<P> The bioecological model is a theoretical model of gene--environment interactions in human development . This model, first proposed by Urie Bronfenbrenner and Stephen J. Ceci, in 1994, is an extension of Bronfenbrenner's original theoretical model of human development, called ecological systems theory . Bronfenbrenner developed the bioecological model after recognizing that the individual was overlooked in other theories of human development, which were largely focused on the context of development (e.g., the environment). </P> <P> The bioecological model of human development can be applied to both children and maturing adults, and is thus a lifespan approach to development . The framework emphasizes the importance of understanding bidirectional influences between individuals' development and their surrounding environmental contexts.In the bioecological model, in contrast to his earlier models, Bronfenbrenner also includes time (known as the chronosystem in his model) as an important component in the way that people and environments change . The bioecological model proposed a new method of conducting research which was heavily influential in developmental psychology and is still considered relevant today . </P> <P> Bronfenbrenner named his original model "Ecological Systems Theory". Through this framework, Bronfenbrenner identified the need to understand individuals' development within their environments . In order to conceptualize environmental contexts, Bronfenbrenner described four ecological systems: </P> <Ol> <Li> Microsystem: The microsystem is the innermost layer of Bronfenbrenner's model . This context is closest to an individual and encompasses interpersonal relationships and direct interactions with immediate surroundings . For example, family members and a child's school are considered part of the microsystem . </Li> <Li> Mesosystem: The mesosystem includes interactions between various aspects of the microsystem . A relationship between a child's family and the child's school can be considered part of the mesosystem, because these two direct influences (parts of the microsystem) may interact . </Li> <Li> Exosystem: The exosystem does not directly affect individuals; rather, the exosystem encompasses aspects of structures within the microsystem . For example, financial difficulties within the family of origin, parental job loss, and so forth may affect a child, but do not involve the child directly . </Li> <Li> Macrosystem: The macrosystem is the outermost layer of Bronfenbrenner's model . This system includes social or cultural ideologies and beliefs that affect an individual's environment . For example, laws may be incorporated into the macrosystem . </Li> <Li> Chronosystem: Bronfenbrenner suggested that individuals constantly interact with these systems . He also stated that both individuals and their environments constantly affect one another . However, in this original model, Bronfenbrenner recognized there was not enough focus on individuals' own role in their development, and thus began further developing this model . </Li> </Ol>

At the center of the bioecological model is the