The Evolution of the Eye

eye

The eye has developed within the animal kingdom for one reason only; to detect the world around the observer. The first evolved eyes were simply an apparatus which had a light sensitive cell referred to as “rhodopsin”. Eventually as time progressed, eyes developed a spherical shape which allowed more light to be captured so that the difference between light and dark was more distinct. Following this, eyes evolved the ability to develop a pupil which acts as a biological aperture which can constrict and dilate letting either more or less light into the eye. This system works in theory but the real world application developed a problem in that when constricting the pupil to focus on an object being looked at, less light is let in which restricts vision. Nature eventually alleviated this issue by placing a lens behind the aperture of the pupil which allowed for precision detail, clarity, and focus. This system was so effective that evolution produced some form of it for nearly every animal and insect on Earth, some being more adept than others, but all using the same principal of light and focus to observe information around them

Herbivore vs. Carnivore Vision

carnivore-vision

Animals which have eyes placed upon the sides of their heads (e.g. squirrels, zebras, frogs etc.) are typically herbivores and prey for carnivores. Herbivores need to have their field of vision constantly focused upon what’s going on around them. Animals which have eyes on the front of their heads (e.g. owls, tigers, human beings etc.) are usually carnivores. Carnivores are predators and because of this they need to constantly be focused upon what is in front of them for activities like chasing down prey in an attempt to capture and eventually kill what they catch. Human beings can demonstrate this difference for themselves by placing one’s hands in front of their eyes as they would binoculars, then crossing their wrists and cupping their hands so that they see only from the sides of their face. This demonstrates the different abilities predator and prey have in respect to what is in focus within a particular classifications field of vision. Panoramic vantage points which herbivore prey have allow for more information to be taken in at once, but binocular vantage points which carnivorous predators have allow for depth perception which most herbivores do not have, and even when they do have it, it’s accuracy is highly limited

The Extinction of Species

extinction

130 species go extinct each day. 99% of all life which has ever lived upon Earth, is now extinct. Most species of mammals only survive 1,000,000 (1 million) years before going extinct. Modern human beings have existed for 200,000 years, but the most distant related ancestors of human beings, creatures more apelike than human but still bipedal and using tools, date back 3,000,000 (3 million) years with that particular ancestor being named “Australopithecus afarensis”

Vision of Toads

toad-eye

If a toad is put into a tank with dead worms, it will starve to death because it won’t recognize the worms as food. Toads have evolved to only see horizontal lines moving as food. This theory was tested in the 1970’s, when scientists put a toad in a glass jar and had a vertical line pass by to which the toad did nothing, almost as if it has no clue of the line in front of it which looked like a worm standing straight up. Once the line was changed to become horizontal, the toad immediately tried to eat the horizontal line which mimicked a wormlike insect. Toads have a very unsophisticated visual spectrum. They basically think that if whatever they’re looking at appears to be a worm, then chances are it is and that it’s safe to ingest. This visual model is flawed because the toad is easily fooled giving it a disadvantage both in catching prey, and in becoming prey

Sharks

sharks

Approximately 66% of a great white sharks brain is dedicated to its sense of smell, being able to smell 1 part per 1,000,000,000 (1 billion) of blood within the water. Great white sharks have their maximum width within 33% of their total length, a width which is nearly 25% of the total length of the body. This tapered shape minimizes drag and allows a shark to move quickly and freely, an ideal which has been shaped by evolution