原始生物大分子动态的数学模型及其进化意义

A Mathematical Model for the Dynamics of Primitive Biological Macromolecules and Its Evolutionary Implications

本文应用生态学上关于种群增长及种间竞争的逻辑斯缔方程,提出原始生物大分子动态的数学模型。对从该模型推导得的几种可能结果进行了分析,得出在生命起源初期的原始生物圈的生物多样性是很低的结论,即原始生物圈中较大量存在的只是一些种类单一的、可复制的原始生物大分子。因此,可以认为生物进化就是建立在这样的一个基础上,并沿着生物多样性不断提高的途径演化。该模型还有助于对广泛存在于现代生物基因组中的重复序列的起源的认识。

A mathematical model, adopted from the logistic equations for population growth and interspecific competition in ecology, was proposed for the dynamics of primitive biological macromolecules:dNm1/dt=rm1Nm1(Km1 - Nm1 - β12Nm2/Km1)dNm2/dt=rm2Nm2(Km2-Nm2-β21Nm1/Km2) where Nm is the copy number of a kind of biological macromolecule in primitive environment at time t.rm is the intrinsic replicating capacity (rate) of the macromolecule.Km is the carrying capacity (resource limit) of the primitive environment.dNm/dt is the instantaneous rate of increase of copy number of the primitivebiological macromolecule β12 and β21 are competition coefficients concerning the inhibition of macromolecule 2 on macromolecule 1 (β12). and macromolecule 1 on macromolecule 2 (β21) other lower indexes in the equations refer to macromolecule 1 or 2.By analysing the possible competition outcomes deduced from the model, a conclusion with evolutionary implications could be drawn that the biological diversity would be very low shortly after the origin of life in the primitive biosphere. In other words, the abundant biological macromolecules capable of replicating in the primitive biosphere would be quite unique in kinds, and this uniqueness would therefore be the initial basis of biological evolution which would then go from low biological diversity to high biological diversity. The model is also helpful for the understanding of the origin of repeated sequences which are widely present in the genomes of modern organisms.