Biology: The Dynamic Science (Mind...

4th Edition
Peter J. Russell + 2 others
ISBN: 9781305389892



Biology: The Dynamic Science (Mind...

4th Edition
Peter J. Russell + 2 others
ISBN: 9781305389892
Textbook Problem

Discuss Concepts In owls and many other birds of prey, the fovea is located toward the top of the retina rather than at the center as in humans. This arrangement correlates with the birds’ hunting behavior, in which they look down when they fly, scanning the ground for a meal. With this arrangement in mind, why do you think a standing owl would turn its head upside down?

Summary Introduction

To review:

The reason due to which owl is able to turn its head upside down while standing.


Eyes are sense organs that receive visual stimulus in form of photons. As the photons hit the photoreceptor cells in the retina of eyes, the optic neurons start to transduce the signals to the visual cortex region of the brain. The retinal is a lipid molecule that is present in the photoreceptor cells. It acts as a pigment and helps in the absorption of light. Two types of photoreceptors are especially important in terrestrial animals, and they are, the rods and cones. The cone cells are located inside the fovea.


The rod cells are important for vision in dim light in many birds and mammals. The cone cells are responsible for vision in bright light, and they allow the animals to distinguish between different colors. The color difference is due to the presence of three types of opsins in cone cells, which are blue, red, and green cone cells. The photoreceptor cells are located in the retina of the eye where image formation takes place.

A small depression in the retina is known as fovea, which is a place where all the cone cells are accumulated. In case of humans, the fovea is located at the center, and thus, the image formation takes place in the center of the retina...

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