Successfully reported this slideshow.
Your SlideShare is downloading. ×


Upcoming SlideShare
Natural selection
Natural selection
Loading in …3

Check these out next

1 of 50 Ad

More Related Content

Slideshows for you (20)

Similar to Evolution (20)



  1. 1. Evolution Presented by: Sehar Mangi(B.Ed VII)
  2. 2. Content • Cause of Diversity • Evolution • Lamarck’s Theory of Evolution • Darwin’s Theory of Evolution • Natural Selection • Evidence of Evolution • Misconceptions • References
  3. 3. 3 “Nothing in biology makes sense EXCEPT in the light of evolution.” Theodosius Dobzhansky
  4. 4. Lets think for a while about planet Earth and Diversity of Living Organism
  5. 5. Cause Of Diversity 1. Theory of Special Creation o All living things came into existence in their present forms especially and specifically created by nature. o Carolus Linnaeuos.
  6. 6. Cause of Diversity 2. Theory Of Natural Selection o Organisms might EVOLVE through time , with one type of organisms giving rise to another type of organisms.
  7. 7. Cause of Diversity 2. Theory Of Natural Selection o Aristotle o Jean Baptiste Lamarck o Charles Darwin
  8. 8. What is Evolution? …
  9. 9. Evolution • It refers to the process that have transformed or changed life on earth from its earliest forms to the vast diversity that we observed today. • Any Change in the heritable traits with in a population across generation.
  10. 10. Evolution • Evolutionary Change is based mainly on the interactions between population of organisms and their environment.
  11. 11. Lamarck’s Theory of Evolution • Organisms constantly strive to improve themselves by changing. • Changes are adaptations to environment acquired in an organism’s lifetime. • A structure is modified or changed by use or disuse • The modification is inherited to the offspring. • Inheritance of acquired characteristics.
  12. 12. Darwin’s Theory of Evolution • Check the video:
  13. 13. Darwin’s Theory of Evolution
  14. 14. Common descent with modification • All organisms are related through descent from some unknown ancestor that lived in the distant past.
  15. 15. Natural selection and Adaptation • He suggested that population of individual species become better adapted to their environment through natural selection. “I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection.” —Charles Darwin from "The Origin of Species“, 1859
  16. 16. Lets Discover what is Natural selection ? Activity : A Paper plan Instructions: • Construct paper planes. • Fly your plane 10 feet. If your plane survives, it will go on to the next test. If it does not survive you will create an offspring of one of the survivors. • The survivors and offspring face a second trial of 15 feet. The survivors will go on to the final round and those that did not survive will create offspring of survivors to go to the final round. • The final test will be at 20 feet. Survivors will be judged for a prize based on beauty, distance and uniqueness.
  17. 17. Theory OF Natural Selection • The Struggle for Existence -members of each species have to compete for food, shelter, other life necessities to reproduce in a specific environment. • Survival of the Fittest-Some individuals better suited for the environment. • Natural Selection-The unequal ability of individuals to survive and reproduce leads to a gradual change in a population, with favorable characteristics accumulating over generations new species evolve .
  18. 18. Natural Selection & Artificial Selection • Natural selection results in changes in inherited characteristics of a population. These changes increase a species fitness in its environment. • Artificial selection- nature provides the variation among different organisms, and humans select those variations they find useful.
  19. 19. Evidence of Evolution 1. Fossils Record • Remains or imprints of past life. • Preserved in sediments. • Occur in layers (strata). • Fossils in different layers of rock (sedimentary Rock Strata) showed evidence of gradual change over time.
  20. 20. Strata layers in Rocks
  21. 21. Fossilized remains of a bird like dinosaur Archeopteryx
  22. 22. Fossil Jellyfish
  23. 23. Fossil Evidence for Evolution • Fossils distributed consistently throughout strata of same age. • Order of fossil appearance shows more complex forms appearing after simpler forms. • Recent fossils (new strata) most closely resemble modern organisms.
  24. 24. Evidence of Evolution 2. Taxonomy • Hierarchical classification structure developed by Linnaeus • Implies that species can be grouped together based on their relatedness • Bears with bears, bees with other bees • A family tree can be made implying descent
  25. 25. Related species of Ursus
  26. 26. Evidence of Evolution 3. Comparative Anatomy • Compares anatomical structures from different organisms. • Similar structures in two or more species are called homologous structures. • Homologous structures may perform different tasks in different organisms.
  27. 27. Comparative Anatomy Structure Evidence of Evolution • Scientists noticed animals with backbones (Vertebrates) had similar bone structure. • May differ in form or function. • Limb bones develop in similar patterns. Arms, Wings, Legs, Flippers
  28. 28. Comparative Anatomy Structure Evidence of Evolution • Structures that have different mature forms but develop from the same embryonic tissues • Strong evidence that all four-limbed animals with backbones descended, with modification, from a common ancestor • Help scientist group animals
  29. 29. Homologous forelimbs
  30. 30. Evidence of Evolution 4. Comparative Embryology • Embryos (young stage of organisms are compared) • Embryonic Structures Of Different Species Show Significant Similarities. • Similar features due to shared ancestry.
  31. 31. Human Fetus – 5 weeks
  32. 32. 39 Chicken Turtle Rat
  33. 33. Evidence of Evolution 5. Biogeography • Distribution of species • Many related species occur across the earth • Isolated areas (islands, Australia) often have unique species • Biogeography explained by continental drift of plates and speciation
  34. 34. Evidence of Evolution 6. Molecular Biology • Includes comparisons of • protein sequences • DNA sequences • chloroplast genomes (plants only) • Used to developed phylogenetic trees (hypothesized relationships)
  35. 35. Evidence of Evolution Lets Explore More /evolution.swf
  36. 36. Misconception about Evolution • Evolution is “just a theory” or the “best guess”, so it is not supported by scientific evidence. • Organisms change and evolve because they have a desire to do so. • We can’t see evolution happening. • Evolution leads to more advanced organisms that are “climbing the evolutionary ladder”. • Evolution occurs in individual organisms.
  37. 37. Lets conclude the session through Mind Map…
  38. 38. Group Activity • Watch the Video. • Make a list of ideas. • Write down ideas on the Chart. • Present it , in front of the Class
  39. 39. Any Question?
  40. 40. References • t • sed.ppt • evolution?qid=9f48c386-d204-40ad-b387- 3876e335f45f&v=&b=&from_search=6 • lutionUnitPlan.pdf • • f • • Biology Textbook Of Class 12 Of Punjab Board