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Evolution The Theory of Natural Selection 15.1 Page 418 Student Performance Standards • SB5. Students will evaluate the role of natural selection in the development of the theory of evolution. – a. Trace the history of the theory. – b. Explain the history of life in terms of biodiversity, ancestry, and the rates of evolution. – c. Explain how fossils and biochemical evidence support the theory. Lesson Essential Question • How is the theory of natural selection related to the theory of evolution? EVOLUTION Is the Genetic change in a species’ gene pool over time. A mechanism of evolution is natural selection. Who helped to develop this theory of evolution? Lamarck and Darwin Jean Baptiste Lamarck 1744-1829 Charles Darwin 1809-1882 Lamarck’s Theory of Acquired Characteristics (1801) • Believed an organism could change its physical features in order to survive. • When the individual reproduced, the changes made during its lifetime would be passed on to it’s offspring. • Hmmmm……. So, if you were to work out every day, or study biology every day, your babies would inherit the traits you acquired. Given our current knowledge of genetics, this is not possible! Was Lamarck’s theory true or false? • Definitely false! Otherwise…….. Charles Darwin (1809-1882) • English Naturalist • Contributed the most to our understanding of evolution. • Sailed around the world to the Galapagos Islands where he • Collected specimens of – plants – animals – fossils Darwin Reached the Galapagos Islands in 1835: – A series of volcanic islands off the coast of S. America – Here, Darwin learned the most about variation in species. – He saw many plants and animals well suited for survival in their environment. – He collected finches and observed that they were all different depending on which island they came from. – Darwin suspected populations from the mainland changed after reaching the Galapagos. Darwin hypothesized that…. • Over long periods of time, species develop adaptations which allow them to survive in their environment. • This is the theory of NATURAL SELECTION. Galapagos Islands Charles Darwin’s Theory of Natural Selection • Organisms can only pass on traits they are born with. • There is variation among organisms of the same species. • Those best suited to their environment will survive and reproduce the most (fitness). • Survival of the fittest Natural Selection (Cont….) • Due to DNA mutations, variation exists among members of the same species. • The environment selects which variations will become adaptations which allow the species to survive. Polar bears wouldn’t do well in the desert, and crocs wouldn’t do well in the arctic! 4 Principles of Natural Selection: 1. Variation - differences within a population exist. 2. Heritability - variations are inherited from parents. 3. Overproduction – populations produce more offspring than can survive. 4. Reproductive Advantage – individuals with variations suitable for the environment will be able to survive and reproduce. So, why do giraffes have such long necks? • Modern evolutionary theory proposes ancestral giraffes probably had short necks but that length varied from individual to individual due to varying genotypes. • When food supply was limited, individuals with longer necks survived better because they could utilize a food source unavailable to the others. So, longer necked giraffes survived to pass on the trait (alleles) and the offspring inherit long necks. Example of Natural Selection • Peppered Moth Environments Change • Peppered Moths Example • Mid 18th century = England’s industrial revolution resulted in tons of soot deposited on trees and rocks. • The discoloration camouflaged dark colored moths. • Where these dark colored moths were once the minority, they are now the majority. On The Origin of Species • 1859 – Darwin compiled evidence for natural selection and his book, On the Origin of Species by Means of Natural Selection, was published END PART 1 • Complete Vocabulary for homework • Handouts are due at end of class for a daily grade . Tuesday • Review terms and practice questions • Breeding Bunnies natural selection activity. Terms We’ve Learned: • Evolution • Genetic change over time • Fitness • the genetic contribution of an individual to the next generation's gene pool • Natural Selection • Gene Pool • “Survival of the fittest” • All the genes in a population Practice Question • Which of the following is true? A. Natural selection B. Natural selection part of it C. Natural selection of evolution D. Natural selection same thing results from evolution includes evolution as is only one mechanism and evolution are the Which is a concept of Lamarck's work? • Change results from the survival of the fittest • Body structure can change according to the actions of the organism According to Darwin's theory of Natural selection, individuals who survive are the ones best adapted for their environment. Their survival is due to the A. Possession of adaptations developed through use B. Possession of inherited adaptations to maximize fitness C. Lack of competition within the species D. Choices made by breeders Evidence of Evolution Ch 15 section 2 Evolution - Any change in the relative frequencies of alleles in a population’s gene pool. - Evolution acts on populations through generations – not on individuals. - Evolution is CHANGE OVER TIME. What’s a theory? • Theories are not educated guesses; they are based on many observations and investigations. PBS Video Clips • http://gpb.pbslearningmedia.org/resour ce/mck03.pd.sci.evtheory/isntevolution-just-a-theory/ • Watch “Isn’t Evolution Just a Theory?” Evidence of Evolution 1. 2. 3. 4. 5. Fossils Comparative Anatomy Comparative Embryology Comparative Biochemistry Geographical Distribution Evidence of Evolution 1. Fossil Record: Fossils - preserved remains of ancient organisms The fossil record is the most significant evidence for evolutionary change. Shows that ancient species share similarities with species that now exist on Earth. Glyptodont Armadillo • The fossil record is an important source of information for determining the ancestry of organisms and the patterns of evolution. 2. Comparative Anatomy - the study of similarities and differences in the anatomy (body plan) of an organism: a. Homologous Structures – anatomically similar structures inherited from a common ancestor. b. Vestigial Structures – structures that are the reduced forms of functional structures in other organisms (wisdom teeth, coccyx, appendix) c. Analogous Structures – similar structures not inherited through common ancestors. Homologous Structures Structures that have different mature forms but develop from the Same embryonic structures suggest a common ancestor: Vestigial Structures The wings of kiwis are too small to be of any use in flight. Wisdom Teeth Mammals once walked on land Once used to chew leaves, nuts, and meats Appendix The coccyx (tailbone) is the remnant of a lost tail. Once used for digesting cellulose Analogous Structures Wing of an eagle and the wing of a beetle have the same function but are constructed in different ways from different material. Insect wings composed of Chitin. Bird wings composed of bone and muscle 3. Comparative Embryology The study of similarities and differences between the embryos of different species. Bird Embryo Human Embryo Embryological Similarities a) The early embryo stages of all vertebrates (with a backbone) is very similar. 4. Comparative Biochemistry common ancestry can be seen in biochemical molecules. - similarities exist in the amino acid sequences (order) of proteins or the nucleotide sequences of DNA - the closer an organism’s amino acid sequences, or DNA sequences, the more likely they are to be related. Organism Amino Acid Sequence Chimpanzee Serine-Valine-Leucine-Stop Human Serine-Valine-Proline-Stop Fruit Fly Serine-Lysine-Valine-Stop – 5. Geographic Distribution - 60,000 years ago, over 100 species of marsupials only existed in Australia. This is because Australia was a continent isolated from the rest of the world. Geographic Distribution of the Ratite Birds due to Plate Tectonics