RBSE Solutions Class 12 Biology Chapter 30 Man-Movement & Locomotion

RBSE Class 12 Biology Chapter 30 Multiple Choice Questions

 

Question 1. The exoskeleton of animal is –
(a) Skull
(b) Ribs
(c) Nails
(d) Sternum
Answer: (c) Nails
In simple words: The exoskeleton is the outer, hard covering of an animal. Out of the given options, nails are the external structures that form part of the exoskeleton.

🎯 Exam Tip: Remember that the exoskeleton refers to the hard outer layer that supports and protects an animal's body.

 

Question 2. Matrix of a bone is of which protein –
(a) Loading [MathJax]/extensions/MathZoom.js
Answer: (The options and full answer are incomplete in the source material.)
In simple words: (The explanation is incomplete due to missing information in the source.)

🎯 Exam Tip: Identify the main protein components that make up the non-cellular part of bone tissue.

 

Question 3. The function of the skeleton is –
(a) Protection of soft organs
(b) Provide space for muscle attachment
(c) Formation of blood corpuscles
(d) All of the options
Answer: (d) All of the options
In simple words: The skeleton does many important jobs for the body. It keeps soft parts safe, gives muscles places to connect, and helps make blood cells.

🎯 Exam Tip: When asked about functions, list all major roles such as support, protection, movement, and blood cell production.

 

Question 4. Reason of the pendular movement of cilia is –
(a) Sliding microtubules
(b) Contraction of microfibres
(c) Extension of cell wall
(d) Change in positions
Answer: (b) Contraction of microfibres
In simple words: Cilia move in a swinging way because tiny fibers inside them contract, pulling them back and forth. This movement helps them push things along.

🎯 Exam Tip: Focus on the internal structures of cilia and flagella, like microtubules and associated proteins, for their movement mechanisms.

 

Question 5. According to sliding filament theory, the responsible molecule to decrease the length of muscle at the time of muscle contraction is –
(a) Collagen
(b) Actin
(c) Myosin
(d) Tyutin
Answer: (b) Actin
In simple words: In muscle contraction, the actin filaments slide over the myosin filaments, making the muscle shorter. Actin is the key molecule that moves to shorten the muscle.

🎯 Exam Tip: Clearly differentiate between actin (thin filaments) and myosin (thick filaments) and their roles in the sliding filament theory.

 

Question 6. Type of elbow joint is –
(a) Loading [MathJax]/extensions/MathZoom.js
Answer: (The options and full answer are incomplete in the source material.)
In simple words: (The explanation is incomplete due to missing information in the source.)

🎯 Exam Tip: Identify the specific type of synovial joint the elbow is, based on its range of motion.

 

Question 7. Contractile protein is –
(a) Troponin
(b) Myosin
(c) Tropomyosin
(d) All of the options
Answer: (b) Myosin
In simple words: Myosin is a protein that can contract. It works with another protein called actin to make muscles move and shorten.

🎯 Exam Tip: Remember that actin and myosin are the primary contractile proteins, while troponin and tropomyosin regulate their interaction.

 

Question 8. Number of bones present in the posterior limbs of man –
(a) 14
(b) 24
(c) 26
(d) 30
Answer: (d) 30
In simple words: Each of a person's posterior limbs (legs) has 30 bones, making a total of 60 bones for both legs.

🎯 Exam Tip: Be able to count and recall the number of bones in major parts of the human skeleton, especially the limbs.

 

Question 9. Storage of which substance in an anaerobic contraction of muscles become painful.
(a) Calcium ion
(b) Myosin
(c) Lactic acid
(d) Creatine phosphate
Answer: (c) Lactic acid
In simple words: When muscles work hard without enough oxygen, they produce lactic acid. This build-up of lactic acid causes a painful, burning feeling in the muscles.

🎯 Exam Tip: Link anaerobic respiration with lactic acid production and its role in muscle fatigue and pain.

 

Question 10. Presence of which ions is essential for –
(a) Calcium
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Answer: (The options and full answer are incomplete in the source material.)
In simple words: (The explanation is incomplete due to missing information in the source.)

