The document discusses two approaches to human development - the traditional approach and lifespan approach. The lifespan approach views development as occurring throughout the entire lifespan from childhood to adulthood, rather than stopping after adolescence. It also describes five key characteristics of lifespan development: it is lifelong, plastic, multidimensional, contextual, and involves growth, maintenance, and regulation. The stages of development span from prenatal to late adulthood. Research methods in child and adolescent development include case studies, observational studies, experiments, and longitudinal studies. Ethical principles require that research does not harm children physically or psychologically. Research impacts teachers by making them more reflective, analytical, and helping them reconstruct their role.