* Increased light gathering: Nocturnal animals operate in low light conditions, often under the moon or starlight. Larger eyes mean a larger surface area for collecting light, improving their ability to see in the dark.
* Larger pupils: Their pupils can dilate significantly, allowing even more light to enter the eye. This is why you see a cat's eyes glow in the dark - the light is reflecting off the large, dilated pupil.
* Increased number of light-sensitive cells: The retinas of nocturnal animals are packed with more rods, the light-sensitive cells responsible for vision in low light. This enhances their ability to detect faint light sources.
* Specialized reflecting layer: Many nocturnal animals have a layer of reflective cells called the *tapetum lucidum* behind their retinas. This layer reflects light back through the retina, increasing the amount of light that reaches the rods and improving their ability to see in the dark.
However, large eyes come with some disadvantages:
* Vulnerability: Large eyes are more prone to damage and may be less mobile, limiting the animal's field of view.
* Metabolic cost: Maintaining large eyes requires a lot of energy, which can be a disadvantage for animals that need to conserve energy.
Despite these drawbacks, the benefits of increased light sensitivity in low light conditions outweigh the costs for nocturnal animals, leading to the evolution of their characteristic large eyes.