In textbooks, adaptation, especially biological adaptation, is generally defined as the method that an organism adopts to better survive in its environment and reproduce. However, in scientific articles, adaptation is not always that simple. An adaptation can be a structure that gives an organism an advantage over other similar organisms, or a behavior that helps the organism survive in its environment against predators. Sometimes even the adaptation itself was not initially intended for its current biological role or for how it is used in the organism's environment; this adaptation is sometimes called preadaptation (Kardong, 2006). Because it is difficult to identify which structures are adaptations and which are preadaptations, the subject generates much controversy in the scientific world. It is often useful to study these adaptations in ancient animals, but because most of them are extinct, scientists can only gather information from their close relatives, and even that is not conclusive enough . For a structure to have a biological role in an organism, it must serve something in the organism. For a biological adaptation to be considered such, it must have some value in the organism in terms of survival against predators or production of offspring. While some structures are already adapted to their environment and biological roles, other structures can become more adaptable to changes in their environment through repeated stimuli. For example, vertebrate bones are adapted to support and protect vertebrate organs, but they can also grow and remodel after mechanical wear (Fratzl and Weinkamer, 2011). Continuous and repetitive remodeling of bone improves its performance and further strengthens and strengthens its biological role. ...... middle of article ...... Comparative anatomy, function, evolution (4th ed.). New York, NY: McGraw-Hill. Brandt, Christian, Christensen-Dalsgaard, Jakob, Madsen, Peter T., Wahlberg, Magnus and Wilson, Maria. 2011. Hearing in the African lungwort (Protopterus annectens): pre-adaptation to hearing by pressure in tetrapods?. Biology Letters, 7 (1), 139-141. Fratzl, Peter and Weinkamer, Richard. 2011. Mechanical adaptation of biological materials – the examples of bone and wood. Materials Science and Engineering: C, 31(6), 1164-1173.Gardner, Andy. 2009. Adaptation as an organismic design. Biology Letters, 5 (6), 861-864. Ishii, Yumiko, Shibao, Harunobu and Shimada, Masakazu. 2010. Rapid adaptation: a new dimension for evolutionary perspectives in ecology. Population Ecology, 52 (1), 5-14. Linde-Medina, Marta. 2011. Adaptation or exaptation? The case of the human hand. Journal of Biosciences, 36 (4), 575-585.