🎯 Exam Tip: Recall the vital ions, especially calcium, and their roles in muscle contraction and bone health.

RBSE Class 12 Biology Chapter 30 Very Short Answer Type Questions

 

Question 1. Write the structural and functional unit of muscle.
Answer: The structural and functional unit of muscle is called a sarcomere. It is the basic unit that contracts.
In simple words: A sarcomere is the smallest part of a muscle that can do work and contract.

🎯 Exam Tip: Define sarcomere and state its role as the fundamental unit of muscle contraction.

 

Question 2. By which structure muscle joint with a bone?
Answer: Muscles are joined to bones by strong, cord-like structures called tendons. Tendons help transmit the force of muscle contraction to the bones.
In simple words: Muscles connect to bones with strong cords known as tendons.

🎯 Exam Tip: Distinguish between tendons (muscle to bone) and ligaments (bone to bone).

 

Question 3. By which process bone joints to bone?
Answer: Bones are joined to other bones by strong, flexible bands called ligaments. Ligaments provide stability to joints.
In simple words: Bones are held together at joints by tough bands called ligaments.

🎯 Exam Tip: Know the difference between a ligament and a tendon and their respective functions.

 

Question 4. How many vertebrae from sacrum bone of man?
Answer: The sacrum bone in humans is formed from five fused vertebrae. These vertebrae are fused together to form a single, wedge-shaped bone.
In simple words: The sacrum bone is made up of five vertebrae that have grown together.

🎯 Exam Tip: Remember the number of fused vertebrae that make up the sacrum and coccyx.

 

Question 5. How many bones participate in the formation of the skull of man?
Answer: The human skull is formed by 29 bones. This includes bones of the cranium, face, ear ossicles, and the hyoid bone.
In simple words: There are 29 bones that make up a human's skull.

🎯 Exam Tip: Recall the total number of bones in the skull, including cranial, facial, and associated bones.

 

Question 6. Give names of the main substances stored in the bones.
Answer: The main substances stored in bones are calcium phosphate, calcium carbonate, and magnesium phosphate. These minerals give bones their hardness and strength.
In simple words: Bones mainly store calcium phosphate, calcium carbonate, and magnesium phosphate, which make them strong.

🎯 Exam Tip: List the primary mineral components that contribute to bone matrix and its strength.

RBSE Class 12 Biology Chapter 30 Short Answer Type Questions

 

Question 1. What are cartilaginous bones? Explain.
Answer: Bones are mainly of three types:
1. Membranous or Investing bones – These bones are formed when membranes beneath the embryonic skin turn into bone. They give strength to soft cartilage parts of the skeleton. Examples include flat bones of the skull, clavicle, and finger bones.
2. Cartilaginous or Replacing bones – These bones develop from hyaline cartilage. The cartilage matrix is broken down by special cells called osteoclasts, and then bone tissue replaces it. Examples are limb bones, vertebral column bones, and some skull bones.
3. Sesamoid bones – These bones are formed when a ligament turns into bone. A common example is the patella, or kneecap.
In simple words: Cartilaginous bones are those that start as soft cartilage and then turn into hard bone. They are one of three main types of bones in the body.

🎯 Exam Tip: When explaining bone types, provide clear definitions and relevant examples for each category.

 

Question 2. Write the main functions of a Skeleton.
Answer: The main functions of the skeleton are:
• The skeleton provides a solid, firm structure that supports the entire body.
• It gives muscles a stable place to attach, allowing for movement.
• The skeleton acts like levers, helping the body move and change its position.
• It protects important soft organs such as the brain, heart, lungs, and spinal cord.
• Red blood cells are made in the red bone marrow found inside bones.
In simple words: The skeleton supports the body, helps muscles move, protects important organs, and makes blood cells.

🎯 Exam Tip: List the key roles of the skeleton, covering support, protection, movement, and hematopoiesis (blood cell formation).

