What is life? What makes us alive? Is it movement, breath, the capacity to reproduce? This unit talks about life and the history of evolution written in our cells through the DNA sequence. Life is said to have begun in a soup of acids under extreme conditions. Some million years later, photosynthetic cells appeared and became the basis for most food chains. DNA gave cells the ability to reproduce. Habitats changed and organisms learned to adapt to them. These adaptations were imprinted in their DNA. Habitats determine which species survive and heredity determines adaptations that allow organisms to survive in the environment. The purpose of this unit is to show the fascinating map of life written in our genes. This unit presents core concepts, like the beginning of life, microbiology, photosynthesis, food chains, habitats, adaptations, heredity, probability, and the evolution of species or changes through time, on a level that is appropriate for 4th grade students and shows the intricate relationship among these concepts. In attempts to prove this relationship, scientists have been able to study a protein present in many species and they have detected the similarities among them. On the other hand the study of fossils give us clues about the sequence of events and the adaptations that had to occur to produce the diversity of species we enjoy today.