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2. Evol (Darwin) New

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  • Lamarck noted how well-adapted organisms were to their environments, and believed that fossils could be understood as less perfect forms which had perished in the struggle for increasing perfection. He explained adaptation as a result of change caused by environmental pressures.
  • The origin of the fauna of the Galapagos, 900 km west of the South American coast, especially puzzled Darwin. On further study after his voyage, Darwin noted that while most of the animal species on the Galapagos lived nowhere else, they resembled species living on the South American mainland. It seemed that the islands had been colonized by plants and animals from the mainland that had then diversified on the different islands
  • Darwin noted that the plants and animals of South America were very distinct from those of Europe. Organisms from temperate regions of South America were more similar to those from the tropics of South America than to those from temperate regions of Europe. Further, South American fossils more closely resembled modern species from that continent than those from Europe.
  • Figure: 14-3 Title: Fossils of extinct organisms Caption: Fossils provide strong support for the idea that today's organisms were not created all at once, but arose over time by the process of evolution. If all species were created simultaneously, we would not expect (a) trilobites to be found in older rock layers than (b) seed ferns, which in turn would not be found deeper than (c) dinosaurs, such as Allosaurus . Trilobites became extinct about 230 million years ago, seed ferns about 150 million years ago, and dinosaurs 65 million years ago.
  • increase in size, loss of toes, increase in size of molars 20-25 mya grasslands became widespread in Norh America molars = easer to eat grass hoof = faster locomotion on grassland
  • The avian nature of the brain and inner ear of Archaeopteryx (Alonso et al. 2004) - Archaeopteryx, the earliest known flying bird from the Late Jurassic period, exhibits many shared primitive characters with more basal coelurosaurian dinosaurs (the clade including all theropods more bird-like than Allosaurus), such as teeth, a long bony tail and pinnate feathers. However, Archaeopteryx possessed asymmetrical flight feathers on its wings and tail, together with a wing feather arrangement shared with modern birds. This suggests some degree of powered flight capability but, until now, little was understood about the extent to which its brain and special senses were adapted for flight. Alonso et al. (2004) investigated this problem by computed tomography scanning and three-dimensional reconstruction of the braincase of the London specimen of Archaeopteryx. A reconstruction of the braincase and endocasts of the brain and inner ear suggest that Archaeopteryx closely resembled modern birds in the dominance of the sense of vision and in the possession of expanded auditory and spatial sensory perception in the ear. Alonso et al. (2004) concluded that Archaeopteryx had acquired the derived neurological and structural adaptations necessary for flight. An enlarged forebrain suggests that it had also developed enhanced somatosensory integration with these special senses demanded by a lifestyle involving flying ability.
  • There are innumerable intermediate & transitional forms Whales as land creatures returning to the water…. Where are the intermediate forms of whale ancestors? Cartoon making fun of this idea. The cartoons disappeared 10-12 years ago when this fossil was found. Ambilocetic natans = “Walking whale who likes to swim” 4-5 intermediate forms all found in last 2 decades Indus River valley in between India & Pakistan.
  • The Mummichog (Fundulus heteroclitus heteroclitus) is a small killifish found in the eastern United States. It is capable of tolerating highly variable salinity and temperatures, and is found in estuaries and saltmarshes as well as less salty waters. A year-round resident of tidal creeks and wetlands, this brownish-green saltwater minnow may reach a maximum length of 5 inches. Its Indian name means "they go in great numbers." It is also known as the common killifish. A hardy fish, the mummichog is an important food source for larger fish and is often used as bait. The mummichog also has been used as a natural method of mosquito control in marsh ponds and ditches. It has been reported that one mummichog can eat as many as 2,000 mosquito larvae ("wrigglers") a day. The mummichog also feeds on other insects, small fish, crustaceans, and plant material. Because of the extreme hardiness of the species, it is sometimes the only species found in severely polluted and oxygen-deprived streams, such as the Hackensack River and the Arthur Kill in New Jersey during the height of the water pollution problem in the United States. In 1973 the Mummichog became the first fish in space when carried on Skylab 3 as part of the biological experiments package later space missions by the U.S., such as Bion 3, have also carried Mummichog.
  • Even though it’s very hot to have a large mane the benefit of attracting mates and successfully producing & rearing young since you have that large mane outweighs the costs. Females who chose these males were more “successful” (more, healthier young) and therefore had a greater opportunity to pass on the trait of being attracted to longer darker manes to their daughters and the trait of having longer, darker manes to their sons.
  • 1 family has a lot of children & grandchildren therefore has a greater impact on the genes in the population than other families Genghis Khan tracked through Y chromosome.
  • Figure: 15-3 Title: Population bottlenecks reduce variation Caption: (a) A population bottleneck may drastically reduce genetic and phenotypic variation because the few organisms that survive may carry similar sets of alleles. Both (b) the northern elephant seal and (c) the cheetah passed through population bottlenecks in the recent past, resulting in an almost total loss of genetic diversity. Question If a population grows large again after a bottleneck, genetic diversity will eventually increase. Why?
  • Small founder group, less genetic diversity than Africans All white people around the world are descended from a small group of ancestors 100,000 years ago (Chinese are white people!)
