SECTION A: VERY SHORT ANSWER QUESTIONS (1 Mark)
Q1. Why are dogs more capable than humans in tracking injured people during earthquakes?
Answer: Dogs have a much larger number of olfactory receptors than humans. While human olfactory cells can fit on a postage stamp, dog olfactory cells would need a large scarf to arrange, making their sense of smell far superior.
Q2. Name the visual pigment present in rod cells.
Answer: Rhodopsin.
Q3. What is the function of the iris?
Answer: The iris controls the size of the pupil and regulates the amount of light entering the eye.
Q4. Which part of the ear helps in maintaining body balance?
Answer: Semicircular canals and vestibule.
Q5. Name the enzyme present in tears and its function.
Answer: Lysozyme - it destroys germs that enter the eyes.
Q6. What is the blind spot in the eye?
Answer: The part of the retina where the optic nerve begins and no photoreceptors are present, resulting in no vision.
Q7. Which vitamin deficiency causes night blindness?
Answer: Vitamin A deficiency.
Q8. Name the three ear ossicles.
Answer: Malleus, Incus, and Stapes.
Q9. What are the basic tastes detected by taste buds?
Answer: Sweet, salt, sour, bitter, umami, and oleogustus.
Q10. What is xerophthalmia?
Answer: A condition caused by prolonged Vitamin A deficiency where the conjunctiva and cornea become dry and opaque, leading to blindness.
SECTION B: SHORT ANSWER QUESTIONS (2-3 Marks)
Q11. Explain the power of accommodation of the eye.
Answer: The power of accommodation is the ability of the eye to adjust the focal length of the lens by changing its curvature according to the distance of the object.
- For nearby objects: Ciliary muscles contract, ligaments relax, lens becomes more curved (shorter focal length)
- For distant objects: Ciliary muscles relax, ligaments stretch, lens becomes less curved (longer focal length)
Q12. Differentiate between rod cells and cone cells.
Answer:
Rod Cells:
- Shape: Rod-shaped structure
- Pigment: Contains rhodopsin
- Function: Enable vision in dim light
- Color detection: Cannot detect colors
- Number: More numerous than cone cells
Cone Cells:
- Shape: Cone-shaped structure
- Pigment: Contains photopsin/iodopsin
- Function: Responsible for color vision
- Color detection: Detect red, green, and blue colors
- Number: Less numerous than rod cells
Q13. How does the pupil regulate light entry into the eye?
Answer:
- In bright light: Circular muscles of iris contract → pupil constricts → less light enters
- In dim light: Radial muscles of iris contract → pupil dilates → more light enters
- This prevents damage to eye tissues and ensures proper vision in different light conditions
Q14. Explain the process of taste detection.
Answer:
- Food substances dissolve in saliva
- Dissolved substances stimulate chemoreceptors in taste buds
- Chemoreceptors generate nerve impulses
- Impulses travel through respective nerves to the brain
- Brain interprets the impulses as different tastes
Q15. What is binocular vision? What is its advantage?
Answer: Binocular vision is the ability to see a single three-dimensional image when both eyes view the same object from slightly different angles. Advantage: Provides depth perception and better judgment of distance, which is crucial for activities requiring precision.
Q16. How do semicircular canals help maintain body balance?
Answer:
- Head movements cause movement of endolymph in semicircular canals
- Moving endolymph stimulates sensory hair cells
- Hair cells generate nerve impulses
- Impulses are transmitted via vestibular nerves to cerebellum
- Cerebellum processes information and maintains body equilibrium
SECTION C: LONG ANSWER QUESTIONS (5 Marks)
Q17. Describe the structure and function of the human eye.
Answer:
Protective Structures:
- Eye socket, eyebrows, eyelashes, eyelids provide physical protection
- Conjunctiva secretes mucus to prevent drying
- Tears clean and lubricate the eye
Layers of the Eye:
- Sclera: Tough outer white layer providing firmness
- Choroid: Middle layer with blood vessels for nourishment
- Retina: Inner layer containing photoreceptors
Important Parts:
- Cornea: Transparent front part that refracts light
- Iris: Colored part controlling pupil size
- Pupil: Central opening regulating light entry
- Lens: Focuses light on retina, changes shape for accommodation
- Ciliary muscles: Control lens curvature
- Aqueous humor: Provides nutrition to eye tissues
- Vitreous humor: Maintains eye shape
Function: Light enters through cornea → passes through pupil → focused by lens → forms image on retina → photoreceptors convert light to impulses → optic nerve carries impulses to brain → brain interprets as vision.
