Evolution The Nature of Change - PowerPoint Presentation

1. EvolutionThe Nature of Changeand Variation

2. What is Evolution?Simply… a change in living organisms over time

3. Why study evolution?Evolutionary concepts provide a solid foundation to much of modern biology - you can’t fully understand current trends in biology or you will have difficulty understanding evolution

4. Evolution involves inheritable changes in organisms through time is fundamental to biology and paleontologyPaleontology is the study of life history as revealed by fossilsEvolution is a unifying theory like plate tectonic theorythat explains an otherwise encyclopedic collection of factsEvolution provides a framework for discussion of life history Why Study Evolution?

5. Many people have a poor understanding of the theory of evolution they hold a number of misconceptions, which include:evolution proceeds or advances strictly by chancenothing less than fully developed structures such as eyes are of any usethere are no transitional fossils so-called missing linksconnecting ancestors and descendantshumans evolved from monkeys so monkeys should no longer existMisconceptions about Evolution

6. Evolutionary theory is the framework tying together all of biology. It explains similarities and differences between organisms, fossils, biogeography, drug resistance, relative virulence of parasites, and much more. What is a scientific “theory”?Theories are structures of ideas that explain and interpret facts. 

7. In the early days...Prior to 1760 -people believed organisms were fixed- that is they didn’t change1744-1829 – Jean Baptiste Lamarck Evolution through the inheritance of acquired characteristicsTraits acquired during an organism’s life could be passed on to their offspringGiraffes long necks explained by repeated stretchinghypothesis rejected

8. According to Lamarck’s theory of inheritance of acquired characteristics Lamarck’s Giraffesancestral short-necked giraffes stretched their necks to reach leaves high on trees.Their offspring were born with longer necks

9. Lamark’s theory was not totally disproved until decades later with the discovery that genes cannot be altered by any effort by an organism during its lifetimeLamarck’s Theory

10. Basic Types of EvolutionMacroevolution = speciation – the formation of new species. The change in species over long periods of time. Not immediately observable.Microevolution = changes in genes/alleles within a population. Can be observed in a human lifetime.

11. Macroevolution/Microevolution Macroevolution1. Large-scale changes in gene frequencies 2. Occurs over a longer (geological) time period 3. Occurs at or above the level of species in separated gene pools4. Consists of extended microevolution Microevolution1. Small-scale changes in gene frequencies2. Occurs over a few generations 3. Occurs within a species or population in same gene pool4. Refers to smaller evolutionary changes

12. Macroevolution/Microevolution Macroevolution5. Has not been directly observed6. Evidence based on remnants of the past 7. More controversial 8. Example: Birds from reptiles Microevolution5. Observable6. Evidence produced by experimentation7. Less controversial 8. Example: Bacterial resistance to antibiotics

13. If all existing organisms descended with modification from ancestors that lived during the past, all life forms should have fundamental similarities:all living things consist mainly of carbon, nitrogen hydrogen and oxygentheir chromosomes consist of DNAall cells synthesize proteins in essentially the same wayBiological Evidence Supporting Evolution

14. Biochemistry provides evidence for evolutionary relationshipsBlood proteins are similar among all mammals Humans’ blood chemistry is relatedmost closely to the great apesthen to Old World monkeysthen New World monkeysthen lower primates such as lemursBiochemical test support the idea that birds descended from reptilesa conclusion supported by evidence in the fossil recordEvolutionary Relationships

15. Organisms in all populations possess heritable variations such assize, speed, agility, visual acuity, digestive enzymes, color, and so forthSome variations are more favorable than otherssome have a competitive edge in acquiring resources and/or avoiding predatorsNot all young survive to reproductive maturityThose with favorable variations are more likely to survive and pass on their favorable variationsNatural Selection—Main Points

16. In common nonscientific usage, natural selection is sometimes expressed as “survival of the fittest”“Survival of the Fittest”This is misleading because natural selection is not simply a matter of survival - but involves differential rates of survival and reproduction

17. One misconception about natural selection is that among animalsonly the biggest, strongest, and fastest are likely to surviveThese characteristics might provide an advantagebut natural selection may favor the smallest if resources are limitedthe most easily concealedthose that adapt most readily to a new food sourcethose having the ability to detoxify some substanceand so on...Not only Biggest, Strongest, Fastest

18. Darwin observed Galapagos finches showing variations in beak shape and size from island to island. He reasoned these differences made the finches better adapted to the food in their particular local environment.Each finch population had developed beaks which were suitable for that particular environment.

