1. Lesson # 4: Evolution (On the Origins of Species + Modern Theory of Evolution)

2. Review Questions

3. What structure does this picture represent? Answer: Homologous Traits

4. What is an adaptation? A) A test for natural selection B) A physical or behavioral characteristic that has developed to allow an organism to better survive in its environment C) A by – product D) A characteristics that has developed to limit the chances of an organisms survival Answer: B

5. Which theorist proposed the theory of geological gradualism? A)James Hutton B)Georges Cuvier C)Jean Baptist Lamarck D)Charles Darwin Answer: A

6. What represents a trait that once served a purpose but is now useless? A)Homologous Trait B)Analogous Trait C)Duplication Mutation D)Vestigial Trait Answer: D

7. On the Origin of Species (Theory of Evolution by Natural Selection) Natural Selection -The way in which nature favours the reproductive success of some individuals within a population over others -Some individuals would have a better chance of success than others -Ex. faster cheetahs would be more likely to catch prey, stronger male lion would be more likely to defend and mate with females -If this were true and these differences were inherited, then traits of favoured individuals would become more common in the next generation and these individuals would produce more offspring -Key is to favour REPRODUCTIVE success

9. Herbert Spencer vs. Darwin Survival of the Fittest -A phrase that has been used to describe the process of natural selection -This phrase can be misleading -An individual that lives a long life or has a strong physical appearance may be seen as physically “fit,” -But if the individual is unable to reproduce and pass on genes to the next generation according to Darwin’s theory such individual would not be “fit” -As previously mentioned, natural selection lies in its ability to favour reproductive success Adaptation -A characteristic or feature of a species that makes it well suited for survival or reproduce success in its environment -Theory of evolution by natural selection can be extended to virtually every biological characteristic or adaptation * Darwin understood that with a diversity of environments, the process of natural selection acting over thousands of generations could produce an unlimited variety of species *

10. Prediction -Theory of natural selection enables scientists to make predictions about how species may change over time, for example that species will evolve in response to climate change because different environmental conditions will favour different traits Testing and Falsification -To be a scientific theory it must have the potential to be falsified and testable to have the possibility of being proven wrong Darwin’s Theories of Evolution

11. Reconsidering the Galapagos Islands

12. Summary  Darwin’s theory of evolution by means of natural selection explains how the environment acts to favour the reproductive success of individuals with certain heritable traits over others  Darwin’s theory of evolution by means of natural selection is able to explain how an adaptation can arise  Darwin’s theory of evolution by means of natural selection can be used to make predictions about the future evolution of species  Darwin’s theory of evolution by means of natural selection is a testable scientific theory

13. The Modern Theory of Evolution The Age of Earth -Until the twentieth C many believed Earth was less than 10,000 years old and that species never changed they just had always been present -Emerging sciences of paleontology and geology started to cast serious doubt on the belief in a young earth Paleontology -The scientific investigation of prehistoric life through the study of fossils Geology -The science that deals with the earth’s physical structure and substance, its history and the processes that act on it Today’s evidence -Scientific consensus that Earth is more than 4.5 billion years old and that the universe is approximately 13 billion years old -This evidence is largely a product of recent advances in technology and understanding

14. Radiometric Dating Radioisotopes -Atoms that undergo radioactive decay - An atom with an unstable nucleus that is capable of undergoing radioactive decay -Paleontologists are able to use radioisotopes to obtain precise estimates of the ages of rocks -The nuclei of these atoms are unstable and release subatomic particles changing from one form, the parent isotope into another, the daughter isotope Radiometric Dating -Based on the ratio of parent isotopes in rock formations -Radioisotopes undergo decay in a very precise way (half – life) Half Life -The length of time required for half the quantity of radioactive substance to undergo decay… the half life is a constant for any given isotope -The time it takes for exactly 50 % of a parent isotope to decay into a daughter isotope

