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Laboratory 6. Video: “What Darwin Never Saw” from “The New Explorers” - Kurtis Productions This video documentary describes how a husband and wife team of scientists studying in the Galapagos Islands are using finches to study evolution. There are 13 species of finches on the islands and the scientists are studying two species of finch located on an isolated island. They describe the variation among the finches and how environmental influences and natural selection events can affect the population of finches. As you watch this video look for relationships between environmental influences, competition, natural selection and evolution. Points to think about and questions to answer as you watch the video: 1. In the first few minutes of the film, the narrator, Bill Kurtis uses two phrases which are technically incorrect in their biological content: a) He said “the finches held the secret to the origin of life.” He should have said “the finches held the secret to the origin of _____________. b) He said “but it was only a theory.” He should have said “but it was __________________________. 2. What did the Grants do when they went ashore on the island to be sure nothing was brought onto the island from the “outside world” (no insects or other creatures which might disrupt the natural habitat on this isolated island)? Why? 3. What is the main enemy of the finches on Daphne Major Island? __________________ 4. What is the finch on Daphne which digs into cactus blossoms? __________ finch. 5. What major biological process have the Grants seen TWICE during their 22 years of studying the islands? 6. In what year did the Grants first come to the island?____________ 7. The three questions they were trying to answer by studying the finches were: a) Do species compete? b) Why are some populations so variable? c) ___________________________________________________ 8. Why was Daphne Island chosen? _________________________________________________________ 9. One species of finch was G. scandens (Cactus finch). The other species was G. fortis. What is its common name? 10. How many finches did they find and band on the island? 11. Your choice: some interesting facts given about Darwin in his experiences on the HMS Beagle – tortoises, etc. 12. What did the Grants find when it didn’t rain for 18 months?__________________________________________________________ 13. They found that natural selection operates under _______________conditions. 14. Birds with ________________beaks tended to survive the drought baest. Why? 15. All but about _________% of all species which have ever existed are extinct now- so what per cent are extinct?_________________ 16. The Grants measured the beaks of the next generation birds (from those which survived the drought). What was the size of those beaks (compared to the average size previously) ___________________ 17. What surprising conclusion did this observation provide good evidence for? 18. Which finches survived best after it rained so heavily (for 8 months)? _____________________ Why?_________________________________ Even though evolution is called a “theory” there is so much evidence in favor of evolution of species that most scientists consider that evolution is a fact. Scientists may still disagree on precisely how evolution occurs- whether gradually, or intermittently in huge changes precipitated by climatic or environmental change. The events in this film describe two climatic changes (first the drought – then the heavy rain) that resulted in two natural selection events. These events occurred over a relatively short period of time- much shorter than Darwin had envisioned. During the period studied the Grants did not see an “evolution” of the finches but observed natural selection events which over many years may lead to evolution of the species. Since there are 13 species of Finches on the islands it is presumed that these all evolved from one original species and that competition and natural selection are responsible for the evolution of the 13 different species of Finches on the Galapagos Islands. The Scientific Method Science is a way of knowing the natural world that involves testing hypotheses or explanations. The scientific method can be applied to the unusual and the commonplace. You use the scientific method when you investigate why your once white undershirt is now pink. Your hypothesis might be that when you wash a red sweatshirt with white undershirts the undershirts turn pink. This hypothesis can be tested through observation and experimentation. Hypothesis: an idea or supposition that provides the basis for further investigation and testing – the hypothesis is an idea to be tested and either confirmed or refuted by experimental data. The investigator should be “neutral” to the results of the experiment – i.e. he/she presents this idea to be tested but has no bias as to whether the idea is confirmed or refuted by the data. In science there is seldom a single test that will provide results that clearly support or disprove a hypothesis. Experimentation: A test or trial to determine something not yet known. The experiment should be designed to “test” the hypothesis. An experiment should be carefully designed to determine whether a “hypothesis” is confirmed or refuted. A poorly designed experiment may yield ambiguous results and will not answer whether the hypothesis is correct or incorrect. If a hypothesis is shown by experiment to be incorrect then the scientist then poses a new hypothesis that will subsequently be tested by experiment. An experiment can disprove the hypothesis but can never prove it, because there is always the possibility of discovering additional information. Control: A baseline for comparison in an experiment. For example, if the investigator wishes to determine the effect of a drug on mice – some mice must not receive the drug, but they would receive the substance in which the drug was dissolved. This provides a basis to determine the effect of the drug alone. A “control” is used to ensure that the results obtained in an experiment are true and not due to some “artifact” or poor design in the experiment. Controlled experiments are not the only way to test a hypothesis. The test of a hypothesis may include experimentation, additional observations, or the synthesis of information from a variety of sources. Considering existing knowledge is important in the scientific inquiry. Watson and Crick won the Nobel Prize for their development of a 3-D model of the structure of DNA. They did not perform a controlled experiment in the laboratory but tested their powerful hypothesis through the use of existing evidence from other research. Some areas of science require comparative observations and the accumulation of data from a variety of sources. Replication: Scientific investigations are not valid if the conclusions drawn from them are based on one experiment with one or two individuals. Generally, the same procedure or observation needs to be repeated several times, providing consistent results. Once data is collected, it must be organized and summarized so that the scientists can determine if the hypothesis has been supported or refuted. Many times the data is compiled into tables or graphs in order to help analyze and interpret the results and to enhance the clarity of the work. Theory: A theory is stronger than a hypothesis. It is a statement of apparent relationships about observed phenomena for which there are multiple verifications. If the data collected supports a hypothesis, it is subject to still more predictions and tests. If this additional data continues to support the hypothesis, confidence in its correctness increases, and the hypothesis comes to be considered a theory. In the case of natural selection it is considered a theory because many researchers from many of the biological fields have continued to validate the theory with their observations and experimentations. After watching the video documentary “What Darwin Never Saw” 1. Describe possible hypotheses studied by the Grants. 2. Did their observations support or refute their hypothesis? 3. What were some of the ways they collected data? 4. How was this data standardized year to year? 5. Describe possible ways to display the data. 6. Did their observations add to the “theory of natural selection”?