  • Humans re so diverse but considered one species, whereas these Meadowlarks look so similar but are considered different species. Meadowlarks Similar body & colorations, but are distinct biological species because their songs & other behaviors are different enough to prevent interbreeding
  • The most comedic species of the Galapagos Islands is the Blue Footed Booby, what a ridiculous outfit and expression! Their name is in fact taken from the Spanish 'bobo' which means clown. The Blue Footed Boobies above display part of their humorous courtship ritual whereby they raise their feet one at a time and then swivel their heads away from the prospective mate looking to the sky. Other interesting Booby features are the highly evolved airbag systems in their skulls which allow them to dive bomb into the sea for fish from great height, and the egg and hatchling nesting boundaries they make which are rings of Boobie poop. They aren't the only Booby on the island — there are also Masked and Red Footed Boobies about.
  • The most comedic species of the Galapagos Islands is the Blue Footed Booby, what a ridiculous outfit and expression! Their name is in fact taken from the Spanish 'bobo' which means clown. The Blue Footed Boobies above display part of their humorous courtship ritual whereby they raise their feet one at a time and then swivel their heads away from the prospective mate looking to the sky. Other interesting Booby features are the highly evolved airbag systems in their skulls which allow them to dive bomb into the sea for fish from great height, and the egg and hatchling nesting boundaries they make which are rings of Boobie poop. They aren't the only Booby on the island — there are also Masked and Red Footed Boobies about.
  • The selection is intense because it directly affects offspring production -- it is affecting sex itself

Transcript

  • 1. Evolution Simp
  • 2. Evolution
    • Evolution is the accumulated inherited changes in a population over time
    • Evolution is one of the most powerful unifying concepts in science and is a critical underpinning to modern biology.
    • It has been stated that without evolution biology, biology makes no sense.
    • Dobzhansky, 1973
  • 3.  
  • 4.  
  • 5. But the Fossil record … OBSERVATION
  • 6. Evolution: Historical Concepts
    • Aristotle (3 rd century BC) observed similarities among organisms; “Scale of Nature”
      • Saw organisms as imperfect but moving toward perfection (concept rejected by modern evolutionary theory)
    • Ancient fossils seen for many hundreds of years
      • DaVinci (15 th - 16 th century AD) interpreted correctly as remains of ancient animals
  • 7. LaMarck
    • Organisms adapted to their
    • environments by acquiring traits
      • change in their life time
        • Disuse organisms lost parts because they did not use them — like the missing eyes & digestive system of the tapeworm
        • Perfection with Use & Need the constant use of an organ leads that organ to increase in size — like the muscles of a blacksmith or the large ears of a night-flying bat
      • transmit acquired characteristics to next generation
  • 8.  
  • 9. Charles Darwin, British Naturalist
    • Father, famous physician (Erasmus Darwin)
    • enrolled him in Edinburgh Medical School
      • Poor student; weakly motivated.
      • Reports of too many interests that dissipated his skills.
      • Charles was a failure at Med School.
    • Father enrolled him in Cambridge Divinity College
      • Charles was a failure in the Seminar also; spent too much time hunting and collecting organisms with friends.
      • Charles became the protégé of Rev. John Henslow, who in turn introduced him to friend, Charles Lyell
  • 10. Charles Lyell
    • In 1833 published Principles of Geology , which popularized the idea that the earth was shaped by slow-moving forces still in operation today.
  • 11. The Beginning of Darwin ’s ‘Dangerous Idea’
    • Lyell introduced Darwin to a major underpinning in geology: uniformitarianism
      • Uniformitarianism states that current Earth processes have always worked as they do now
    • Lyell also introduced him to Fitzroy, captain of the Beagle
      • The HMS Beagle was to prepare navigational charts for the British Navy
  • 12. Voyage of the HMS Beagle
    • Charles was invited as ship’s naturalist and companion to the Capt. on Fitzroy’s voyage in the Beagle , 1831-1836 (22 years old!)
    • Charles eventually fell out with Fitzroy, and just devoted his time to collections.
    • As a result of his isolation, he was left to his own devices and collected a vast catalog of rocks and biological samples that filled the ship’s hold, material for studies for the rest of his life.
    Robert Fitzroy
  • 13.
    • Stopped in Galapagos Islands *
      • 500 miles off coast of Ecuador
    Voyage of the HMS Beagle
  • 14. The Beagle ’s Travels
    • From Plymouth England to South America, with 2 months in the Galapagos Islands, 600 mi west of Ecuador
    • Darwin noted the birds and their similarities to the mainland birds
    • Impressed, generally, that the island animals were generally similar to the coastal animals of Ecuador,
    • Also, observed that there were differences in both birds and reptiles between the islands
  • 15. 5 years’ travel on the Beagle resulted in 3 major observations
    • Succession of Types .
      • Knew of fossils, saw correlating evidence in current species
      • Progression of organisms in space and time
      • Concluded that there was a lineage to all species
    • Representative Types .
      • Similar species types in similar environmental conditions
        • Rheas in Argentinian, ostriches in African, moa in the New Zealand plains.
    • Oceanic Island Biotas
      • Coastal and island biotas different, but clearly derived (Canaries from North Africa, Galapagos from Equador)
      • Galapagos finches’ phenotypes varied across different environments among the different islands.
  • 16. 1. Succession of types Armadillos are native to the Americas, with most species found in South America. Why should extinct armadillo-like species & living armadillos be found on the same continent? Glyptodont fossils are also unique to South America.
  • 17. Mylodon (left) Giant ground sloth (extinct) “ This wonderful relationship in the same continent between the dead and the living will…throw more light on the appearance of organic beings on our earth, and their disappearance from it, than any other class of facts.” Modern sloth (right)
  • 18. Rheas (South American) Ostriches (African) Moa New Zealand
    • Representative Types .
