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How an eye works in the wildness of savannah

FROM Moshi through Dar es salaam to Dodoma, scientists describe eyes as organs of vision which work after they detect light and convert it into electro chemical impulses, zoologists put more emphasis in this complicated organ by saying an eye is a complex optical system which collects light from the surrounding and the environment in which the animal is dwelling.

Scientists say an eye regulates light intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through another complex system made by neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain.

Some scientific researches indicate that the first animal to evolve with what may be called an ancient eye appeared about 600 million years ago, but through genetic features researchers have discovered that the real eye among vertebrates evolved about 540 million years ago.

Historians say during that time it was the ancient predators that evolved with powerful vision which helped them to chase and capture their prey but with time moving on very fast in the world which was going through different changes things got tough about 485.4 million years ago when the planet was recovering from an earlier weather condition which was dominated by falling of snow from the sky.

From that point millions of years passed and the world changed and allowed evolution of the first generation of equids between 66 and 56 million years ago, that was the time which started with mass extinction which marked the end of dinosaur’s superiority on the ancient world which unleashed itself other creatures including mammals such as the horse family which include the zebra of Serengeti, Mikumi, Saadani and other national park where mammals, reptiles, birds and insects thrive.

From a standing position a cheetah is covered about 7 metres in one stride, while cruising at 120 kilometres per hour the cat must be able to locate its prey which is also moving very fast while throwing sandy, fine particles which penetrate into the eye with its eyes aching the big cat will be forced to abandon the mission and deal with affected eye.

To hunt effectively in challenging environment, the cheetah is equipped with different mechanism that enables it sprint like no one on Earth, for camouflaging it has yellow and black spotted body, a 65-centimeter- long tail for balancing, lightweight skeleton, flexible or fast twitching fibers, elastic back muscles, bendable spine, and powerful heart, a very small head with large nostrils and forward facing eyes.

The cheetah’s eyes face forward, and from any position the cat has maximum information from area that covers more than 200 degree compared to 180 degrees which humans see, not only that a cheetah is capable to see details from several miles away and the passion of its eyes allow the cheetah to judge the distance it has to cover to catch its prey, the eyes also have an image stabilization system to keep the prey in sharp focus when the cheetah is running.

While on duty with its body accelerating between 10 and 40 metres per second to click 40 metres per hour the cheetah is equipped with one of most powerful eyes on the earth, scientists say this ability enable the cat to capture 40 to 50% of its prey between 100 to 300 metres from the initial point.

Cheetah is differentiated from a leopard by black “tear marks” running from the corner of its eyes down the sides of the nose to its mouth, different scientific researches indicate the lines work to keep sunlight out of its eyes and aid in hunting and seeing long distances, furthermore scientist say the cat hunts by vision whereby a prey is captured between ten to thirty metres which are covered within shortest period of time.

These factors make the cheetah to prefer to work in daytime whereby the black lines is used to absorb sunlight before it passes into the eyes, although it can hunt in the afternoon when the sun is up in sky and temperature is high the cheetah will be forced to hunt in the morning or evening because it eyes cannot work effectively during darkness.

Night is dominated by darkness and that means poor vision to most mammals in the savannah where most herbivorous retreat to safer places where big cats are not able to find them, on their side when they feel like hunting, lions may organize themselves for a hunting activity but after two hours if they found it’s very difficult to locate, chase and capture a prey they will wait for a night where darkness is their greatest allies.

Scientists say when light fade as night approaches, both human, primates and bovine’s eyes adjust themselves immediately because they have evolved to work in a dimly light environment only because of a smart brain which process and translate faded picture of an object, with that great ability of our minds, as the night grow older our vision become poor to point that whenever we want to go outside we need assistants from artificial source of light.

Unlike others, lions are mammals that have eyes which have at the same level like human eyes during day light but at night these predators see eight times more than human being, scientists say lions see mainly in blue and greens environment, with highly developed night vision mechanism, this doesn’t mean they can see in the dark because if they work on a pitch which is black they will be blind.

Lion’s eyes are designed to work effectively in darkness where they are able to pick and use very little light available even from stars and moon, lions have more rod cells than cone cells in the retina of the eye, these are photoreceptor or light sensitive cells which function to convert visible electromagnetic radiations or light into signals which stimulate biological process.

Scientists say lion’s eyes are equipped with two photoreceptor cells which are rods and cones, each of these cells contributing information used by the visual system to form a representation of the visual activities, cones cells are wider and work as colour detector while rods cells are narrow and responsible for light as they are distributed differently across the retina.

This feature shows that lions have more light sensitive cells packed tightly in the fovea a most sensitive area of the retina, this means their eyes need little amount of light to see something in the darkness than human eyes.

Lions have a Tapetum lucidum, this is a reflective layer of cells positioned behind the retina, this means that light entering into the lion’s eye’s will be absorbed by either the rod or cone cells, light that passes through the retina and the photoreceptor cells is reflected back by the mechanism while the light sensitive cells have a second chance to absorb the light waves, this is a very effective mechanism that work in doubling the effectiveness of their night vision.

Not only that, outside each eye of lions, there is white patches which are located under each eye and work to enhance a little amount of light available while enabling the super predator to work effectively at night. From a long distant position, Peregrine falcons are capable to identify their prey using big eyes which are armed with sharp vision capable of locating a pigeon flying many miles away or mice trotting on the ground.

Falcon’s eyes transmit the picture of the intended prey to the brain which analyzes its position, feature and weight, all for a quick decision which lead to a speedy attack. From this point a Peregrine falcon will dive high then bust into a top speed of 320 kilometres per hour which is three time higher than the top speed of Cheetah of Serengeti, Tarangire and Ruaha national parks.

rstanslaus@yahoo.com Mobile: 0754362330

Author: Reginald Stanislaus Matillya

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