Evolution Notes

1. Evolution Notes Unit 6

2. The History of Life Chapter 14 14.1 Fossil Evidence of Change Land Environments • Earth formed about 4.6 billion years ago.

3. The History of Life Chapter 14 14.1 Fossil Evidence of Change Clues in Rocks • A fossil is any preserved evidence of an organism. • Why are there gaps in the fossil record? Most organisms decompose before they have a chance to become fossilized.

4. The History of Life Chapter 14 14.1 Fossil Evidence of Change

5. The History of Life Chapter 14 14.1 Fossil Evidence of Change Fossil Formation • Nearly all fossils are formed in sedimentary rock.

6. The History of Life Chapter 14 14.1 Fossil Evidence of Change Dating fossils • Relative dating is a method used to determine the age of rocks by comparing them with those in other layers.

7. The History of Life • Radioactive isotopes that can be used for radiometric dating are found only in igneous or metamorphic rocks. Chapter 14 14.1 Fossil Evidence of Change Radiometric Dating • Uses the decay of radioactive isotopes to measure the age of a rock

8. The History of Life Chapter 14 14.1 Fossil Evidence of Change The Geologic Time Scale • The geological time scale is a model that expresses the major geological and biological events in Earth’s history.

9. The History of Life Chapter 14 14.1 Fossil Evidence of Change The Paleozoic Era • The ancestors of most major animal groups diversified in what scientists call the Cambrian explosion.

10. The History of Life Chapter 14 14.1 Fossil Evidence of Change • A mass extinction ended the Paleozoic era at the end of the Permian period. • Between 60 and 75 percent of the species alive went extinct.

11. The History of Life Chapter 14 14.1 Fossil Evidence of Change • Platetectonics describes the movement of several large plates that make up the surface of Earth.

12. Terminology to know! • Hypothesis An “If…then” statement or proposal of an outcome of an experiment. (Ex. If I study, then I will pass the test.) • Theory A hypothesis that has withstood extensive testing by a variety of methods, and in which a higher degree of certainty may be placed (Ex. Theory of Evolution) • Law Considered universal and invariable facts of the physical world (Ex. Law of Gravity)

13. The History of Life Chapter 14 14.2 The Origin of Life Origins: Early Ideas • Spontaneous generation is the idea that life arises from nonlife. • Francesco Redi, an Italian scientist, tested the idea that flies arose spontaneously from rotting meat.

14. The History of Life Chapter 14 14.2 The Origin of Life • Thetheory of biogenesis states that only living organisms can produce other living organisms. • Louis Pasteur designed an experiment to show that biogenesis was true even for microorganisms.

15. The History of Life Chapter 14 14.2 The Origin of Life Cellular Evolution • Scientists hypothesize that the first cells were prokaryotes. • These would compare to our modern day bacteria

16. The History of Life Chapter 14 14.2 The Origin of Life The Endosymbiotic Theory • Eukaryotic cells arose from communities formed by prokaryotic cells. • This theory explains the origin of chloroplasts and mitochondria.

17. The History of Life Chapter 14 14.2 The Origin of Life

18. Evolution Chapter 15 15.1 Darwin’s Theory of Natural Selection Darwin on the HMS Beagle • His job was to collect biological and geological specimens during the ship’s travel.

19. What can explain the large extent of biological diversity on earth? • Evolution – change over time • How life has changed over time

20. Evolution Chapter 15 15.1 Darwin’s Theory of Natural Selection The Galápagos Islands • Darwin began to collect mockingbirds, finches, & other animals on the 4 islands. • He noticed that the different islands seemed to have their own, slightly different varieties of animals.

21. The Galapagos Islands • West of South America • Group of islands each with different climates • Tortoises varied from island to island in neck length and shell shape • Finches varied in beak shape • Characteristics of plants and animals varied from island to island

22. Evolution Chapter 15 15.1 Darwin’s Theory of Natural Selection

23. Evolution Chapter 15 15.1 Darwin’s Theory of Natural Selection Darwin Continued His Studies • Darwin inferred that if humans could change species by artificial selection, then perhaps the same process could work in nature.

24. Evolution Chapter 15 15.1 Darwin’s Theory of Natural Selection Natural Selection • Individuals in a population show variations. • Variations can be inherited. • Organisms have more offspring than can survive with available resources. • Variations that increase reproductive success will have a greater chance of being passed on. • “Survival of the Fittest”

25. Evolution Chapter 15 15.1 Darwin’s Theory of Natural Selection The Origin of Species • Darwin published On the Origin of Species by Means of Natural Selectionin 1859. • It is a means of explaining how evolution works.

