Changes

In the human, and most mammals, the eye consists of several structures.  The cornea is a protective outer layer.  The iris is an aperture through which light enters.  The lens is controlled by muscles to focus the light on the retina at the back of the eye.

In the human, and most mammals, the eye consists of several structures.  The cornea is a protective outer layer.  The iris is an aperture through which light enters.  The lens is controlled by muscles to focus the light on the retina at the back of the eye.

The retina has many specialized cells (photoreceptors) that are able to react to light and send their signals via the optic nerve to the brain for interpretation. There are two types of photoreceptor cell called rods and cones. Rods are by far the most numerous (around 120 million) and are sufficiently sensitive to allow basic black/white vision even at very low light levels. Cones (6-7 million) only function at higher light levels, but enable us to perceive colour. <ref>http://hyperphysics.phy-astr.gsu.edu/hbase/vision/rodcone.html</ref>  

The retina has many specialized cells (photoreceptors) that are able to react to light and send their signals via the optic nerve to the brain for interpretation. There are two types of photoreceptor cell called rods and cones. Rods are by far the most numerous (around 120 million) and are sufficiently sensitive to allow basic black/white vision even at very low light levels. Cones (6-7 million) only function at higher light levels, but enable us to perceive color. <ref>http://hyperphysics.phy-astr.gsu.edu/hbase/vision/rodcone.html</ref>  

Typically eyes come in pairs, to allow binocular vision and hence depth perception, but most [[spider]]s (for example) have eight eyes (though some have less or none at all), and [[scallop]]s may have several dozen.

Typically eyes come in pairs, to allow binocular vision and hence depth perception, but most [[spider]]s (for example) have eight eyes (though some have less or none at all), and [[scallop]]s may have several dozen.

== Evolution of the eye ==

== Evolution of the eye ==

Numerous, unrelated organisms possess eyes of varying degrees of complexity. Evolutionists allege that these all evolved independently to meet a common need; this is discussed in some detail in ''[[Climbing Mount Improbable]]'', by [[Richard Dawkins]]. <ref>http://www.trueorigin.org/dawkrev2.asp</ref>

Numerous, unrelated organisms possess eyes of varying degrees of complexity. [[Evolutionist]]s allege that these all evolved independently to meet a common need; this is discussed in some detail in ''[[Climbing Mount Improbable]]'', by [[Richard Dawkins]]. <ref>http://www.trueorigin.org/dawkrev2.asp</ref>

Creationists commonly argue that, in order to offer even basic functionality, the eye must be so complex as to preclude an evolutionary explanation for its development. The eye is thus, a perfect example of [[Irreducible Complexity]].

Creationists commonly argue that, in order to offer even basic functionality, the eye must be so complex as to preclude an evolutionary explanation for its development. The eye is thus, a perfect example of [[Irreducible Complexity]].