Shulou(Shulou.com)11/24 Report--

After the birth of life, the species on earth began to evolve for billions of years, and finally formed a rich and diverse species group.

Due to the continuous birth of new species and the extinction of old ones, we were unable to record all species before human civilization developed, so there is no way to confirm how many species have evolved in the world since the birth of life.

To be sure, the vast majority of species have become extinct, and the number of existing species is only a small fraction of that of all species since the birth of life.

Source: how to classify pexels animals and plants if we want to know and understand these species, we must classify them systematically.

Long before the advent of words, humans began to classify living things. Many naturalists began to group species with the same characteristics, arranging them one by one in the order of "evolution" or "evolution" from scratch and from simple to complex.

The schematic map of the biological evolution tree will give these naturalists an idea: when and where did life originate, and is there any internal connection? What kind of creature is the ancestor of all living things today?

In ancient Europe, animals have been classified according to the bifurcation method proposed by Plato.

For example, animals are divided into aquatic animals and land animals, winged animals and wingless animals, which is a kind of animal classification with obvious opposing characteristics. Although there is some truth in this simple classification, it has fatal defects, and it is easy to artificially split the same species, which makes people feel obviously that this classification is incorrect.

For example, it is obviously inappropriate to classify winged ants among winged animals and wingless ants among wingless animals. Therefore, after this classification came out, many scholars expressed doubts.

Whether the simple way of classification is "evolution" or "evolution" Aristotle, a student of Plato, gave birth to a preliminary taxonomic idea and thought that a more reasonable way of classification could be found. He described more than 500 animals and classified them. He divides animals into bloodless animals and bloodless animals according to whether they have red blood or not.

Although now, this classification is too simple, but at that time, this classification is still of great value.

In fact, we now know that classifying according to the blood of animals is a relatively complicated thing. Some lower animals, such as protozoa Hydra, planaria, tapeworm, Ascaris lumbricoides, have no blood because their bodies are not highly differentiated and can meet the corresponding circulatory oxygen supply needs through body fluid infiltration.

In addition, the color of biological blood is not always red.

The blood of horseshoe crabs is blue in oxygenated state, colorless or white in non-oxygenated state, red in oxygenated state and green in non-oxygenated state in some polycaterpillars, such as broom caterpillar family and green in non-oxygenated state. The blood of brachiopod is purplish red in oxygenated state and brown in non-oxygenated state; the blood of shrimp, spiders, squid and other animals is cyan. The blood of arthropods is colorless or light blue.

Aristotle believes that red blood is blood, and animals with other colors of blood will be classified as bloodless animals in his theory.

Aristotle Limulus is the first European scholar to establish the theory of zoological classification, and he is also the first scholar to classify animals according to animal characteristics.

At the same time, he also did a lot of work in plant classification, and his research results were not preserved for various reasons, but his student and botanist Theophrastos made a clear distinction between animals and plants and clarified the difference between the two.

He put forward a very interesting point: after the loss of part of the body, plants will be easily renewed, while animals after the loss of part of the body, the renewal is extremely limited. This has become one of the important features to distinguish between animals and plants.

The number of biological species in the whole nature is extremely abundant. At present, the number of known biological species is about 2 million, while the number of extinct biological species is as high as 15 million.

Therefore, if there is no recognized way of classification, various research institutions or scholars talk to themselves, then it will not only lead to a large number of repeated research and waste of resources, but also not conducive to the transmission and exchange of information.

Swedish naturalist Carl von Linne, a pioneer in biological taxonomy, spent five months in the field and collected a large number of plant specimens. Through on-the-spot investigation, he classified the plant specimens, grouped them according to similar morphological characteristics, and began to think in his mind what kind of characteristics are the classification criteria of the whole plant kingdom.

In 1735, Linnai received his doctorate in the Netherlands and published his first natural history book, the Natural system. Although animals in nature, such as monkeys, eagles and flies, are called by the same name in daily life, there may be multiple species under each name in the study, and the same species has different names in different places. Therefore, it is urgent to formulate a unified naming rule.

Linnai proposed that the species in nature should be classified systematically according to the classification of kingdom, class, order, genus and species, and put forward the naming rule of double-name nomenclature. The first name is the genus name, and the second name is the species name.

For example, the scientific name Homosapiens of human beings is formulated by Linnai, in which Homo belongs to the genus Homo sapiens and sapiens means wisdom, so it can be called Homo sapiens. Linnai classifies species in biology into a multi-level classification system for the first time.

Each level has become a taxonomic element and has been used so far, and now it has been gradually perfected into seven basic order elements, which are in the following order: boundary, phylum, class, order, family, genus and species.

Some subunits can also be added, such as a suborder in the order and a superfamily in the family.

Taxonomy systematically classifies animals and plants in nature according to boundaries, phyla, classes, orders, families, genera and species, and sums up similar organisms together according to the similarity of organs to form a complete biological evolution pedigree.

Source: "telling teenagers about Life Science" author: Liu Rui part of the picture source network copyright belongs to the original author Editor: Zhang Runxin this article comes from Wechat official account: Origin Reading (ID:tupydread), author: Liu Rui

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