Evolution - genes in the long transmission process, affected by the external environment and mutation, this variation is retained from generation to generation, by time continuous accumulation and amplification, in hundreds of thousands of years, millions of years of precipitation, mutation occurred, organisms completed an evolution.
Gene
Biological evolution arises from genetic variation, a process that includes the generation, selection, and genetic metamorphosis of genetic variation, which together lead to changes in the morphology, behavior, physiology, and ecological characteristics of organisms.
The theory of biological evolution is one of the core of modern biology, which describes the origin and development of biodiversity, and also provides an important theoretical basis for the development of taxonomy, ecology, medicine and biotechnology.
Some organisms reproduce so fast that their evolution can be directly observed. For example, when studying antibiotic resistance, it can be judged by looking at how quickly bacteria spread, whether the number of bacteria multiplying doubles every half hour.
While some organisms reproduce more slowly and evolve for a long time, scientists must look for evidence of variation from multiple sources, such as genetics, anatomy, and fossil studies, to figure out how these variations or evolution shaped these lives over time.
Variation and differentiation
Natural selection acts on biological variation resulting from genetic mutations to adapt to the environment.
Organisms have evolved over many generations, and their anatomy and animal behavioral instincts have changed so radically that it is difficult for scientists to identify and classify them biologically.
The same species group diverges with changes in habitat climate, topography and geomorphology, diet and living habits, and different populations evolve in different directions along different paths.
These evolutions in different directions may take millions of years to accumulate for vertebrates, but for microbes that reproduce very quickly, this may already happen in a matter of days.
Tracking of species kinship
Chemical sequence analysis of genes helps reveal relationships between species.
For example, some analyses have shown that humans are closest to chimpanzees and are "sister species"; But there are fewer genetic similarities with gibbons, so we are more distantly related to gibbons.
Man and chimpanzee
The same genetic studies suggest that cetaceans – whales, dolphins and porpoises – share a common ancestor with hippos because they all evolved from ungulated mammals.
Scientists can estimate the random rate of change in the accumulation of genetic mutations over time, and thus design a biological evolution "molecular clock" to roughly estimate the age of species differentiation. With the help of this "molecular clock," scientists concluded that the ancestors of whales and hippos began diverging in different directions between 50 million and 60 million years ago.
Of course, the information that genes can provide is limited in "time", and genes can never show the appearance and living habits of biological ancestors. To this end, scientists have found a different way, by looking for fossils, to depict the appearance of distant ancestors of organisms. At the same time, fossils can show a great difference between the anatomical structure of prehistoric creatures and those living today.
Although the DNA of some organisms has degenerated and their anatomical structures are fragmented, the meticulous observation of scientists can still reveal important relationships between organisms separated by millions of years.
Through the determination of fossil age, it can be roughly inferred that the time and living habits of ancient creatures, the climatic conditions and environmental changes at that time, which are all verification of the "molecular clock" of biological evolution.
Although scientists may never be able to determine that life in fossil form is the direct ancestor of living life, their relative position in the evolutionary tree of life can be judged and labeled.
For example, cetaceans, there are still dozens of animal fossils on their evolutionary trees at the bottom of the cetacean family tree, tens of millions of years before modern cetaceans. But studying them not only helps show how walking limbs evolved into swimming flippers, but also chemical analysis to determine whether these animals live in fresh or salt water.
After nearly 4 billion years of evolution, there are millions of different species on Earth, and many more have survived and gone extinct in the past. Everything on the tree of life is connected to the past and to the present.
Classification of biology
Ever since naturalists tried to study living things, they have been exploring ways to classify them.
Early principles of species taxonomy were guided entirely by specific needs. For example, pharmacists classify medicinal plants according to their characteristics.
The ancient Greek thinker Aristotle classified plants and animals according to his "scala naturae" and gave each creature a "perfect form."
Aristotle's "Stairway of Nature"
Between the basic minerals at the bottom of the "ladder of nature" and the human (God) at the top, Aristotle made a distinction between vertebrates and invertebrates, a form of classification that is still used today. He believed that every living thing had an ideal form, a description of the "essence" of such creatures.
Early naturalist
From the 16th century, botany and zoology began to develop rapidly, when researchers made meticulous and profound observations and studies of a wide variety of living things without relying on the wisdom recognized by ancient philosophers.
Renaissance anatomists such as Andreas Vesalius (1514–64) explored the structure of the human body through dissection.
Andreas Vesalius
100 years later, the invention of the microscope (Leeuwen Hook) opened the door to the world of cells and microbes. Naturalists began to design their own species classification systems to make it clearer and more meaningful.
Levine Hooke microscope
The British naturalist John Ray (1627-1705) recognized whales as mammals, not fish. He also conducted exhaustive studies of plants and animals, and he was the first observer to propose the concept of biological species. He believed that a biological species is an organism that constantly reproduces and eventually becomes the same form.
British naturalist John Ray
As more species were discovered, naturalists found they lacked a standard naming system until a Swedish botanist was about to change that.
Nomenclature of species
A botanist named Carl von Linnaeus (1707-78) had been studying the biological structure of flowers to determine where their reproductive organs were and to classify their diversity.
In 1735 he published a pamphlet called Systema Naturae. At first it simply outlined a hierarchical classification of all known life.
Classes – such as reptiles, birds and mammals.
Purpose - such as pigeons, owls and parrots.
Genus – defines the basic form of an organism, such as a bear, cat, or rose.
As was customary at the time, the specific type (the equivalent of John Ray's species) was still described in a cumbersome Latin.
It wasn't until 1753 that Linnaeus's Plant Species changed this when he named plants in one word.
Linnaeus's Plant Species
He made the same classification of animals in the tenth edition of The System of Nature, published in 1758. For example, brown bears — listed as bears in 1735 — are now given the specific name of the bear, bear.
Linnaeus's Natural Systems
Linnaeus's articles in 1753 and 1758 marked the beginning of modern recognized botanical and zoological names, respectively. This dual-name naming system is still commonly used in biology today.
The first name (Ursus) indicates the genus,
The second name (arctos) indicates the species.
Linnaeus's classification system has been used so far, with only some modifications and additions.
As our understanding of relationships between species continues to grow, many species move to other genera.