  • 19. Correlation of species to food source 3. Oceanic Island Biotas
  • 20. Many islands also show distinct local variations in tortoise morphology… … perhaps these are the first steps in the splitting of one species into several?
  • 21. Artificial selection This is not just a process of the past… It is all around us today
  • 22. Selective breeding the raw genetic material (variation) is hidden there
  • 23. Selective breeding
    • Hidden variation can be exposed through selection !
  • 24. Darwin found… birds
    • Collected many different birds on the Galapagos Islands.
    Finch? Sparrow? Woodpecker? Warbler? Thought he found very different kinds…
  • 25.
    • Darwin was amazed to find out:
    • All 14 species of birds were finches …
    But Darwin found… a lot of finches Finch? Sparrow? Woodpecker? Warbler? Large Ground Finch Small Ground Finch Warbler Finch But there is only one species of finch on the mainland! How did one species of finches become so many different species now? Veg. Tree Finch
  • 26. Tree Thinking Large-seed eater? Small-seed eater? Warbler? Leaf-browser? Large Ground Finch Small Ground Finch Warbler Finch Veg. Tree Finch Ancestral species Descendant species
  • 27. Correlation of species to food source Adaptive radiation Seed eaters Flower eaters Insect eaters
  • 28. Darwin’s finches
    • Differences in beaks
      • associated with eating different foods
      • survival & reproduction of beneficial adaptations to foods available on islands
    Warbler finch Woodpecker finch Small insectivorous tree finch Large insectivorous tree finch Vegetarian tree finch Cactus finch Sharp-beaked finch Small ground finch Medium ground finch Large ground finch Insect eaters Bud eater Seed eaters Cactus eater Warbler finch Tree finches Ground finches
  • 29. Darwin’s finches
    • Darwin’s conclusions
      • small populations of original South American finches landed on islands
        • variation in beaks enabled individuals to gather food successfully in the different environments
      • over many generations, the populations of finches changed anatomically & behaviorally
        • accumulation of advantageous traits in population
        • emergence of different species
  • 30.
    • Differences in beaks allowed some finches to…
      • successfully compete
      • successfully feed
      • successfully reproduce
        • pass successful traits onto their offspring
    Darwin’s finches
  • 31. In historical context
    • Other people’s ideas paved the path for Darwin’s thinking
    competition: struggle for survival population growth exceeds food supply land masses change over immeasurable time
  • 32. A Reluctant Revolutionary
    • Returned to England in 1836
      • wrote papers describing his collections & observations
      • long treatise on barnacles
      • draft of his theory of species formation in 1844
        • instructed his wife to publish this essay upon his death
        • reluctant to publish but didn’t want ideas to die with him
  • 33.
    • November 24, 1859, Darwin published
    Voyage: 1831-1836 “ On the Origin of Species by Means of Natural Selection”
  • 34. Mechanism for Evolution
    • Natural Selection The ultimate goal of any population is that it must produce the next generation. This is complicated by four basic characteristics of life:
      • Overpopulation Each generation produces more offspring then the environment can support.
      • 2. Competition with finite resources and and increase in population there is a competition of those resources leading, a survival of the fittest .
      • *The environment is the agent of natural selection determining which species will survive.
      • 3. Variation among individuals means they individually have different ability to obtain resources. Sexual reproduction promotes variation in a species.
      • 4. Reproduction Individuals that survive and then reproduce transmit these variations to their offspring.
  • 35.  
  • 36. Modern examples of Observed Evolution
    • Bacterial antibiotic resistance (blue book)
    • Pesticide resistant insects
    • Thermal Melanism in Ladybugs (blue book)
    • Peppered Moth: Industrial Melanism
    • Heavy metal tolerance in plants (blue book)
    • Galapagos Finches: size and shape of beaks
  • 37. Evidence for Evolution (D.3)
  • 38. Evidence supporting evolution
    • Fossil record
      • transition species
    • Anatomical record
      • homologous & vestigial structures
      • embryology & development
    • Biogeography (Contential Drift)
    • Molecular record (Neo-Darwinsim)
      • protein & DNA sequence
  • 39. I. Fossil Record
    • Sedimentary rock is laid down over time… new on top, older rocks below
    • As one digs down, find related fossils, which are progressively older as one digs deeper
    • Consistent and steady increases in size/complexity of structures or the whole organism, or just the opposite, are seen in successive stratigraphic layers
  • 40. I. Fossil record
    • Layers of sedimentary rock contain fossils
      • new layers cover older ones, creating a record over time
      • fossils within layers show that a succession of organisms have populated Earth throughout a long period of time
  • 41. Mount Everest 29,002 ft above sea level
  • 42. Hillary’s Step Fossilized Sea Shell Find
  • 43.  
  • 44. Fossil Record
  • 45. Fossil Preservation
    • Petrified
    • Prints and moulds
    • Resins which turn to Amber
    • Tar
    • Peat which is acidic preventing decay
    • Frozen in Ice or Snow
    • Sediments which turn to rock
  • 46. Fossil record
    • A record showing us that today’s organisms descended from ancestral species
  • 47. Evolutionary change in horses Millions of years ago 50 100 150 200 250 300 350 400 450 500 550 60 55 50 45 40 35 30 25 20 15 10 5 0 Equus Hyracotherium Mesohippus Merychippus Nannippus Body size (kg)
  • 48. Case study: evolution of the horse Hyracotherium Eocene Miohippus Oligocene Merychippus Miocene Equus ( horse) to present Florida Museum of Natural History Oligo Paleocene Eocene Oligocene Pliocene Pleistocene 65 mya present
  • 49. Evolution of birds
    • Archaeopteryx
      • lived about 150 mya
      • links reptiles & birds
    Smithsonian Museum, Washington, DC
  • 50. Where are the transitional fossils? Land Mammal Whale Evolution ? ? ? ?
