The occurrence and development of biological species in the development process of earth history
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Phylogeny（Greekφυλογένεση，φύλο，Modern Greek: f í lo - species, gender and γε νν 需 η, modern Greek: j é nnissi - birth, birth).Also calledSystem occurrence。It refers to the occurrence and development of biological species in the history of the earth.
This concept is not only applied to the occurrence and development of animal species, but also to taxons at all levels of systematics.It will also be used in the evolution of a certain feature in the process of biological development.
Comparison and study of fossil morphological and anatomical characteristics,
Morphology of living organisms,anatomyAnd physiological characteristics,
The ontogeny of living things, especially living things,
DNA analysis, such as sequencing and molecular phylogenetic methods.
Through these data, people can build a phylogenetic tree (evolutionary tree) for organisms, which describes the possible kinship between various species.
Research difficulties
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The biggest difficulty in phylogenetic research is that the evolutionary process of phylogeny cannot be directly confirmed by observation and experiments.Therefore, all aspects of evidence should be integrated and analyzed.Due to the different emphasis on these evidences, there will often be many different versions of the evolutionary tree, such as whether several phyla of protostomes belong to molting animals (evidence from genetics) or joint animals (evidence from morphology).
Features are divided into homology and isomorphism.
Same origin, such asHomologous organOr homologous behavior, will show the same basic structure of the body, because the environment is different and evolved into different shapes or functions.The shape and function of homologous organs can vary greatly.A good example is the forelimbs of vertebrates.They can become feet, wings (birds, pterosaurs, bats), fins (fish, penguins, ichthyosaurs, whales), hands (humans, apes, and some dinosaurs), and digging tools (voles, naked Hamsters, pocket moles).But their bone structure is similar.These similarities can only be explained by the theory of phylogeny.
Homologous features confirm the kinship among species, and are a powerful means to reconstruct the evolutionary tree.Homologous phenomena in biology can be further divided into orthologous (orthologous means that a gene in different species comes from the same ancestor) and paralogous (gene replication between species).
The same function, for example, the shape of the same function organs is similar, but they are developed independently through convergence and evolution.For example, the eyes of cuttlefish and vertebrates are similar in shape and structure, and their function is light sensitivity.However, as can be seen from the microscope, their fine structures are different.Ontogenetic studies have shown that they developed from different embryonic layers.The phenomenon of equal work is not evidence of kinship.
