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Transcript
6/10/13 Science Starter ! I ndicate whether each statement is true or false, in terms of your current understanding of evolution. ! We will go over them together. 2. Evolution is something a person should either believe in, or not believe in. 1. Evolution is as much a fact as the fact that planets go around the Sun. ! True! ! Has extensive evidence and no evidence against it 3. Evolution is a process that includes the origin of life. ! False! ! It’s based on science, not faith ! False! ! It only deals with the origin of species, not the origin of life 4. Evolution was first proposed and explained by Charles Darwin. 5. Evolution is also known as "Natural Selection". ! False! ! Others proposed it first, Darwin used extensive research to support it ! False! ! Natural selection is one way evolution happens 1 6/10/13 6. Evolution is something that happened in the past; it is not happening now. 7. Evolution is something that happens to individual organisms. ! False! ! It’s still happening, we create new dog breeds and new species are still evolving ! False! ! Populations evolve and adapt 8. Evolution is a totally random process, a series of accidents. 9. In order to accept evolution as a real process, you cannot believe in God. ! False! ! The environment and mate selection put limits on it. ! False! ! Evolution is neutral, God is not required or eliminated, for all we know, evolution could be God’s creation 10. Evolution is only a theory. Evolution ! False! ! A theory is a scientific fact, just like the theory that the Earth revolves around the Sun, and the theory of gravity ! T he process by which new species arise from earlier species by accumulated changes ! Genetic differences are passed down from parent to offspring 2 6/10/13 How does Evolution Happen? 1. Mutations ! Mutations introduce new genes 2. Migration ! Traveling individuals can introduce new genes 3. Genetic Drift ! Some just do better just by chance 4. Natural Selection ! A gene increases survival Fitness ! T he ability to pass on your genetics ! Having offspring ! Does not mean the strongest or fastest Darwin (1809-1882) Darwin’s Four Principles of Natural Selection 1. Individuals in a population have variations (they are different) 2. Variations are inherited 3. Living things overproduce 4. Variations that increase fitness will be more common in the next generation Lamarck (1744-1829) Believed that . . . ! Life changed over time ! Changes in organisms were due to wants or needs ! Unused body parts would disappear ! Those changes were passed onto its offspring Types of Natural Selection ! Used research to support theory ! Wants and needs have no effect ! Those organisms with traits better suited to their environment did better ! Had more offspring ! Passed on their genes ! Those not so well off, died off or had less offspring 3 6/10/13 Stabilizing Selection ! T he extremes of certain traits are disadvantageous and eliminated. Disruptive Selection ! S election favors the extremes for particular traits rather than the mean, which is selected against. ! This often results in divergence into two new species How does Evolution Happen? 1. Mutations ! Natural or environmental 2. Migration ! Gene flow 3. Genetic Drift ! Founder Effect ! Genetic Bottleneck 4. Natural Selection Directional Selection ! One extreme for certain traits are disadvantageous and are selected against. The other extreme is selected for. Sexual Selection ! When males or females select a mate based on secondary sexual characteristics like flashy colors or long antlers. ! These traits are often harmful and not helpful for survival but they increase the chance of breeding. Mutations ! M utations are random and can be caused by a copying mistake or by the environment. ! Example: Antibiotic resistant bacteria 4 6/10/13 How does Evolution Happen? 1. Mutations ! Natural or environmental 2. Migration ! Gene flow 3. Genetic Drift ! Founder Effect ! Genetic Bottleneck 4. Natural Selection How does Evolution Happen? 1. Mutations ! Natural or environmental 2. Migration ! Gene flow 3. Genetic Drift ! Founder Effect ! Genetic Bottleneck 4. Natural Selection Effects of Genetic Drift ! Y ou can by chance, lose a trait because it wasn’t inherited ! This happens faster in a small population Migration (gene flow) ! W hen individuals migrate, they introduce new genes and genetic variation where they go ! This increases genetic variation and is a good thing Genetic Drift ! S ome individuals may, by chance, have more offspring and pass on their genes ! They were “lucky” not better or healthier Genetic Bottleneck ! O ccur when a population’s size is reduced for at least one generation ! This reduces the genetic variation and the population can lose traits 5 6/10/13 Founder Effect ! O ccurs when a new colony is started by a few members ! There is reduced genetic variation ! The colony is a non-random sample and can be missing traits 1. Allopatric Speciation (Geographic Isolation) ! A physical barrier divides one population into two or more ! Mountain range, river, lava, island ! A fter a long period of time, the two populations will be separate species 3. Coevolution ! T wo species can evolve together ! Example: Flowers have marking that guide bees to nectar ! T he bees gather nectar, they pollinate the flower Speciation ! O ccurs when a population reproduces in isolation 1. 2. 3. 4. Allopatric Speciation (Isolation) Adaptive Radiation Coevolution Convergent Evolution 2. Adaptive Radiation ! O ccurs when one species evolves in a short period of time into a number of new species ! Can occur when a species evolves a new, useful trait, or arrives in a new habitat 4. Convergent Evolution ! Unrelated organisms in different places evolve to resemble one another ! Can produce organisms with similar physiology and behavior even though they are unrelated ! Example: Porcupines and hedgehogs 6