All life uses genetic code to translate DNA-based genetic information into proteins.
Most life forms consist of twenty different types of amino acids, and add to that twenty tRNA molecules, who link to the correct amino acid with help from enzymes. Scientists view this process as a molecular computer, whereas it translates the correct amino acids to the correct molecules and puts it all together like a jigsaw. The enzymes are in two different, distinct classes each having ten members. The enzymes are called aminoacyl-tRNA synthetase who scientists say are responsible for ‘loading’ the amino acids onto the transfer RNA molecules, that are essentially an adapter, and each class of enzymes attach to the acceptor stem on opposite sides. Class 1 attaches to the minor groove side, whereas class 2 attaches the the major groove side, to carry the building block protein (enzyme) into the molecule’s assembly line known as a ribosome. A ribosome links amino acids in an order given from the RNA that direct genetic information from DNA, to create gene expression which involves two stages. The instructions in the message and a functional product derived from the message. Scientists say that a similar class structure exists for amino acids, so it’s argued that it must also apply to tRNA molecules.
This is all very complicated, and it gets much more complicated, but is essentially part of the four macromolecule building blocks of life.
• nucleic acids
Charles Carter, PhD (biophysics) , and Peter Wills, PhD (biochemistry) suggest that life hasn’t always had 20 amino acids, 20 tRNA molecules and 20 enzymes and likely this has developed over time through Evolution, and early, primitive life will have just had a pair of each, and as time passed they will have augmented by new variants until there were ten in each class.
How could life have evolved in complexity from the simplest molecules?
Planet Earth is 4.543 billion years old, and it took a billion years before single cell life began, and I’m sure you’ll agree that’s a long time for the preparation of life, and it was another 2.9 billion years after that multicellular animals existed. This kind of time frame is incomprehensible, considering our short existence in space and time.
The big question scientists ask is why, after 2.9 billion years, did the highly successful and abundant single cell life form develop into multicellular? As we well know, humans work better as a society, all having different jobs to do, than we do alone having to do everything. Well perhaps this was the same for unicellular life, and working together formed the basis of multicellular life?
It’s known that single cell organisms can mutate to preserve life via Evolution, and the most perfect, and simple example of Evolution is bacteria. Place antibiotics on a Petri dish with enough bacteria & wait a few days. There’ll be bacteria that is immune to the antibiotic & it’ll be multiplying. This is an example of natural selection.
Natural selection is the change of biological heredity of a population through generations. Considering bacteria mostly has such a short life span, then several generations can happen very fast. Some microbes can live for hundreds of years on a surface, and some, like HIV only last seconds, but most don’t last very long at all.
Scientists claim that they think unicellular to multicellular is in principal the same as a ‘ratcheting mechanism‘, in that it can only go one way. What this means is a scenario is created where it’s only beneficial to a group, and destructive to anything alone, meaning there is no reversion to the state it was in before. In other words unicellular life banded together as a group and became reliant on each other, so there was no chance of a mutation to turn multicellular life back into unicellular life. In a group state, mathematically there’s more chance of mutation, but a mutation to go forward, and not backwards. This is Microevolution at work when there are small, but significant changes at a molecular and cellular level, caused from selection, genetic drift, gene flow and of course mutation. This is certainly a possibility of how life went from unicellular to multicellular.
Convergent evolution studies how significantly distinct species have evolved the same way through evolution, like the wing details in the above image, which are called analogous structures.
Or the strikingly similar features of a shark and a dolphin, despite one being a fish and one being a mammal. To look at they are similar, but anatomically they are very different. A shark has gills and cartilage structure, whereas a dolphin has bones and breathes fresh air. Physically they are very similar in that they have evolved for a common goal. To swim fast and efficiently through water.
Divergent Evolution takes us back to unicellular life, and how the diversity of modern life came from it, and how life can develop from a common ancestor. Darwin’s finches is a perfect example of this. It shows how one species can adapt to change due to its competition regarding territory, food source and defence. When Charles Darwin visited the Galápagos Islands, he collected the Finches that were all of a dull colour, but ranged in size and beak, and were a perfect example of the rapid evolution of ecologically different species from a common ancestor, that will forever remain synonymous with Darwin.
Last Universal Common Ancestor, or Common descent is a theory that all life on Earth descended from one common ancestor, and this is due to the fact that all living organisms are encoded the same way with DNA and RNA, and the similarities in Amino acids.
‘A growing body of evidence suggests that there was so much sharing of genetic material among the single-celled organisms at the base of the tree of life that the different strands cannot be separated. Some scientists go so far as to treat the entire community of organisms alive at the time as essentially a single superorganism which shuffled genes freely between components.’ NCSE
In the below video, scientists have witnessed a unicellular organism mutate into a multicellular organism which happened over a fifty week period. Scientists witnessed this after introducing a single cell eating predator.
What this proves is not only is Evolution real, BUT it could also explain a potential theory on how a predatory single cell organism triggered the mutation into multicellular life, and eventually over millions of years, the human race.
This experiment was conducted by Stanley Miller, and Harold Urey
Who were American Chemists who created experiments trying to understand how the origin of life could have begun, but creating a mock version of what is understood to be a primitive Earth. It led many scientists to seriously consider that a chemical evolution potentially created the ingredients for life from non-organic matter, and an explanation as to what initially triggered life on Earth.
The experiment involves the use of water, methane, ammonia and hydrogen, which created a simulated atmosphere that mimicked early Earth. The water was heated to cause it to evaporate and electrical charges were exposed to the gaseous mixture to simulate lightning, and then it was cooled, and heated again.
Miller identified five amino acids, which were; aspartic acid, glycine, alpha-amino-butyric acid, and two versions of alanine on blotting paper. Bear in mind that this experiment was 66 years ago, and rightfully so, modern biologists deem it as primitive compared to modern standards.
Miller published his findings, but never published one of his experiments, and this involved air flow that intended to simulate volcanic activity that scientists claim the Earth was littered with. His equipment went into storage, and many years later, scientists studied his equipment with modern equipment. They found that more amino acids had been created than Miller thought.
Johnson added, ‘Many of these other amino acids have hydroxyl groups attached to them, meaning they’d be more reactive and more likely to create totally new molecules, given enough time.’ NASA
Did multicellular plants evolve from algae?
Did sea life evolve from primitive sponge like life?
Did animals evolve from Dickinsonia?
It makes interesting research when you look into the possibilities of how we came to live in such a diverse world.