Natural Selection BIOL 212.ppt

Descent with Modification and Natural Selection R. Murcia 1 Descent with Modification and Natural Selection I. Introduction II. Darwin’s View of Life III. The Evidence For Evolution R. Murcia 2 Learning Objectives Compare and contrast catastrophism and uniformitarianism Describe Lamark’s hypothesis...

Descent with Modification and Natural Selection R. Murcia 1 Descent with Modification and Natural Selection I. Introduction II. Darwin’s View of Life III. The Evidence For Evolution R. Murcia 2 Learning Objectives Compare and contrast catastrophism and uniformitarianism Describe Lamark’s hypothesis of evolution Explain what Darwin meant by “Descent with Modification” Describe the process of Natural Selection R. Murcia 3 Learning Objectives Evaluate the role of fossils and biogeography evidence in support of Darwin’s view of evolution Compare and contrast homologous, analogous, and vestigial structures Explain how molecular homologies can be used to identify evolutionary relationships Explain what is an evolutionary tree R. Murcia 4 I. Introduction A. The appearance of a species is an indicator of the place where it lives. Example: Mantid insects have the ability to blend with their surrounding environments. R. Murcia 5 B. Evolution of Drug-resistant Bacteria 1. The bacterium Staphylococcus aureus is commonly found on people 2. One strain, methicillin-resistant S. aureus (MRSA) is a dangerous pathogen 3. S. aureus became resistant to penicillin in 1945, two years after it was first widely used 4. S. aureus became resistant to methicillin in 1961, two years after it was first widely used R. Murcia 6 C. Explaining how populations change and adapt to environmental changes is the main goal of Evolutionary Biology. D. Charles Darwin was not the first person to suggest that species evolve. However, he proposed the currently accepted mechanism for evolution. E. Evolution is defined as the changes in the characteristic of a species over time. R. Murcia 7 F. Views of life through history: 1. 2. 3. 4. 5. 6. Life is immutable: Aristotle Life’s Creation: Judeo-Christian Culture Catastrophism: Georges Cuvier (1769-1832) Uniformitarianism: C. Lyell (1797-1875) Lamarckism: J. B. Lamarck (1744-1829) Descent with modification: Charles Darwin (1809-1882) R. Murcia 8 G. Geology Principles that Influenced Darwin’s View Paleontology, the study of fossils, was largely developed by French geologist Georges Cuvier Cuvier advocated catastrophism, speculating that each boundary between strata represents a catastrophe Geologists James Hutton and Charles Lyell perceived that changes in Earth’s surface can result from slow continuous actions still operating today Lyell’s principle of uniformitarianism states that the mechanisms of change are constant over time R. Murcia 9 H. Lamark’s Hypothesis of Evolution Lamarck hypothesized that species evolve through use and disuse of body parts and the inheritance of acquired characteristics The mechanisms he proposed are unsupported by evidence R. Murcia 10 II. Darwin’s View of Life A. The Origin of Species presents Darwin’s idea of “descent with modification”, and natural selection as the process by which the environment allows some members of a population to survive and reproduce based on their characteristics. R. Murcia 11 Darwin never used the word evolution in the first edition of The Origin of Species The phrase descent with modification summarized Darwin’s perception of the unity of life The phrase refers to the view that all organisms are related through descent from an ancestor that lived in the remote past R. Murcia 12 B. How Natural Selection Works: Observation 1: Not all the individuals born in a population survive and/or reproduce. Observation 2: Limited resources keep populations at a stable size. Conclusion 1: A struggle for survival results from the presence of more individuals than the environment can support. Observation 3: Individuals in a population show great variation in their characteristics. Beneficial characteristics that aid in survival and reproduction are called adaptations. Conclusion 2: Differential reproduction results when better adapted individuals leave more offspring than less fit individuals. R. Murcia 13 C. Artificial selection is the purposeful breeding of domesticated plants and animals. Artificial selection, through purposeful crossing, can produce many forms in a short period of time. Ex. Broccoli, cabbage, Brussel sprouts, Swiss chard were derived from the wild mustard plant. Can natural selection have similar results through random mutations and environmental changes over millions of years? Ex. Beak size changes in Galapagos medium ground finch. R. Murcia 14 D. In the Darwinian view, the history of life is like a tree with branches representing life’s diversity R. Murcia 15 E. Evolutionary Trees Evolutionary trees are hypotheses about the relationships among different groups Homologies form nested patterns in evolutionary trees Evolutionary trees can be made using different types of data, for example, anatomical and DNA sequence data R. Murcia 16 Figure 22.17 Branch point Lungfishes Mammals 2 Amnion Lizards and snakes 3 4 Homologous characteristic Amniotes Digitbearing limbs Crocodiles 5 Ostriches Feathers Hawks and other birds R. Murcia Birds 6 17 Tetrapods Amphibians 1 III. The Evidence For Evolution A. The fossil record. Fossils are traces of living things that have been preserved in sedimentary rocks. What the record shows: 1. Older layers of rock contain simple life forms. 2. Newer layers contain more complex forms. 3. Relatively few transitional fossils forms. R. Murcia 18 B. Biogeography. Biogeography is the study of the geographic distribution of living things. What this shows: Although slightly different, island organisms are very similar to those from the nearest continent. R. Murcia 19 C. Comparative anatomy. This is the comparison of body parts between different species. What this shows: Closely related species share a similar design and possibly a common ancestor. R. Murcia 20 D. Molecular biology. The study of the molecules of life shows that : 1. The DNA in all living things has the same structure. 2. Closely related species share similar proteins. R. Murcia 21