In grade two students developed simple notions of inheritance and variation within a species. Those notions are foundational for the study of evolution, as are the studies in grade three of adaptations to an environment and the processes of extinction. Charles Darwin was a naturalist who traveled widely; students in grade three are retracing his steps when they develop their knowledge of organisms in a wide variety of earth biomes. Students in grade four learn about the survivability (or fitness) of plants and animals in an environment, and students in grade six are provided with a background in earth science. The standards in this set provide a foundation for learning about natural selection in grade seven and understanding the fossil record to be a line of evidence for the evolution of plants and animals.