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Evolution: Change in Population Over Time

Explore the concept of evolution and its various aspects, including natural selection, extinction, and evidence for evolutionary theory. Learn about influential scientists like Darwin, Lamarck, Lyell, and Malthus, and understand the role of fossils, comparative anatomy, embryology, biochemistry, and genetics in supporting the theory of evolution.

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Evolution: Change in Population Over Time

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  1. Evolution

  2. Evolution Evolution- change in population over time

  3. Evolution- Darwin Darwin • father of modern evolutionary theory • Galapagos Islands • HMS Beagle

  4. Scientists who influenced Darwin • Lamarck- organisms change due to the pressures of their environment, traits are acquired • He proposed that by using or not using its body parts, an individual tends todevelopcertaincharacteristics, which itpasseson to itsoffspring.

  5. Scientists who influenced Darwin- Lamarck • Example: A giraffe acquired its long neck because its ancestor stretched higher and higher into the trees to reach leaves, and that the animal’s increasingly lengthened neck was passed on to its offspring.

  6. Scientists who influenced Darwin Lyell • Principles of Geology • plant and animal species emerged, developed variations and then became extinct

  7. Scientists who influenced Darwin • Malthus- populations outgrew their food supplies causing competition Essay on the Principle of Population (1798)

  8. Natural Selection • Natural Selection- organisms with traits best suited to the environment have a higher survival rate, • “descent with modification”

  9. Natural Selection • 1.organisms produce more offspring than can survive • 2.variation (differences) exist in all populations • 3.organisms best suited to environments will have more offspring • 4. over time organisms with certain advantageous variations make up most of the population

  10. Natural Selection • Example: Peppered Moths during the Industrial Revolution

  11. Natural Selection • Fitness- reproductive efficiency of various individuals or genotypes in a population • depends on probability that one individual will contribute its genetic information to the next generation

  12. Natural Selection Extinction- permanent loss of a species 5 mass extinctions throughout history • Permian period- 96% of marine invertebrates • Cretaceous period- 60-75% of marine species

  13. Evidence for Evolution • 1. Fossils • 2. Comparative anatomy • 3. Comparative embryology • 4. Biochemistry • 5. Genetic evidence • 6. Direct evidence

  14. Evidence for Evolution 1.Fossils • mold or cast of organism left in rock, fossilized bone and teeth • life becomes more complex over time • record is incomplete

  15. Evidence for Evolution • Most complete fossil record is for the horse

  16. Evidence for Evolution Relative dating- • layers in rock bed used to date organisms

  17. Evidence for Evolution • Radioisotope dating- uses half-life of isotope to approximate age of organism Carbon is used frequently

  18. Evidence for Evolution • Half-life

  19. Evidence for Evolution • phylogeny- description of the lines of descent of plants and animals as they lived from one to the next

  20. Evidence for Evolution 2.Comparative Anatomy- the study of the structures of different organisms homologous parts modified structures among different groups of descendants

  21. Evidence for EvolutionComparative Anatomy

  22. Evidence for EvolutionComparative Anatomy • analogous parts-structures in organisms that have no common origin but serve the same function • Example: bird’s wing, bat’s wing and insect’s wing

  23. Evidence for EvolutionComparative Anatomy • vestigial organs- organs having no functions in the living organism Vestigial toes in the horse Vestigial pelvis and femur in whales

  24. Evidence for Evolution 3.Comparative Embryology the study of developing plants and animals Below is the pictures of embryos for a fish, human, rabbit, tortoise, and chicken. Can you guess which one is each type of organism? 1 2 3 4 5

  25. Evidence for Evolution • Comparative Embryology Here the pictures of the second set of development is added. Can you tell now? 1 2 3 4 5

  26. Evidence for Evolution • How about now? 1 2 3 4 5

  27. Evidence for EvolutionComparative Embryology- The complete picture

  28. Evidence for Evolution • 4. Biochemistry • comparison of DNA and proteins in the body • Example: comparison of hemoglobin (blood protein) in human, chimp, and dog. Human and chimp hemoglobin more alike than dog

