Class 6 Notes

Class 6 Science Notes Chapter 8 (Body Movements) – Science Book

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Philoid

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Science
Detailed Notes with MCQs of Chapter 8: Body Movements. This is an important chapter, not just for understanding our own bodies, but also how different animals move. Pay close attention, as concepts from this chapter often appear in various government exams.

Chapter 8: Body Movements - Detailed Notes for Exam Preparation

1. Introduction: Movement vs. Locomotion

  • Movement: A change in the position of any part of the body. Examples: Blinking eyes, breathing, bending a finger.
  • Locomotion: Movement of the entire body from one place to another. Examples: Walking, running, swimming, flying.
  • All locomotion involves movement, but not all movement is locomotion.

2. The Human Skeletal System

  • Function: Provides shape and support to the body, protects internal organs, and helps in movement.
  • Composition: Made up of bones and cartilage. Humans have 206 bones in adulthood.
  • Bones: Hard, rigid structures. Can be felt. X-rays can show the shapes of bones.
  • Cartilage: Firm but flexible connective tissue. Not as hard as bone. Found in parts like the ear lobe, tip of the nose, and between joints. It reduces friction between bones.

3. Joints: Where Bones Meet

  • Definition: Places where two or more bones meet, allowing movement (except for fixed joints).
  • Types of Movable Joints:
    • Ball and Socket Joint: Allows movement in multiple directions (circular motion). The rounded end (ball) of one bone fits into a cup-like cavity (socket) of another.
      • Examples: Shoulder joint, Hip joint.
    • Pivotal Joint: Allows rotation around a central axis. A cylindrical bone rotates in a ring.
      • Example: Joint between the neck and the head (allows turning the head sideways, up, and down).
    • Hinge Joint: Allows back-and-forth movement in only one plane, like the hinge of a door.
      • Examples: Elbow joint, Knee joint, Finger joints, Toe joints.
  • Fixed Joints (Immovable Joints): Bones are fused together and do not allow any movement.
    • Examples: Bones in the skull (except the lower jaw), Joint between the upper jaw and the rest of the head, Joints between bones of the pelvic girdle.

4. Key Parts of the Human Skeleton

  • Rib Cage:
    • A cage-like structure formed by curved ribs joined to the chest bone (sternum) in the front and the backbone in the back.
    • Protects vital organs like the heart and lungs.
    • Typically 12 pairs of ribs. The last two pairs (floating ribs) are only attached to the backbone.
  • Backbone (Vertebral Column):
    • Runs from the neck to the lower back.
    • Made up of many small, ring-like bones called vertebrae (33 vertebrae in total, though some fuse).
    • Flexible, allows bending.
    • Protects the spinal cord.
  • Shoulder Bones (Pectoral Girdle):
    • Consists of the collar bone (clavicle) and the shoulder blade (scapula).
    • Connects the arm bones to the main skeleton.
  • Pelvic Bones (Pelvic Girdle):
    • Forms a large, basin-shaped structure.
    • Supports the lower part of the body, protects organs like the bladder and intestines.
    • Connects the leg bones to the main skeleton. Site where you sit.
  • Skull:
    • Bony structure protecting the brain.
    • Made of several flat bones joined together (fixed joints).
    • Only the lower jaw bone (mandible) is movable.

5. Muscles and Movement

  • Function: Muscles work with bones to produce movement.
  • Mechanism: Muscles can only pull, they cannot push. They work in pairs.
    • When one muscle in a pair contracts (shortens and thickens), it pulls the bone.
    • The other muscle in the pair relaxes (lengthens).
    • To move the bone back, the relaxed muscle contracts, and the first muscle relaxes.
    • Example: Biceps and Triceps in the upper arm work together to bend and straighten the elbow.

