Evolution:  A history and a process

Evolution: A history and a process PowerPoint PPT Presentation


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Charles Darwin= Father of the Theory of Evolution. Evolution= all of the changes that have transformed life over an immense timeTwo ideas persisted before DarwinSpecies are fixedEarth was less than 10,000 years old and also unchanging. Before Darwin

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Evolution: A history and a process

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1. Evolution: A history and a process

2. Charles Darwin= Father of the Theory of Evolution Evolution= all of the changes that have transformed life over an immense time Two ideas persisted before Darwin Species are fixed Earth was less than 10,000 years old and also unchanging

3. Before Darwin… 1700s Georges Buffon Study of fossils led him to believe Earth was older Observed specific fossils to be similar in some ways 1800s Jean Baptiste Lamarck Proposed that life evolves and that species are not permanent Process of adaptation

4. Adaptation= an inherited characteristic that improves an organism’s ability to survive and reproduce in a particular environment Ex: the muscular hind legs of a kangaroo

5. HMS Beagle Young Darwin

6. HMS Beagle 1831, 22 year old Darwin hitched a ride on a voyage around the world Wanted to study the geology, plants, and animals he encountered Observed and collected thousands of specimens from South America and maintained detailed journals of his observations Once he returned to England, he was convinced that species DO change From geologic observations he concluded that the Earth changed as well

7. HMS Beagle 1831-1836

8. Galapagos Islands

9. Galapagos Islands Relatively young volcanic islands near South America Most of the species observed were similar to, but different from, the plants and animals of the nearest land Each island in the chain had a few of its own species, different from the other islands

10. The Beagle was at sea for 5 years Darwin returned home to study all of the specimens he had sent to England He analyzed his specimens and was convinced that the Earth was ancient and that species change He constructed a scientific theory based on his own observations as well as the observations of others

11. Other scientists Charles Lyell- geologist Proposed the gradual and observable geologic processes Erosion, formation of mountains Darwin confirmed this when he witnessed an earthquake in Chile that moved a portion of land above sea level Thomas Malthus Proposed that a population’s growth is influenced by resources

12. Darwin left England as a young graduate He returned as a famous naturalist 1844 Darwin wrote a 200 paper essay that described his idea…but was not published 1858 Alfred Wallace came to the same conclusions as Darwin Within a month, some of Wallace’s, as well as Darwin’s ideas, were presented to the public jointly One year later, Darwin published his book The Origin of Species

14. Darwin made two points in his book: Species on Earth today descended from ancestral species These descendants spread into different habitats around the world and acquired adaptations for a diversity of life “Descent with modification” Ex: jackrabbit and showshoe hare Natural selection is the mechanism for evolution Natural selection is the process by which individuals with inherited characteristics that are ideal to the environment leave more offspring on average than do other individuals

15. Evolution leaves signs Evolution leaves evidence in The fossil record The diverse assortment of modern species Fossil record Fossils= preserved remains or markings left by organisms that lived in the past Found mostly in sedimentary rocks Sedimentation causes rock formation as particles accumulate in layers; any given stratum (layer) is older than the one above it, and younger than those below

16. Paleontologist= scientist who studies fossils Oldest fossil evidence of life consists of chemical traces in rocks that are 3.8 billion years old Found in Greenland Prokaryote fossils have been found and dated as 3.5 billion years old

17. Fossil example: Basilosaurus= an early whale found to have remnants of hind leg bones

18. Geographic Distribution Darwin observed the similarities and differences of organisms from different parts of the world Darwin proposed that organisms present today evolved from ancestral forms Geographic distribution can be used as a clue for the evolution of species Biogeography is the study of the distribution of plants and animals throughout the world The world’s six biogeographical regions have their own distinct mix of living things Continental drift refers to the changing positions of the continents over time