  29. Evidence for Evolution • 5.Genetic Evidence • Mutations- mistakes in the genetic code • Causes changes in populations over time • Population genetics- researchers use mathematical descriptions of genetic make ups to help them trace evolutionary trends within populations • Selective Breeding- humans choose plants/animals with most desirable traits and breed them to pass those traits to offspring

  30. Evidence for Evolution Biodiversity • Ecosystem diversity- variety of habitats, living communities and ecological processes in the living world • Species diversity- different organisms on Earth • Genetic diversity- different forms of genetic information carried by all living things on Earth • Example Myosin- protein in muscle cells causing contractions. Also found in yeast cells- used to move cell parts

  31. Evidence for Evolution • 6. Direct Evidence • Rapid Evolution • Strains of bacteria becoming resistant to antibiotics • Weeds and herbicides • Insects and pesticide

  32. Adaptations • Adaptation- change in a species that makes it better suited to its environment A hump to store nutrition during long trips or when food or water is scarce Fur inside the ears to protect inner ear from sand Long eyelashes to protect their eyes from the sand when the wind is blowing Nostrils that close to keep sand out Calluses on the the knees to protect from abrasion Large feet for standing in the sand

  33. Types of Adaptations Structural • Changes in structure or anatomy • Example: bird’s beak or claws • Mimicry- a harmless species resembles a harmful one, predators learn to avoid both species • Camouflage- species features blend in with the environment

  34. Mimicry

  35. Camouflage

  36. Types of Adaptations Physiological • Changes in chemical makeup • Examples: digestion enzymes, snake venom, octopus ink

  37. Types of Adaptations • Behavioral • Responses to the environment • Example: bird migration

  38. Mechanisms for Evolution • Species- group of organisms that can interbreed AND produce viable offspring • Populations evolve NOT individuals

  39. Origin of a Species Common Misperception: • Individuals Evolve Species evolve NOT individuals “And now there go the Wilsons!... Seems Like everyone’s evolving except us!”

  40. Mechanisms for Evolution • Gene pool- all the alleles for a trait in the population • Over time gene pools shift to traits that are best suited to the environment • Allelic frequency- the percent of any specific gene in a population • Genetic Equilibrium- when the percentage of alleles in a population remains stable over time

  41. How does evolution occur? • 1.mutation- change in genetic code • caused by environmental factors like radiation/chemicals or by chance • 2.genetic drift- allelic frequency changes by chance, usually in small populations • 3. movement of individuals in and out of populations

  42. Genetic Drift

  43. Natural Selection acts on variation in a population • 1.stabilizing – favors average individual • 2.directional – favors one extreme variation • 3.disruptive – favors both extremes of variation • 4.diversifying- two or more phenotypes develop, different selective pressures operate at the same time • 5. heterozygote advantage- heterozygote (Aa) has higher fitness than either homozygote (AA or aa) • Example- sickle cell anemia

  44. Natural Selection acts on variation in a population

  45. Diversifying Selection

  46. Heterozygote Advantage • In sickle cell anemia, heterozygous individual has normal and sickle cells • May be an advantage to surviving malaria Normal (AA)- gets malaria and dies Heterozygous (Aa)- survives malaria Sickle cell homozygous (aa)- die from sickle cell

  47. Origin of a Species • Speciation – formation of a new species, members of similar populations no longer interbreed

  48. Origin of a Species 1. Geographic Isolation • Physical barrier divides population • River, canyon, mtn. splits group Two species of squirrel split by the Grand Canyon

  49. Origin of a Species • 2.Reproductive Isolation • Members in a population can no longer interbreed • Caused by seasonal, mechanical, and behavioral differences

  50. Origin of a Species 3.Polyploidy • Mistakes during mitosis or meiosis results in individuals with multiple chromosomes

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