Transcript Chapter 15
Chapter 15 & 16 Theory of Evolution Population Genetics and Speciation History of Evolution I. Evolution – is the theory that species change over time. II. Theory of evolution before Darwin – Jean Baptiste de Lamarck Inherited characteristics not in use will disappear. No evidence or experiences to support. Jean Baptiste De Lamarck Charles Darwin III. Charles Darwin (1809-1882) Failure in school. Studied to be a doctor Studied to be a clergy Became naturalist on the HMS Beagle – a 5 year mapping and collecting expedition to South American and the South Pacific Observed changes in land – if habitats changed animals would have to adapt. Giant Tortoise Blue Footed Booby Blue Feet Galapagos Islands Map Studied fossils – compared homologous structures- similar structure with possibly different function and Vestigial Organsstructure that works in one species, but does not function in other. Example: appendix. Fossils of similar species should be more similar in the past – fossil records. What is a species? IV. What is a species? Species comes from the Latin meaning kind or appearance. **Species members can reproduce and produce fertile offspring. V. Species classified by: 1. Morphology – similarities and differences in internal and external structures. Includes biochemistry- actual chemical make up and embryonic development- development in womb between similar species more closely related. Some members of the same species may not look alike. Ex: Flicker – 2 morphologically different parents produce hybrid. All the same species just different appearance. 2. Classification expanded to include reproductive capability. If an organism is classified solely on breeding capability it is classified by the Biological Species Concept (BSC). 3. Using both Morphology and BSC can explain how species change. VI. What is a population? 1. The number of a species in a specific area at a specific time 2. Scientist study variation in population Genotype/Phenotype 3. Collection of genes of a population is its gene pool. 4. Gene pool contains all possible alleles for all genes. 5. Allele frequency = % of specific allele of a gene in gene pool. 6. If allele frequency does not change from generation to generation = genetic equilibrium. Population will look the same generation to generation. VII. Conditions for genetic equilibrium: 1. No mutations 2. No migrations 3. Large populations 4. Mate randomly 5. Natural selection doesn’t occur If conditions change genetic equilibrium, evolutionary change or change in species may occur. VIII. The conditions for genetic equilibrium were outlined by Godfrey Hardy (British Mathematician) and Wilhelm Weinberg (German Physician) = Hardy Weinberg Principle IX. Types of change: 1. Mutation – is a physical change in the gene or chromosome 2. Migration – changes allele frequency, disrupts genetic equilibrium 3. Gene flow – movement of genes in or out of a population. 4. Genetic drift – allele frequencies change as a result of random events, significant in small & medium populations. • X. Thomas Malthus – Essay on the principal of population stated that: Population will double every 25 years. • Natural resources do not increase at same rate. Struggle for existence becomes struggle for resources XI. Natural Selection XI. Natural Selection – most advantageous variations most likely to survive and reproduce 1. Inherited variation could change a species or can create a whole new species – process called speciation. 2. Adaptive radiation – changes forming related species to adapt to different habitats and reduce competitions 3. Divergent evolution- related species becomes more and more dissimilar. 4. Convergent evolution- an unrelated species becomes more and more similar. 5. Coevolution- 2 or more species through interactions develop a specialization for other. Example: predator/prey provider/host (parasite) flowers/insects Convergent Examples Peppered Moth XII. Natural selection does occur: 1. Stabilizing selection – average is best – bell curve 2. Directional selection – one extreme or the other is best. 3. Disruptive selection – either extreme is advantage 4. Sexual selection – preferred choice of mate