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Evolution

Evolution. Fossil: physical evidence of an org. that lived long ago, most found in sedimentary rocks Help identify how ecosystems and org. have evolved and changed. Formation: 1. org. is buried in sediment soon after it dies 2. sediments build up & stop decay

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Evolution

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  1. Evolution

  2. Fossil: physical evidence of an org. that lived long ago, most found in sedimentary rocks • Help identify how ecosystems and org. have evolved and changed. • Formation: • 1. org. is buried in sediment soon after it dies • 2. sediments build up & stop decay • 3. depending on conditions so portions of the org. may be preserved or may transform into rock

  3. Types: • 1. Trace: indirect evidence • -footprint, trail, or burrow

  4. 2. Casts: minerals fill in space left by org. after is decays

  5. 3. Molds: Org. buried in mud decays leaving an empty space

  6. 4. Petrified: minerals have replaced hard parts of org.

  7. 5. Amber/Frozen: Org. is quickly encased in sap or flash frozen

  8. What can fossils tell us? • -information about structural relationships • e.g.-T-rex used big tail for balance • -footprints show behavior patterns, speed, & relationships to other org. • -sediments help tell when org. lived & what the env. was like • -fossils found in groups show behavior patterns & relationships to other org. • -help create Geologic Time Scale-Earth’s history divided into major eras & periods based on physical & organic characteristics

  9. Determining Fossil Age • -helps create fossil record (history of life) • 1. Relative Dating: create a comparative age of fossils based on their level in the rock

  10. Interpretation for relative dating • -Correlation: matching rock layers in different areas to show geographic & organic evolution (in a specific region)

  11. -Index fossil: org. that appeared over wide ranges • -allows for relative dating between different regions • -e.g. Trilobites

  12. 2. Absolute dating: provides an accurate age • -Radiometric dating: Elements decay over time and change into different elements/isotopes. • -By measuring the ratio of isotopes/elements in the rocks surrounding a fossil, its age can be determined.

  13. -Carbon-14 is used for organic fossils • -half-life = 5700 years • -it decays into Nitrogen-14 • -can’t be used for org. older than 50,000 yrs • -Uranium-238 (half-life = 4.46 billion years) or Potassium-40 (half-life = 1.27 billions years) are used for older fossils • -must be tested on igneous (volcanic) rock that is in the same layer as the fossil

  14. Evolution & Natural Selection

  15. EE x ee • Ee • EE Ee ee

  16. Evolution: change in the genetic make-up of a population over time • -doesn’t have to create a new species, may modify a population • -individuals don’t evolve, populations do because an ind. genes don’t change

  17. Macroevolution: evolution above the level of species (speciation) • Microevolution: evolution at or below the level of species • -changes in the genetic equilibrium of a population based on differential reproduction

  18. 1809- J. B. de Lamarck • -1st major theory of evolution • -believed species aren’t constant, they evolve from pre-existing species • -evolution involved 2 principles • 1. Law of Use & Disuse • -the more an org. uses a body part the stronger/better developed it becomes • 2. Inheritance of Acquired Characteristics • -characteristics developed thru use & disuse could be passed on • -e.g. giraffe’s

  19. -theory incorrect because inheritance of DNA isn’t affected by acquired characteristics

  20. Charles Darwin: founder of the modern evolutionary theory • -boarded HMS Beagle in 1831 as a naturalist on 5 year round-the-world trip • -collected org., rocks, & fossils • -recorded how species change over time • -most information collected from Galapagos Islands (finches, tortoises, & marine iguanas) • -Once home he spent 20 years collecting & analyzing data & experimenting • -Bred pigeons to demonstrate artificial selection: breeding org. with specific traits to produce offspring with desired traits

  21. Natural Selection: survival of the best adapted • -based on which org. can survive and reproduce more successfully • -changes allele proportions of the population • -survival of the “fittest” (best about to reproduce) • Thomas Malthus: found that populations tend to grown geometrically (2,4,8,16,32), but food supply grow arithmetically (1,2,3,4) • -populations are kept in check by limiting factors

  22. Darwin used Malthus’ ideas to help create the idea of natural selection • Coauthored paper with Alfred Russell Wallace who was working on natural selection at the same time. Darwin reported his findings first.

