Selina Concise Solutions for ICSE Class 9 Biology Chapter 12 Movement And Locomotion

Exercise 1

Question A:
Answer: 1. (b) Cartilage
2. (d) Hip
3. (a) Cervical-7
4. (b) Ear ossicles
These options identify specific types of connective tissues and bone locations within the human body. For example, cervical vertebrae are located in the neck and always number seven in most mammals.
Teacher's Tip: Remember "C-7" stands for the seven vertebrae in your "Collar" or neck area.
Exam Tip: Always write the full name of the option along with the letter to avoid any confusion during marking.

Question B.1:
Answer: Parts of the skeleton - Location
Transverse process - Neural arches in vertebra
Glenoid cavity - Pectoral girdle
Shoulder-blade - Shoulder girdle
Acetabulum - Pelvic girdle
This matching set links specific skeletal structures to the major bone groups or "girdles" that support our limbs. The acetabulum and glenoid cavity are particularly important as they are the sockets for our hip and shoulder joints.
Teacher's Tip: Associate "Acetabulum" with "Acid" (vinegar cup in Latin) to remember it is the deep cup-shaped socket in the hip.
Exam Tip: For location-based questions, use precise anatomical terms like "Pectoral girdle" instead of just "Shoulder."

Question B.2:
Answer: 1. External Ear
2. Tip of the nose
These two body parts are made of cartilage rather than hard bone, which allows them to be flexible yet hold their shape. This flexibility is important for protecting the ear and allowing the nose to move without breaking.
Teacher's Tip: Wiggle your nose or ear; that flexibility is thanks to cartilage!
Exam Tip: If asked for examples of soft skeletal parts, these are the two best examples to provide.

Question C.1:
Answer: True rib - Floating rib
1. The first seven pairs of ribs are called true ribs.
1. The last two, i.e., 11^th and 12^th pairs of ribs are called floating ribs.
2. They are attached in front of the sternum by means of costal cartilages.
2. They are not attached to the sternum at all.
True ribs provide a solid cage for your heart and lungs by connecting directly to the breastbone. Floating ribs are only attached to the spine at the back, giving your lower torso more room to expand.
Teacher's Tip: Think of floating ribs like "floats" in a pool that aren't tied to the side of the deck (sternum).
Exam Tip: Mention the specific rib pair numbers (11^th and 12^th) to show you have detailed knowledge.

Question C.2:
Answer: Muscles pull the structure. A muscle has two ends; a fixed end where the muscle originates and a movable end that pulls some other part. The movable end is drawn out to form a tough structure known as a tendon that is attached to the bone. When a muscle is stimulated by a nerve, it contracts and becomes shorter and thicker and this pulls the bone at its movable end. Muscles can only contract and relax, they cannot lengthen.
Muscles work like living ropes that can only pull things toward them by getting shorter. Because they cannot push, your body needs pairs of muscles to move your bones back and forth.
Teacher's Tip: Remember: Muscles PULL, they never PUSH.
Exam Tip: Use the word "contract" instead of "shrink" to describe muscle movement professionally.

Question C.3:
Answer: Bones - Corresponding bones
Humerus - Thigh bone (Femur)
Tarsals - Carpals
Metacarpals - Metatarsals
Ulna - Fibula
Radius - Tibia
The human skeleton is designed with a similar pattern in both the arms and the legs. For every bone in your arm, there is a "matching" bone in your leg that performs a similar structural role.
Teacher's Tip: Think of the "Humerus" in your arm as the "Femur" of your leg - they are both the single big bone at the top.
Exam Tip: Be careful not to swap "Carpals" (wrist) and "Tarsals" (ankle) in your answers.

Question C.4:
Answer: Once a structure has been moved by a muscle, it cannot return to its original position without another muscle acting on it. Muscles that cause opposing movements are known as antagonistic muscles.
Example of antagonistic muscles:
When you flex your arm at the elbow, the muscle that lies above the upper arm, i.e. the biceps is seen and felt bulging. This muscle bulges due to contraction and becomes smaller in length, stiffer and thicker. Contraction of biceps draws the forearm towards the upper arm. However, relaxation of biceps cannot push the forearm back to its original position. When the arm is extended or straightened, the muscle at the back of the upper arm, i.e. the triceps contracts. The two muscles work antagonistically or in opposite directions to bend or flex and straighten the arm at the elbow.
Antagonistic pairs ensure that for every movement in one direction, there is a way to move back. When one muscle of the pair is "working" (contracting), the other is "resting" (relaxing).
Teacher's Tip: Think of "Antagonistic" like "Antagonists" in a story - they are always working against each other!
Exam Tip: Use the Biceps and Triceps example whenever you are asked to explain muscle coordination.

Question C.5:
Answer: Some joints like shoulder joint, knee joint need to be held firmly in position to be well-lubricated. Such joints contain a lubricating fluid called synovial fluid, which serves as a cushion between the bones and removes friction during movements. As we age, the joint movement becomes stiffer and less flexible because the amount of lubricating fluid inside the joints decreases and the cartilage becomes thinner. Ligaments also tend to shorten and lose some flexibility, making the joints feel stiff.
Synovial fluid acts like oil in a car engine, preventing the hard bones from grinding against each other. As this "oil" runs low over time, our joints lose their smooth glide and can become painful.
Teacher's Tip: Think of "Synovial" fluid as "Slide" fluid for your joints.
Exam Tip: Mention both "synovial fluid" and "cartilage" when explaining why joints get stiff with age.

