1. Biology-Unit 15 The Theory of Evolution

2. Evolution- The process of change over time Evolution- The process of change over time Theories of evolution assume that modern life forms have evolved (changed) from previously existing life forms. Theories of evolution assume that modern life forms have evolved (changed) from previously existing life forms.

3. 1. Evidence of Evolution Attempts to describe the mechanisms by which organisms change over time have formed the basis of the evolutionary theory. Attempts to describe the mechanisms by which organisms change over time have formed the basis of the evolutionary theory.

4. includes Evidence of Evolution Physical remains of organisms Common ancestral species Similar genes which is composed ofwhich indicateswhich implies The fossil record Geographic distribution of living species Homologous body structures Similarities in early development

5. Theories of Evolution Attempt to explain the diversity of life forms on earth Attempt to explain the diversity of life forms on earth Species diversity is actually based on the variety of ADAPTATIONS that different species may possess. Species diversity is actually based on the variety of ADAPTATIONS that different species may possess.

6. Adaptations - any structural, functional, or behavioral characteristic of a species that helps it to better survive in its environment Adaptations - any structural, functional, or behavioral characteristic of a species that helps it to better survive in its environment

7. Evidence of Evolution continued: A. Comparative Cytology -Organisms with very similar cell structures are usually considered to be more closely related.

8. B. Comparative Biochemistry -Analysis of enzymes and other proteins show that a great deal of similarity exists in organisms known to be related genetically.

9. C. Comparative Anatomy -Similar organisms can be shown to have limbs, internal organs, or other structures that are constructed similarly. -These structures are known as homologous structures.

10. D. Comparative Embryology -Reproductive processes in many different organisms reveal patterns of similarity among closely related organisms.

11. E. Geologic Record Fossils are commonly discovered in sedimentary rock layers. Water carries small rock particles to lakes and seas. Dead organisms are buried by layers of sediment, which forms new rock. The preserved remains may later be discovered and studied.

12. -The oldest fossils of the simplest life forms are generally found in the bottom layers. -While the younger fossils of more complex organisms are found in the top layers. -This is an example of relative dating.

13. Scientists can determine the age of fossils through radioactive dating. Sedimentary rocks form in horizontal layers When part of Earth’s crust is compressed, a bend in a rock forms, tilting the rock layers. As the surface erodes due to water, wind, waves, or glaciers, the older rock surface is exposed. New sediment is then deposited above the exposed older rock surface

14. F. Vestigial Structures: structures that do not seem to have any use (are also reduced in size) but are remains of structures that were probably functional in ancestral organisms. F. Vestigial Structures: structures that do not seem to have any use (are also reduced in size) but are remains of structures that were probably functional in ancestral organisms. Human examples: appendix, tailbone (coccyx), wisdom teeth, muscles that move the ears and nose Human examples: appendix, tailbone (coccyx), wisdom teeth, muscles that move the ears and nose Animal examples: whales and pythons have vestigial hind leg bones embedded in body wall Animal examples: whales and pythons have vestigial hind leg bones embedded in body wall

16. 2. Evolutionary Scientists: A. John Lamarck - Proposed the idea of evolution that included two main ideas: 1. Use and Disuse 1. Use and Disuse -The more a structure was needed, the more efficient it would become. -A structure that was not used would eventually disappear. 2. Transmission of Acquired Traits 2. Transmission of Acquired Traits -Traits developed as needed within the life of an organism.

17. An organism could pass these “acquired traits” to future generations through the process of reproduction. An organism could pass these “acquired traits” to future generations through the process of reproduction. The favorable “adaptations” would result in improved survival ability for the species. The favorable “adaptations” would result in improved survival ability for the species.

18. Lamarck’s theories were an important First Step in the development of a scientific view of the evolutionary process. Lamarck’s theories were an important First Step in the development of a scientific view of the evolutionary process. Later Experiments conducted by August Weismann and others failed to support Lamarck’s theories. Later Experiments conducted by August Weismann and others failed to support Lamarck’s theories.

19. C. Charles Darwin 19th Century naturalist from England 19th Century naturalist from England Devised a theory of evolution based on variation and natural selection. Devised a theory of evolution based on variation and natural selection. His theory forms the basis of the modern theory of evolution. His theory forms the basis of the modern theory of evolution.

20. Darwin’s Five Main Ideas: 1. Overproduction: species have a tendency to produce far more offspring than can possibly survive. 2. Competition: Within each species there is a struggle for survival that may eliminate many individuals before they reach reproductive maturity. 3. Variation: Darwin noticed variation within a species even though he could not explain. He knew nothing of genes.

21. 4. Survival of the Fittest: Animals better able to resist disease, withstand environmental conditions, and produce more offspring are more likely to survive. 5. Reproduction: Adaptive advantages of one generation may be passed on to the next, perpetuating them in the species. -This process is known as SPECIATION

22. Lamarck and Darwin compared Lamarck: Giraffes have long necks due to years of stretching to reach leaves on tall trees and the passing on of the long necks to offspring. Lamarck: Giraffes have long necks due to years of stretching to reach leaves on tall trees and the passing on of the long necks to offspring.

23. Lamarck and Darwin compared Darwin: Giraffes necks naturally vary in length. Those giraffes that possess a long neck were able to reach the leaves on the tall trees and survive. They then passed the gene for a long neck on to their offspring. Darwin: Giraffes necks naturally vary in length. Those giraffes that possess a long neck were able to reach the leaves on the tall trees and survive. They then passed the gene for a long neck on to their offspring.

