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Stated Clearly presents:
Can science explain the origin of life?
A full scientific explanation for the origin of life does not currently exist,
but research groups around the globe are tackling the
mystery.
Here we'll take a look at a few of their discoveries.
Darwin's theory of biological evolution
tells us that all life on Earth may have originated from a single,
relatively simple reproducing creature, living in the distant past.
This idea is based on many observations one of which is that when living things reproduce
children are often born with random new traits. Those with negative new traits are
less likely to survive and reproduce,
those with positive new traits are more likely to survive
and pass those traits on to their children. Over multiple generations
positive traits build up allowing relatively simple life forms to evolve
into complex life forms
and even split into multiple different species.
a careful look at the fossil record overwhelmingly confirms Darwin's theory,
life forms get simpler and simpler as we go back in time.
The record suggests that all life on Earth emerged from primitive cellular colonies
which first appeared roughly three and a half billion years ago.
But how did those first reproducing creatures come about?
Even the simplest bacteria alive today
are far too complex to have popped into existence in a single step.
Furthermore, the first reproducing creature could not have developed through
biological evolution,
because biological evolution requires reproduction in order to work.
The origin of life needs its
own explanation. The most promising idea right now,
the one which is consistently leading scientist to new discoveries,
is the idea that life emerged from chemistry!
Chemistry is the study of matter.
Particularly, how atoms interact and combine to form molecules,
and how those molecules interact and combined to form larger systems and structures.
Everything is made of chemicals,
the air we breathe, the ground we walk on,
the shoes on our feet, even
the feet inside our shoes.
That said the chemistry of life is special in two very important ways.
First, the chemistry of life is organized
into metabolic pathways. If you look at the cells of any living thing,
even a plant which you wouldn't normally think of as being very lively,
you discover a world activity! Chemical reactions occur in continuous orderly
paths,
each reaction sparking the next. Scientists call these strange reactions
metabolic pathways.
the second oddity of life's chemistry, is that living cells are made of special molecules
building blocks like amino acids and sugars
which we once thought could not be found outside of life. These building blocks
combine
to form highly complex and orderly structures like genes,
proteins, and cell membranes.
In the past, scientist had no idea what powered the strange activities of life,
and produced its unique chemicals. They concluded that life must be fueled by a mysterious energy
they called it: The Vital Force!
In 1828 a chemist by the name of Friedrich Wöhler
accidentally produced urea in his lab. Urea is one of the main components of urine
One of many chemicals that the scientists of his time thought could only
be produced by the Vital Force, acting inside a living creature.
The artificial production and urea suggested
that life might not be powered by a mysterious force,
but instead is powered by normal chemical reactions,
which could be studied and understood.
Since that time, numerous molecules and cellular activities have been recreated in the lab,
clearly demonstrating a life is powered by normal chemical reactions,
and suggesting that life may have emerged from non-living chemistry.
Researchers have recently discovered that many of the building blocks of life,
amino acids and sugars, exist inside of meteorites, rocks which have fallen to the earth from outer space.
This tells us that these
special molecules are being produced spontaneously
all throughout our solar system and may have been common on the ancient Earth.
We've also discovered a process now referred to
as Chemical Evolution. When simple molecules are left alone with an energy source,
they interact with one another often forming larger more complex molecules as time goes on.
Experiments in the lab have shown that chains of chemical
reactions can develop,
some of which resemble the metabolic pathways of life!
Surprisingly we've also found that certain molecules have the remarkable ability
to self-assemble into complex orderly structures.
Some self-assemble into hollow spheres
almost identical to the membranes of modern living cells.
Others self-assemble into long columns
remarkably similar to the strains of DNA found in life.
Scientists still have many questions to answer about life's origins:
How did different types the molecules first start working together,
eventually producing the genetic code?
What were the original reproducing creatures actually like? Were they similar
to the cells we have today?
Or were they something much simpler? And finally,
possibly the most interesting question of all, how likely is it the life
has formed
or is forming, in other regions of our galaxy?
So...
back to the original question, can science explain the origin of life?
Science has not explained the origin of life
in full detail, but researchers are building a theory intended to one day
describe, start to finish,
how basic chemistry can give rise to living cells!
I'm Jon Perry
and that's the origin of life, as we understand it so far,
Stated Clearly.
コツ:単語をクリックしてすぐ意味を調べられます!

読み込み中…

Can Science Explain the Origin of Life?

960 タグ追加 保存
learn 2015 年 10 月 27 日 に公開
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