Question D.1:
Answer: Uses of skeleton:
1. Support and shape: The skeletal system provides a framework to the body. It provides support to all soft parts and gives a definite shape to the body and all body parts.
2. Protection: The skeleton protects the internal delicate and important organs of the body. For example in human beings, the skull protects the brain, ribs protect the heart and lungs, vertebral column protects the spinal cord, etc.
3. Movement: The skeletal system helps in movement. It co-ordinates the movement of attached bones and muscles to bring about locomotion.
4. Leverage: Some bones and joints of the skeletal system form levers and help in magnifying, either the movement or the force. For example, slight contraction of biceps moves the hand to a distance of about a foot.
5. Formation of blood cells: The skeleton is the site of haematopoiesis. Various types of blood cells like red blood cells, white blood cells and platelets are formed in the bone marrow of some long bones.
6. Storehouse for minerals: The bones are a storehouse of calcium and phosphorus for the rest of the body.
The skeleton is much more than just a frame; it is an active organ system that builds your blood and stores your minerals. Without this rigid structure, your body would just be a soft pile of tissues unable to stand or move.
Teacher's Tip: Use the "Big Three" to start your list: Support, Protect, Move.
Exam Tip: Don't forget to mention "blood cell formation" as it is a vital function often overlooked by students.

Question D.2:
Answer: Types of joints - Example
Immovable joint - Skull bones
Partially movable joint - Joints between vertebrae
Freely movable joint - Hip joint
Gliding joint - Ankle bones
Pivot joint - Joint between atlas and axis vertebrae
Hinge joint - Elbow
Ball and socket joint - Shoulder joint
Each type of joint is designed for a specific range of motion, from the locked-tight skull to the wide-circling shoulder. This variety allows us to perform complex movements like nodding our heads or throwing a ball.
Teacher's Tip: A "Hinge" joint works just like a door hinge - it only goes one way (open and shut).
Exam Tip: If the question asks for a "Ball and Socket" example, the shoulder or hip are both perfect answers.

Question D.3:
Answer: Ligament - Tendon
Structure
1. Ligament connects two or more bones together.
1. Tendon connects muscle to a bone.
2. They are elastic.
2. They are inelastic.
3. They are arranged freely.
3. They are arranged in bundles.
4. They are formed of yellow or elastic fibres.
4. They are formed of white or collagen fibres.
Function
1. They help to stabilize joints.
1. They carry tensile forces from muscle to bone.
2. Prevent dislocation
2. Attach muscles to portions of the skeleton.
Ligaments act like strong rubber bands that keep your bones from falling apart at the joints. Tendons are like tough anchor ropes that allow your muscles to pull on your bones to create movement.
Teacher's Tip: Remember: "L-B-B" (Ligament-Bone-Bone) and "M-T-B" (Muscle-Tendon-Bone).
Exam Tip: Focus on the difference in elasticity (ligaments are elastic, tendons are not) for a strong comparison.

Question D.4:
Answer: (i) Bone is a strong, hollow and non-flexible connective tissue.
(ii) It is hard, greyish-white tissue, composed of 2/3^rd of inorganic substances or minerals like calcium, phosphorus, carbonates, etc. and 1/3^rd of organic substances.
(iii) The outer surface of the bone is called periosteum. Periosteum is a thin, dense membrane that consists of outer fibrous and inner cellular layer, nerves and blood vessels that nourish the bone.
(iv) The next layer is made up of compact bone. This part is highly calcified, very hard and rigid connective tissue. This tissue gives bones a smooth, white and solid appearance.
(v) The middle layer of bone consists of bone cells called osteocytes, which are arranged in the form of concentric rings. They are embedded in a hard matrix made up of collagen fibre and mineral deposits.
(vi) The innermost hollow cavity of long bones contains bone marrow, which produces blood cells. Red bone marrow is present at the ends of the bone and produces majority of red blood cells, platelets and most of the white blood cells. Yellow bone marrow contains higher amount of fat cells than red marrow and helps in the production some white blood cells.
(vii) Bones are living tissue as long as they are present in the living body. However, when they are taken out of the body, their cells die and the bones are then said to be dead.
Bones are complex, layered structures that are very much alive and filled with blood vessels and nerves. The combination of minerals for hardness and collagen for slight flexibility makes them incredibly strong and lightweight.
Teacher's Tip: Think of a bone like a "Living Pipe" - hard on the outside, but filled with a busy factory (marrow) on the inside.
Exam Tip: Mention that bones are 2/3^rd minerals and 1/3^rd organic matter for a detailed scientific answer.

Question D.5:
Answer: 1: Cranium/Skull; 2: Clavicle, Scapula; 3: Sternum; 4: Humerus; 5: Ulna; 6: Coccyx; 7: Ribs; 8: Radius; 9: Femur; 10: Fibula; 11: Tibia
The human skeleton diagram
This list identifies the major bones that make up the human frame from head to toe. Knowing these scientific names is essential for studying anatomy and understanding how our body provides structure and protection.
Teacher's Tip: Remember that the "Radius" is on the thumb side of your arm - "Radius is Radical (Thumb's up)."
Exam Tip: Practice labeling the Radius and Ulna carefully, as they are the two bones in the forearm that students often swap.