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Our Incredible Eyes

For about 2 to 3 billion years, primitive life forms on Earth had no way of detecting light; they had to live out their lives in a pitch-black world.

By A B ForbesPublished 2 months ago 3 min read
Top Story - December 2023
21
Our Incredible Eyes
Photo by Amanda Dalbjörn on Unsplash

Here are three of my short articles.

British spelling.

1/3

Early primitive life on Earth had no eyes; then came simple eyespots or light receptors. Now, for the first time, organisms could detect some light and be aware of their environment.

We know that Trilobites evolved compound eyes by studying their 550 million-year-old fossils. We still see compound eyes in some animals today.

From those first simple eyespots, we now witness a wide diversity of complex eyes throughout the animal kingdom.

Surprisingly, there is a species that has only one eye; they are from a genus called copepods. They are small creatures measuring just a few millimetres in length.

A weathervane scallop has around one hundred simple eyes.

The prize for the largest eyes in the animal kingdom goes to the colossal squid. Their eyes can measure as much as 27 centimetres across, or over 10 inches, the size of a soccer ball, and maybe the largest eyes of any creature that has ever existed.

In the image below you can see how big squids eyes are in comparison to their bodies.

By kate estes on Unsplash

Over thousands of generations, little evolutionary improvements were made to primitive eyes before some animals finally evolved complex camera-style eyes like those reading this article.

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2/3

Someone asked me how far is 40 light-years

The vast distances in space are unfathomable.

By Mathew Schwartz on Unsplash

Light travels at 300,000 kilometres per second, which equates to 1,080 million kilometres per hour. 

To find the answer to the question, multiply 1,080 million kilometres by the number of hours in a year, then multiply the answer by 40. 

It works out at just over 378 trillion kilometres. 

A trillion is 1 followed by 12 zeros. 

The distance to the centre of our galaxy, the Milky Way, is 26,000 light-years, or almost 246,000 trillion kilometres. 

But, considering the size of the universe, that number is minuscule. 

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3/3

What they can withstand is truly amazing.

I am describing near-microscopic Tardigrades.

By Andy Holmes on Unsplash

Tardigrades are the hardiest organisms on our planet.

Tardigrades were discovered in 1773; they were found to have eight legs, each one tipped with four to eight claws.

There are currently 1,300 known species in the tardigrada phylum classification category.

They are also known as “water bears” or “moss piglets.”

They are found on the highest mountain peaks and in the deepest parts of any ocean.

It seems that the hardiest of them live on land in wet, damp areas.

Most tardigrades are less than one millimetre long. They have a specialised mouthpart that allows them to suck the nutrients out of plants and other microorganisms.

Tardigrades are known for their ability to survive in extreme environments, including very high and very low temperatures and pressures.

A few weeks ago, I accidentally put my hand under the boiling water tap or faucet. You can imagine how quickly I withdrew my hand, but I still had large blisters and a very painful hand.

At sea level, water boils at 100 degrees Celsius, or 212 degrees Fahrenheit.

You would think that no living thing could survive in boiling water, but a Tardigrade can. They can survive for up to an hour in boiling water.

That last statement is a bit misleading. To survive in boiling water, tardigrades must be in a stage of dormancy that resembles death, called the tun state. It is thought that some tardigrades could be in a state of dormancy for 30 years.

They have a strategy for surviving harsh conditions called cryptobiosis. Dry conditions can trigger cryptobiosis.

To enter the tun state, these amazing animals have to get rid of almost all of the water in their bodies; their metabolism goes down to as little as 0.01% of its normal rate.

Their cells are protected from damage by proteins that are unique to tardigrades. They retract their heads and legs and curl up. The final outcome is a lifeless-looking, crusty ball in a state of suspended animation.

Researchers have found that tardigrades in the tun state can, for a certain period of time, withstand temperatures of minus 200 degrees Celsius or minus 328 degrees Fahrenheit.

The end.

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You may find some of my easy-to-understand stories about the universe and life interesting and educational.

Free to read. Enjoy

studentNature
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About the Creator

A B Forbes

Someone with a lifelong passion for that gargantuan area we call the universe. I also write stories about life itself. Enjoy

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  • Phil Flannery2 months ago

    I do like to read interesting facts of nature. My hope is that I can recall them when needed. Interesting article

  • As always very interesting. Well written and well researched. Great work. I thought I was subscribed to you... now I am.

  • Susan Fourtané2 months ago

    I enjoyed these bite-sized pieces of interesting knowledge. Tardigrades must be some of the most ancient organism living on this planet.

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  • Scott Christenson2 months ago

    Interesting, first I've learned about tardigrades.

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  • All your posts are incredibly informative and easy reads, this should be a top Story most definitely

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