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Evolution Do Now: View the finches. What characteristics do they have in common? What can you infer from these similarities? What characteristics are different? Why do you think they evolved these differences? Charles Darwin (1809 – 1882) British Naturalist 5 year voyage of HMS Beagle around the world Credited with the theory of natural selection Darwin’s Influences Erasmus Darwin All life was “produced by a simple life filament” Organisms change over time Jean Baptiste Lamarck Inheritance of acquired characteristics Law of use and disuse Discredited with the discovery of genes Charles Lyell Principles of Geology – the present is the key to the past Thomas Malthus “Essay on the principle of population” Population – a group of individuals that belong to the same species, live in a defined area, and breed with others in the group Populations have the potential to increase faster than the available food supply…but this doesn’t occur because of death by disease, war, and famine Facts About Evolution It is a Scientific Theory (just as Gravity is) A vast majority of scientists accept it It is supported by a large body of evidence There is no scientific evidence contradicting evolution General Knowledge: Selective Breeding Selective Breeding aka Artificial Selection Farmers and/or breeders mate plants or animals with desirable genetic traits to produce offspring with desired traits Inbreeding Examples: Dog Breeding Horse Breeding Any domesticated plant or animal Darwin’s Observations Found fossils of extinct armadillos Plants and animals of Galapagos islands are similar to those in Ecuador Conclusion: species migrated from S. America to islands and changed after they arrived – “descent with modification” Darwin’s Theory of Evolution by Natural Selection (1844) Natural Selection: individuals that posses superior physical or behavioral attributes are more likely to survive, reproduce, and pass on the favorable traits to the offspring 1. 2. 3. 4. Overpopulation Variation among species Competition for resources Successful reproduction Adaptation – the changing of a species in response to its environment Controversy over evolution Lamarck and other’s ideas of change over time severely criticized by church and government Alfred Wallace develops same theory (1858) Darwin publishes book in 1859: On the Origin of Species by Means of Natural Selection People outraged with the idea of being related to apes Darwin’s theory and evidence (and more recent evidence) were so compelling they became widely accepted by the scientific community Darwin’s Ideas have been Updated Microevolution: change occurring within a species over time Isolation leads to species formation Natural Selection causes the frequency of certain genes within a population to change over time Populations of the same species living in different locations tend to evolve in different directions Isolation – 2 populations of the same species are separated from one another When individuals of the 2 populations can no longer interbreed, they are considered to be different species Extinction leads to species replacement Extinct – species permanently disappears usually due to a change in environment Species that are better suited to the new conditions may replace those that have become extinct Macroevolution – change creating a new species over time Geographic Isolation and Evolution Members of the original species migrated to different areas…one area perhaps had trees, and the other did not. The Tree Finches had to adapt to get insects from the trees. The Ground finches adapted to be able to open seeds. Note the beaks. Evolution of Antibiotic Resistance After treatment with antibiotics The bacteria have EVOLVED to become more resistant (more of the population is resistant). This occurred through NATURAL SELECTION (the ones more equipped to survive the antibiotic treatment were able to reproduce successfully) Evidence of Macroevolution Fossils Change over time can be observed in the fossil record Darwin predicted that “missing links” would eventually be found, and many were! 1990’s fossils linked whales to land mammals Whale Evolution Horse Evolution Radiometric Dating of Fossils Radioactive isotopes decay a a constant rate called a half life Different isotopes have different half lives Ex. C-14 N-14 5,730 years U-238 Pb-206 4.5 billion years Calculation Half-Lives If this chart represents K-40 which has a half life of 1.3 billion years, how old is a sample that contains 25% of its original K-40? Evidence of Macroevolution Anatomy Homologous structures: similar structures though functions may vary Analogous structures: different structure, but similar functions Ex. Human arm, bat wing, alligator arm, and penguin arm Ex. Butterfly wings and bird wings Vestigial Structures: structures that are present but reduced in size or nonfunctional as compared to related organisms Ex. Coccyx, appendix, ear muscles, wings on flightless birds Homologous Structures Analogous Structures Analogous structures evolve separately in different organisms in order for them to adapt to common functions Vestigial structures – getting smaller due to lack of use Evidence of Macroevolution Biochemical Evidence The species characteristics change as a result of changes in DNA, ultimately as a result of mutations Therefore changes in DNA should accumulate over time as species become more different Compare amino acid sequences to test relativity The molecular record has shown the same relationships indicated by the fossil record Evidence of Macroevolution Embryonic Development Vertebrate embryos develop similarly Suggests that development evolved as new genetic instructions were layered on top of older ones Tail, limb buds, pharyngeal pouches Embryonic Evidence of Evolution New ‘directions’ are carried out over the old ‘directions”. SO – embryos develop similarly at first, then the new directions begin to be carried out, resulting in the differences in embryonic development Do Now - Journal What does “FITTEST” mean – as in “survival of the fittest”? Does an individual’s ability or desire to reproduce make it less fit? What did Darwin mean? The term ‘survival of the fittest’ was first coined by Herbert Spencer, not Darwin Darwin did begin using the term to replace “natural selection”, but not until the 5th edition of Origin of Species He did not mean strongest, as is sometimes assumed. Any individual that successfully reproduces is contributing to the survival of its species. Therefore, the term “fit” can be considered synonymous with “able to reproduce” Patterns of Evolution Does evolution occur gradually or in spurts? Gradualism: Change generally occurs over long periods of time Punctuated Equilibrium: periods of little or no change are interrupted by periods of rapid change Biologists disagree, however fossil evidence provides evidence for both! Gaps in fossil record Sudden disappearance of some organisms Some organisms unchanged for long periods of time Some organisms changed gradually Phylogenic Tree Phylogenic Tree – shows how organism are related through evolution Each fork in the tree represents a common ancestor Examples of Microevolution Industrial Melanism: the darkening of populations of organisms over time in response to pollution Ex. European peppered moth Biston betularia Dark variety rare until 1850, by 1950 most populations dark Kettlewell tested to see if natural selection caused changes Sickle cell Anemia Sickle Cell is advantageous in central Africa where sickle cell individuals resist malaria Antibiotic Resistance of bacteria Mutation provides resistance and easily gets passed to future generations Patterns of Microevolution Directional Selection: selects for one extreme trait Balancing (stabilizing) Selection: selects for intermediate trait Ex. Where malaria is not present, sickle cell allele is selected against Ex. Human birth weight – too small is too weak and too large provides complications during birth, therefore an intermediate size is selected for Disruptive Selection: both extremes are selected for Ex. Shell Color – light shells blend in with the sand, and dark shells blend in with rocks Speciation Speciation: the process by which a new species forms; over time separate populations of the same species become very different from one another Divergence: the accumulation of differences between groups Ecological Races: populations of the same species that differ genetically because of adaptations to different living conditions, but not different enough to be considered different species Ecological races may continue to diverge until they can no longer reproduce…forming a new species Maintaining a species Reproductive isolation: the prevention of mating between formerly interbreeding groups Geographical Ecological Temporal Behavioral Mechanical Reproductive failure Microevolution leads to Macroevolution As changes continue to accumulate over time, living species may become very different from their ancestors and from other species that evolved from a common ancestor Biologists agree that changes within a species eventually lead to the appearance of a new species Do you think… That if evolution is occurring on an ongoing basis, we would discover new species? How often do you think new species are discovered? When do you think is the last time a new species was discovered? New Species Discovered •Cercopithecus Lomamiensis •Discovered in the Lomami forest in DR Congo •Discovered in 2012 New Species Discovered •Trogloraptor marchingtoni •Found in an Oregon Cave •Discovered in 2012
