• Environmental factors that affect living beings consist of inorganic factors and other biological factors. The actions through which environmental conditions change according to the existence of living beings is called environment-forming effect.
  • The dynamic pattern of populations is regulated through mutual interaction between living beings such as competition, predation action, etc. The effect of population density, coexistence through competitive exclusion, etc. and niche segregation, as well as periodic oscillation of the number of individuals through the principle of predator and prey etc. occur.
  • Biocenosis is a "relationship network" that is linked through mutual interaction between living beings. Theories that explain the coexistence of multiple species in biocenoses are the biocenoses theory based on niche segregation and the nonequilibrium coexistence theory.
  • Ecosystems form characteristic cycles (material cycles) with carbon, nitrogen, etc. as main elements.
  • Regarding the flow of energy, light energy from the sun is converted to chemical energy through photosynthesis, and then used by animals belong to a higher trophic level. In this process, the ecologic efficacy of energy transformation and assimilation up to the highest trophic level is only about 10%.
  • Currently, human society is facing various problems regarding the conservation of the earth's environment and biodiversity, and efforts are being made to solve these through international cooperation.

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