Life Science: Organization of Living Things, Heredity, Evolution Fifth grade presents an appropriate time for introducing the study of human biology. Students develop an understanding of the main function of specialized animal systems (digestive, circulatory, respiratory, skeletal, muscular, nervous, excretory, and reproductive) and how animal systems work together to perform life’s activities. Students explore the traits of individuals and examine how traits are influenced by the environment and genetics of the individual. They distinguish between acquired and inherited traits of humans as well as other living things. Further study of organisms’ individual traits demonstrates how behavioral and physical characteristics help them survive in their environments. In the investigation of physical characteristics, students relate similarities in anatomical features to the classification of contemporary organisms. Students conclude their investigations into animal characteristics and evidence of change by analyzing the relationship of environmental change and catastrophic events to species extinction and survival. They explore fossils to provide evidence of previously living things and environmental conditions, and how both have changed over long periods of time.