Question

In frog, the lower eyelid is
(a) Rapidly movable
(b) Slightly movable
(c) Immovable
(d) Absent

Answer 1

Hint: They are amphibians and are known for their special abilities like jumping, making croaking sound, and having bulging eyes with slimy skin. They live all over the world and are among the most diverse animals in the world with more than 6000 species

Complete step by step answer:
- Frogs have transparent eyelids, one on the bottom, one on the top, and a third semi- transparent eyelid called the nictitating membrane.
- Lower eyelid in frogs stays still and is not movable. The upper eyelid is slightly movable. The third eyelid i.e. nictitating membranes acts as a protective covering over the frog's eyes.
- The nictitating membrane in the red- eyed frogs resembles tiger- stripes hiding their red eyeball and healing with a good vision. Also, serves as a protection layer underwater and keeps it moist on the ground.
- It is also known as haw that extends from the frog’s lower lid. Having no muscles, it is just the epithelial tissues like the frog’s skin with blood vessels and connecting tissue collagen.
So, the correct answer is ”Immovable”.

Additional information:
- Frogs can regenerate structures of the eye after damage and serve as a scientific model to study this process. The current research aimed at blindness prevention in humans involves the chemical induction of cell regeneration.
- Frogs sometimes swallowing food may use their eyes. After a frog has caught prey in its mouth, you will see the eyeballs retract into the head, pushing the food down and allowing the frog to swallow.
- The vision in frogs is primitive and a frog’s mobility is essential for them to survive as they would starve to death if they will not be moving. Thus, their evolution happened in such a way that their vision focuses on objects in motion.

Note: There are two types of photoreceptors, rods, and cones, in the eyes of humans and frogs. Whereas, Humans have only a single type of rod, with max absorption of light till green in the light spectrum. On the other hand, a frog’s eye contains one additional rod with a peak absorption of light at 433 nm (blue light). This rod allows superior detection of blue light in amphibians.