 

Question 3. Write a note on the sternum.
Answer: The sternum, also known as the breastbone, is a flat bone located in the middle of the chest. It has several important functions and parts:
1. The sternum helps form the "respiratory basket" or rib cage, working with the ribs and thoracic vertebrae to protect the heart and lungs.
2. It is a flat bone with distinct front and back surfaces.
3. The sternum has three main parts:
• Manubrium: This is the top part, where the collarbone (clavicle) and the first pair of ribs attach.
• Sternum body (or Gladiolus): This is the middle and largest part, where the 2nd to 7th pairs of ribs connect.
• Xiphoid process (or Ensiform): This is the small, triangular-shaped lower tip of the sternum.
In simple words: The sternum is the breastbone in your chest. It helps protect your organs, and ribs attach to it. It has three main sections: a top, a middle, and a small tip at the bottom.

🎯 Exam Tip: Describe the sternum's location, its three main parts, and its role in forming the rib cage.

 

Question 4. Draw a neat and labelled diagram of the pelvic girdle
Answer:The pelvic girdle is a basin-shaped structure that supports the spine and connects the lower limbs to the axial skeleton. It is made of two hip bones joined at the back to the sacrum and at the front to each other at the pubic symphysis.
In simple words: The pelvic girdle is like a bony ring that connects your legs to your back. It helps you stand and move, and protects organs inside.

🎯 Exam Tip: When drawing diagrams, ensure all key parts are clearly labeled and the overall structure is accurate. Use simple lines to represent major bones and joints.

 

Question 5. Differentiate between ligament and cartilage.
Answer:

Ligaments and tendons are both types of fibrous connective tissue, but they have different roles. Ligaments connect bones to other bones, giving support to joints. Tendons connect muscles to bones, allowing movement when muscles pull.
In simple words: Ligaments hold bones together at joints. Tendons connect muscles to bones so you can move.

🎯 Exam Tip: Clearly state the connections (bone-to-bone vs. muscle-to-bone) and key characteristics (elasticity) for both ligaments and tendons.

 

Question 6. How muscle gets excited about contraction?
Answer: Muscle excitation for contraction happens in these steps:
• A nerve impulse arrives at the neuromuscular junction, which is where the nerve meets the muscle. This causes the release of a chemical called acetylcholine.
• Acetylcholine makes the muscle cell's outer membrane (plasma membrane) more open to sodium ions (\( \text{Na}^+ \)).
• Because of this, sodium ions rush into the muscle cell, changing the electrical charge inside. The inside of the membrane becomes positive, creating an 'action potential'.
• Normally, the inside of the muscle cell membrane is negative. This positive change quickly spreads across the entire muscle cell membrane.
• This action potential is the "excitation state" of the muscle, signaling it to prepare for contraction.
In simple words: A nerve tells a muscle to move by sending a chemical signal. This signal makes the muscle cell's wall let in tiny charged particles, changing its electricity and telling it to get ready to squeeze.

🎯 Exam Tip: Explain the role of acetylcholine, sodium ions, and action potential in initiating muscle excitation at the neuromuscular junction.

 

Question 7. If all joints of an arm of man become non-movable than what happens?
Answer: If all joints in a person's arm become completely non-movable, then movement of the arm and any form of locomotion (moving from one place to another using that arm) would become impossible. The arm would be rigid and fixed.
In simple words: If arm joints couldn't move, a person couldn't use their arm for any movement or to help them walk.

🎯 Exam Tip: Emphasize the critical role of movable joints in facilitating both fine motor skills and overall locomotion.

 

Question 8. What is osteoporosis?
Answer: Osteoporosis is a disease where bones become weak and fragile. The main problem is a loss of bone mass, meaning there's less organic material (matrix) and minerals (like calcium) in the bones. This makes the bones thin, less elastic, and weaker. People with osteoporosis are more likely to break bones, even from a small bump or fall. The disease affects the whole skeleton but is most common in the pelvis, wrist, and spine. It usually gets worse with age, especially in older women due to less estrogen. Other hormones like calcitonin, PTH, and glucocorticoids can also play a role.
In simple words: Osteoporosis is a bone disease that makes your bones thin, weak, and easy to break. It happens when bones lose too much of their building materials, especially calcium.

