THE origin of life on planet Earth is, without a doubt, a subject that intrigues all of humanity. Several have already been hypotheses created to explain such an event, but to date none has been completely proven. In this text we will approach some of the main ideas of the genesis of life.
Read too:Abiogenesis and biogenesis: theories that try to explain the origin of life
creationism
According to creationism, all living beings appeared on Earth through a creationdivine. According to this idea, God created all living beings, including human beings, as reported in the Bible. This idea of the origin of life is one of the oldest and is still accepted by many believers around the planet. If you are more curious about this topic, read our text: creationism.
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panspermia
panspermia is a hypothesis which claims that life on the planet may have been initiated based on particles of life that arrived on Earth through space. According to the Greek philosopher
Anaxagoras, existed seeds of life In all the Universe. Thus, life may not have originated here, but arrived on the planet later.This idea gained momentum in the 19th century, when chemists thenard, Vauquelin and Berzelius found out compoundsorganic in samples of a meteorite. In 1871, physicist William Thomson proposed that meteors or asteroids, when colliding with planets that contained life, could have ejected rocks containing living beings. Thus, rocks containing life may have brought or collaborated with the origin of life on Earth.
According to the panspermia theory, life may have arrived on the planet via a meteorite.
Fragments of the Murchison meteorite, for example, contain more than 80 different amino acids. Furthermore, these fragments, which fell in Australia in 1969, contain, in addition to amino acids, other fundamental organic molecules. If you are more interested in the subject, read our text: panspermia.
Read too:Solar System - origin, planets, stars, curiosities
Oparin and Haldane Theory
Independently, scientists oparin and Haldane raised a hypothesis that is today considered to moreaccepted origin of life. They proposed that the Earth's primitive atmosphere contained compounds that suffered from action of rays and ultraviolet radiation, giving rise to simple molecules. These organic molecules were found in the primitive oceans, forming a kind of “primitive soup”.
According to the researchers, the atmosphereprimitive terrestrial was basically composed of ammonia, hydrogen, methane and water vapor. The water vapor from atmosphere it condensed and gave rise to rain. The water, when falling to the ground, evaporated quickly, since the earth's surface was still hot, thus starting a cycle of rains. In this scenario, it was still observed dischargeselectric and the radiationultraviolet of the Sun, which caused the elementsatmospheric reacted and formed compounds, the amino acids.
The rainwater took these amino acids to the earth's surface. These, when they find conditionsfavorable, began to form structures similar to proteins. With the formation of the oceans, these "primitive proteins" were dragged to these places and formed the coacervate, which can be defined as protein aggregates surrounded by Water. After some time, these coacervates became stable and more complex.
The Oparin-Haldane idea was later tested by the researchers Miller and Urey, in 1953. They created a experiment when it was possible simulate the conditions of primitive earth. The result was impressive, having been able to produce amino acids and other organic compounds. Thus, both concluded that organic molecules could be spontaneously generated under conditions equivalent to those of the early Earth.
Representation of the experiment carried out by Miller.
However, it was later discovered that the primitive atmosphere was probably not an environment as suggested by Oparin and Haldane. Still, even considering the newdiscoveries for the characteristics of the atmosphere of the early Earth, it was possible to produce organic molecules.
It is also worth noting that the primitive atmosphere could be reduced in small portions, such as those near the openings of volcanoes. Experiments performed under these conditions also generated amino acids.
Feeding the first living being: autotrophic and heterotrophic hypotheses
In addition to understanding how living things came to be, scientists are also looking to find out how they survived in such a remote environment. There is still much debate about whether the first living being was autotrophic or heterotrophic, it is possible to observe a lot of disagreement among textbook authors in this regard. See below these two hypotheses:
Heterotrophic Hypothesis: states that the first living being was not capable of producing its own food. Thus, these first beings fed on organic molecules that were present in the environment. Those who defend this idea claim that primitive living beings would be very simple and incapable of producing their own food. These organisms probably extract energy from food by carrying out fermentation.
Autotrophic Hypothesis: claims that the first living beings were able to produce their own food. The authors who support this idea believe that the Earth did not have enough organic molecules to feed these first beings. However, it is worth noting that the first organisms probably managed to obtain their food through the chemosynthesis process, which does not require light energy, such as photosynthesis. In chemosynthesis, living beings produce organic molecules using chemical energy from inorganic compounds.
Read too:Differences between autotrophic and heterotrophic organisms
By Ma. Vanessa Sardinha dos Santos
There is a process in which food and beverages, such as milk, are heated at an ideal temperature to destroy microorganisms that can cause disease if they are not eliminated. This process does not change the properties of food and beverages. What name is it known by?
( 1 ) Theory in which a living being originates from similar beings
( 2 ) Hypothesis in which the animals emerged from eggs invisible to the naked eye
(3) Process for the generation of offspring
( 4 ) Theory in which life arises from inanimate matter
( ) Reproduction
( ) Redi Experiment
( ) Biogenesis
( ) Spontaneous Generation