15. The Modern Synthesis  The knowledge and understanding of genetics and other fields of biology have been combined with Darwin’s theory of natural selection to form the modern evolutionary synthesis  Biologists define evolution as changes in the gene pool of a species over time Gene Pool -The complete set of all alleles contained within a species or population -Individuals vary in their traits because they inherit different combinations of alleles -Natural selection acts to favour some genetic combinations over others

16. Mutations: The Source of Variation  Different individuals have different combinations of the many alleles that are already present in the population  Sexual reproduction recombines these alleles and produces an almost unlimited number of combinations  New or altered traits arise when new alleles and genes are produced by mutation and acted upon by natural selection Genetic Mutation -Change in DNA -The bases that make up DNA may be switched or lost, and / or new bases may be inserted  Mutation event can also result in an individual having duplicate copies of genes  Duplication events are usually the result of mismatches during crossover in meiosis

17. Crossing Over -The exchange of chromosome segments between homologous pairs during synapsis -A misalignment of the chromosomes during crossover causes an unequal exchange – transferring a portion of one chromosome to another and that transferred portion is likely to contain many genes -Gametes that receive a chromosome that is missing a section will have a low chance of survival, while gametes that receive a chromosome with duplicated genes are often viable Crossing Over

18. Gene Duplication  Gene duplication is an important type of mutation because it is a source of a new genes  The extra copy of the gene is free to mutate and may gain a new function  If a mutation in a gene results in a new protein that can no longer perform a vital function, the organism may die (even if it is beneficial in some other way)  But might result in the creation of a new and potentially beneficial protein  The duplication and mutation of gene copies can result in entire “families” of closely related genes

19. The Effects of Mutations  Most mutations are neutral because they occur in non – coding portions of DNA and therefore produce no visible change in an individual Neutral Mutation -A mutation that does not result in any selective advantage or disadvantage -The environment does not favour or select against individuals with neutral mutations Beneficial Mutation -Any mutation that increases that reproductive success of an organism -Relatively rare but are favoured by natural selection and accumulate in populations over time Harmful Mutation -Any mutation that reduces the reproductive success of an individual and is therefore selected against -May make an organism less able to resist disease or avoid predators, or less efficient at obtaining food -Less successful at reproductive success and tend to disappear

20. Mutation Rates  Individual mutation rates are very difficult to estimate, but recent studies suggest that species with large genomes are likely to have mutations averaging more than one per individual  Humans may average 20 or more mutations per individual (almost always neutral)  Human population carries over 100 billion genetic mutations  Relatively low for individuals but can be numerous in population overall Duplication Mutations -Often neutral and so do not immediately benefit the individual, but provide a source of new genetic material with the potential to evolve into new genes

21. Homologous Genes and Pseudogenes  Closely related species inherit homologous genes  These genes inherited from a common ancestor mutate and evolve over time  Similarity between genes provides good evidence for the degree of related species  More closely related two species are, the more similar we would expect their homologous genes to be Pseudogenes -A vestigial gene that no longer codes for a functioning protein -Genes that have undergone mutations and no longer serve a useful purpose -Are found in virtually all species -Ex. human dysfunctional copy of the GULO gene (necessary for production of vitamin C, but we don’t need it because we normally produce adequate amounts of this in our diet)

22. Modern Paleontology  Distribution of fossils provided Darwin with important evidence for his theory of evolution Today’s evidence -Human ancestors and primitive whales in Pakistan -Feathered dinosaurs in China -Fossils of dinosaurs in Canada  Until the 1960s, the locations of some fossils were quite puzzling, specifically when the discovery of fossils of the same species in Africa, India and Antarctica (but nowhere else)  Today the study of biogeography has been complemented by great advances in the study of plate tectonics and continental drift Plate Tectonics -The scientific theory that describes the large scale movements and features of earth’s crust (accounts for many large surface features i.e. mountains, volcanoes)

23. THE END!!