Some birds must return to roost as darkness approaches. This is because their eyes contain
A)cones, but no rods.
B)rods, but no cones.
C)too many cones.
D)too many rods.
E)more rods than cones.

Question

Quizplus · Accepted Answer

Birds that must return to roost as darkness approaches typically have eyes that contain cones, but no rods. Cones are responsible for color vision and function well in bright light, while rods are more sensitive and enable vision in low light. The absence of rods in these birds' eyes makes it difficult for them to see in the dark, necessitating their return to roost at dusk.

Some Birds Must Return to Roost as Darkness Approaches