Assertion and Reason: Body Movements | Class 6: Additional Practice PDF Download

The questions below consist of an assertion and a Reason. Use the key to choose the appropriate answer.

Q1: Assertion: There are some important internal parts of our body that lie protected inside this cage.
Reason: The chest bone and the backbone together form a rib cage which has 12 ribs on each side of the chest
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans: (a)

Both the assertion and the reason are correct. The ribcage, formed by the chest bone (sternum) and the backbone (vertebral column), serves as a protective cage for vital internal organs such as the heart and lungs. It is also true that there are 12 pairs of ribs attached to the vertebral column on each side of the chest. The reason accurately explains why the ribcage is important for protecting internal organs.

Q2: Assertion: Birds fly in the air and walk on the ground.
Reason: Birds fly because their bodies are well suited for flying bird's bones are hollow and light.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans: (a)

Both the assertion and the reason are correct. Birds are unique in that they can both fly and walk. The reason provides an accurate explanation for why birds can fly – their bones are lightweight and hollow, which makes them well-suited for flight. This adaptation allows them to be agile and efficient flyers while also being capable of walking on the ground.

Q3: Assertion: The human skeleton is composed of around 305 bones at birth.
Reason: All the bones in our body also form a framework to give a shape to our body.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans: (b)

The assertion is correct; newborns have approximately 305 bones in their bodies. However, the reason, although true, does not provide a direct explanation for the number of bones at birth. The statement about bones forming a framework for body shape is accurate but does not explain why there are around 305 bones specifically at birth. The number of bones changes as a person grows, as some bones fuse together over time.

Q4: Assertion: The ball and socket joint allows movement in all directions.
Reason: This joint is found in the shoulder and hip and it consists of a bone with a rounded end that fits into a cup-like cavity of another bone.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans: (a)

The ball and socket joint in our body, such as the shoulder and hip joint, allows rotational movement and movement in all directions because of its structure where a bone with a rounded end fits into a cup-like cavity of another bone.

Q5: Assertion: The skeletal system provides the basic framework for the body.
Reason: The skeletal system is composed of muscles.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

Ans: (c)

The skeletal system is not composed of muscles, but of bones. These bones provide support and form the basic framework of the body. Muscles are part of the muscular system, which works closely with the skeletal system to facilitate movement.

Q6: Assertion: Hinge joints allow movement only in one direction.
Reason: Hinge joints are found in the knee and elbow.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans: (a)

Similar to the hinge on a door, hinge joints in our body like those found in our knee and elbow allow movement only in one direction - back and forth.

Q7: Assertion: The backbone protects the spinal cord.
Reason: The spinal cord is made up of small bones called vertebrae.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans: (b)

Assertion: "The backbone protects the spinal cord." True. The vertebrae of the backbone form a protective canal that encases and safeguards the spinal cord.

Reason: "The spinal cord is made up of small bones called vertebrae." False. The spinal cord is not made up of vertebrae. It is a bundle of nerves enclosed within the vertebral column, which is composed of small bones called vertebrae.

Thus, the assertion is correct, but the reason is incorrect.

Q8: Assertion: The pivot joint allows rotational movement.
Reason: This joint is found in the neck which helps in moving the head in different directions.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans: (a)

The pivot joint in our neck, which allows the head to rotate and tilt, is a perfect example of how this type of joint allows rotational movement. The structure of the pivot joint, where a bone rotates in a ring of another bone, enables this type of movement.