  • 51. Where in the fossil record is a transition to tetrapods ?
  • 52. Eusthenopteron
    • The genus Eusthenopteron is a lobed fine fish that lived during the Late Devonian period, about 385 million years ago
  • 53. Coelacanth
    • Coelacanth are believed to be indicative of the order's place as a transitional evolutionary link due to the presence of leg-like structures
  • 54. Where is the connection to tetrapods?
  • 55. Where is the connection from land to water?
  • 56. Early tetrapods
  • 57. 2006 Fossil Discovery of Early Tetrapod
    • Tiktaalik
      • “ missing link” from sea to land animals
  • 58. Radioactive Dating
    • Unstable atomic isotopes that decay over time. Organisms incorporate these isotopes in their bodies. This can be detected and used to radioactive dating a fossil, because radioactive decay follows a predictable exponential decay with time.
      • For instance, organisms take up C, both as 14 C and 12 C but the 14 C decays away, so that one can determine how old the fossil is by the ratio of 14 C to 12 C in the fossil. The older it is, the greater the relative quantity of 12 C vs. 14 C.
    • Then, as with 14 C dating, the age in half lives can be deduced from the decay curve
    • Half life of 14 C is 5730 years , so it is useful for dating samples that are between 1000 & 100,000 years old
  • 59. Potassium-Argon dating
    • Proportions of parent 40 K atoms and daughter 40 Ar atoms are measured
    • Half-life of 40 K is 1250 million years so it is very useful for dating samples older than 100,000 years old.
  • 60. Scale of Biological Time (FYI)
    • The total scale of biological time can be mapped into a 12 hour period
    • Precambrian would start at 12 am
      • 3.8 bybp
    • Paleozoic would start at 10:18 am
      • 543 mybp
      • Appearance of complex organisms
    • Mesozoic at 11:13 am
      • 251 mybp
      • Age of dinosaurs
    • Cenozoic at 11:52 am
      • 65 mybp
      • Age of mammals
    • The vast preponderance of time has been in the Precambrian!
  • 61. II. Comparative Anatomy
    • A. Homologous structures
    • B. Analogous structures
            • Convergent evolution
            • Parallel Evolution
    C. Vestigal Organs D. Embryology
  • 62. II. Comparative Anatomy
    • A. Homologous structures
      • similarities in characteristics resulting from common ancestry
  • 63. Homologous structures
    • Similar structure
    • Similar development
    • Different functions
    • Evidence of close evolutionary relationship
      • recent common ancestor
  • 64. Homologous structures spines tendrils succulent leaves colored leaves leaves needles
  • 65. B. Analogous structures
    • Separate evolution of structures
      • similar functions
      • similar external form
      • different internal structure & development
      • different origin
      • no evolutionary relationship
    Solving a similar problem with a similar solution
  • 66. Convergent evolution
    • Flight evolved in 3 separate animal groups
      • evolved similar “solution” to similar “problems”
      • analogous structures
  • 67. Convergent evolution
    • Fish: aquatic vertebrates
    • Dolphins: aquatic mammals
      • similar adaptations to life in the sea
      • not closely related
  • 68. Parallel Evolution
    • Convergent evolution in common niches
      • filling similar ecological roles in similar environments, so similar adaptations were selected
      • but are not closely related
    marsupial mammals placental mammals
  • 69. Parallel types across continents Niche Placental Mammals Australian Marsupials Burrower Mole Anteater Mouse Lemur Flying squirrel Ocelot Wolf Tasmanian “wolf” Tasmanian cat Sugar glider Spotted cuscus Numbat Marsupial mole Marsupial mouse Anteater Nocturnal insectivore Climber Glider Stalking predator Chasing predator
  • 70.
    • describes a characteristic of organisms that have seemingly lost all or most of its original function through evolution.
    • Fossil record supports the hypothesis that whales are derived from ancient vertebrates called mesonychids that moved to the sea approximately 50-60 million years before present (mybp)
    • Ambulocetus is much like a modern whale but has legs (~50 mybp)
    • Rodhocetus from 45-50 mybp shows changes in vertebrae allowing vertical tail movement
    • Basilocetus from 40 mybp shows nearly modern structure with reduced hind limbs not seen externally in modern whales,
    • Vestigial hind limbs are present in modern whales internal bones . Vestigial limbs are found in many animals, including the python.
    C. Vestigial Structures
  • 71. D. Embryology
    • Similar features seen in developmental stages of related organisms
    • Gill pouches and tails seen in developing vertebrates
    • They have a common ancestor
  • 72. III. Biogeography (Continental Drift)
    • Convergent Evolution and ‘Similar Types’
    • Organisms tend to evolve in such a way as to best fit their environment
    • Since physical conditions in different continents can be very similar, each continent tends to have very similar (not identical) organisms
      • Ostriches in Africa
      • Rheas in South America
      • Moas in Australia/New Zealand
    • Examples from the book: Aardvark (N. Africa), anteater (Central/South America) and pangolin (Africa/Asia)
  • 73. Continental Drift
  • 74. Continental Drift
    • Alfred Wegner (1915) proposed that the planetary surface changed over time and that it once was a single large mass called Pangaea.
    • This has been shown to be true and that the land masses ‘float’ on continental plate that are pushed apart by actively spreading zones in the ocean floors. This area of study is called plate tectonics .