24. D. Modern Evolutionary Theory Based primarily on Darwin’s theory of natural selection. Based primarily on Darwin’s theory of natural selection. In addition it incorporates the information available from the mechanisms of genetics. In addition it incorporates the information available from the mechanisms of genetics.

25. Five Main Ideas: 1. Production of variation -The reproductive process, meiosis and fertilization provide the method by which new combinations of both old and new traits may be “tried out” as new varieties within a species. -Mutation -An important process in providing the new genes that may lead to the production of new traits.

26. 2. Natural Selection Individuals that survive are “selected” and are assumed to be those best adapted to survive under the particular set of environmental conditions. Individuals that survive are “selected” and are assumed to be those best adapted to survive under the particular set of environmental conditions. Survivors tend to pass on the genes associated with their adaptive advantages. Survivors tend to pass on the genes associated with their adaptive advantages.

27. 3. Speciation When enough unique adaptations have been accumulated, in a species’ population, a new species arises from the parent species. When enough unique adaptations have been accumulated, in a species’ population, a new species arises from the parent species.

28. 4. Reproductive Isolation If two populations of species are geographically separated from each other for a sufficiently long period, they may change so greatly that even if geographic barriers are removed the two species will not be able to interbreed and reproduce. If two populations of species are geographically separated from each other for a sufficiently long period, they may change so greatly that even if geographic barriers are removed the two species will not be able to interbreed and reproduce.

29. or, another example… the “Founder Effect”

33. Time Frame for Evolution –Gradualism – Assumes that evolutionary change is slow and gradual, and continuous. -Supported by fossil records -Gradual change of organisms seen from each sedimentary layer

34. Punctuated Equilibrium – Assumes that species experienced long geographic periods of stability (millions of years or more) in which little or no change occurred. Punctuated Equilibrium – Assumes that species experienced long geographic periods of stability (millions of years or more) in which little or no change occurred.

35. This stability is “punctuated” by brief periods (a few thousand years) in which dramatic changes occur within a species. This stability is “punctuated” by brief periods (a few thousand years) in which dramatic changes occur within a species. Punctuated equilibrium is supported by fossil evidence in which little change is noted between most sedimentary layers but sudden “bursts” of change are evident in the fossils of a few sedimentary layers. Punctuated equilibrium is supported by fossil evidence in which little change is noted between most sedimentary layers but sudden “bursts” of change are evident in the fossils of a few sedimentary layers.

37. Heterotroph Hypothesis – how life began -Assumes that the first primitive life forms were not able to manufacture their own food. -Heterotrophs… (they had to eat)

38. Conditions of the Early Earth  Earth formed from clouds of cosmic dust and gas over 5 billion years ago.  After condensing to a semi-solid form, the earth required hundreds of millions of years to cool.

39.  During that period, the earth remained a hot environment filled with simple inorganic substances such as H2O, NH3, CH4, and H2 -These substances were mixed together in the primitive atmosphere and oceans to form a “HOT, THIN SOUP” in which random chemical reactions could occur at a rapid rate.

40. It is believed that these random chemical reactions led to the synthesis of simple sugars, lipids, and amino acids which then formed larger molecules. It is believed that these random chemical reactions led to the synthesis of simple sugars, lipids, and amino acids which then formed larger molecules.

41. The large molecules came together to form aggregates which are assumed to have formed the first simple cell-like organisms  “living”  able to reproduce. The large molecules came together to form aggregates which are assumed to have formed the first simple cell-like organisms  “living”  able to reproduce.

42. Stanley Miller Stanley Miller -Set up a controlled environment that simulated the hot, thin soup theory -He was able to make simple organic substances.

43. Mixture of gases simulating atmospheres of early Earth Spark simulating lightning storms Cold water cools chamber, causing droplets to form Liquid containing amino acids and other organic compounds Water vapor

44. -The natural by-products of living cells is CO2. -Organisms evolved to use the CO2 to make their own organic food. These were the first autotrophs! -These pioneer autotrophs produced free O2 which was released into the atmosphere. -This is the first photosynthesis!

45. Evolution of Life Early Earth was hot; atmosphere contained poisonous gases. Early Earth was hot; atmosphere contained poisonous gases. Earth cooled and oceans condensed. Earth cooled and oceans condensed. Simple organic molecules may have formed in the oceans. Simple organic molecules may have formed in the oceans. Small sequences of RNA may have formed and replicated. Small sequences of RNA may have formed and replicated.

46. First prokaryotes may have formed when RNA or DNA was enclosed in microspheres. First prokaryotes may have formed when RNA or DNA was enclosed in microspheres. Later prokaryotes were photosynthetic and produced oxygen. Later prokaryotes were photosynthetic and produced oxygen. An oxygenated atmosphere capped by the ozone layer protected Earth. An oxygenated atmosphere capped by the ozone layer protected Earth.

47. First eukaryotes may have been communities of prokaryotes. First eukaryotes may have been communities of prokaryotes. Multicellular eukaryotes evolved. Multicellular eukaryotes evolved. Sexual reproduction increased genetic variability, hastening evolution. Sexual reproduction increased genetic variability, hastening evolution.