“Evolution of the Eye”
By Maziar Aptin July 2011
Updated October 2013

                                         

A few weeks ago I wrote an article titled “Is it Creation or Evolution!”

http://maziaraptin.blogspot.com/2012/02/is-it-creation-or-evolution.html

 I recently received the latest issue of “Scientific American” magazine. In that; an article titled “Evolution of The Eye” attracted my attention. It was written by Trevor D. Lamb who is an investigator in the department of neuroscience at the John Curtin School of Medical Research and in the ARC Center of Excellence in Vision Science at Australian National University in Canberra. His research focuses on the rod cone photoreceptors of the vertebrate retina.

After reading the article, I was happy to see that his finding confirms my opinion about the evolution that; all living things, including humans, have started from microorganism billions of years ago.

We all know that the planet Earth was formed about 4.6 billion years ago. Trevor Lamb, in his article indicates and I quote; “We humans have an unbroken line of ancestors stretching back nearly four billion years”.

Lamb continues: “Around a billion years ago simple multicellular animals diverged into two groups: One had a radially symmetrical body plan (a top, side, and bottom side no front or back), and the other- which gave rise to most of the organisms we think of as animals- was bilaterally symmetrical, with left and right sides that are mirror images of one another and a head end. The bilateria themselves then diverged around 600 million years ago into two important groups: one that gave rise to the vast majority of today’s spineless creatures; or invertebrates, and one whose descendants include our own vertebrate linage. Soon after these two lineages parted ways, an amazing diversity of animal body plans proliferated- the so-called Cambrian Explosion that famously left its mark in the fossil record of around 540 million to 490 million years ago. This burst of evolution laid the groundwork for the emergence of our complex eye.”

Lamb indicates that about 600 million years ago, (about 60 million years prior to the Cambrian Explosion), a shellfish type creature, living in the bottom of the ocean, out of necessity, had developed a light sensor to distinguish between night and day. That light sensor gradually evolved into a primitive vision organ and finally to eye.

The above finding has confirmed Charles Darwin’s argument about evolution of the eye. 

Darwin argued that “The human eye could have evolved from a simple light-catching patch of tissue of the kind that animals such as flatworms grow today. Natural selection could have turned the patch into a cup that could detect the direction of the light. Then, some added feature would work with the cup to further improve, better adapting an organism to its surroundings, and so this intermediate precursor of an eye would be passed down to future generations. And, step-by-step, natural selection could drive this transformation to increased complexity because each intermediate form would provide an advantage over what came before.”

This discovery is very important in regard to argument of “evolution vs. creation”.  Last decade or so the creationists, by recruiting a few religious scientists and paying them lavishly, started claiming that the eye which is the most complicated organ could not have evolved by itself but must have had an "intelligent designer". Now this discovery will put an end to such claim.  
  

To read the rest of Lamb’s article about “Evolution of the Eye” please refer to “Scientific American” July 2011 issue, page 64. You could go on their website;   http://www.scientificamerican.com/

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Some scientific info about origin of life:

How the life began on Earth

 

Three Domains

Current understanding of early evolution is that life (based on an analysis of the RNA in their ribosomes) split into two domains one of which later split into two. Hence there are now three domains, called Bacteria, Archaea and Eukaryotes, related as follows:

Possible relationships between three main domains of life

Note that the Bacteria and Archaea appear very similar to each other and very different from more advanced Eukaryotes, so Bacteria and Archaea are often grouped together under the heading prokaryotes. Biologists think that the Archaea are perhaps older than the Bacteria.

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Archaea 3.9  Bya ? (Billion years ago)

Based on their structure and biochemistry we believe the earliest cells were similar to the living Archaea (which used to be called the Archaebacteria). Archaea are probably living fossils, similar to the earliest cells.

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Bacteria 3.5  Bya?

In some of their chemistry, Archaea resemble more advanced cells which we will meet later (eukaryotes). But there is another domain of simple, single-celled organisms which resemble them in size and shape, the Bacteria.

It seems that early cells divided into these two domains, and while the Archaea remain fairly specialized, the Bacteria, have diversified and now form the largest domain of prokaryotes.

The oldest fossil Bacteria found so far are in rocks from Western Australia dating from the Archaean 3.5 billion years old.

These are the simplest cells we find on Earth today, called bacteria (sometimes called germs). Note that one of these is called a bacterium.

