Correct Option
The correct option is (b).
Explanation
The the optical structure and adaptations of eyes in various animals. These biological structures function as natural optical instruments, evolving specific features such as compound lenses or variable apertures (pupils) to suit the animal's environment and survival needs.
Statement-wise Analysis
- Statement 1 is Incorrect.
Crabs have eyes that are often situated on stalks. This anatomical arrangement allows them to look all around, not just in the front. This wide field of vision enables them to sense predators approaching even from behind.
- Statement 2 is Correct.
Butterflies possess large compound eyes composed of thousands of individual optical units called ommatidia (described as "little eyes"). This structure grants them a very wide field of view, allowing them to see the front, sides, and back, which is essential for detecting fast movements.
- Statement 3 is Incorrect.
Owls are nocturnal birds that need to see in low-light conditions. To facilitate this, their eyes are adapted to gather as much light as possible. Therefore, they possess a large cornea and a large pupil to maximize light entry. A small pupil would restrict light, which is contrary to the requirements of night vision.
Key Takeaway
Nocturnal vision requires a large aperture (large pupil and cornea) to maximize light collection, whereas compound eyes in insects provide a mosaic vision with an exceptionally wide field of view.