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AP Biology

AP Biology. Absent students/make-up Chapter 22- go over quickly Lab results/complete and turn in. Evolution . Evolution- change over time OR descent with modification Proposal that Earth’s species are descendants of ancestral species that were very different from those alive today.

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AP Biology

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  1. AP Biology Absent students/make-up Chapter 22- go over quickly Lab results/complete and turn in

  2. Evolution • Evolution- change over time OR descent with modification • Proposal that Earth’s species are descendants of ancestral species that were very different from those alive today. Pattern- data driven based on observations of the natural world. Process- mechanisms produce diversity of living things.

  3. How Did We Come to Evolution? • Aristotle- 384-322 A.D.- opposed evolution, scale of nature everything is fixed, from simplicity to complexity. • Linnaeus (1707-1778) – developed naming system. Grouped based on similar characteristics into general categories, from the pattern of their creation. • Cuvier (1769-1832) – paleontology, thought catastrophism- boundaries due to catastrophes that destroyed a species

  4. Hutton (1726-1797) – Proposed gradualism- said that geologic changes took place through the cumulative effect of slow continuous change • Lyell (1797-1875) - Uniformatarianism which stated that things don’t change over time • Lamarck (1744-1829) – Believed in several lines of descent called it inheritance of acquired characteristics.

  5. Darwin (1840’s) – proposed the idea of natural selection in which individuals with certain inherited characteristics leave more offspring than individuals with other characteristics. • He called these ADAPTATIONS – characteristics of organisms that enhance their survival and reproduction in a specific environment. Darwin never coined the term evolution rather: “descent with modification”

  6. 3 Major Contributions from Darwin • Organisms are related through descent from a common ancestor that lived in the past – that explains the unity of life. • These descendants have accumulated diverse modifications, or adaptations, that allow them to survive and reproduce, • Over long periods of time this descent with modification has led to the rich diversity we have today.

  7. Darwin’s proposed mechanisms • Artificial selection Humans have modified a variety of domesticated plants and animals over many generations by selecting individuals with the desired traits as breeding stock • Natural selection • Organisms have heritable traits that enable them to reproduce at a higher rate • Overtime these traits increase a match between organism and environment. • If the environment changes or if individuals move to a new environment, a new species could result in the process.

  8. Important points • Individuals do not evolve – populations do. • Natural selection can act only on heritable traits. • Environmental factors vary from place to place and from time to time.

  9. Sounds Great- Where’s the Data? 4 major types of data: • Direct observation • Fossil record • Homology • Biogeography

  10. 1. Direct Observation • Page 461 – Case Study • Page 462 – Case Study

  11. 2. Homology

  12. Homology • Homologous structures – same structure different function • Vestigial structures – remnants of features that served a function in the organism’s ancestors • Molecular similarities • Embryology

  13. Tree • Evolutionary tree- diagram that reflection evolutional relationships among groups of organisms

  14. Different Cause of Resemblance • Convergent evolution – independent evolution of similar features in different lineages. • Analogous- different structure, same function as a result of convergent evolution

  15. 3. Fossil record • Fossil record is NOT complete • Can be used as indirect or direct evidence in some situations.

  16. 4. Biogeography • This relates to the geographic distribution of species. Influenced by many factors • Continental drift • Endemic- species on island are found nowhere else in world.

  17. AP Biology Quiz today!!!

  18. Quiz • Describe the difference between direct and indirect evidence supporting evolution. • Explain the difference between homologous and analogous structures. • Explain natural selection and how natural selection was developed.

  19. Is the finch evolving?

  20. Smallest unit of Evolution • Individuals DO NOT evolve – populations do • Natural selection acts on individuals meaning traits affect its survival and reproductive success • The effects of natural selection are only apparent in changes within a population over time

  21. Microevolution – change in allele frequencies in a population over time • What affects change in allele frequency? 1. Natural selection 2. Genetic drift – events that alter frequency 3. Gene flow – transfer of alleles between populations

  22. Genetic variation • Differences among individuals in the composition of their genes or other DNA segments. • Not all phenotypic variation is heritable only

  23. Darwin and Mendel • Discrete characters – determined by a single locus • Quantitative characters- vary along a continum

  24. Genetic Variation contd. • Variation occurs between populations • Geographic variations- differences in genetic composition of geographically separate populations

  25. Mutation • New genes and new alleles originate by mutation • Sexual reproduction results in genetic variation as existing alleles and genes are arranged in new ways • New alleles arise by mutation

  26. Mutation rates • Some organisms mutate faster than others • Compare: sexual reproduction to HIV • HIV- no DNA, RNA mutates faster (that is why a single treatment is not effective) • Sexual reproduction – crossing over, independent assortment, fertilization

  27. Hardy-Weinberg • Population – a group of individuals of the same species that live in the same area and interbreed to produce fertile offspring • Gene pool- the total alleles for the individuals in a population

