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Taxonomy has been changing with the enrichment of biological knowledge, such as blue-green algae being renamed cyanobacteria, and termites being identified as a cockroach.
The two large taxonomic hierarchies of animals and plants have not been strongly questioned, but there are still some small dark clouds floating in the taxonomical sky, and taxonomists have decided to wipe these dark clouds by hand. Plant taxonomy moves relatively quickly, they expel themselves from the plant world that they cannot explain in their taxonomic theory, in the form of publishing taxonomic works that do not include certain organisms, and if their expulsion of prokaryotes and fungi can still cause some resonance, then their expulsion of certain algae Is a bit strange.
Why did they ban some of their algae from their plant households? Because these algae are a bit like animals, such as naked algae, also called eye worms, single-celled organisms, have no cell walls, have chlorophyll, can be self-nourishing, and also have flagella capable of moving around.
Schematic diagram of naked algae
The species introduced next is widely known as dinoflagellates, which is obviously a plant name, and was once classified as an animal due to its flagellanic structure capable of swimming.
Schematic diagram of dinoflagellates
Dinoflagellates, single-celled organisms, also known as dipterocarella, mostly have armor-like cell walls, contain chlorophyll and various carotene species, and are self-nourishing, so they were initially considered plants. Dinoflagellates have 1-3 flagellar, usually two, one with long, backward hairs and the other known as lateral hairs. The flagellar is exposed from the whiplash pores on the outer wall of the cell, the spiral waving of the lateral hyphragm provides most of the propulsion, and the long flagellae mainly serve as a rudder and rarely provide propulsion.
In 1981, the taxonomist Thomas Cavalier-Smith had a vague classification of such creatures, so he looked at the shapes of these creatures, considered the history of biological evolution, and finally decided to collectively call these all Chromista to classify red algae and dinoflagellates and their offspring, which was so unique that it caused great controversy.
Since then, the physiological research on dinoflagellates has also continued to deepen, and many scientists have found that there are very few purely autotrophic dinoflagellates, and dinoflagellates can rely on heterotrophic ways to live.
A study published in 1997 showed a way for dinoflagellates to prey:
Berlin polyforman preys on injured nematodes
1. The abdomen of The Berlin polyforman is close to an injured nematodes
2. Release the capture wire
3. Ingestion tube suction (deformation of the upper body of the cell due to pressure action)
4. Leave the ingested nematodes (there are still residues of catching silk)
Next, scientists discovered another heterotrophic way of dinoflagellates, using a cage structure to prey on, and dinoflagellates can even use flagella to create water streams in local areas to prey on bacteria.
All this shows that dinoflagellates have animal characteristics: movement, heterotrophic.
By 2005, taxonomicists decided to call these flagella-haired algae Chromalveolata, and later they classified all flagellaria with the highest taxonomic level "boundary" and included more species, even ciliates (representing biological grasshoppers) and oomycetes (water mold).
Therefore, animals do not have cell walls because taxonomists have expelled those with cell walls.
Taxonomy has been influenced by the dual influence of social culture and insufficient discovery of its own disciplines, which has brought trouble not only to the academic community itself, but also to the public, for example, recently they like to hype kelp is no longer classified as a plant, and they are not afraid to openly admit that in fact, the animal taxonomy has expelled grasshoppers more than a decade ago.
From the perspective of biophysiology and biological evolution, red algae that originated more than a billion years ago may be the common ancestor of animals and plants, and the algae that maintained the cell wall eventually landed and evolved into various plants. Soon after the emergence of red algae, primitive algae and bacteria in the ocean had some endosymbiosis effects, and eventually lost the cell wall, which made the evolution of animal cells more possible, and also evolved animals.
Author:Five Lotus Blossoms (Zhihu Users)
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