According to the biology study notes of Isabela, the biological history of life can be defined by evolution, a notion heavily influenced by British biologist Charles Darwin. Darwin saw a variety of adaptations in species that improved their survival in diverse settings when studying the plants and animals along the coast of South America. He came to the conclusion that species change as a result of environmental adaptation. Modern evolutionary theory was founded on this theory, which is backed by data from fossils and DNA.

On the other hand, Isabella underlines in her notes, French naturalist Jean Baptiste Lamarck also observed that species changed throughout time. According to Lamarck's theory of evolution, evolution is a process of adaptation in which an organism acquires traits by using or not using certain body components, which are subsequently passed on to their progeny. But this idea, called the "inheritance of acquired characteristics", does not have the same level of empirical backing as Darwin's hypothesis.

There is ample evidence for evolution, and one important piece of that evidence is the fossil record, as suggested by the study notes. It keeps the remnants of extinct species preserved in tar, ice, amber, or rock layers. Evolutionary timelines are further supported by the dating of these fossils, whether the dating is absolute (using radiometric techniques and natural atomic decay to estimate age) or relative (determining the age based on the sequence of rock layers). The foundation of evolutionary biology is firmly established by the extensive data supporting Darwin's contributions, according to Pranav’s study notes that further explain natural selection, variation, genetic variation, behavioural, structural, and psychological adaptations, and endosymbiotic theory.