Publisher: Chorus Secret Garden
Source: BigThink
compilation: Sail2008
Editor: Sunnisky
Neil Shubin, a member of the American Academy of Sciences and professor of biology at the University of California, will give you the endosymbiosis theory of Lynn Margulis, the pioneer of eukaryotic evolution in popular science. Let us witness the alternative legend of biological evolution.
Throughout the history of biological evolution, organisms have been "stealing" , instead of starting from scratch.
For example, the tiny "organs" in cells were once independent bacteria.
Now,Humans extract the CRISPR sequence from bacteria and use it as a gene editing technology.
Wheels have been on the earth for more than 6000 years, and suitcases have existed for centuries. The suitcase on wheels was only invented decades ago, and it has changed the lives of many travelers.
The relationship between innovation and new component combinations is by no means an alternative insight. It is not only part of the 4 billion-year evolutionary history of the earth, but also part of the future of mankind.
In the 1960s, Lynn Margulis, a graduate student of at the University of California, Berkeley , observed the diversity of biological cells in his first research project and proposed a new theory of its production mechanism .
According to her memory, the paper was rejected by about 15 magazines after completion. But she was not discouraged, and finally found a place to publish her paper in a lesser-known theoretical biology journal.
Lynn Margulis
Margulis' bold persistence in the face of a negative comment is amazing.At the beginning of her career, this young female scientist chose to antagonize deep-rooted orthodoxy.
Margulis studied the cells that make up the bodies of animals, plants and fungi. These cells have the complexity that bacteria do not have. There is a nucleus in animal and plant cells, and the genome is in it. There are many micro-organs called organelles around the nucleus. The most prominent of these is the organelles that power cells.
There are chlorophyll in the chloroplast of plants, which can convert chlorophyll into photosynthetic energy and use sunlight. Similarly, animal cells have mitochondria , and mitochondria can generate energy from oxygen and sugar.
Chlorophyll
Margulis observed that these organelles look like tiny cells in the cell.Each organelle has its own cell membrane around it to separate it from the rest of the cell. Mitochondria and chloroplasts reproduce in the cell by dividing into two halves. This process is called two divisions .
When they divide, the organelles stretch and shrink in the middle to look like dumbbells, and then separate to form two new individuals. These organelles even have their own genome, which is separate from the genome of the nucleus.
However, the genome of the organelle is completely different from the genome of the nucleus. The DNA chain in the nucleus is linear _strong 52 span, 5span DNA and a chloroplast 52 span. ring structure .
Endosymbiosis theory
has its own cell membrane, two-division reproduction, DNA forming a loop, these organelles have some similar structures to Margulis. Where did she see these features before, yes, in bacteria.
bacteria also use two-split propagation,Surrounded by a similar cell membrane, there is a genome that looks very similar to the genomes of chloroplasts and mitochondria. The organelle that powers plant and animal cells looks more like bacteria than the nucleus of the cell in which it is . From these observations, Margulis proposed a new theory of evolutionary history. Chloroplasts were originally a kind of independent living cyanobacteria (also known as blue-green algae ) , and they were absorbed by another cell and used as free "labor" for the metabolism of the new city to power it.
Similarly, mitochondria are bacteria that live independently at first, and they merge with another cell and are used to power them.
mitochondria
Margulis' theory has been met with either general contempt or complete disregard. Fortunately, technology has caught up with her ideas. With the development of DNA sequencing technology in the 1980s, the evolutionary history of genes in organelles can be compared with the evolutionary history of cell nuclei, and the pedigree diagrams that emerge are even more stunning.
mitochondria and chloroplasts are not genetically related to the DNA of their own cell nucleus. Chloroplasts are more closely related to different types of cyanobacteria than to anything else in plant cells. Similarly, mitochondria are the offspring of an oxygen-consuming bacteria and have nothing to do with their nucleus.
Today, every animal or fungal cell has two life families, one is the nuclear family and the other is the bacterial family, whose ancestors were bacteria that once lived independently. There is a third family in plant cells , whose ancestors were cyanobacteria that once lived independently.
The more we observe, the more we discover that the characteristics of one species can be borrowed, stolen, and modified by another species for new purposes. In this way, the owner inherits the ready-made invented parts without having to re-invent it himself. It may be the combination of these components and the resulting new types of individuals that have opened the door to evolutionary opportunities.
For billions of years, life has existed in the form of single cell metabolism, and this invention uses the form of single cell metabolism. Energy and chemicals. With the emergence of more complex individuals, new ways to make protein, move around, and eat have emerged.
creatures with bodies,For example, animals, plants and fungi are relatively new members of life on earth, and the cells that make up them are all merged by different individuals.
The emergence of the body opened up a new way of biological evolution. An organism composed of multiple cells, each cell powered by organelles, can grow up and develop new tissues and organs.
As a result, the diversity of tissues and organs helps animals fly to the highest altitudes and swim on the sea floor. More advanced human species have also designed satellites to detect distant regions of the solar system.
is stealing, but in a clever way
The fusion, borrowing, and reuse of technologies and inventions from other species are part of the past billions of years of evolutionary history.
2020 Nobel Prize in Chemistry was awarded to two women who helped design CRISPR-Cas, a new technology for editing genomes. In nature, CRISPR is a defense mechanism used by bacteria to resist virus invasion.
We finally figured out what cells and genomes have been doing for billions of years,The methods invented by bacteria are used to alter the genomes of other bacteria.
As a result, as Lynn Margulis has seen, a proper technique can change evolution with a little patch.
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