flexible joints? Explain with examples.
Ans: Rigid bones provide support, shape, and protection (e.g., skull protects brain; ribs guard heart and lungs). However, without flexibility, we could not move. Joints introduce controlled flexibility at specific points, allowing useful motions—hinge joints let us walk and grasp; ball-and-socket joints allow circular arm swings; pivot joints enable head rotation for awareness. This combination of rigidity and flexibility ensures strength with mobility—essential for daily tasks, sports, and survival.
7. Discuss how “form follows function” using the example of the human hand and arm.
Ans: The human hand has multiple small bones and hinge-like finger joints for fine control, while the thumb’s opposability allows strong grip and precision pinch. The wrist permits small gliding movements for positioning the hand. The elbow hinge provides powerful bending and straightening, and the shoulder ball-and-socket enables wide-range rotation. Tendons transmit muscle pull to bones, and nerves provide feedback for accurate control. This arrangement shows how the form (bones, joints, muscles) is specialized for the function (grasping, throwing, writing, tool use).
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