  • 75. Distributions of Fossil Organisms
    • The distribution of fossil animals and plants follows the pattern of attachment between the edges of the tectonic plates.
    • Shows a direct relationship between the fossil record and known geological features
    • Timing of the occurrence of these organisms and the loss of their connections are observed to coincide with the separation of the land masses
  • 76. IV. Molecular record
    • Comparing DNA & protein structure
      • universal genetic code!
        • DNA & RNA
      • compare common genes
        • cytochrome C (respiration)
        • hemoglobin (gas exchange)
    • Closely related species have sequences that are more similar than distantly related species
      • DNA & proteins are a molecular record of evolutionary relationships
    0 25 50 75 100 125 0 25 50 75 100 Millions of years ago Horse/ donkey Sheep/ goat Goat/cow Llama/ cow Pig/ cow Rabbit/ rodent Horse/cow Human/rodent Dog/ cow Human/ cow Human/kangaroo Nucleotide substitutions
  • 77. Comparative hemoglobin structure Number of amino acid differences between hemoglobin (146 aa) of vertebrate species and that of humans 10 0 20 30 40 50 60 70 80 90 100 110 120 Lamprey Frog Bird Dog Macaque Human 32 8 45 67 125
  • 78. Building “family” trees
    • Closely related species (branches) share same line of descent until their divergence from a common ancestor
  • 79. Neo-Darwinism
    • Incorporates new knowledge of genetics to create a modern synthesis that incorporates Darwinism & Neo-Darwinism
    • Viewing evolution through population genetics
        • Frequency of genes (factors effect changes)
        • Distribution of genes (population genetics)
  • 80. Neo-Darwinism
    • Variation in a population results from the recombination of alleles (crossing over) during meiosis and fertilization (mutations).
    • Adaptations may occur as the result of an allele frequency increasing in a pop.’s gene pool over a # of generations (microevolution)
    • Evolution of one species into another species involves the accumulation of many advantageous alleles in the gene pool of a pop. Over a period of time.
    • A species is a potentially interbreeding pop. Having a common gene pool.
  • 81.
    • Frequency of genes (factors effect changes) Genetic Variation
    • Heritable differences among individuals
    • Raw material of evolution
    • Happens in 3 ways
            • A. Mutations
            • B. Recombination (meiosis)
            • C. Fertilization
  • 82. A. Mutations
    • Permanent change in genetic variation
    • Only source of new alleles
    • Do not arise out of need
    • Causes of mutation
      • Spontaneous occurrence
      • Radiation
      • Chemicals
      • Transposons
  • 83. Results of Mutations
    • Harmful
      • Nonadaptive
      • Eliminated by selection
    • Beneficial
      • Adaptive
      • Selected and persist
    • Neutral
      • Neither adaptive nor nonadaptive
      • May or may not persist in gene pool
  • 84. Example of a gene mutation: phenylketonuria (PKU)
    • C to T base-substitution mutation results in wrong amino acid (similar to sickle-cell mutation)
    • Individuals can not metabolize amino acid phenylalanine an enzyme needed to degrade phenylalanine is not made so it accumulates in the brain and causes mental retardation.
  • 85. Example of a point mutation
  • 86.
    • Example of a gene mutation: Cystic Fibrosis
    • Caused by the removal of base pairs from a DNA sequence is called a deletion mutation
    • Disorder in which chloride channels fail to form and this results in a blockage of mucous membranes and the onset of respiratory failure.
  • 87. Example of a chromosomal mutation: Klinefelter’s syndrome :
    • receipt of an extra ‘X’ chromosome by males-> result is feminization of secondary sex characteristics, sterility and learning impairment may be present.
    • Chromosomal mutations tend to have less evolutionary significance because they typically cause death or sterility and will not be passed on.
  • 88. B. Recombination
    • Major source of genetic variation
    • Two processes
        • Segregation
        • Independent assortment
  • 89. C. Fertilization
  • 90. 2. Distribution of genes (population genetics)
    • is the study of genetic variability in a population
    • *Extension of Mendelian genetics
    • Populations are individuals of the same species that live in the same locations
      • Exhibit variation in traits
    • Examination of the assemblage of traits reveals genetic information and shows the kind and proportion of alleles in a population
  • 91. Populations evolve
    • Natural selection acts on individuals
      • differential survival
        • “ survival of the fittest”
      • differential reproductive success
        • who bears more offspring
    • Populations evolve
      • genetic makeup of population changes over time
      • favorable traits (greater fitness) become more common
    Presence of lactate dehydrogenase Mummichog
  • 92. Genes and Populations
    • Gene pool : The collection of genes in a population
        • Because diploids have only two versions of each gene, each has only a small fraction of possible alleles in a population
    • Genotype : The genetic makeup of an individual at a given locus, taking into account the two possible alleles
        • Genotype frequency is the proportion of a given genotype in the population
        • Allele frequency refers to the proportion of a particular allele, such as A or a
    • Phenotype : the traits of an individual
        • Phenotype frequency is the proportion of a given phenotype in the population
        • Phenotype frequency is influenced by the dominance characteristic of an allele
  • 93. Alleles and Population Genetics
    • Although individuals are affected by the process of natural selection, it is the makeup of the population that is critical for determining the subsequent generations
    • Changes in the gene pool refer to changes in the frequency of the alleles
    • If the allele frequencies in a population do not undergo change over time, we say that the population is in genetic equilibrium
  • 94. Population Stability
    • The conventional view might be that dominant alleles would eventually come to dominate the gene pool, and the recessives disappear
    • They do not necessarily do so; in fact, allele frequencies change only when influenced by other factors.
