The beginning of Life on Earth



The theory of evolution explains how all the different species in the world came into being - mutations in the DNA of single-celled animals led to the diversity of single-celled animals before they evolved and then evolved into multicellular animals. - However, we do not know how the unicellular life on Earth began.

Our body is made up of trillions of cells - more or less each of them has a nucleus in which the genetic code is stored in the form of a DNA molecule - there is a thin membrane around the nucleus outside the cell There are various organs called organelles - the cell has many complex systems that generate energy for the cell, control the cell's copying system, and extract the right information from the cell's DNA to make the right protein. And then this protein does its specific job - the question is how such a complex feedback control system came into being inside the cells.

We know that human cells are eukaryotic cells that are much more complex, while unicellular bacteria are prokaryotic cells that are relatively less complex. Dan agrees that life began with prokaryotic cells and that eukaryotic cells evolved later. The genetic information of prokaryotic cells is also stored in the form of DNA. Experts also agree that when Earth But in the environment of the time when life began, it was virtually impossible for DNA molecules to form - so most experts believe that life began with RNA, not DNA, that is, genetic information at that time. A. I was safe, not in DNA - so the challenge for scientists is to find out how life on Earth began.

What is life?

Before we get into any discussion about life, it is important to agree on what the definition of life is - many people think of life as just human life - but this thinking is not correct. Most species are actually single-celled prokaryotic animals - so when it comes to the definition of life, individual cells are usually discussed - although multicellular animals are more complex, their bodies are made up of cells. And in every cell of their body the basic biological interactions that are the basis of life are taking place. 

Here are some features of life:

1. Cells - All types of life are in the form of cells, that is, single-celled animals or made up of cells.

2- A special order of interactions. Natural systems are usually chaotic, but life has a special order in this chaotic system.

3- Response to external stimuli ie response to stimulus- living beings save their lives in case of danger i.e. run away from danger, if the temperature is low they go towards heat, they turn towards whichever food is more. Are-

4- Making your own copies in the case of the next generation. The survival of animal species depends on the animals producing the next generation.

5- Use of energy to maintain your system- Basic interactions of life derive energy from the environment, store it and use this energy when needed.

6- Evolution - As the environment changes, so do species, which is due to genetic diversity and natural selection.

7- Organic stability ie homeostasis - Biological organisms in their system keep the water acidity i.e. pH, energy gradient, density of different chemical molecules, and body temperature in a certain range in the case of mammals and birds regardless of the external environment. Whatever

Basic element of life:

There is currently no authoritative theory about the origin of life - however, many scientists agree that organic molecules first came into being on Earth that led to the beginning of life, the earliest living cells. Were simple and the biological complexities found in existing prokaryotic cells evolved later - millions of years after the evolution of prokaryotic cells, and perhaps billions of years later, eukaryotic cells evolved - so let's see how biological cells first appeared on Earth.

All the biological species that are currently found on Earth are carbon-based. All the structures in our body are made up of protein molecules. Protein molecules are mainly composed of chemical bonds from other elements of carbon atoms. First we try to understand what is so special about carbon that all biological structures are formed around the same atom. The last shell of a carbon atom has four electrons and you know that any atom It needs eight electrons in its last shell to stabilize - this means that carbon atoms try to get four extra electrons in every possible way, and this process involves hydrogen, oxygen, nitrogen, phosphorus and many others. Atoms form bonds - the result is that carbon has the ability to form many complex molecules - that's why biological molecules that are so complex are formed around carbon atoms.

Earth was formed about four and a half billion years ago - we have clear evidence that simple biological cells are now four billion years old.

The first (ie, only 500 million years after the formation of the Earth) was formed - the average temperature of the Earth at that time was much higher than the current temperature, in which volcanoes were emitting a lot of lava and various gases and There were many meteors falling on the earth. Water came to the earth because of these meteors. These meteors brought with them not only water but also simple organic molecules. Such molecules are found everywhere in the universe. Oxygen was not present and the atmosphere was composed of nitrogen and carbon dioxide - these simple molecules were abundant around volcanic eruptions in the deep oceans and in the presence of heat these simple organic molecules were transforming into relatively complex molecules

Ingredients of life:

The simplest way of life required only two components - a bubble that would not burst immediately and preserve its contents, and a molecule capable of storing information and making copies. Water bubbles are extremely fragile and break down very quickly - but there are some molecules that make bubbles relatively strong and hard to break - these molecules are called lipids and these molecules have been in the oceans since the earliest times. I have been present frequently - lipid molecules naturally form a membrane that immediately takes on a spherical shape - this spherical membrane could have been the outer surface of the early cells - (every cell in modern life has such an outer membrane) Is made up of lipid molecules) - If more lipid molecules are added to the membrane, the size of the sphere increases. If the size of the sphere exceeds a certain limit, the membrane does not retain its spherical shape. And begins to take on an elliptical shape - when it gets bigger, this elliptical shape breaks into two separate spherical membranes. It divides into two more spherical membranes. As more lipid molecules are added to these two spherical membranes, they begin to grow again and break down to form more spherical membranes. This is the beginning of the basic process of cell division. Have made successful experiments to make this type of spherical shell from molecules and the process of making spherical shells of these lipid molecules in the natural environment has also been observed

At that time many complex organic molecules existed in the oceans in the form of long strings - one of which was the RNA molecule which is also capable of making its own copy - this molecule is made up of nucleotide molecules Are formed and are connected to each other with the help of a sugar molecule called ribose - hence it is called ribonucleic acid or RNA - this molecule is not only capable of making its own copies but also It also acts as a catalyst, meaning that in its presence certain chemical reactions take place more rapidly and many new and complex organic molecules are formed - laboratory experiments have shown that in the ocean floor In the vicinity of existing volcanoes, RNA molecules not only form but are also stable enough to make their own copies and act as catalysts for other interactions.

Beginning of life:

If lipids are forming, dispersing, and copying RNA molecules in the ocean or in the water of a lake or lake, it is very likely that Some RNA molecules will also be trapped inside these cells - experts believe that the first biological cells could be formed in the same way - RNA molecules are trapped in these shells of lipids - thus RNA molecules such as As they make their own copies, these cells would grow larger in size. After growing to a certain extent, the cell shells would become elongated and then split into two separate cells, each containing copies of the RN molecule. Because the RNA molecule is also a catalyst, these RNA molecules also began to form extra biological molecules in the cells. The structure of these extra molecules depended on the arrangement of nucleotides in the RNA molecule. Proteins and these proteins regulate the anatomical structures of all unicellular and multicellular animals

It is possible for mutations to occur in the process of making copies of RNA molecules. These mutations also cause changes in the biological molecules that form in these early cells. In other words, these mutations cause diversity in cells. Began to form - biological molecules in some of these cells proved to be beneficial to the cells (for example, they began to supply more raw material for cell division) - such cells began to divide faster than the rest of the cells and thus The process of natural selection began, and these cells gradually became more complex.

Although this process of initiating biological cells has not yet been fully replicated in the laboratory, the interactions that take place at each step of this process have been successfully generated in the laboratory and these individual steps have been carried out in the natural environment. Scientists are confident that we have fully understood the process of the beginning of life on Earth and that in the next few decades we will be able to integrate natural organic molecules into a single cell in the laboratory.

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