🎯 Exam Tip: Define osteoporosis as a loss of bone density, list its main causes (age, hormones, mineral deficiency), and mention common symptoms (increased fracture risk).

RBSE Class 12 Biology Chapter 30 Essay Type Questions

 

Question 1. (Question text incomplete in source)
Answer: Muscle contraction and relaxation both need energy, which comes mainly from ATP (adenosine triphosphate). Muscles only store a small amount of ATP, so they need to get more energy from other places during contraction.
• Creatine phosphate, found in muscles, gives energy very quickly because it has a high-energy bond. This process is helped by an enzyme called creatine kinase.
• Muscles usually get energy for contraction by burning glucose with oxygen. However, if there isn't enough oxygen for a long time, this method doesn't work. In this case, muscles break down glycogen (a stored sugar) without oxygen, which is a longer-lasting way to get energy.
• When glycogen breaks down without oxygen, it creates lactic acid. This lactic acid travels to the liver through the blood. In the liver, about 80% of the lactic acid is changed back into glycogen, and the remaining 20% is broken down into carbon dioxide (\( \text{CO}_2 \)) and water (\( \text{H}_2 \)), releasing energy. This released energy is then used to make more glycogen.
In simple words: Muscles need energy (ATP) to work. They get it quickly from creatine phosphate or by breaking down glucose with oxygen. If there's no oxygen, they break down stored sugar (glycogen) into lactic acid, which then goes to the liver to be recycled or broken down further for energy.

🎯 Exam Tip: Describe the energy sources for muscle contraction, distinguishing between immediate ATP, creatine phosphate, aerobic respiration of glucose, and anaerobic glycolysis (lactic acid fermentation).

 

Question 10. If nerve going to skeletal muscle is cut, what will be an effect on contraction?
Answer: If the nerve going to a skeletal muscle is cut, there will be no contraction in that muscle. Skeletal muscles need nerve impulses to be activated and contract. Without nerve signals, the muscle cannot receive the command to move.
In simple words: If the nerve to a muscle is cut, the muscle cannot get signals and will not contract or move.

🎯 Exam Tip: Understand that skeletal muscles are voluntary and require nerve stimulation for any movement.

 

RBSE Class 12 Biology Chapter 30 Essay Type Questions

 

Question 1. (Question text incomplete in source)
Answer: (This appears to be a multi-part answer related to muscle structure and joints, likely a continuation or different part of a comprehensive essay question.)
The skeletal muscles of the tongue and the upper part of the esophagus are not attached to the skeleton. These are sometimes called fatigued muscles, phasic muscles, or striated somatic muscles.
• The basic unit of these muscles is called a muscle fiber.
• Each muscle fiber has many nuclei and is surrounded by a membrane called the sarcolemma. Muscle fibers are grouped together into bundles called fasciculi, which are covered by a layer called endomysium.
• Fasciculi are also grouped, and each group is surrounded by perimysium, made of connective tissues.
• The entire skeletal muscle is enclosed by an epimysium.

Fine structure of muscle Fibre:
• Muscle fibers can be up to 30 cm long, with a diameter of 0.01 to 0.1 mm. They are enclosed by the sarcolemma. The cytoplasm inside (sarcoplasm) has many mitochondria (called acrosomes) and a type of endoplasmic reticulum called sarcotubules.
• Sarcoplasm contains three soluble proteins: myogenin, myoglobin, and albumin.
• It also stores glycogen and has small amounts of sodium (Na), calcium (Ca), phosphorus (P), and magnesium (Mg), but more potassium (K).
• Each muscle fiber contains many myofibrils. Myofibrils are as long as the muscle fiber itself and are 1 to 3 micrometers thick.
• Myofibrils have alternating dark (A-bands, Anisotropic) and light (I-bands, Isotropic) bands.
• A zigzag line called the Z-line (or Krau's membrane) runs through the middle of each I-band.
• The middle region of the A-band is called the H-zone, which has a central M-line.
• The distance between two Z-lines is called a sarcomere, which is the functional unit of muscle contraction.
• Each sarcomere includes one complete A-band and two half I-bands, one on each side.
• The A-band is mainly made of myosin filaments, which are 1.5 micrometers long and 100 Angstroms in diameter.
• The I-band is mainly made of actin filaments, which are 2 micrometers long and 50 Angstroms in diameter.
• The ends of the actin filaments overlap slightly with the A-bands (about 0.2 micrometers on each side).
• During rest, the A-band is 1.5 micrometers long, and each half I-band is 0.8 micrometers long. This means the overall length of the sarcomere is the sum of these parts.
• The cross-links from the myosin filaments point towards the actin filaments at a 60-degree angle, spaced 60-70 Angstroms apart. The H-zone does not have these cross-links.

