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Evolution. Spontaneous Generation living things come from nonliving things. Disproven by: Redi Spallanzani Pasteur. Where does life come from?. Francesco Redi’s Experiment. Uncovered Flask = Maggots & Flies. Lazzaro Spallanzani’s Experiment. Louis Pasteur.
EvolutionSpontaneous Generation living things come from nonliving thingsDisproven by:RediSpallanzaniPasteurWhere does life come from?Francesco Redi’s ExperimentUncovered Flask =Maggots & FliesLazzaro Spallanzani’s ExperimentLouis PasteurSo Then, How Did Life Begin On Earth?
  • Oparin’s Hypothesis
  • CH4 + NH3+ CO2 + H2O vapor + heat and light energy organic compounds
  • The Miller-Urey Experiment
  • Created conditions of Oparin’s hypothesis in a lab setting
  • Organic compounds, including amino acids, were formed
  • Isn’t That The Same As Spontaneous Generation?
  • No
  • Formation of life took a billion years
  • Spontaneous generation took 1-2 weeks
  • Formation of life required extreme heat and energy
  • How old is the Earth?
  • Earth = approximately 4.6 billion years old
  • Life began approximately 3.6 billion years ago
  • How Do We Know The Age of the Earth?
  • Radioactive Dating of Fossils & Rocks
  • Ex: Carbon-14, Uranium 238
  • Fossils
  • 2 methods of determining age –
  • Relative age – based on position in rock strata (layers)
  • Absolute age – based on radioactive dating
  • OK, so what were the first organisms on Earth?
  • Archaebacteria
  • Chemosynthetic (due to where they lived) – use inorganic molecules as source of energy instead of sunlight
  • The appearance of eukaryotes; or, the story of endosymbiosis
  • Endosymbiosis
  • Proposed by Lynn Margulis
  • Led to cells w/chloroplasts and mitochondria
  • Mass Extinctions
  • Throughout history, there have been five mass extinctions (mass extinction = over 50% of species on Earth died rapidly, due to meteor impact, Ice Age, etc.)
  • Some mass extinctions allowed new life forms to dominate the Earth
  • The last mass extinction allowed mammals to dominate the land.
  • How do organisms evolve?
  • 2 proposed hypotheses
  • Lamarck – acquired traits – use and disuse
  • Darwin – descent with modification due to natural selection
  • Jean Baptiste de Lamarck
  • Acquired traits are passed on to offspring
  • Long necks from reachingfor trees - passed on to offspring.A Common MisconceptionCharles DarwinTwo Important Influences On Darwin
  • Thomas Malthus
  • Human population growth is controlled by limited resources
  • Charles Lyell
  • Uniformitarianism – geologic processes occuring today are the same as they were millions and billions of years ago
  • Darwin’s Theory #1: Descent With Modification
  • New forms in fossil record = modified forms of ancestral species
  • Darwin’s Theory #2: Natural Selection
  • Environment limits growth of populations
  • Due to variations among individuals in a species, some members of a population compete better for limited resources, so they survive and reproduce, while others do not.
  • Notice The Variation In These Individuals Of A House Finch PopulationSome are more likely to surviveand/or mate due to differences incolorationStabilizing SelectionDirectional SelectionDisruptive SelectionNature selects the average form of a trait (human baby size)Nature selects one extreme form of a trait (e.g. only the very long tongue in anteaters, not the short tongue)Nature selects both the extreme forms of a trait (e.g. very bright shell and very dull shell)3 General Types of Natural SelectionThe 3 Types of Natural SelectionDisruptiveSelectionStabilizing SelectionDirectionalSelectionSexual Selection: A Special Type of Directional Selection
  • Individuals of one sex (usually males) of a species are more likely to get picked as partners by the other sex if their characteristics are bolder, brighter, louder or stronger than other members of the same sex.
  • Sexual Selection in PeacocksOf Course, Being More Noticeable Does Have Its Disadvantages . . .Other Factors Can Affect Genetic Variation In A Population
  • Other factors besides meiosis/sexual reproduction and mutations create the variation in the genetic material (gene pool) of a population on which natural selection acts
  • Migration
  • Assortative (nonrandom) mating = sexual selection
  • Genetic Drift
  • Genetic Drift
  • Change In Allele Frequency Caused By Random Chance
  • Random chance = natural disasters, disease, hunting, etc.
  • Has a greater affect on small populations
  • Often causes reduction in alleles (not always the weakest alleles) present in the gene pool.
