The Making of the Fittest: Natural Selection and Adaptation The Making of the Fittest: Natural Selection and Adaptation TEACHER MATERIALS Got Lactase? The Co-evolution of Genes and Culture Updated October 2014 Page 1 of 10 IN-DEPTH FILM GUIDE DESCRIPTION Human babies drink milk; it’s the food especially produced for and given to them by their mothers. But when they grow into adults, most humans lose the ability to digest lactose, the sugar in milk. Why then do adults in some cultures think nothing of drinking a glass of cow’s milk? In this film, human geneticist Dr. Spencer Wells tracks down the genetic changes associated with the ability to digest lactose as an adult—a trait called lactase persistence—tracing the origin of the trait to pastoralist cultures that lived less than 10,000 years ago. Combining genetics, chemistry, anthropology, and biology, this story provides one of the most compelling and fascinating examples of gene-culture co-evolution. KEY CONCEPTS A. Humans, like all species, evolve and adapt to the environment through natural selection. Lactase persistence is an example of a human adaptation that arose within the last 10,000 years in response to a cultural change. B. Mutations occur at random; for evolution to occur there must be selection for or against the traits affected by those mutations. C. Both the physical and cultural environment can affect selective pressures. The practice of dairying provided an environment in which lactase persistence was advantageous. D. Different mutations can produce the same phenotype. Scientists have identified distinct mutations among northern Europeans and the Maasai people of eastern Africa that resulted in lactase persistence. E. Similar phenotypes can evolve independently under similar selective pressures. The lactase-persistence trait arose independently among African and European pastoralist populations. F. Mutations occur not only in coding regions of genes but also in the regulatory regions that determine when and where a gene is turned on. All known mutations giving rise to lactase persistence are in a genetic “switch” that regulates expression of the lactase gene. G. Food has to be converted into simpler molecules that can be absorbed and used by cells in the body. The lactase enzyme breaks down the disaccharide lactose into glucose and galactose. CURRICULUM AND TEXTBOOK CONNECTIONS Curriculum Standards NGSS (April 2013) MS-LS3.B, MS-LS4.B, MS-LS4.C HS-LS1.A, HS-LS3.A, HS-LS3.B, HS-LS4.B, HS-LS4.C AP (2012-13 Standards) 1.A.1, 1.A.2, 1.C.3, 2.A.2, 2.D.2, 2.E.1, 3.B.1, 3.C.1, 3.C.2, 4.A.1, 4.C.3 IB (2009 Standards) 3.2, 3.6, 4.1, 5.4, 6.1, A.3.1, D.3.10 PRIOR KNOWLEDGE It would be helpful for students to • know what a gene is and that genes can code for proteins that determine traits; • have a basic understanding of natural selection and adaptation; and • have a basic understanding of what an enzyme does.
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- Evolution, lactase, LACTASE PERSISTENCE, Genes and Culture, in-depth film guide