19. Two hundred twenty-five million years ago, all the present land masses belonged to one continent (Pangaea) The distribution of plants and animals is consistent with continental drift Organisms, such as certain seed plant groups or reptiles, are widely distributed throughout the world Other groups, such as mammals that arose after the continents broke up, have great differences in species on different continents

21. Clues to evolutionary history Similarities in Structure Example: mammal forelimb Homologous structures= similar structures in species haring a common ancestor

22. “Descent with modification” Proposed by Darwin Modification of structures to take on new functions

23. Vestigial structures= remnants of structures that may have served an important function in an ancestral species, but have no clear function in some of the modern descendents Often smaller in size

24. Ballene whale

25. Developmental similarities Embryos of closely related species have similar stages of developmentf Bones of the skeleton form in a common pattern

27. Molecular biology Comparison of DNA sequences between species If the two species’ sequences match closely then it is thought that the two species are related to a common ancestor If the two species’ sequences have many differences they probably do not share common ancestry

28. Comparison of Hemoglobin

29. Darwin knew the key to understanding evolution was to explain how adaptations come about Population= a group of individuals of the same species living in the same area at the same time Example: 13 islands make up the Galapagos chain, each has its own unique species of the Galapagos finch Each species is very similar to one mainland finch species Beak shape is key characteristic How did their beaks get this way?

31. Darwin’s basis for his theory of natural selection All species produce excess offspring In nature there are limited resources Leads to a struggle of existence….competition Usually only a small percentage of offspring will survive Variation among the individuals in a population Variation= differences among members of the same species Much of this is heritible From these two ideas, Darwin developed his idea of natural selection

32. Summary of Natural Selection

34. Artificial selection= selective breeding of domesticated plants and animals to produce offspring with genetic traits that humans value Munchkin cats

35. Artificial Selection

36. In contrast, natural selection favors traits that are beneficial to the organisms in their environment The environment does the “selective breeding” Resulting in evolutionary adaptation

37. Natural Selection of Flies

38. Experimental evidence can demonstrate natural selection at work; Endler’s experiments with guppies: In predator-free environments there’s an increase in number of male guppies with large and brightly colored tails, because they are favored by females; but when predators are reintroduced the number of male guppies with smaller, less conspicuous tails increases again because the flashier fish are eaten by predators.

39. Darwin could not explain how variations passed from one individual to the next Gregor Mendel to the rescue!! Microevolution…a change in a population’s gene pool Gene pool= consists of all the alleles in all the individuals that make up a population Where genetic variation is stored Example: Wild mustangs What leads to genetic variation? Mutations Sexual recombination

40. Natural selection is not random Why? The environment favors combinations of genes that contribute to survival and reproductive success Some alleles may become more common in a gene pool than others Frequency of alleles= how often certain alleles occur in the gene pool Usually expressed as a percentage Microevolution Blending of Mendel’s and Darwin’s theories to look at evolution based on genetics Generation to generation changes (smallest scale)

41. Microevolution

42. In contrast to microevolution, populations that do not have changes occurring within their gene pool are not evolving Hardy-Weinberg equilibrium= condition that occurs when the frequency of alleles in a particular gene pool remain constant over time Rarely do populations exist in Hardy-Weinberg equilibrium

43. What causes gene pools to change? Genetic drift= a change in the gene pool of a population due to chance All populations are subject to genetic drift Bottleneck effect…a drastic reduction in the size of a population Usually by natural disaster…and only a few remaining individuals are left to start a new population Ex: cheetah population in Africa Founder effect…genetic drift in a new colony When a few individuals leave the original population and start a new population Natural selection We know what this is by now…right??!!!

44. Genetic Drift

45. Other mechanisms that play a role in changes in gene pool Gene flow= movement of alleles between populations Occurs when fertile individuals mate with individuals from other populations Ex: a wind storm might blow pollen from a population of only red flowers to a population consisting of only white flowers Reduces the genetic differences between populations Can eventually mix the two populations

46. Mutation= a change in an organism’s DNA If carried by a gamete the mutation can enter the gene pool Ex: albino deer

47. Fitness = the contribution that an individual makes to the gene pool of the next generation compared to the contributions of other individuals So what does “survival of the fittest” mean?