Q18. Explain the process of hearing with the help of a flowchart.
Answer:
Process of Hearing:
Sound waves → Pinna → Auditory canal → Tympanum vibrates → Ear ossicles (Malleus, Incus, Stapes) amplify vibrations → Oval window vibrates → Fluid in cochlea moves → Hair cells in Organ of Corti stimulated → Nerve impulses generated → Auditory nerve → Brain (Cerebrum) → Sensation of hearing
Detailed Explanation:
- Sound collection: Pinna collects sound waves and directs them into auditory canal
- Vibration: Tympanum vibrates in response to sound waves
- Amplification: Three ear ossicles amplify and transmit vibrations to oval window
- Fluid movement: Vibrations cause movement of fluid (endolymph) in cochlea
- Stimulation: Moving fluid stimulates hair cells in Organ of Corti
- Impulse generation: Stimulated hair cells generate nerve impulses
- Transmission: Impulses travel via auditory nerve to brain for interpretation
Q19. Discuss various eye defects and diseases with their causes and remedies.
Answer:
A. Vision Defects:
- Myopia (Short-sightedness): Cannot see distant objects clearly
- Hypermetropia (Long-sightedness): Cannot see near objects clearly
B. Nutritional Defects:
- Night blindness:Cause: Vitamin A deficiency → reduced rhodopsin production
- Remedy: Vitamin A rich diet
- Xerophthalmia:Cause: Severe Vitamin A deficiency
- Remedy: Immediate Vitamin A supplementation
C. Other Eye Diseases:
- Color blindness:Cause: Defective cone cells
- Effect: Cannot distinguish red and green colors
- Glaucoma:Cause: Increased pressure due to poor aqueous humor drainage
- Remedy: Laser surgery
- Cataract:Cause: Lens becomes opaque
- Remedy: Surgical lens replacement
- Conjunctivitis:Cause: Bacterial or viral infection
- Remedy: Antibiotics, maintain hygiene
- Computer Vision Syndrome:Cause: Excessive use of digital devices
- Remedy: Limit screen time, take breaks
Q20. Explain the chemistry of vision in photoreceptors.
Answer:
Components of Visual Pigments:
- Rhodopsin (in rod cells): Opsin protein + Retinal (Vitamin A derivative)
- Photopsin (in cone cells): Opsin protein + Retinal
Process:
- In darkness: Visual pigments remain intact
- Light exposure: Light energy causes dissociation of visual pigments
- Rhodopsin → Opsin + Retinal
- Photopsin → Opsin + Retinal
- Chemical change: Dissociation triggers chemical changes in photoreceptor cells
- Impulse generation: Chemical changes generate nerve impulses
- Transmission: Impulses travel via optic nerve to visual cortex in brain
- Vision: Brain interprets impulses as visual images
Importance of Vitamin A:
- Essential for retinal formation
- Deficiency leads to reduced pigment production
- Results in vision problems, especially night blindness
SECTION D: APPLICATION-BASED QUESTIONS
Q21. A person cannot see distant objects clearly but can see nearby objects. What is this condition called? How can it be corrected?
Answer: This condition is called Myopia or short-sightedness. Correction: Can be corrected using concave lenses in spectacles or contact lenses that help focus distant objects properly on the retina.
Q22. Why do we not sense taste properly when we have a cold?
Answer: During a cold, the nasal passages are blocked with mucus, which affects our sense of smell. Since taste and smell are closely related (aromatic particles from food also stimulate olfactory receptors), the blocked nose reduces our ability to smell, which in turn affects our perception of taste.
Q23. How do visually impaired people read Braille script using their fingers?
Answer: The fingertips have a very high concentration of touch receptors compared to other parts of the body. This high density of receptors makes fingertips extremely sensitive to touch, allowing visually impaired people to feel the raised dots of Braille script and interpret them as letters and words.