    • The stability of populations over time is explained by the Hardy-Weinberg Equilibrium.
  • 95. 5 Factors Upset Genetic Equilibrium
    • 1. Mutation
    • 2. Nonrandom mating
    • 3. Genetic Drift
    • 4. Gene Flow
    • 5. Natural Selection
      • All of these are conditions that were required by the H-W equilibrium to NOT occur
      • They cause changes in allelic frequency, and result in microevolution
      • They all occur routinely
  • 96. 1. Mutation Increases Variability
    • Mutation is the basic mechanism to produce changes in gene pool
    • Mutations can be:
        • Changes in bases
        • Rearrangements of gene location
        • Breakage of chromosomes
    • Some genes mutate relatively often; others rarely
    • Most mutations are lethal
    • Mutations can be ‘silent’ in DNA not used to code for protein
    • Sometimes they are adaptive (very rare)
    • Mutations can occur anywhere in an organism.
        • For a mutation to be passed on it must occur in the germ line
        • The germ line produces gametes
  • 97. Types of Evolution
    • Macroevolution: The generation of major change in the assemblage of organisms: speciation
    • Microevolution: Changes in the gene pool of a population that result in changes in allele frequencies; they arise without the influence of selection pressure
  • 98. Drosophila mutants
    • The vestigial wing mutation results in a fly that endures windy environments better than the normal ‘flight-ready’ fly…
    Normal Fly Vestigial Wing
  • 99.  
  • 100. 2. Nonrandom Mating
    • Mates select each other based upon morphological, behavioral phenotype. Reduces genetic variability
    • Types of nonrandom mating
          • A. Inbreeding
          • B. Mate selection
  • 101. A. Inbreeding
    • In inbreeding the homozygous condition is enhanced
    • In most populations inbreeding causes decreased adaptiveness
      • Called inbreeding depression
      • May occur due to increased homozygosity (and decreased diversity) in the population
  • 102.  
  • 103. Inbreeding Depression
    • Inbred wild white mice ( Peromyscus leucopus ) compared with normal wild mice with regard to ability to survive after release back to the wild
    • The non-inbred population displayed better survivorship over time
  • 104. B. Mate selection
    • Acting on reproductive success
      • attractiveness to potential mate
      • fertility of gametes
      • successful rearing of offspring
  • 105. Sexual selection It’s FEMALE CHOICE, baby !
  • 106. The lion’s mane…
    • Females are attracted to males with larger, dark manes
    • Correlation with higher testosterone levels
      • better nutrition & health
      • more muscle & aggression
      • better sperm count / fertility
      • longer life
    • But imposes a cost to male
      • HOT! Is it worth it??
  • 107. Sexy = fitness markers
  • 108. 3. Genetic drift
    • Effect of chance events
      • bottleneck
        • some factor (disaster) reduces population to small number & then population recovers & expands again
      • founder effect
        • small group splinters off & starts a new colony
    Warbler finch Tree finches Ground finches
  • 109. Genetic Drift
    • Exchange of genes (alleles) within a population
    • No gene flow, no immigration or movement in or emigration, movement out
    • It is an important evolutionary process which leads to changes in allele frequencies over time. It may cause gene variants to disappear completely, reduce genetic variability .
  • 110. Population Size Is Very Important
    • Small population – loss of one individual has big effect
    • Larger population – loss of one individual has little effect
  • 111. Bottleneck effect
    • When large population is drastically reduced by a disaster
      • famine, natural disaster, loss of habitat…
      • loss of variation by chance event
        • alleles lost from gene pool
          • not due to fitness
        • narrows the gene pool
  • 112. Example of Bottleneck
    • Elephant seals (due to hunting in the early 19th century). Since then, under legislative protection in the United States and Mexico, northern elephant seals have recovered dramatically in number, although their genomic diversity was greatly reduced to less then a 1% difference.
  • 113. time event causing bottleneck resulting population original population
  • 114. Founder effect
    • When a new population is started by only a few individuals
      • some rare alleles may be at high frequency; others may be missing
      • skew the gene pool of new population
        • human populations that started from small group of colonists
        • example : colonization of New World
  • 115. Example: Founder Effect
    • Small population can cause extreme genetic drift
    • Small gene pools allow for rapid change
    • Example: polydactyly in Pennsylvania Amish
  • 116. People and the Founder Effect
    • Initial colonization and subsequent isolation probably responsible for very uniform genetics of the Finns who carry the recessive traits of blues eyes and blond hair
  • 117. Example: Extinction
    • Death of all members of a species
    • Major factors leading to extinction
        • Localized distribution
        • Overspecialization
        • Reduced genetic variability
        • Habitat destruction
  • 118. 4. Gene flow
    • Gene flow occurs when alleles are exchanged between two populations. 
    • Gene flow occurs when individuals migrate
    • (immigrate or emigrate) and breed in a new population (contributing their genes to that population).
    •   Gene flow may increases the variability of the gene pool by adding new alleles.
    • If gene flow is maintained between two populations can also lead to a combination of the two gene pools, reducing the genetic variation between the two groups acting against speciation, by recombining the gene pools of the groups, and, repairing the developing differences.
  • 119.  
  • 120. 4. Gene Flow Increases Variation
    • Two populations can remain stable for a long time, experiencing only genetic drift, and mutations accompanied by natural selection — all of which tend to be slow processes.