48. How does 1 species become 2 species? Species = a population or group of populations whose members can interbreed and produce fertile offspring Speciation = the formation of a new species Reproductive isolation = when populations become reproductively isolated, they can evolve into two separate species Interbreeding links members of a species genetically If the members stop interbreeding, then the gene pool can split

49. 3 ways Reproductive Isolation can develop Behavioral isolation = when two populations develop differences in courtship rituals or other behaviors that prevent them from interbreeding Eastern and Western Meadowlarks don’t respond to eachothers songs Eastern on left and Western on rightEastern on left and Western on right

50. 3 ways the reproductive isolation can develop Geographic isolation = when two populations are separated by geographical barriers (rivers, mountains, bodies of water) Grand Canyon isolated a small population of Albert’s squirrel on the northern rim Separate gene pools formed, natural selection and genetic drift worked separately on each group which led to the formation of a distinct subspecies called the Kaibab Squirrel Albert’s Squirrel on left and Kaibab Squirrel on rightAlbert’s Squirrel on left and Kaibab Squirrel on right

51. 3 ways the reproductive isolation can develop Temporal isolation = when two or more species reproduce at different times of the day, season, or year Wood frog on left and leopard frog on rightWood frog on left and leopard frog on right

52. There are 13 billion known species of organisms This is only 5% of all organisms that ever lived!!!!! New organisms are still being found and identified Species of Organisms

53. What is Classification? Classification = is the arrangement of organisms into orderly groups based on their similarities Classification is also known as taxonomy Benefits: Accurately and uniformly names organisms Prevents misnomers Ex: jellyfish, seahorse

54. Confusion in Using Different Languages for Names

55. Latin Names are Understood by all Taxonomists

56. Carolus Linnaeus 1707 – 1778 18th century taxonomist – “Father of Taxonomy” Classified organisms by their structure Developed naming system still used today

57. Standardized Naming Two-word name (Genus & species) = Binomial Nomenclature Latin or Greek Genus is capitalized, species is not Italicized in print Underlined if handwritten

58. Binomial Nomenclature

59. Rules for Naming Organisms The International Code for Binomial Nomenclature contains the rules for naming organisms All names must be approved by International Naming Congresses (International Zoological Congress) This prevents duplicated names

60. Classification Groups Taxon ( taxa-plural) is a category into which related organisms are placed There is a hierarchy of groups (taxa) from broadest to most specific Domain, Kingdom, Phylum, Class, Order, Family, Genus, species

61. Domain Kingdom Phylum Class Order Family Genus Species Hierarchy – Taxonomic Groups Genus and species are the two names used to identify specific organisms in the binomial system of classification. Division is used for plants.Genus and species are the two names used to identify specific organisms in the binomial system of classification. Division is used for plants.

62. 62 Dumb King Phillip Came Over For Gooseberry Soup!

63. 63

64. Broadest, most inclusive taxon Three domains Archaea and Eubacteria are unicellular prokaryotes (no nucleus or membrane-bound organelles) Eukarya are more complex and have a nucleus and membrane-bound organelles Domains

65. Cladogram Diagram showing how organisms are related based on shared, derived characteristics such as feathers, hair, or scales

66. 66 Primate Cladogram

67. Dichotomous Keying Used to identify organisms Characteristics given in pairs Read both characteristics and either go to another set of characteristics OR identify the organism

68. Dichotomous Key 1a Tentacles present – Go to 2 1b Tentacles absent – Go to 3 2a Eight Tentacles – Octopus 2b More than 8 tentacles – 3 3a Tentacles hang down – go to 4 3b Tentacles upright–Sea Anemone 4a Balloon-shaped body–Jellyfish 4b Body NOT balloon-shaped - 5

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