The curriculum uses themes and perspectives to connect and integrate major concepts, principles and basic facts. Three Themes run throughout the curriculum: Evolution (inherited changes in organisms accumulate over time), Unity and Diversity (organisms possess common characteristics while exhibiting a wide range of variability), and Dynamics of Biological Systems (living systems continually respond to their external and internal environments by making changes necessary to sustain life). Each theme will be presented from two Perspectives: Human Impact (the interactions between humans and the biological world) and Scientific Process (the testing of new ideas, questions or hypotheses through observation and experimentation).