    10,000 years
  • 121. Gene Flow
    • Results from migration
    • Induces changes in local populations due to cross-breeding between migrants and locals
    • In contrast, migration of individuals between two populations can result in much faster changes in the recipient population
    50 yrs ‘ Green’ migrates to ‘blue’ and interbreeds to produce ‘aqua’ that establishes itself in the second population
  • 122. 5. Natural Selection Increases Adaptation
    • Natural Selection is the basic mechanism of evolution… selects for individuals most fit leading to adaptive evolutionary change in a population
    • This selection works on the heritable components of the phenotype (which is expression of genotype)
  • 123. Polygenic Control of Phenotype
    • Polygenic control of phenotype is typical
    • Interaction between different alleles causes a very finely graded set of variable characteristics in individuals of a population
    Range of trait Number of individuals
  • 124. Selection
    • No Selection population doesn’t change with succeeding generations
      • If selection pressure is applied (down arrow) then those not receiving selection pressure tend to predominate…
    • b. Stabilizing the extremes are selected against; center stays same and grows in numbers
  • 125. Selection
      • Directional : one tail of the distribution is selected against and the opposite tail grows in numbers
      • Disruptive : a mid-group is selected against; the tails are allowed to predominate and grow compared to middle
  • 126.
    • Childbirth Weight Shows
    • Human babies have an
    • optimal size because of
    • birth-induced stress
    • on the mother and child
    B. Example: Stabilizing Selection
  • 127. C. Example: Directional Selection
    • Directional selection is seen if one phenotype is strongly selected. That phenotype will predominate and give rise to a population bearing a predominance of that phenotype
  • 128. D. Example: Disruptive Selection
    • If the extreme phenotypes have selective advantage, they tend to produce a bimodal population
    • Galapagos finches have shown such variation during periods of drought
    • Was observed during a drought in Galapagos — birds changed feeding mode during drought
    • Changed back when rains came
  • 129. Genetic Polymorphism
    • Occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form .
    • Evidenced by the phenotype, as in these snail shells
  • 130. Genetic Polymorphism
  • 131. Balanced Polymorphism
    • Balanced polymorphisms are polymorphisms that persist over extended periods of time and that usually involve 2 or more alleles relates to a balance or equilibrium between morphs. Polymorphism has survival value, and the selection of modifier genes may reinforce the polymorphism.
        • Supported by
            • Heterozygote advantage
            • Frequency-dependent selection
  • 132. Heterozygote Advantage
    • Sometimes, the heterozygote confers a distinct advantage to the individual
      • Sickle cell anemia in the heterozygous form is less severe,
      • Imparts resistance to the attack of the malarial parasite, Plasmodium falciparum; more fit than either homozygote
    • Sickle cell anemia (tan/red) and P. falciparum malaria (green)
  • 133. * Transient Polymorphorism
    • If one allele is gradually replacing another
    • Industrial Melanism: peppered moths
    • Ladybugs: pops. of ladybugs that changed from having red wing cases with black spots to black wing cases.
  • 134. Alleles and Population Genetics
    • Although individuals are affected by the process of natural selection, it is the makeup of the population that is critical for determining the subsequent generations
    • Changes in the gene pool refer to changes in the frequency of the alleles
    • If the allele frequencies in a population do not undergo change over time, we say that the population is in genetic equilibrium
  • 135. Population Stability
    • The conventional view might be that dominant alleles would eventually come to dominate the gene pool, and the recessives disappear
    • They do not necessarily do so; in fact, allele frequencies change only when influenced by other factors.
    • The stability of populations over time is explained by the Hardy-Weinberg Equilibrium.
  • 136. Frequencies Add up to 1.0
    • e.g. — a population has two alleles, A and a
      • A is dominant over a
    • The allele frequencies must sum to 1.0
      • (frequency of A ) + (frequency of a ) = 1.0
    • The genotype frequencies must sum to 1.0
      • (frequency of AA ) + (frequency of A a ) + (frequency of aa ) = 1.0
    • The phenotype frequencies must sum to 1.0
      • (frequency of AA and A a phenotype) + (frequency of aa phenotype) = 1.0
  • 137. Hardy-Weinberg: A Case of Genetic Equilibrium
    • Premise is that change in a population can be so slow, that the frequency of the alleles in a population can be thought of as NOT changing
    • This condition can be modeled as the Hardy-Weinberg Equilibrium, which requires:
          • Large population size
          • No migration
          • Random mating
          • No net mutations
          • All genotypes have similar selective value
    • This is idealized and rarely actually occurs, but is a useful tool
    • SO no natural selection is occurring
  • 138. The Ps and Qs of H&W
    • Imagine 2 alleles, A and a
        • p is the frequency of A
        • q the frequency of a
    • So, p + q = 1
    • The mathematical equivalent of a random mating can be given by multiplying this relationship by itself
    • Therefore, (p + q) 2 = 1 = p 2 + 2pq + q 2
        • p 2 = frequency of AA
        • 2pq = frequency of Aa
        • q 2 = frequency of aa
    • Given this condition, we can always work out the frequencies of each allele in a sexual population that is not evolving.
  • 139. H-W: Example
    • Remember, since (p + q) 2 = 1
    • p 2 + 2pq + q 2 = 1
    • Let’s say that a population has the following genotypic and allelic frequencies
    • Note how all frequencies add up to 1.0
  • 140. Allelic and Genotypic Frequencies of the Next Generation Are the Same!