Q24. Why are people with color blindness not suitable for jobs like pilots or drivers?
Answer: Color blindness affects the ability to distinguish between certain colors (usually red and green). This is dangerous for:
- Pilots: Need to distinguish colored lights and signals for safe navigation
- Drivers: Must differentiate between traffic light colors for road safety
- Military personnel: Need to identify color-coded maps, signals, and equipment
Q25. Explain why eye donation is called "life donation."
Answer: Eye donation is called "life donation" because:
- Donated corneas can restore sight to blind people
- One person's eye donation can help two people regain vision
- It gives a "new life" to visually impaired individuals by enabling them to see
- The donated eyes continue to "live" and function in the recipient's body
- It's a precious gift that dramatically improves the quality of life
SECTION E: DIAGRAM-BASED QUESTIONS
Q26. Draw a labeled diagram of the human eye and explain the function of any three parts.
Answer: [Students should draw the eye diagram with labels: Cornea, Iris, Pupil, Lens, Retina, Optic nerve, Sclera, Choroid, Ciliary muscles, etc.]
Functions:
- Cornea: Transparent layer that refracts light rays to focus them on the retina
- Iris: Controls the size of pupil and regulates light entry into the eye
- Retina: Contains photoreceptors that convert light energy into nerve impulses
Q27. Identify the parts of the ear from the given diagram and explain their functions.
[For any ear diagram provided] Answer: Students should identify and label parts like:
- Pinna: Collects sound waves
- Tympanum: Vibrates with sound waves
- Cochlea: Contains auditory receptors for hearing
- Semicircular canals: Help maintain body balance
SECTION F: HIGHER ORDER THINKING QUESTIONS
Q28. Compare the sense organs of humans with those of other organisms mentioned in the chapter.
Answer:
Humans:
- Specialized feature: Binocular vision
- Function: 3D depth perception
- Advantage: Precise judgment of distance
Dogs:
- Specialized feature: Enhanced olfactory receptors
- Function: Superior smell detection
- Advantage: Better tracking abilities
Snakes:
- Specialized feature: Jacobson's organ
- Function: Chemical detection
- Advantage: Prey detection and navigation
Sharks:
- Specialized feature: Lateral line
- Function: Water movement detection
- Advantage: Predator/prey awareness
Insects:
- Specialized feature: Compound eyes (ommatidia)
- Function: Wide-angle vision
- Advantage: 360-degree awareness
Planaria:
- Specialized feature: Eye spots
- Function: Light detection
- Advantage: Basic light-dark differentiation
Q29. Analyze the relationship between structure and function in sense organs.
Answer: The structure of sense organs is perfectly adapted to their functions:
- Eye:
- Curved cornea and lens → Focus light precisely
- Variable pupil → Regulate light intensity
- Rod and cone arrangement → Different light conditions and color vision
- Ear:
- Funnel-shaped pinna → Collect maximum sound
- Chain of ossicles → Amplify sound vibrations
- Fluid-filled cochlea → Convert vibrations to impulses
- Semicircular canals → Detect directional movement
- Nose:
- Mucus-lined cavity → Dissolve aromatic particles
- Large surface area → Maximum receptor exposure
Conclusion: Each structural feature has evolved to maximize the efficiency of stimulus detection and response.
Q30. Discuss the importance of sense organs in the survival of organisms.
Answer:
Survival Functions:
- Food detection: Smell and taste help identify safe vs. harmful food
- Predator avoidance: Vision, hearing help detect danger
- Mate selection: Various senses help in reproduction
- Navigation: Vision, balance help in movement
- Environmental adaptation: Sensors detect environmental changes
Examples:
- Earthquake rescue: Dogs' superior smell saves human lives
- Snake hunting: Jacobson's organ detects prey chemicals
- Shark predation: Lateral line detects prey movement
- Insect survival: Compound eyes provide wide-angle predator detection
Conclusion: Sense organs are crucial for survival as they provide information about the environment, enabling organisms to respond appropriately to various stimuli and successfully adapt to their surroundings.
Note: Practice drawing all diagrams mentioned in the chapter and be able to label them accurately. Understanding the relationship between structure and function is key to scoring well in this chapter.