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Darwin’s Theory of Evolution Note Outline Goal: to understand how natural selection is the driving force that has caused organisms to change over time. Chapter 16.1 Darwin’s Voyage of Discovery Darwin’s Epic Journey Geologists were just beginning to suggest that the earth was _______________ over time. Biologists were suggesting that ________________ would explain how modern organisms evolved over long periods of time through descent from a common ancestor. Observations aboard the Beagle As Darwin travelled aboard the Beagle he observed three distinct patterns of biological diversity; species vary ___________, species vary ___________ and species vary _________ __________. Species Vary Globally o Darwin noticed that similar yet ____________ animals inhabited similar habitats around the world. Example: flightless, ground dwelling birds (rheas) lived in grasslands of South America. They looked and acted like ostriches but ostriches could only be found in Africa. Darwin also found emus in Australia’s grassland and they too were similar to ostriches. Species Vary Locally o Darwin noticed different, yet related, animals lived in ____________ habitats within a local area. Example: while travelling the Galapagos Islands Darwin noticed that island slightly differed in their ecological conditions. He found giant tortoises varied slightly in their shells from island to island. 1 Species Vary Over Time o Darwin collected fossils and he noticed that some fossils of extinct animals were ____________ to living species. Example: A fossil of a giant armoured animal was very similar to that of a present day armadillo. 16.2 Ideas That Shaped Darwin’s Thinking An Ancient, Changing Earth Hutton recognized that certain _____________ ___________ were responsible for certain geological features. Example: Hutton proposed that forces pushed the earth surface upwards and this gave rise to mountains. Lyell’s principle of ____________________ stated that geological processes we see today must be the same forces that shaped earth millions of years ago. Example: ancient rivers carved channels and canyons just as our present rivers do today. Darwin realized that if _____________ could change over time ___________ _________ could change over time. Lamarck’s Evolutionary Hypothesis Lamarck suggested that all living things urge to become more ___________ and ___________-. As a result organisms change and acquire characteristics to make them more successful in their environment. This was known as “___________ __________”. 2 Example: the black – necked stilt’s long legs were a result of the bird’s ability to stretch their legs. Over time, future generations would have their legs could get longer. Lamarck also suggested that these acquired traits could be passed on their offspring. This was known as “____________ ___ ______________ ______________”. Population Growth Malthus suggested that human populations tend to grow _________ than food supply. He reasoned that war, hunger and disease would keep population in __________. Darwin reasoned that the same notion could be true for other ___________. He wondered why others of a same species ____________ and others perished. Artificial Selection Darwin took up breeding plants and pigeons to test the idea of _____________ ___________. The animals and plants provided the variations and humans selected those variations they find useful. Darwin realized that variation in a population provided the raw material for _______________. 16.3 Darwin Presents His Case Evolution by Natural Selection Darwin used Malthus’s reading to come up with the notion of a struggle for ________________. All members of a population must compete for necessities of life. 3 Darwin thought that the ______________ in a population played a role in who survived. Some variations are better suited for the environment than others and this increased the organism’s ability to live and _____________. These organisms had better adaptations. Those organisms with the best _____________ were more likely to reproduce, meaning they had better fitness. The difference in reproduction rates refers to the “_________________________”. Natural selection takes into account that there are _____________ in a population, those best suited will survive and produce more offspring. From generation to generation, populations continue to change as they become better __________, or as the _______________ changes. Common Descent Darwin suggested that over many generations, adaptations could cause successful species to evolve into new __________. This explains the diversity of life and that species change over time. ___________ with ____________ proposes that all living species are descended from common ancestors. A tree of life links all living things. 16.4 Evidence of Evolution Biogeography ________________ is the study of where organisms live now and where they and their ancestors lived in the past. Darwin saw two patterns related to biogeography. One pattern had closely related species ___________ slightly when the climate changed. Populations on islands were slightly different from the mainland species. 4 The second pattern had very distantly related species develop ______________ in similar environments. Similar habitats around the world had similar plants and animals that were very distantly related. Darwin suggested that ________________ pressures had caused very distantly related species to develop similar ________________. Age of Earth and Fossils _____________ ________ indicates that the earth is approximately 4.5 billion years old, plenty of time for evolution to occur. Darwin didn’t have enough __________ evidence to show the evolution of a modern species from their ancestors. Recent discoveries show the evolution of whales from ancient land mammals. Comparing Anatomy and Embryology Darwin suggested that animals with similar structures evolved from a ____________ _____________. The structures shared by a related species that have been inherited from a common ancestor are called __________________ structures. Similarities and differences among homologous structures indicate how _______________ these species shared a common ancestor. Draw the diagram of Figure 16-14 5 ____________ ___________ are inherited from ancestors but have lost much of their function if not all their function. Dolphins have hipbones that of are no use yet they may have played a role in their locomotion while on land. Embryological development of vertebrates is very similar, providing evidence that organisms have descended from a ____________ _____________. Genetics and Molecular Biology Our advancements in genetics indicate that all living things share the same ________ and ________ to carry information from one generation to the next. Genetics provides some of the strongest supporting evidence of evolution. _____________ molecules show structural and chemical similarities at the molecular level. An example is cytochrome c, a protein which functions in cellular respiration for all types of cells. Testing Natural Selection Use the area below to explain how recent research on the Galapagos finches has supported Darwin’s theory of evolution. This can be done in point form. 6