How did plants survive from ancient times to the present day?

Dear friends, have you ever thought about this: the earth has existed for so many billions of years, and animals have undergone earth-shaking evolution, but what about plants? How did they evolve?

In fact, the earliest plants on Earth had no leaves! (Warning: plants today are different from plants in ancient times, this is just for the sake of understanding.) Plants at that time should have looked like this.

Why do plants today have luxuriant branches and leaves? How did leaves evolve? Today, I will talk to you about the evolutionary history of plants from four aspects.

01. The History of Plants on Earth

Here, I will briefly review the history of plants on Earth. The earliest plant ancestors should be a group of photosynthetic bacteria, about 3 billion years ago.

In fact, the oldest photosynthetic bacteria are not green, but purple bacteria, which still exist today. Green bacteria finally won a decisive victory. As for why, it should be related to the selective absorption of light. Because from the beginning, they reflected green light, which is why the world is green.

This is one of the greatest pages in Earth's history. It is also one of the foundations of our final emergence.

Because, with the emergence of photosynthetic bacteria, oxygen began to appear on the earth. They gave birth to life on the earth. Without them, our planet would be like Mars. With oxygen and the ozone layer, we are no longer afraid of ultraviolet rays. Why do organisms grow in the ocean? Because the ocean can withstand countless rays, especially ultraviolet rays.

Later, at some point, these bacteria evolved into the oldest plants, which are the countless green algae in the sea water.

About 400 million years ago, in the late Silurian period (440-410 million years ago), a great new chapter began on Earth. Plants began to land! This landing changed the Earth.

Due to the lack of competitors, soon (about 100 million years), the earth was covered with green.

Due to the photosynthesis of plants, the oxygen content on Earth gradually increased. After about 100 million years of wild growth, in the Carboniferous period (360-280 million years), the oxygen content on Earth reached an unprecedented high of more than 30%. The high concentration of oxygen gave rise to countless giant animals and prehistoric monsters, such as dragonflies that were more than one meter long (the reason is still that the increase in oxygen content made it possible for insects to grow. Because many insects absorb oxygen through tracheae throughout the body or part of the body. In the same environment, the larger the body size, the larger the trachea (respiratory system). But when the oxygen concentration is high, organisms do not need to increase the volume of the respiratory system to provide more oxygen for the increased body size, so the restrictive effect of the respiratory system on body size is reduced, allowing organisms to evolve to a larger body size.)

However, the first crisis in plant history occurred!

02. What was the first plant crisis?

Regarding this crisis, we still have to start with the principle of plant photosynthesis.

Light + Water + Carbon Dioxide = Glucose + Oxygen

In this formula, light comes from the sun, water is abundant on the earth, and a core limiting factor, carbon dioxide, becomes a rope around the neck of plants.

At that time, plants were absorbing carbon dioxide like crazy, and then, in an instant, the earth’s carbon dioxide was not enough!!! What the hell, not enough carbon dioxide? Yes, seeing the greenhouse effect today, don’t you think it’s weird?

But the fact is that there is not enough carbon dioxide on Earth for photosynthesis. Plants rely on carbon dioxide for survival. Once carbon dioxide is gone, plants cannot survive, so countless plants die. The first crisis on Earth was born. And this crisis almost destroyed the Earth (nature).

03. The birth of leafy plants

At this time, some plants began to look for new paths, and leaves began to appear on the stage (remember the core of evolution, mutation is random, selection is directional. Back here, leaves appear randomly, and low concentration of carbon dioxide is just a natural selection process, there is no direct cause and effect relationship between the two) In addition, the picture here is angiosperms, which appeared in the Jurassic period, and earlier was gymnosperms. Algae-moss-ferns-gymnosperms-angiosperms

The appearance of leaves is a great page in the history of plant evolution. Because of the appearance of leaves, plants no longer rely on trunks and branches for photosynthesis, but use leaves for photosynthesis.

The leaves of plants increase the range of photosynthesis by millions of times, and the leaves can better utilize the thin carbon dioxide in the air for photosynthesis.

So the plant survived.

However, the tragedy continues.

Because of the appearance of leaves, plants can absorb more carbon dioxide, and they do survive, but in essence, the earth's carbon dioxide is still decreasing, and it is decreasing at an accelerated rate (absorbing more vigorously). If there is no new source of carbon dioxide, then all plants will die, or they will switch to other gases, such as nitrogen fixation.

04. A stroke of genius: fungi

However, at this time, fungi saved the earth. You can refer to the works of the great Pavlov for this content.

Perhaps in the beginning, no one thought about decomposing plant fibers, not even animals. A large number of plant corpses would be a garbage paradise. Until one day, the earth could no longer bear it. Fungi began to show their talents. They decomposed plants, making the carbon cycle flow successfully and filling in the last missing link.

This is today's green world.

Supplement: Teach a man how to fish. I am not a botany or geologist, so I am bound to make omissions and even many mistakes in principle during the writing process. Of course, I am also lazy, such as the shape of the earth during the Carboniferous period.

The main references of this article include but are not limited to the following contents, all of which are very interesting.

1. Harrison CJ, Corley SB, Moylan EC, et al. Independent recruitment of a conserved developmental mechanism during leaf evolution[J]. Nature, 2005, 434(7032): 509-514.

2. Edwards, D., Feehan, J. & Smith, DG A late Wenlock flora from County Tipperary, Ireland. Bot.J. Linn. Soc. 86, 19–36 (1983).

3. Gifford, EM & Foster, AS Morphology and Evolution of Vascular Plants (Freeman, New York, 1989).

4. Boyce, CK & Knoll, AH Evolution of developmental potential and the multiple independent origin of leaves in Paleozoic vascular plants. Paleobiology 28, 70–100 (2002).

5. Kenrick, P. & Crane, PR The Origin and Early Diversification of Land Plants: A Cladistic Study (Smithsonian Institution Press, London, 1997).

In addition, those who are interested in plants can watch a documentary, How to Grow a Planet (Plant Song/Earth Cultivation Plan). This documentary was also used as a reference during the writing of this article.