26. Lamarck’s Theory • Pre-Darwin scientist • Inheritance of acquired traits • Organs used a lot could grow and change shape • Organs not used would shrivel and disappear • Theory was incorrect but significant because he was the first scientist to recognize that organisms had changed over time

27. Evolution Chapter 15 15.2 Evidence of Evolution Support for Evolution • The fossil record • Provide a record of species that lived long ago. • Show that ancient species share similarities with species that now live. Armadillo Glyptodont

28. Evolution Chapter 15 15.2 Evidence of Evolution Support for Evolution • Geographic Distribution • The distribution of plants and animals that Darwin saw first suggested evolution to Darwin. Rabbit Mara

29. Evolution Chapter 15 15.2 Evidence of Evolution • Derived traits are newly evolved features, such as feathers, that do not appear in the fossils of common ancestors. • Ancestral traits are more primitive features, such as teeth and tails, that do appear in ancestral forms.

30. Homologous Structures • Anatomically similar structures inherited from a common ancestor

31. Evolution • Same function but different structure • NOT inherited from common ancestor. Chapter 15 Analogous Structures

32. Evolution • Evolutionary theory predicts that features of ancestors that no longer have a function for that species will become smaller over time until they are lost. Chapter 15 15.2 Evidence of Evolution Vestigial Structures • Structures that are the reduced forms of functional structures in other organisms.

33. Evolution Chapter 15 15.2 Evidence of Evolution • Comparisons of the similarities in organisms are seen in comparative anatomy and in the fossil record. • Organisms with closely related morphological features have more closely related molecular features.

34. More Terms • Fitness – ability of an individual to survive and reproduce in a specific environment • Adaptation – inherited characteristic that increases an organism’s chance of survival • Can be physical traits as well as behavioral traits

35. Evolution Chapter 15 15.2 Evidence of Evolution Camouflage • Allows organisms to become almost invisible to predators Leafy sea dragon

36. Evolution Chapter 15 15.2 Evidence of Evolution Mimicry • One species evolves to resemble another species. California kingsnake Western coral snake

37. Evolution Chapter 15 15.3 Shaping Evolutionary Theory Natural Selection • Acts to select the individuals that are best adapted for survival and reproduction

38. Evolution Chapter 15 15.3 Shaping Evolutionary Theory • Stabilizing selectionoperates to eliminate extreme expressions of a traitwhen the average expression leads to higher fitness. • Ex. Siberian Husky

39. Evolution Chapter 15 15.3 Shaping Evolutionary Theory • Directional selectionmakes an organism more fit. • Favors the extremes • Ex. Greyhound Dog

40. Evolution Chapter 15 15.3 Shaping Evolutionary Theory • Disruptive selectionis a process that splits a population into two groups. • Ex. Black, White, & Gray Rabbits

41. Evolution Chapter 15 15.3 Shaping Evolutionary Theory Mechanisms of Evolution • Population genetics • Hardy-Weinberg principle states that when allelic frequencies remain constant, a population is in genetic equilibrium.

42. Evolution Chapter 15 15.3 Shaping Evolutionary Theory Write these down & know these!

43. Evolution Chapter 15 15.3 Shaping Evolutionary Theory Genetic Drift • A change in the allelic frequencies in a population that is due to chance and random mating • In smaller populations, the effects of genetic drift become more pronounced, and the chance of losing an allele becomes greater. • Marble Example

44. Evolution Chapter 15 15.3 Shaping Evolutionary Theory Nonrandom Mating • Promotes inbreeding & could lead to a change in allelic proportions favoring individuals that are homozygous for particular traits

45. Evolution Chapter 15 15.3 Shaping Evolutionary Theory Founder Effect • The loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population Island 1 Island 2 Mainland Island 3

46. Evolution 15.3 Shaping Evolutionary Theory Bottleneck • a significant percentage of a population or species is killed or otherwise prevented from reproducing and can rebound later • Often caused by a natural disaster

47. What is a gene pool? • Gene pool – combined genetic info of all members of a population • Contains two of more alleles (genes) for the same trait • Allele frequency – number of times an allele occurs in a gene pool compared to the number of times another allele occurs (expressed in percents)

48. Relative Frequencies of Alleles Section 16-1 allele for brown fur allele for black fur Sample Population 48% heterozygous black Frequency of Alleles 16% homozygous black 36% homozygous brown

49. Gene Flow • Genes entering or leaving a population • AKA. Migration • Emigration Genes LEAVING a population • Immigration INCOMING genes in a population

50. What are sources for genetic variation? • Mutations – random change in the DNA, may cause evolution in future populations • Genetic shuffling – occurs in meiosis when gametes are formed