  28. Hardy-Weinberg • This principle states that the frequencies of alleles and genotypes in a population will remain constant from generation to generation if these conditions are met: • NO mutation • Random mating • No natural selection • Extremely large population size (genetic drift) • NO gene flow (immigration/emigration)

  29. Hardy-Weinberg p + q = 1 p - the allelic frequency of P q - the allelic frequency of p

  30. Hardy-Weinberg ( p + q )( p + q ) = 1 Or p2 + 2pq + q2 = 1 p2 – frequency of PP 2pq – frequency of Pp q2- frequency of pp

  31. H-W 400 total flowers in the population. 100 white flowers are homozygous recessive genotype pp. • Determine the pp of the population? Means: 100/400 = ¼ = _____ • How can we calculate q and p? q2 = ______ p + q = 1 q = p = 1 - q q = ______ p = 1 – 0.5 = 0.5

  32. H-W 500 wildflowers in the population 1000 total genes CRCR – red (320) CWCW – white (20) CR CW - pink (160) Lets find the allelic frequencies CR 1. Find the # of CR in the pink flowers ____ 2. Find the # of CR in the red flowers ___________ 3. CR frequency = ______________________

  33. H-W 500 wildflowers in the population 1000 total genes CRCR – red (320) CWCW – white (20) CR CW - pink (160) Find CW frequency • Find CW in the pink flowers _______ • Find CW in the white flowers ______ • Allele frequency ___________

  34. Changes to H-W can alter allele frequencies in population • Nonradom mating- can affect the frequencies but usually have no effect on allele frequencies in the gene pool. • Natural selection – Alleles are passed on to the next generation in frequencies different from their relative frequencies in the present population.

  35. Changes to H-W can alter allele frequencies in population • Genetic drift – chance fluctuations in allele frequencies in small populations • Large populations allele frequencies do not change from generation to generation by chance alone. • The smaller the population the greater chance of deviation • Small populations fall into 2 groups • Founder effect - • Bottleneck effect

  36. Founder’s effect When a smaller group establishes a new population whose gene pool differs from the source population • Bottleneck effect Sudden change in environment, a severe drop in population

  37. Gene flow – the transfer of alleles among populations due to the migration of fertile individuals or gametes

  38. Three modes of Selection • Directional selection – • Stabilizing selection – • Disruptive selection -

  39. AP Biology • If you didn’t turn in your quiz last class please do so now • H-W quiz later in class period • Chapter 24-25 today • Study guides/lab finish

  40. Sexual selection • Sexual dimorphism – differences between sexes in secondary sexual characteristics (size, coloration, ornamentation) • Intrasexual selection – direct competition among individuals of one sex for mates of the opposite sex (battles/patrol/rituals) • Intersexual selection – mate choice, when memebers of 1 sex (usually female) select mates.

  41. Heterozygote Advantage • Determined at genotype level • Heterozygote advantage maintains genetic diversity at the human gene • Sickle cell- • SS – normal rbc’s • Ss – Protected against malaria • ss – sickle cell

  42. Chapter 24 • Speciation – process by which one species splits into two or more species. • Speciation concept EMPHASIZES reproductive isolation • Reproductive isolation – biological barriers that prevent members of two species

  43. Reproductive isolation • Prezygotic barriers – fertilization block • Postzygotic barriers – fertilization occurs but may prevent hybrid zygote from developing into a viable, fertile adult

  44. Prezygotic • Habitat isolation – different habitats even if in same geographic area • Behavioral isolation – courtship behavior to attract mate • Temporal isolation – breed at different times • Mechanical – anatomically incompatible • Gametic– gametes do not form a zygote

  45. Postzygotic • Reduced hybrid viability – genetic incompatibility, may abort or produce frail offspring • Reduced hybrid fertility – even if hybrid is vigorous, hybrid may be infertile • Hybrid breakdown – first-generation is viable and fertile, but next generation is feeble or sterile

  46. Speciation • Allopatric speciation – geographic separation of population restricts gene flow • Geographic barriers (mountain ranges, glaciers, land bridges, canyons etc)

  47. Speciation • Sympatric speciation – speciation occurs between populations that live in the same geographic area. • Note** reproductive barriers must exist for this to occur. • Example: polyploidy, habitat differentiation, sexual selection,

  48. Speciation • Polyploidy – results in extra sets of chromosomes • Autopolyploid – individual that has more than two chromosome sets all derived from a single species • Allopolyploid – when two different polyploids mate

  49. How long does this take? • Gradulaism – slow steady continuous change • Punctuated equilibrium – rapid change followed by stasis

  50. AP Biology • Quiz today last H-W quiz  • Please turn in pGLO labs if you haven’t yet • Email me H-W modeling lab

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