All questions of Animals: Organs and Systems for Grade 10 Exam

Understanding Color Vision
Color vision is primarily facilitated by specialized cells in the retina known as cones.
What are Cones?
- Cones are photoreceptor cells located in the retina of the eye.
- They function in bright light conditions and are responsible for detecting fine detail and color.
Types of Cones
- There are three types of cones, each sensitive to different wavelengths of light:
- S-cones (short wavelength) - sensitive to blue light.
- M-cones (medium wavelength) - sensitive to green light.
- L-cones (long wavelength) - sensitive to red light.
How Cones Work
- When light hits these cones, it triggers a chemical reaction that sends signals to the brain.
- The brain processes these signals to produce the perception of color.
- The combination of signals from different cones allows us to see a wide range of colors.
Contrast with Rods
- Rods are another type of photoreceptor in the retina, but they are not responsible for color vision.
- They are more sensitive to light but do not detect color, making them essential for night vision.
Conclusion
In summary, cones are the key players in our ability to perceive color, while rods assist in low-light vision. Understanding the role of cones helps highlight the complexity and beauty of human vision.

Understanding Myopia
Myopia, commonly known as nearsightedness, is a visual condition where individuals struggle to see distant objects clearly. This condition occurs when the eyeball is slightly elongated or the cornea is too curved.
Key Characteristics of Myopia:
- Blurred Distant Vision: Objects that are far away appear fuzzy or unclear, while close objects can be seen clearly.
- Common Symptoms:
- Difficulty in reading signs from a distance
- Squinting to see better
- Eye strain or fatigue after prolonged visual tasks
Causes of Myopia:
- Genetic Factors: A family history of myopia increases the likelihood of developing this condition.
- Environmental Influences: Extended near work, such as reading or using screens, can contribute to its progression.
Treatment Options:
- Glasses or Contact Lenses: The most common method to correct myopia is through prescription lenses that help focus light correctly onto the retina.
- Refractive Surgery: Procedures like LASIK can reshape the cornea to improve distance vision.
Conclusion:
In summary, myopia is specifically characterized by the inability to see distant objects clearly, making option 'A' the correct answer. Understanding this condition is essential for seeking appropriate treatment and maintaining good eye health.

Protective Function of Eyelids
The correct answer to the question of which part of the eye protects it from dust and debris is indeed the eyelids. Here's a detailed explanation of their protective role.
Role of Eyelids
- Physical Barrier: The eyelids serve as a physical barrier, closing over the eyes to shield them from environmental elements like dust, debris, and even excessive light.
- Blink Reflex: The process of blinking is essential. It occurs automatically and helps to remove small particles that may have settled on the surface of the eye. Each blink spreads tears across the surface, which also helps wash away irritants.
Additional Protective Features
- Tears and Lubrication: When eyelids close, they help in the distribution of tears, which not only keeps the eye moist but also traps and flushes out foreign particles.
- Sensitivity: The eyelid margin is highly sensitive, containing nerve endings that trigger the blink reflex when something approaches the eye, preventing potential injury.
Conclusion
In summary, while other parts of the eye, like the lens and cornea, serve specific functions related to vision, the eyelids play a crucial protective role. They not only block harmful particles but also facilitate the removal of any debris through blinking and tear production. Thus, the eyelids are essential for maintaining eye health and comfort.

Understanding Light Adaptation
When a person transitions from a dark environment to a brightly lit one, the phenomenon that occurs is known as light adaptation. This process allows the eyes to adjust to the increased light levels, enhancing visual clarity and comfort.
What is Light Adaptation?
- Light adaptation is the physiological process where the eyes adjust to brighter conditions.
- It involves the rapid adjustment of photoreceptors in the retina, particularly the cones, which are responsible for color vision and function best in bright light.
How Does It Work?
- Cones Activation: In bright light, cones become increasingly active while rods (which are more sensitive to low light) decrease their activity.
- Chemical Reaction: The photopigments in the cones undergo a chemical change that allows them to respond effectively to the new light intensity.
- Time Frame: Light adaptation can occur within seconds to minutes, depending on the intensity of the light environment.
Importance of Light Adaptation
- Visual Comfort: This adaptation helps to prevent glare and discomfort when moving to well-lit areas.
- Improved Vision: It enhances visual acuity, allowing individuals to see details and colors more clearly in bright conditions.
Conclusion
In summary, light adaptation is a crucial mechanism that enables our eyes to cope with changes in lighting, ensuring that we can see clearly and comfortably in various environments.