    • When mating occurs, sperm and egg will unite the genes
    • Note that the same allelic frequencies will occur (check back for the formula)
    • This is H-W in action
  • 141. A Fun Experiment in Class
    • Tongue rolling is described by a simple dominant character, T and we can study the HW equilibrium using this trait, in this class
    • 1. Find the frequency of homozygous recessives (q 2 )in the class
      • Can you roll your tongue? If so you are either TT or Tt
        • Note how many can roll tongues ________
      • If not, you are tt
        • Note how many cannot roll tongues ________
        • Take this number and divide by the class total: ______; this is the frequency of homozygous recessives (q 2 ).
    • 2. What is the frequency of p?
      • Since p + q = 1, then 1 - q = p
      • Take the root of q 2 from above. ___________
      • We can now calculate p. p = 1 - q
  • 142. Complete the Calculations
    • Assume stasis and mate at random (theoretically, of course!)(Watch your p’s and q’s!)
    • Now calculate the expected distribution of the different genotypes in the next generation
    • p 2 + 2pq + q 2 = 1
    • p 2 = ____________
    • 2pq = ___________
    • q 2 = ____________
    • 4. Now calculate the number of roller alleles T
      • p 2 + ½ (2pq) = _______
    • As a check , calculate the frequency of nonrollers
      • 1 – p = ________
    • Squirrel Example: Biozone
  • 143. Concept of Species
    • Speciation -Individuals that are no longer able to mate with each other, they are classified as different species.
      • population whose members can interbreed & produce viable, fertile offspring
      • reproductively compatible
    • This is cause of speciation is cause by reproductive isolation . This occurs when members of 2 populations cannot interbreed with each other to produce fertile offspring. There are 6 was in which populations can become isolated. 1. Geographic isolation
    • 2. Ecological isolation
    • 3. Temporal isolation
    • 4. Behavioral isolation
    • 5. Mechanical isolation
    • 6. Gametic isolation
  • 144. So…what is a species? Western Meadowlark Eastern Meadowlark Distinct species: songs & behaviors are different enough to prevent interbreeding
  • 145. How and why do new species originate?
    • Species are created by a series of evolutionary processes
      • populations become isolated
        • geographically isolated
        • reproductively isolated
      • isolated populations evolve independently
    • Isolation
      • allopatric
        • geographic separation
      • sympatric
        • still live in same area
  • 146.
    • Obstacle to mating or to fertilization if mating occurs
    PRE-reproduction barriers behavioral isolation geographic isolation ecological isolation temporal isolation mechanical isolation gametic isolation
  • 147. 1. Geographic Isolation
    • Species occur in different areas
      • physical barrier
      • allopatric speciation
        • “ other country ”
    Harris’s antelope squirrel inhabits the canyon’s south rim (L). Just a few miles away on the north rim (R) lives the closely related white-tailed antelope squirrel
  • 148. 2. Ecological isolation
    • Species occur in same region, but occupy different habitats so rarely encounter each other
      • reproductively isolated
    2 species of garter snake, Thamnophis , occur in same area, but one lives in water & other is terrestrial
    • lions & tigers could hybridize, but they live in different habitats:
    • lions in grasslands
    • tigers in rainforest
  • 149. 3. Temporal isolation
    • Species that breed during different times of day, different seasons, or different years cannot mix gametes
      • reproductive isolation
      • sympatric speciation
        • “ same country ”
    Eastern spotted skunk (L) & western spotted skunk (R) overlap in range but eastern mates in late winter & western mates in late summer
  • 150. 4. Behavioral isolation
    • Unique behavioral patterns & rituals isolate species
      • identifies members of species
      • attract mates of same species 
        • courtship rituals, mating calls
        • reproductive isolation
    Blue footed boobies mate only after a courtship display unique to their species sympatric speciation?
  • 151. Apple Maggot Flies
    • Females generally choose to lay their eggs on the type of fruit they grew up in, and males tend to look for mates on the type of fruit they grew up in. So hawthorn (apples native to America) apples flies generally end up mating with other hawthorn flies and domestic (introduced apples) apple flies generally end up mating with other domestic apple flies.
  • 152. 5. Mechanical isolation
    • Morphological differences can prevent successful mating
      • reproductive isolation
    Even in closely related species of plants, the flowers often have distinct appearances that attract different pollinators. These 2 species of monkey flower differ greatly in shape & color, therefore cross-pollination does not happen. Plants sympatric speciation?
  • 153. Mechanical isolation
    • For many insects, male & female sex organs of closely related species do not fit together, preventing sperm transfer
      • lack of “fit” between sexual organs: hard to imagine for us… but a big issue for insects with different shaped genitals!
    Damsel fly penises Animals
  • 154. 6. Gametic isolation
    • Sperm of one species may not be able to fertilize eggs of another species
      • mechanisms
        • biochemical barrier so sperm cannot penetrate egg
          • receptor recognition: lock & key between egg & sperm
        • chemical incompatibility
          • sperm cannot survive in female reproductive tract
    sympatric speciation?
  • 155. Rate of Speciation
    • Two different theories proposed by scientists to
    • address the rate of evolution:
    • 1. Gradualism - proposes that evolutionary change is slow, gradual, and continuous.
    • 2. Punctuated Equilibrium - proposes that species have long periods of stability (several million years) interrupted by geologically brief periods of significant change during which a new species may evolve.
  • 156. Gradualism
    • Gradual divergence over long spans of time
      • assume that big changes occur as the accumulation of many small ones
  • 157. Punctuated Equilibrium
    • Rate of speciation is not constant
      • rapid bursts of change
      • long periods of little or no change
      • species undergo rapid change when they 1 st bud from parent population
  • 158. Gradualism Punctuated Equilibrium