19. Phylogenic TreePhylogenic trees trace patterns of shared ancestry between lineages. Each lineage has a part of its history that is unique to it alone and parts that are shared with other lineages.

20. Natural selection works on existing variation in a populationIt could not account for the origin of variationsCritics reasoned that should a variant trait arise, it would blend with other traits and would be lostThe answer to these criticisms existed even then in the work of Gregor Mendel, but remained obscure until 1900Limits of Natural Selection

21. Evidence of ChangeFossil Record EmbryologyMolecular Biology-Amino Acids, Nucleotides, DNA sequencing, mitochondrial DNAAnatomy commonalitiesVarious adaptations

22. EVIDENCE OF EVOLUTIONSTRUCTURAL ADAPTATIONSMIMICRYCAMOUFLAGEhttp://evolution.berkeley.edu/evolibrary/home.phphttp://science.howstuffworks.com/animal-camouflage2.htm

23. Fossil RecordFossils are a major source of information about changes in life during the distant pastIn general, fossils show that life has increased in diversity and complexity over time

24. Fossil RecordInterpretation of the distribution of fossils in the rock initially based on the principle of superposition - in undisturbed rock layers, older fossils will be found lower in the rock than younger fossils -radiometric dating confirms thisIn general older life forms tend to be less complexPeriods of diversity are interrupted by mass extinctions – followed by new life formsFossil Record is incomplete – estimated only 1 in 10,000 extinct species are represented – Why?

25. EmbryologyAll vertebrate embryos have Gill slits on sides of the throatPost anal tail The fact that organisms without gills, or tails have them as embryos is taken as evidence of a common ancestry with organisms that had bothWhich is the fish, rabbit, human, chicken, tortoise?

26.

27. Comparative AnatomySimilarities in structure between organisms was used to determine evolutionary relationships

28. Other Proof From AnatomyVestigial structures – structures that are greatly reduced with little or no function - they are thought to be left over from ancestorsPelvis and leg bones in snakesReduced toe in horseAppendix in humanCoccyx (tail bone) in humans

29. Vestigial Structures

30. Comparative AnatomyAnalogous StructuresSimilar function but different structure - Insect’s wing, Bird’s wing and Bats wings – all allow flight, but are structurally differentEyes of Mollusks and Vertebrates – both allow sight, but are different in structure

31. Comparative AnatomyHomologous StructuresHave a similar structure but different functionThe forelimbs of vertebrate animals all have the same structural design, but they have different functionsThis similarity of structure shows a common ancestry

32. Homologous StructuresAnalogous structures

33. Molecular Biology Comparisons of the sequences of amino acids in proteins or nucleotides in DNA can show the relationships between organisms the number of differences in the sequences of amino acids or nucleotides indicates how closely related two organisms are

34. Hemoglobin ComparisonSpecies AA differences from humansGorilla 1Rhesus Monkey 8Mouse 27Chicken 45Frog 67

35. Hemoglobin Cladogram

36. Cladogram (family tree) created from a fossil record

37. Bird Evolutionary TreePhylogenic Trees and Cladograms are also created using comparative DNA sequences. If the DNA is very similar to each other, it means they share a fairly recent common ancestor.

38.

39.

40. During his voyage, Darwin observed fossil mammals in South America that are similar to yet different from present day animals.Ex. Llamas, sloths, and armadillos. The finches and giant tortoises lining on the Galapagos Islands vary from South America, even though they differ in subtle ways.These observations convinced Darwin that organisms descended with modification from ancestors that lived during the past which was his central claim of the theory of evolution. Darwin Developed the Theory

41. Charles DarwinAlfred WallaceDescent with modification.The Origin of Species. 1859Species were not created in their present forms but evolved from an ancestral species.Natural selection, the mechanism by which change occurs (Explanation of how evolution occurs).

42. Darwin and Alfred Russel Wallace (1823-1913) read John Malthus’ book and came to the same conclusion, that a natural process was selecting only a few individuals for survivalDarwin’s and Wallace’s ideacalled natural selectionwas presented simultaneously in 1859Darwin and Wallace