In vertebrates, joints are where two bones meet, or where a bone meets cartilage. These points of contact allow for body movements.

Based on movement, joints are of three types:
1. Synarthrosis (Fixed or Immovable Joints):
• The bones are held together by dense, strong bundles of white fibrous connective tissue that cannot stretch.
• No movement is possible in these joints.
• An example is the sutures (joints) between the bones of the skull.

2. Amphiarthrosis (Partially Movable Joints):
• These are tough joints where bones are connected by a disc of white fibrous cartilage that can stretch a little.
• Only limited movement is possible.
• An example is the pubic symphysis.
• There are two types:
a. Pivot Joint: Found between the atlas and axis vertebrae, allowing side-to-side (lateral) movement.
b. Gliding Joint: Here, the end of one bone slides over a part of another bone, allowing movement in different directions. Examples include joints between tarsal bones in the ankle, carpal bones in the wrist, and between the sternum and clavicle.

3. Synovial (Diarthrosis or Movable Joints):
• Bones connected by synovial joints can move freely in one or more directions. A smooth, thin layer of hyaline cartilage covers the bone surfaces at the joint.
• This cartilage reduces friction between the bones. There is a space between the bones called the synovial cavity. Many ligaments connect the bones and form a capsule, which is lined by a synovial membrane.
• This membrane produces synovial fluid, which contains mucin. This fluid nourishes the hyaline cartilage and lubricates the joint, allowing smooth movement. Examples include the hip, knee, and finger joints, as well as the joint between the occipital condyle and atlas.
• Ellipsoidal Joint: Allows movement of one bone over another in about two axes. Examples include joints between metacarpals and phalanges in the hand, metatarsals and phalanges in the foot, and the joint between the radius and carpals.
In simple words: This answer covers the detailed structure of muscle fibers, including sarcomeres and bands, and how energy is made for muscle action. It also explains different types of joints in the body: fixed (like in the skull), slightly movable (like the pelvis), and freely movable (like knees), explaining how each type allows or restricts movement.

🎯 Exam Tip: For detailed questions, break down the answer into clear sections (e.g., muscle structure, joint types). Use bullet points for easy readability and include specific examples where possible.

 

Question 3. Describe the mechanism of muscle contraction with diagrams.
Answer: The mechanism of muscle contraction is explained by the "Sliding Filament Theory." This theory was proposed by A.F. Huxley, J. Hensen, and H.E. Huxley.
• According to this theory, the thick myosin filaments stay still, while the thin actin filaments slide over them, with the help of cross-links.
• During contraction, the length of the A-band (dark band) does not change, but the length of the I-band (light band) and the H-zone (middle of A-band) become shorter.
• In the H-zone, the actin filaments slide over each other.

