Evolution of Populations

1. Evolution of Populations Chapter 16 (M)

2. Evolution a continuing process of change in a population of organisms over long periods of time

3. History • 1700s Scientists believed that “Species are Fixed” and do not change • Mid 1700s fossil records lead Georges Buffon to say • Earth is older than 6000years • Different species arose from variation from a common ancestor • 1800s Lamarck explained fossil records & species diversity

4. Lamarck • Proposed the theory of “Inheritance of Acquired Characteristics” body changes developed during an organisms life time could be passed on to the offspring

5. Short neck ate up grass had to stretch neckto reach trees

6. Lamarck • Acquired characteristics would have to modify DNA to be inherited no evidence of this • Lamarck’s theory was rejected • Set the stage for Darwin

7. Variation in the population long & short necks Long necked survived reproduced population was gradually changed to long necked animals

8. Darwin(1809-1882) • Started his voyages at the age of 22 on the HMS Beagle • Was responsible for collecting specimens of fossils • He was aware of geological formations of land masses could explain fossils of snails from mountains • Studied his collections for the next 22 years

9. Darwin’s Key Observations • Fossils & fossil records show that organisms  simpler  complex • Overproduction of offspring • Limited supply of resources in an environment • Survival in a limited environment depends in part on features inherited from parents

10. Information that influenced Darwin • Charles Lyell geologist proposed that the Earth was very old and had slowly been changing for millions of years • Thomas Malthus economist  social problems as a result of the exponential growth of the human population • Artificial selection by breeders

11. Darwin Concluded • Descent with Modification • Natural Selection

12. Descent with Modification • All present day organisms are related through descent from unknown ancestors in the past. • These descendants of earliest organisms spread into different habitats adapted to diverse ways of life

13. Natural Selection • Individuals whose inherited characteristics adapt them best to their environment are most likely to survive and reproduce • Basic Mechanism of Evolution Natural Selection

14. Natural Selection • Occurs over a vast period of time • Individuals undergo selection, but do not evolvePopulations Evolve

15. Evidence of Evolution Section 16.4(M)

16. Evidence • Fossil Records • Comparative Anatomy • Embryonic Structures • DNA Homology

17. Fossils • Remains, traces or imprints of an organism preserved in the earth’s crust • Imprint • Mold • Cast • Petrified

18. Fossil Records • Fossils & the order in which they appear in layers of rocks • Fossil records show that animals & plants have appeared in a historical sequence, fossils found in rocks of different ages differ because life on Earth has changed through time

19. Each Layer represents a particular time period

20. Comparative Anatomy • The comparison of body structures in different species • Homologous Structures • Analogous Structures • Vestigial Structures Ex: common descent evident in anatomical similarities between species in the same taxonomic group

21. Homologous Structures • Structures that are similar & have been derived from a common ancestor, but have been adapted to different functions. ex: humans, cats, whales, bats all mammals Whales’ flipper does not have the same function as a bat’s wing

22. Homologous Structures

23. Analogous Structures • Body parts similar in function but have different structures Ex: wings of insects and birds

24. Vestigial Structures • Body parts reduced in size & appear to serve no function

25. Embryonic Structures • Embryos of closely related organisms often have similar stages in development

26. DNA Homology • Comparison of genes and proteins shows the relationships between species

27. Darwin’s Natural Selection : A Mechanism of Evolution

28. Natural Selection • Regional and timely • Adapts organisms to their local environment • Environmental factors vary from place to place & time to time adaptation in one situation may be useless in another Example: Biston betularia peppered moth

29. Peppered Moth • England  two varieties dark & light • 1850 almost all were light industrial revolution pollution tree trunks turned black light moths became easy prey • Dark survived & reproduced • End of century  almost all were dark

30. Biston betularia : peppered moth

31. Populations • A group of individuals of the same species living in the same place at the same time • Mainland animal species colonizes a chain of distant and isolated islands separate population. • These populations adapt to their local environments. • Over time, the isolated populations would become more and more different. • And over many generations, the populations could become different enough to be separate species.

32. Darwin’s Finches adapted to different food sources beak Structures

33. Differences among members of the same Species Variation

35. Adaptation • Inherited trait that Improves the Chances Of Survival & Reproduction • Structural mimicry organism copies the appearance of another species • Physiological changes in the organisms metabolic process penicillin drug resistant bacteria • Behavioral inherited behavior pattern that allows organism to survive

36. Monarch tastes bitter birds avoid them because they get sick Viceroy(extra black lines on wings) not bitter, look & act like Monarchs birds avoid them Adaptation- Mimicry

37. Adaptation:Camouflage • Protective adaptation that allows an organism to blend into its surroundings • The better the camouflage, the more likely it is for the organism to survive and reproduce

38. Adaptation: Camouflage

39. Artificial Selection • Selective breeding of domesticated plants and animals to produce offspring with genetic traits that humans value.

40. From Wild Mustard to our Table

41. Pesticides- Natural Selection in Action • Spraying crops kill insect pests favored the reproduction of insects with inherited resistance to the poisons