Transcript Gene Pool
The Theory of Evolution Vocabulary Evolution = process by which modern organisms have descended from ancient organisms. A change in populations over long periods of time. Scientific Theory = well-supported, testable explanation of phenomena that have occurred in the natural world. Charles Darwin **In 1831, Darwin set sail from England aboard the H.M.S. Beagle for a voyage around the world. **During his travels, Darwin made numerous observations and collected evidence that led him to propose a hypothesis about the way life changes over time. (natural selection) Natural Selection also known as: Survival of the Fittest Process by which individuals who are better adapted for their environment survive and reproduce successfully. In the Galapagos Darwin notices that there were variations among members of the same species. Example: Finches, Giant Tortoise Three species of tortoises each inhabit a different island in the Galápagos Testudo abingdonii, inhabits the Pinta island and has a longer neck to reach vegetation Pinta Marchena Pinta Island Fernandina Intermediate shell Isab ela James Santa Cruz Santa Fe Floreana Isabela Island Dome-shaped shell Tower Hood Hood Island Saddlebacked shell Fitness: the ability for an organism to survive and reproduce in its environment. It’s a result of adaptation. Hummingbirds have adapted to their environment in two ways: 1.Very fast flight to keep them steady. 2.Long beak and tongue to reach into flowers and extract nectar. Adaptation: any inherited characteristic that increases an organism’s chances for survival. Peppered Moths The evolution of the peppered moth over the last two hundred years has been studied in detail. Originally, the vast majority of peppered moths had light coloration, which effectively camouflaged them against the light-colored trees and lichens upon which they rested. However, due to widespread pollution during the Industrial Revolution in England, many of the lichens died out, and the trees which peppered moths rested on became blackened by soot, causing most of the lightcolored moths, to die off due to predation The Peppered Moth Scenario is an example of ______. a. Transcription b. Natural Selection c. Artificial Selection d. Translation Mosquito Count Mosquitos 60,000 50,000 40,000 30,000 20,000 10,000 0 Mosquitos 1 2 43 6 58 10 7 12 914 16 11 18 13 15 17 Weekly Spraying 1 A small Texas town recorded the above mosquito data every week for a 5-month period of time. During this time insecticide was sprayed to try and reduce the large number of mosquitoes. What is the best explanation for the decreased effectiveness of the insecticide over time? A Mosquitoes that were resistant to the insecticide lived and produced offspring. B The insecticide was sprayed only once. C The insecticide harmed the mosquito’s DNA causing mutations that prevented reproduction. D The temperature decreased the effectiveness of the insecticide. Evidence of evolution. DARWIN INFLUENCED BY THE STUDIES OF VARIOUS PEOPLE SUCH AS: LYELL AND HUTTON - Geologists who proposed that the earth was millions of years old and that geological events such as volcanic eruptions and earthquakes have changed and shaped the earth over long periods of time and continue to do so. THOMAS MALTHUS – An Economist who predicted that if populations continued to grow out of control, there would be less resources like food, water and space to sustain the populations. Jean Baptiste Lamarck – A French naturalist who was one of the first to recognize that organisms change over time but proposed that traits were acquired through use or disuse such as the long neck of the giraffes. Evidence that living things have been evolving for millions of years includes: The fossil record Some of the fossils resembled organisms that were still alive. Others looked completely unlike any creature he had ever seen. Homologous, analogous, and vestigial structures Embryology Geographic distribution of living things Biochemistry What are fossils? Remains of once living organisms Like the hard parts of organisms (i.e. bones), impressions, or casts. Water carries small rock particles to lakes and seas. Dead organisms are buried by layers of sediment, which forms new rock. The preserved remains may later be discovered and studied. Portrayed by remains of ancient life forms. When fossils are discovered they can be added to the fossil record based on age and similarities. Found mainly in Sedimentary Rock Similar in structure but functions differently Examples: flying, swimming, grasping etc. Structures that have a similar function, but different structures. Example: Butterfly and bird both use their wings for flying, but wings are structured differently, one has bones, one has network of veins. Structures that serve no useful purpose in an organism. In whales, there is a vestigial pelvis and femur. In horses, there is a vestigial toe. In snakes, there are vestigial hips Can you name any vestigial structures in humans? Similarities in Embryology In their early stages of development, chickens, turtles and rats look similar, providing evidence that they shared a common ancestor. Biochemistry: DNA and Proteins Closely related species share common genetic base sequences Based on modern knowledge of genetics, we now know that natural selection is dependent on genetic variation within the gene pool. Gene Pool: consists of all the genes including all the different alleles that are present in a population. A population is a group of individuals that inhabit the same area. A species is a group of similar organisms that can breed and produce fertile offspring. Speciation: Geographic Isolation: When two populations of a species becomes separated by geographic barriers such as rivers or mountain ranges resulting in the formation of 2 separate gene pools. Ex: Abert Squirrels vs. Kaibab Squirrels. a change in allele frequencies that occur in small populations. These changes are associated with random events . founder effect small group splinters off & starts a new colony bottleneck some factor (disaster) reduces population to small number & then population recovers & expands again Bottleneck Effect diverse population “catastrophic event” (hunting, earthquake, volcanic eruption, etc. small % of the original population remains & repopulates less diverse population When large population is drastically reduced by a disaster famine, natural disaster, loss of habitat… loss of variation by chance event alleles lost from gene pool not due to fitness narrows the gene pool All cheetahs share a small number of alleles less than 1% diversity as if all cheetahs are identical twins 2 bottlenecks 10,000 years ago Ice Age last 100 years poaching & loss of habitat Small population gets separated by chance (storm, earthquake, etc.) Develop different adaptations over many generations If they come in contact later, they are too different to interbreed Ex. Galapagos finches fly to nearby island When a new population is started by only a few individuals some rare alleles may be at high frequency; others may be missing skew the gene pool of new population human populations that started from small group of colonists example: colonization of New World Genetic Flow: the transfer of genes or alleles from one population to another. Movement of individuals & alleles in & out of populations seed & pollen distribution by wind & insect migration of animals sub-populations may have different allele frequencies causes genetic mixing across regions reduce differences between populations Gene flow in human populations is increasing today transferring alleles between populations Are we moving towards a blended world?