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Photosynthesis 3.5 Bya

Bacteria began to trap sunlight and use that energy to make food, such as sugar. This process is called photosynthesis, meaning “constructing with light”. This was a great leap forward. Sunlight-using bacteria appeared soon after the first cells did, about 3.5 billion years ago, and sunlight has been the main source of energy for all life ever since. These bacteria are called blue-green bacteria or cyanobacterias (and sometimes wrongly called blue-green algae).

Many blue-green bacteria can also “fix“atmospheric nitrogen. In Southeast Asia, nitrogen-fixing blue-greens often are grown in rice paddies, removing the need for nitrogen fertilizers.

Blue-greens are important in our story for several reasons:

►    they were probably the first bacteria which could perform photosynthesis, so leading to the great oxygen poisoning of 3 billion years ago

►    they formed a symbiosis with fungi to create lichen, which was probably the first living thing to live on land

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How photosynthesis works

A cell uses sunlight to create sugar

As they captured sunlight energy to make sugar so carbon dioxide and water were taken in, and oxygen was given out. This oxygen had a huge effect upon the whole world.

Today we obtain almost all of our food from plants, or from animals which have eaten plants, and so it might be interesting to know a bit about how photosynthesis works. It is a fascinating story of molecular changes.

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Paleoproterozoic Era 2.5 to 1.6 Bya

The Paleoproterozoic (“old first life”) was a time when the continents finally stabilized, with modern land forms becoming recognizable.

This was the time of the most dramatic change ever in the nature of the Earth’s atmosphere.

Bacteria able to make use of sunlight for energy continued to grow, resulting in the great oxygen poisoning.

This might also have been the time when larger and more advanced cells (eukaryotes) first appeared.

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Great Oxygen Poisoning 2.4 Bya

During the next 1.7 billion years the Earth’s environment changed dramatically. Up to this point, the atmosphere has been rich in hydrogen compounds such as ammonia and methane gas. Any iron which happened to reach the Earth’s surface remained shiny and bright. But everything changed when blue-green bacteria began to release oxygen.

Once photosynthesis by blue-greens began to release oxygen, iron minerals in the rocks and oceans of the Earth began to combine with the oxygen and turn brown -- the world began to rust. Gradually the whole chemistry of the Earth was changed.

By 1.8 billion years ago all the minerals in the rocks and oceans had rusted. Now the oxygen made by blue-green bacteria began to collect in the atmosphere, which began to change into the air we know today. Never since has the world seen such a drastic change.

This had a terrible effect upon most bacteria. Oxygen attacked many of life’s molecules, combining with them, changing their structure and giving out carbon dioxide and heat. It is the process we call burning. Burning can happen quickly, as in a fire, or slowly, as when a cut apple goes brown.

The new oxygen slowly burnt the proteins and chromosomes inside the bacteria and most of them died in the Great Oxygen Poisoning (also called the Great Oxygenation Event or the Oxygen Catastrophe) of about 2.4 bya, most but not all. Some anaerobes hid away in places where there was no oxygen, such as in the mud at the bottom of swamps. They managed to survive in any place without oxygen, and we still find them living there. These are the anaerobic bacteria which make dead matter putrefy, giving off bad smells.

The Ribosome

The ribosome is central to the process of life. In life today, ribosome occurs both as free particles within cells and as particles attached to membranes inside cells. A ribosome is made of about 40% protein and 60 % nucleic acid. It is composed of four nucleic acid molecules and about 70 different proteins.

Ribosomes are very numerous in a cell and account for a large proportion of its total nucleic acid. 

Viruses

A virus has no ribosomes, water molecules or cell membrane. It cannot build any proteins itself, so it is not a living thing, but it does contain genetic material, either DNA or RNA, which it can inject into a living cell.

Some viruses inject DNA into a cell which is taken into the cell’s chromosome. Others inject RNA which is either used by the cell’s ribosomes to create new protein or converted first into DNA. Viruses which cause the latter process are called retroviruses.

Once inside the chromosome, the new DNA begins to give out messages for making new viruses. The host cell is thereby turned into a factory for making new copies of the virus.

When it is full of viruses the cell bursts open, sending out millions of viruses to infect more cells.

A virus seems like a totally destructive thing, killing cells without doing any good. Usually this is true, but viruses can carry useful genes from one cell to another. Genetic engineers use viruses for this reason.

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Origin of Viruses

Nobody is sure how viruses began. The existence of very large viruses (megaviruses) which contains enough genes to encode about one thousand proteins, more than most bacteria, suggests that they were originally cells which lost the ability to reproduce on their own, adopting instead a parasitic way of life.

However the existence of bacterial spores suggests that perhaps they evolved into viruses.