Toshiyuki Nakajima

Learn More
The current theory of natural selection explains that adaptive evolution occurs because genotypes with greater survival or reproductive tendencies, due to their particular biological properties, tend to increase in frequency over the lesser ones in a common environment; therefore, the former will eventually replace the latter. In nature, such a selection(More)
As an increasing number of Web sites consist of an increasing number of pages, it is more difficult for the users to rapidly reach their own target pages. So the intelligent systems supporting the users in navigation of the Web contents are in high demand. In this paper, we describe an intelligent recommendation system called the system L-R, which(More)
Encounters between objects play a crucial role in creating specific patterns of organization in many biological systems. This paper explores a general, quantitative principle of encounter probabilities, applicable over various levels of organization, as a fundamental step toward a comprehensive theory of biological probability ranging from cells through(More)
Epistatic interactions between genes in the genome constrain the accessible evolutionary paths of lineages. Two factors involving epistasis that can affect the evolutionary path and fate of lineages were investigated. The first factor concerns the impact of competition with another species lineage that has different epistatic constraints. Five enteric(More)
Evolution by natural selection requires the following conditions: (1) a particular selective environment; (2) variation of traits in the population; (3) differential survival/reproduction among the types of organisms; and (4) heritable traits. However, the traditional (standard) model does not clearly explain how and why these conditions are generated or(More)
We investigate an ecological mechanism by which endosymbiotic associations evolve, with a particular focus on the relationship between the evolution of endosymbiosis between auto- and heterotrophic organisms, and the stages of ecosystem development. For this purpose we conducted a long-term microcosm culture composed of three species, a green alga(More)
The ecological mechanisms underlying the diversification of autotrophic species into endosymbiotic lifestyles and the ways in which the evolution of endosymbiotic species is ecologically and evolutionarily affected by sister lineages/lines that are adapted to extra-host environments remain unclear. In this paper, we investigated a differentiation process of(More)
The same event may not necessarily occur against a given cognition (action) upon repetition. The degree of certainty in which a particular event actually occurs following a current cognition is the probability of the event viewed (experienced) by the focal cognizer. This is the internal concept of probability, which is contrasted with the external(More)
We investigated directly an early stage of the development of an endosymbiosis between an alga and a ciliate, beginning from a non-associated stage by conducting a long-term microcosm culture composed of a green alga (Chlorella vulgaris), a bacterium (Escherichia coli) and a ciliate (Tetrahymena thermophila) for three years. During this(More)