Natural evolution
Evolution is a historical process, while natural evolution lasts for billions of years, and the traces of its evolution are generally difficult to detect. However, after all, biological evolution is a continuous process and will continue to develop in the future. Based on this feature, we can still study it through some ways.
1. Explore the ancient and the secret
Because biological evolution is a continuous historical process, although it is not easy to find traces of evolution from modern creatures, they still left some of their own figures on this long road, that is, fossils. For example, paleontologists found fossils of leaves and seeds of grapes in Cenozoic tertiary strata, which proved that grapes existed in Europe, Asia and North America millions of years ago. Later, with the separation of continents and the change of climate, Eurasia was covered by large glaciers, and most members of the grape family disappeared. Only one Eurasian grape population in the Mediterranean region was not completely swallowed up by glaciers, and gradually multiplied into a prosperous grape descendant on the earth, which roughly described the natural evolution of grapes. Through the study of paleontological fossils, we can explore the evolutionary history of a certain organism.
2. Discuss the past with the present.
This paper discusses how modern organisms mutate, how to pass the mutation on to future generations, thus causing population changes, and can also be traced back to the historical process of this evolution, the so-called past and present discussion method. This method involves a wide range, such as exploring the evolutionary relationship by comparing the evidence of anatomy, embryology, cytology, molecular biology, genetics, biochemistry, geographical distribution and changes of domestic organisms. At present, isozyme, pollen, chromosome, protein, pigment, DNA and other indicators and their relationships are also used to study the natural evolution of various fruit trees. There are many reports about this, for example, Li's 1993 is a hybrid of pear and pear according to sporopollen data; Cheng Jiasheng et al. (1986) used the fuzzy clustering analysis method of isozyme data to determine the genetic relationship among different apple varieties. Niu Lixin et al. (1993) used 83 characters, such as morphological characteristics, growth characteristics, sporopollen and so on, to study the compound leaf grape originated in China. Cluster analysis showed that the differentiation of compound leaf grapes was very different. It can be seen from the tree cluster diagram (Figure 2-2-2) that the types of 18 can be divided into three categories according to the combination line L 1: I {8}, II {6, 4, 5, 17, 2, 7, 3,1. The differentiation in type ⅱ is more complicated, which can clearly show the genetic relationship of grapes with different compound leaf types, which is helpful for further species classification.
Figure 2-2-2 Tree Diagram of Cluster Analysis of 83 Characters of Foliate Grapes
1. Liu-102. Mei -43. Baishui -3 14. Baishui -405. Hua-16. Hua -27. Gan -9 18. Mei -69. White -22. 02. Liu -8 13. South -2 14. Liu -7 15. Bai -40 16. Liu -6 17. Liu -9 18. Gu Ning -65438+.
The evolution of fruit plants must go through such a process: collecting wild → managing wild → cultivating, and its evolution is closely related to the development of human cultural activities. The history of human use of different fruit trees is different, and some of them can be traced back to prehistoric times (such as walnuts and chestnuts). ), and some are only nearly a hundred years (such as strawberries) or even shorter (such as seabuckthorn, etc.). Therefore, it is not easy to study human plant selection activities, which depends on various methods and means.
1. Investigation of evolutionary relics
Because the evolution of fruit trees has experienced the development process of collecting wild, people can inspect this process in some relatively late and primitive places. Vavilov (193 1) once found in the Caucasus, the Middle East and Tianshan Mountains that when people in mountainous areas cultivated wheat fields in wild woodlands, they dug up trees and bushes in turn, leaving high-quality pears, apples and cherry plums in their original places.
2. Historical records
According to historical records, it is also an important research method to understand the cultivation and utilization of fruit trees and reveal the evolution of some fruit trees. For example, Professor Xin Shuzhi (1962) suggested that peach, plum, plum, jujube, hazel, chestnut, thorn, tunnel, Du, Di, Tang, Gou and mulberry had been used in China from the Western Zhou Dynasty to the early Spring and Autumn Period (from the tenth century BC to the sixth century BC), and thought that peach was among them. According to historical records, European grapes were introduced to China in the Han Dynasty. There are many ancient books and abundant local chronicles in China, which provides convenience for studying the evolution of fruit trees through historical books.
However, we should also see some defects in Historical Records. For example, the early historical documents, both at home and abroad, are limited by local conditions, and the records of fruit trees are either "vague" or not standardized and scientific. Often what kind of plant a name refers to remains to be verified by many parties. In addition, there are many problems such as the age of the book, the authenticity of the book and so on. Nevertheless, historical records are still a key to the artificial evolution of fruit trees.
3. Linguistics
Linguistics, including dialects, is a very useful tool to study the evolution of cultivated plants. Famous botanists such as De Candolle and Lanfer have used this method to judge the spread and utilization of a certain plant. However, it should be noted that linguistic methods can only play an auxiliary role all the time, otherwise linguistic data will be overestimated and misunderstood.
4. Historical archaeology
It is a very effective method to study people's utilization of fruit trees in the unrecorded era through archaeology. Especially after the Stone Age, archaeological excavations recorded before this period of time can often obtain direct evidence before and after the invention of agriculture, thus obtaining correct judgments. For example, the dispute over whether walnuts originated in China is judged in this way. Horticultural circles at home and abroad have long believed that walnuts originated in Iran, and walnuts cultivated in China were introduced from abroad, but archaeologists have corrected this mistake. Sporopollen of walnut was found in the cultural relics unearthed from the tribal site of primitive clan commune in banpo village, Xi 'an, 6000 years ago. In addition, a primitive social site (Neolithic Age) 733 15 100 years ago was found in Cishan Village, Wu 'an County, Hebei Province. Among the unearthed cultural relics, carbonized walnuts were identified as ordinary walnuts by the Institute of Botany, Chinese Academy of Sciences, thus denying the legend in the ancient literature Natural History (Zhang Hua, 3rd century AD) that walnuts were introduced to the western regions by Zhang Qian.
5. Practice verification
For some historical problems, modern biological sciences, such as cytology, genetics, experimental biology and systematics, can also be used to provide powerful means for experimental verification.