It refers to the stage division of biological development process, especiallyform、physiology、ecologyEqual quality difference.Generally, sexual maturity is the boundarymaintainIts function can be roughly divided into potential stage and exposed stage.
[1] In general, the two can be further divided into several stages without dramatic morphological changes like metamorphosis.T.D. Lysenko YesWheatIn the development process of annual plants, such as, etc., special attention is paid to "the physiological requirements of plants to change the external environment" and they are divided into development stages (development stage theory).This theory has been widely noticed for a period of time.It is known that the changes in nutritional requirements with the development of plants are also carried out in stages.The development stage of perennial herbs and woody plants is still unclear, which is related to the morphological particularity of woody plants. From the base of the trunk to the top, the nature of young gradually decreases in morphology and physiology.During the development of fish, the external morphological changes related to ecology are adapted to the changes of environment, and the development stages can be identified according to these changes.Each development stage of organisms maintains a stable period of adaptation to the environment, but the transition period to the next stage, on the one hand, has new characteristics in morphology, function and ecology, and on the other hand, is a shaking period in which forms and functions formed before this may disappear.In the next stage of development, the transition period for obtaining new adaptability, especially for animals, is often a critical period with high mortality.Because different development stages, even under the same environmental conditions, have different impacts on the same organism, most people believe that the analysis of development stages is helpful to understand variation, species differentiation and phylogeny.The developmental stage is generally divided into different developmental processes in morphology from the perspective of morphogenesis, especially aboutembryoOccurrence of.Therefore, the occurrence stage is not necessarily regarded as the development stage.
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[2] YesVasniezov(V.V. Vasnetsov) (1946).That is to say, it is important to unify and master various situations of maintaining relatively constant forms and functions and the stability of ecological characteristics after entering some development stages.Although growth and development are carried out in each stage, there is no qualitative change in morphology and function, which is very adaptive to life.In the transition period to the next stage, almost all organs have undergone qualitative changes.Generally, fish begin to transition to the next stage after reaching a certain body length under the same conditions, so body length can be used as an indicator to distinguish development stages.Understanding the concept of fish development from this point of view is called the developmental stage theory.This theory is also applicable to the research on the application of fish protection, proliferation and aquaculture.Vasniezov believes that the comparative study of ontogeny based on this theory is also of great significance to clarify the rules of phylogeny.However, due to the lack of analysis of the late ontogeny process, and the lack of clarification on whether this is applicable to animals other than fish, the theory of developmental stages is still incomplete.Although the theory of development stages in plants is generally not strongly advocated, in the Soviet Union, the stages of individual development are divided according to the differences in plant morphology and function, that is, embryonic stage, seedling stage, mature stage, aging stage, and often called development stage.
