London, May 20 (Talk) From its humble origins, life has infected the entire planet with endless beautiful forms. The origin of life is the oldest biological phenomenon that has left no clear evidence other than the existence of life.
This leaves many questions open, and one of the most staggering is how many times life has magically emerged from inanimate elements.
Did all life on Earth evolve only once, or were different organisms cut from different cloth? The question of how difficult it is for life to emerge is an interesting one – at least it sheds light on the possibility of finding life on other planets.
The origin of life is a central question in modern biology and difficult to study. The event took place four billion years ago, and it happened at a molecular level – meaning there is little fossil evidence.
Many lively beginnings have been suggested, from tasteless primordial soups to outer space. But the current scientific consensus is that life arose from nonliving molecules in a natural process called abiogenesis, mostly in the darkness of deep-sea hydrothermal vents. But if life appeared once, why not many times? What is apiogenesis? Scientists have proposed various sequential steps for apiogenesis. We know that Earth is rich in many chemicals, such as amino acids, nucleotides, or a class of molecules called sugars, which are the building blocks of life. Laboratory experiments, such as the iconic Miller-Urey experiment, show how these compounds could form naturally under conditions similar to the early Earth. Some of these compounds may also have made it onto meteorites that cruised by Earth.
Next, these simple molecules form complex molecules such as lipids, proteins or nucleic acids. Importantly, nucleic acids – such as double-stranded DNA or its single-stranded cousin RNA – can store the information needed to build other molecules. DNA is more stable than RNA, but in contrast, RNA can be part of chemical reactions in which a compound replicates itself – self-replication.
The „RNA world” hypothesis suggests that early life may have used RNA as the material for both genes and replication before DNA and proteins appeared.
When an information system duplicates itself, natural selection begins. Some of the new copies of these molecules (some call them „genes”) contain errors or mutations, and some of these new mutations improve the ability to copy. of molecules.
So, over time, copies of these mutants outnumber other molecules, and some of them accumulate more new mutations, making them faster, more numerous, and so on.
Eventually, these molecules probably form a lipid (fat) boundary that separates the organism’s internal environment from the external, forming protocells. Protocells synthesize and finely organize the molecules required in biochemical reactions, providing a contained and efficient metabolism.
Life on repeat? Abiogenesis may have occurred more than once. Earth may have given birth to self-replicating molecules many times, and for thousands or millions of years, early life consisted of different self-replicating RNA molecules, of independent origin, competing for the same building blocks. Alas, due to the ancient and microscopic nature of this process, we may never know.
Many laboratory experiments have successfully reproduced different stages of apiogenesis, proving them more than once, but we have no certainty that these occurred in the past.
Perhaps a related question as you read this is whether new life originates through abiogenesis. Although this is highly unlikely. The early Earth was sterile of life and the physical and chemical conditions were very different. Nowadays, if the conditions are right for new self-replicating molecules to appear somewhere on the planet, they are immediately destroyed by existing life.
What we do know is that all extant life is descended from a single shared last universal common ancestor (also known as LUCA). If there were other ancestors, they left no descendants. Substantial evidence supports the existence of LUCA.
All life on Earth uses the same genetic code, the correspondence between nucleotides in DNA called A, D, C, and G, and the amino acids they encode in proteins. For example, an ATG sequence of three nucleotides always corresponds to the amino acid methionine.
However, theoretically, there could have been more genetic code variation between species. But all life on Earth uses the same code with some minor changes in some lineages. Biochemical pathways, such as those used to metabolize food, support the presence of LUCA; While many independent pathways may have evolved in different ancestors, some (such as those used to metabolize sugar) are shared by all organisms. Similarly, there are hundreds of homologous genes in different organisms that can only be explained by derivation from LUCA.
My favorite support for LUCA comes from the Tree of Life. Independent analyses, using some anatomical, metabolic or genetic sequencing, have revealed a hierarchical pattern of association that can be represented as a tree. This shows that we are more closely related to chimps than any other species on Earth. Chimps and we are closely related to gorillas, and together to orangutans and so on.
You can pick any random organism, from the lettuce in your salad to the bacteria in your bioactive yogurt, and if you travel back in time, you’ll share a real common ancestor. This is not a metaphor, but a scientific fact.
This is one of Darwin’s most mind-blowing ideas in the science of the unity of life. If you’re reading this text, it’s thanks to an uninterrupted chain of reproductive events going back billions of years. As exciting as it is to think about the repeated emergence of life on our planet or elsewhere, it is even more exciting to know that we are related to all life on the planet. (Dialogue) MRJ MRJ
(This story was not edited by DevDiscourse staff and was generated automatically from a syndicated feed.)