The process of muscle contraction and relaxation involves four main phases:
1. Excitation:
• When a nerve impulse reaches the end of the axon at the neuromuscular junction, it causes the release of a chemical called acetylcholine.
• This chemical changes how easily the muscle's plasma membrane lets sodium ions (\( \text{Na}^+ \)) pass through.
• As a result, sodium ions enter the muscle cell, which causes an electrical change (axon potential) where the inside of the plasma membrane becomes positive.
• Normally, the inner surface of the plasma membrane has a negative charge. This positive change spreads across the entire muscle plasma membrane, creating an action potential, which is the muscle's excited state.
2. Excitation - Contraction Coupling:
• As soon as active sites on actin are exposed, the myosin filament connects with the actin, and the contraction process begins.
3. Contraction:
• Contraction happens through the sliding filament process, starting when actin and myosin form a "transverse bridge."
• Before the active filament joins at the active site, an ATP molecule attaches to the head of the transverse bridge. The ATPase enzyme then breaks down this ATP into ADP and Pi.
• ADP and Pi stay attached to the myosin head. Then, the myosin head joins with the active site on the actin filament.
• When the head joins, it changes shape, causing it to bend (like bending a finger). This pulls the actin filament towards the center of the sarcomere (H-zone), using energy released from the ATP breakdown.
• As the myosin head bends, ADP and Pi are released. Immediately, a new ATP molecule attaches to the myosin head.
• When the new ATP attaches, the myosin head separates from the actin. This ATP is then broken down again, and the myosin head reattaches, repeating the process.
• This repeated attachment and pulling by the transverse bridges cause the active filament to slide, leading to muscle contraction. Contraction continues as long as calcium ions (\( \text{Ca}^{++} \)) are attached to troponin.

4. Relaxation:
• When nerve impulses stop, the muscle sends calcium ions (\( \text{Ca}^{++} \)) back into its sarcoplasmic reticulum (a storage area). This frees troponin-C from calcium ions, which then blocks the active sites on the actin filament.
• Without the active sites being open, actin and myosin cannot join or bond. The filaments return to their original positions, and the muscles relax.
In simple words: Muscle contraction happens when thin actin filaments slide past thick myosin filaments, making the muscle shorter. This starts with a nerve signal that releases a chemical, opening channels for charged particles to enter the muscle cell. This electrical change then causes calcium to be released, allowing myosin heads to pull on actin using energy from ATP, like tiny oars. When the signal stops, calcium goes back, and the muscle relaxes.

🎯 Exam Tip: Systematically explain each phase: excitation (nerve impulse, neurotransmitter, action potential), excitation-contraction coupling (calcium release), contraction (sliding filament, cross-bridge cycle, ATP hydrolysis), and relaxation (calcium reuptake, active site blockage).

 

Question 4. Write the structure of girdles and their significance.
Answer:
Pectoral Girdle:

• It holds up the arms and protects organs in the chest.
• It is made of two matching parts.
• Each side has a collar bone (clavicle) and shoulder blade bones (scapula-coracoid).
• The clavicle is a thin, rod-shaped bone, also known as the collar bone.
• The scapula is a wide, flat bone found in all mammals, like a shoulder blade.
• The coracoid bone joins with the scapula, forming a part called the coracoid process.
• Humans do not have a supra scapula bone in their shoulder girdle.
• The back of the scapula has a ridge called a spine. Its front and bottom parts extend further.

Pelvic Girdle:

• It supports the legs.
• It has two matching halves, and each half is called an os-innominate.
• Both os-innominate halves are connected by a pubic symphysis, which is a strong, flexible cartilage.
• A rabbit's pelvic girdle is shaped like the letter W.
• Each os-innominate in a rabbit has four bones: the Ilium, Ischium, Pubic, and Cotyloid.
• Each os-innominate has a hollow space called the acetabulum, where the thigh bone (femur) fits.
• In rabbits, the pubic bone does not help form the acetabulum. There is a small cotyloid bone found between the acetabulum and the pubic bone.
• Humans do not have a cotyloid bone. So, each os-innominate in humans has three bones: Ilium, Ischium, and Pubic. All these bones help form the acetabulum.
• A hole called the obturator foramen exists between the pubic and ischium bones.

In simple words: Girdles are sets of bones that connect the limbs to the main skeleton. The pectoral girdle supports the arms, while the pelvic girdle supports the legs, and both protect important organs.

🎯 Exam Tip: When describing bone structures, clearly state their main function and list the key bones that form them. Mentioning differences between species can add extra points.