6. Gait of Animals (How Animals Move)

  • Earthworm:
    • Body: Made of many rings joined end-to-end. Has muscles. No bones (invertebrate).
    • Movement: Uses alternate expansion and contraction of body muscles. Tiny hair-like structures called bristles (setae) under its body grip the ground. Secretes slimy substance (mucus) to aid movement.
  • Snail:
    • Body: Soft body, carries a hard shell on its back (outer skeleton or exoskeleton, but not made of bone). Shell is for protection, not movement.
    • Movement: Moves using a large, flat muscular foot. Waves of muscle contractions move along the foot. Secretes mucus to reduce friction and aid movement. Slow movement.
  • Cockroach:
    • Body: Covered by a hard outer skeleton (exoskeleton) made of different units joined together, allowing movement.
    • Movement:
      • Walking/Running/Climbing: Has three pairs of legs.
      • Flying: Has two pairs of wings attached to the breast. Strong breast muscles move the wings.
  • Birds:
    • Body: Streamlined shape (reduces air resistance).
    • Adaptations for Flight:
      • Bones: Hollow and light.
      • Wings: Forelimbs modified into wings covered with feathers.
      • Muscles: Strong breast muscles (flight muscles) to flap wings.
    • Other Movement: Walk, hop, perch using hind limbs (legs).
  • Fish:
    • Body: Streamlined shape (reduces water resistance). Head and tail are smaller than the middle portion.
    • Movement (Swimming):
      • Muscles: Strong muscles cover the skeleton. Front part of the body curves one way, tail part curves the opposite way, forming a loop. This pushes the water and propels the fish forward.
      • Fins: Help maintain balance and change direction.
      • Tail Fin: Used mainly for changing direction and providing thrust.
  • Snakes:
    • Body: Long backbone, many thin muscles connecting backbone, ribs, and skin.
    • Movement (Slithering/Crawling): Moves in loops. Each loop pushes against the ground, propelling the snake forward. Moves very fast, not in a straight line. Uses scales on the underside to grip the ground.

Key Terms Recap:

  • Skeleton: Framework of bones and cartilage.
  • Joint: Point where bones meet.
  • Cartilage: Flexible connective tissue.
  • Muscle: Tissue that contracts to produce movement.
  • Locomotion: Movement from one place to another.
  • Gait: Manner of moving (walking, running, swimming, etc.).
  • Streamlined: Body shape tapered at both ends (like a boat or fish) to reduce resistance.
  • Exoskeleton: Hard outer covering (e.g., cockroach, snail shell).
  • Endoskeleton: Internal skeleton (e.g., humans, fish, birds).
  • Bristles (Setae): Hair-like structures used by earthworms for grip.

Multiple Choice Questions (MCQs)

  1. Which type of joint allows movement in multiple directions, like the shoulder?
    a) Hinge joint
    b) Pivotal joint
    c) Fixed joint
    d) Ball and socket joint

  2. Cartilage can be found in which of the following human body parts?
    a) Upper arm bone
    b) Tip of the nose
    c) Thigh bone
    d) Lower jaw

  3. How do muscles cause movement at a joint like the elbow?
    a) One muscle pushes the bone, the other pulls it.
    b) Both muscles push the bone simultaneously.
    c) Muscles work in pairs; one contracts (pulls) while the other relaxes.
    d) Muscles expand to push the bones apart.

  4. Which part of the human skeleton protects the brain?
    a) Rib cage
    b) Backbone
    c) Skull
    d) Pelvic bones

  5. An earthworm moves by:
    a) Using its muscular foot and mucus.
    b) Contracting and expanding its body muscles and using bristles.
    c) Slithering in loops using its backbone.
    d) Using three pairs of legs and wings.

  6. A streamlined body shape is an adaptation for movement primarily seen in:
    a) Earthworms and snails
    b) Cockroaches and snakes
    c) Fish and birds
    d) Humans and snails

  7. Which of these animals has an exoskeleton?
    a) Fish
    b) Bird
    c) Human
    d) Cockroach

  8. The joint between the upper jaw and the rest of the head is an example of a:
    a) Hinge joint
    b) Ball and socket joint
    c) Pivotal joint
    d) Fixed joint

  9. Snakes move by forming loops. What helps them push against the ground?
    a) Their slimy skin
    b) Their legs
    c) Their scales and muscles
    d) Their hollow bones

  10. Which statement about the gait of animals is INCORRECT?
    a) A snail moves using a muscular foot.
    b) Birds have hollow bones to aid in flight.
    c) An earthworm uses its shell to move.
    d) Fish use fins for balance and direction.

Answer Key for MCQs:

  1. d) Ball and socket joint
  2. b) Tip of the nose
  3. c) Muscles work in pairs; one contracts (pulls) while the other relaxes.
  4. c) Skull
  5. b) Contracting and expanding its body muscles and using bristles.
  6. c) Fish and birds
  7. d) Cockroach
  8. d) Fixed joint
  9. c) Their scales and muscles
  10. c) An earthworm uses its shell to move. (Earthworms do not have shells)

Study these notes carefully. Understanding the structure and function related to movement in humans and different animals is key. Let me know if any part needs further clarification.

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