  • The Bottleneck Effect
  • A direct result of genetic drift
  • As a result of some random event, several alleles are lost from a population when only a small number of individuals in the population survive to reproduce.
  • Northern Elephant Seals – pop. reduced to 20 individuals due to hunting in 1890’s.
  • Pop. rebounded to 30,000 now
  • Very little genetic variation
  • Hardy-Weinberg Equation
  • Mathematical equations used to determine if a population is evolving.
  • In order for no evolution (change in gene pool) 5 conditions:
  • Large population
  • No mutations
  • No genetic drift/natural selection
  • No migration
  • Random Mating
  • p = frequency of dominant allele
  • q = frequency of recessive allele
  • p + q = 1
  • Hardy-Weinberg
  • p2 = frequency of homozygous dominant individuals
  • 2pq = frequency of heterozygous individuals
  • q2 = frequency of homozygous recessive individuals
  • p2+ 2pq + q2 = 1
  • In a population of 1000 individuals, 360 cannot taste PTC paper. Which value in the equation is that?
  • Evidence Of Evolution
  • Homologous Structures
  • Analogous Structures
  • Vestigial Structures
  • Embryological Similarities
  • Macromolecule (DNA, RNA, Proteins) Similarities
  • Homologous Structures
  • Similar features from a shared common ancestor
  • Analogous Structures
  • Similar features, but no shared common ancestor
  • Show that the environment selects for certain abilities.
  • Vestigial Structures
  • Show that organisms carry genes for structures that were useful in ancestors, but genes for these structures have been turned off in modern day organism.
  • Human Vestigial StructuresEmbryological similarities
  • Show genes organisms have in common.
  • These genes are used early in development, but turned “off” later.
  • Macromolecule Similarity
  • The more similar the DNA, RNA or proteins between two organisms, the more recently they shared a common ancestor.
  • Before We Go On, An Important Question: What is a species?
  • Members of a species are morphologically (physically) similar, and can successfully interbreed (produce fertile offspring).
  • How Do New Species Form? Speciation
  • Isolation
  • Isolating Mechanisms
  • Prezygotic Isolation
  • Postzygotic Isolation
  • Geographic Isolation
  • Physical separation of members of a population (by formation of a canyon, mountain, river, etc.)
  • Leads to different adaptations on each side of barrier, and eventually new species (allopatric speciation)
  • Geographic Isolation = New Species: An Example2 Species of Squirrels FormedWhen They Were Separated ByThe Grand CanyonPrezygotic Isolating Mechanism #1:Temporal Isolation
  • Species isolated because they reproduce in different seasons or times of day
  • Prevents species from ever breeding together – keeps two species separate but usually arises after species have formed.
  • Prezygotic Isolating Mechanism #2:Behavioral Isolation
  • Species Differ In Their Mating Rituals (e.g. different bird songs, mating colors, dances, pheromones, etc.)
  • Prezygotic Isolating Mechanism #3Ecological Isolation
  • Ecological Isolation
  • Species inhabit the same area, but different habitats, so they don’t encounter each other
  • Prezygotic Isolating Mechanism #4:
  • Mechanical Isolation
  • Body structure prevents mating
  • In layman’s terms - the parts don’t fit
  • Bush BabyBush Baby Isolating MechanismPrezygotic Isolating Mechanism #5
  • Gametic Isolation
  • The sperm is unable to fuse with the egg.
  • Postzygotic Isolation
  • Some barriers to successful breeding arise after fertilization and are called postzygotic isolating mechanisms
  • Hybrid sterility
  • Sterile offspring (e.g. Horse + Donkey = Mule)
  • How quickly do new species form?
  • 2 hypotheses
  • Gradualism
  • Many transitional forms between common ancestor and modern organisms
  • Punctuated Equilibrium
  • Sudden shifts in form from an ancestor to newer organism, so not many transitional forms between common ancestor and modern organisms
  • Patterns of Evolution
  • Convergent Evolution
  • Divergent Evolution
  • Adaptive Radiation
  • Artificial Selection
  • Coevolution
  • Convergent Evolution
  • Organisms appear similar, but aren’t closely related
  • Why?
  • Similar environments select for similar traits
  • Divergent Evolution
  • Related populations or species become less and less alike
  • AdaptiveRadiationA Second Type Of Divergent Evolution
  • Artificial Selection
  • Humans, rather than nature, select traits
  • One More Example of Artificial SelectionCoevolution
  • Two or more species in close association w/one another change together
  • Predator/Prey
  • Parasite/Host
  • Plant/Pollinator
  • Finally – THE END!
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