  23. 6 main points of Darwin’s theory • A. Overproduction: species produce extra offspring because many won’t live to reproduce • B. Competition: species must compete for resources, not all survive • C. Variation: differences in characteristics of inds. in a species • -variations that increase survival are passed on • D. Adaptations: any trait the increases the chance of survival & reproduction

  24. E. Natural Selection: env. selects org. that are best adapted to survive to reproduce & pass on genes • F. Speciation: formation of new species • -over generations, adaptations accumulate & result in new species • e.g. Giraffes • -some had longer necks & could reach food unavailable to others • -as env. changed & grass disappeared those who could reach leaves on trees survived & passed on trait

  25. Evidences • Of • Evolution

  26. A. Fossils • -examining fossil evidence helps to create a map of the org. that have appeared • -determining age and environment helps link related org. and show change over time (precursors)

  27. B. “Living Fossils” • -org. that have changed very little over time • -helps link current and past org. • -provides understanding of successful adaptations

  28. C. Structural Adaptations • -parts of org. that allow them to better survive & reproduce • -e.g. Darwin’s Finches

  29. D. Mimicry • -one species resembles another • -usually a harmless resembles a harmful species • OR • -harmful species resemble each other

  30. E. Camouflage • -enables species to blend into its surroundings • -harder for predators/prey to see & more likely to survive/reproduce

  31. F. Physiological adaptations • -Changes in an org’s metabolism due to changes/mutations in DNA • -Causes: • -drug-resistant strains of bacteria & viruses • -need for a new flu vaccine every year • -chemical-resistant species of insects & weeds

  32. G. Homologous Structures: • -Body parts with similar structure/arrangement, function may be different • -Shows phylogenetic relationship (phylogeny- evolutionary relationships)

  33. H. Analogous Structures: • -Body parts with similar functions but different structures • -Shows how the environment can “select” orgs. with specific adaptations to be most successful (natural selection) • -Don’t show phylogeny

  34. I. Vestigial Structures: • -body parts found in present-day organisms that no longer serve their original purpose • -may have developed into something else, or may be non-functional • -still inherited because the DNA of that org. still contains the information to make that part

  35. J. Embryology: • -Comparing embryos of different organisms • -Scientists look for similarities • -e.g. tail, pharyngeal (gill) pouches

  36. -Haeckel’s recapitulation theory • -Ontogeny recapitulates phylogeny • -development of the individual of every species fully repeats the evolutionary development of that species • -has proven to be incorrect

  37. K. Biochemistry • -Comparing DNA, RNA, and proteins to identify similarities in make-up

  38. Organisms don’t change because the environment changes, the variations already exist within the population and some of the individuals are more successful.

  39. Mechanisms Of Evolution

  40. Populations evolve • -ind. can’t change their genotype over the course of their lifetime • -evolution is a change in the genetic make-up of a population over time • -Some genes are more successful (cause org. to survive & reproduce better) • -Gene pool: all the alleles in a population’s genotype • -Allelic frequency: % of a specific allele in the gene pool • -Genetic equilibrium: pop. where the allelic frequency doesn’t change over generations

  41. Is this population evolving?

  42. -pop. that is in genetic equilibrium is not evolving • -mutations cause new genes/alleles/ phenotypes to appear in a population • -many are lethal and quickly eliminated • -some have no effect • -those that are beneficial will be passed on • Gene flow • -can change the allelic frequency • -immigration: movement of ind. into population • -emigration: movement of ind. out of population

  43. Genetic drift: alteration of allelic frequencies by chance events • -occur in small, isolated populations that have become separated from their original gene pool • -new pop. gene pool is different from original

  44. Speciation: • -evolution of a new species • -ind. of similar pop. no longer interbreed • -can occur when a pop. gets divided by a physical barrier (Geographic isolation)

  45. -Reproductive isolation – can occur by geographic isolation, drift, or mutations • -some change causes ind. to stop interbreeding

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