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Evolution. 3/27/12. Objective: Introduce origins theories Do Now: Hand in popular science questions Do Later: Read sections 13.1-3. Diversity of life. Estimated 10 million species on earth Phylogenetic trees show relationships. Origins Theories. Lamarck Spontaneous generation

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3 27 12
  • Objective: Introduce origins theories
  • Do Now: Hand in popular science questions
  • Do Later: Read sections 13.1-3
diversity of life
Diversity of life
  • Estimated 10 million species on earth
    • Phylogenetic trees show relationships
origins theories
Origins Theories
  • Lamarck
    • Spontaneous generation
      • Simple organisms are more recent
      • Complex organisms are older, gained complexity over time
    • Theory of Acquired Characteristics
      • Characteristics acquired by parents get passed on to offspring
origins theories2
Origins Theories
  • Catastrophism
    • Rapid, catastrophic events shape geology and extinction
  • Gradualism
    • Slow change of geologic features and life forms over time

Georges Cuvier

Charles Lyell

origins theories3
Origins Theories
  • “Descent with modification”
    • Species have natural variation
    • Certain characteristics are favored over time
natural selection
Natural Selection
  • Condition 1: Variation
    • Populations must have variation in traits for selection to occur
natural selection1
Natural Selection
  • Condition 2: Competition
    • “Survival of the fittest”
      • Scarce resources, avoiding predators, etc.
    • Only the best adapted species survive
natural selection2
Natural Selection
  • Condition 3: Inheritance
    • Favorable traits are passed on to offspring
    • Genetic inheritance
natural selection3
Natural Selection
  • Theory of Natural Selection
    • Heritable traits that confer an advantage in survival and reproduction will increase in frequency in a population.
    • Gradually a population will change as a result of natural selection.
artificial selection
Artificial Selection
  • Selection performed by a conscious agent.
    • Dog breeding
    • Crop selection
4 2 12
  • Objective: To examine speciation and evidence for natural selection
  • Do now:
    • Discuss with a partner – What is a species?
    • Come up with a definition in pairs
  • Do later: Read 13.5-6 in text
    • On separate paper: Pg. 275 #1, 3-7, 12
  • A species is a group of organisms that are able to interbreed and produce fertile offspring.

Mules are the offspring of a male donkey and a female horse. They are sterile.

hybrid species
Hybrid Species

Zebra + horse  zebroid (sterile)

Tiglons can occasionally reproduce with difficulty.

  • How do new species come to be (speciation)?
    • 1) Population is separated
    • 2) Each population changes due to natural selection
    • 3) Differences accumulate to make interbreeding impossible
evidence for natural selection
Evidence for Natural Selection
  • Biogeography
    • Geographic distribution of species

Why do all marsupials live in Australia?

evidence for natural selection1
Evidence for Natural Selection
  • Homologous Structures
    • Anatomically similar structures in groups of related organisms
    • May serve different functions
evidence for natural selection2
Evidence for Natural Selection
  • Molecular Biology
    • DNA sequencing can confirm the relationship between two species
      • Few genetic differences = closely related
      • Many genetic differences = distantly related

98.5% similar

4 3 12
  • Objective:
  • Do Now:
    • Pick two evidences for evolution and explain (in writing) how they show “descent with modification”. (3 minutes)
  • Do Later:
evidence for natural selection3
Evidence for Natural Selection
  • Vestigial Structures
    • Structure that is no longer used in an organism
    • Artifact of a useful structure in an ancestor
vestigial genes
Vestigial Genes
  • Vestigial genes – organisms have genes in their DNA that are no longer active
  • Chicken teeth
    • Genes for teeth can be turned back on in chickens
transitional forms
Transitional forms
  • Fossil evidence of an intermediate form between a present day species and an ancestor.
transitional forms1
Transitional Forms
  • Archaeopteryx – transitional form between dinosaurs and modern birds

Archaeopteryx – between dinosaurs and aves (birds)

transitional forms2
Transitional forms
  • Tiktaalik
    • Transitional form between aquatic and land animals
    • “lobe finned fish”
transitional forms3
Transitional Forms

Basilosaurus – intermediate between land mammals and whales


comparative embryology
Comparative Embryology
  • Early stages of development are similar across the animal kingdom
  • Objective: To discuss pesticide and antibiotic resistance
  • Do later: Popular Science – Pesticide and antibiotic resistance
pesticide resistance
Pesticide Resistance
  • Application of pesticides selects for pesticide resistance

Red = pesticide resistant

White = wild type (‘normal’)

pesticide resistance1
Pesticide Resistance
  • Colorado Potato Beetle
    • Agricultural pest
    • Resistant to all major classes of insecticides
pesticide resistance2
Pesticide Resistance
  • Can you think of any ways to combat pesticide resistance?
    • Pesticide rotation
    • Natural predators
    • Diversifying crops

The fungus Beauveriabassianais toxic to many beetles but non-toxic to humans

Diversifying crops can limit the spread of pests

antibiotic resistance
Antibiotic Resistance
  • Use of antibiotics selects for antibiotic resistant bacteria.
    • Drug resistance evolves over time.
antibiotic resistance1
Antibiotic Resistance
  • Methicillin-Resistant Staph Aureus (MRSA)
    • “Staph infection”
    • Resistant to many classes of anti-staphylococcus drugs
antibiotic resistance2
Antibiotic Resistance
  • Extensively Drug Resistant Tuberculosis (XDR-TB)
    • Lung disease
    • Resistant to three or more major anti-TB drug classes
    • High mortality (50% +)
antibiotic resistance3
Antibiotic Resistance
  • Solutions?
    • Limit prescription of antibiotics
    • Limit use of antibiotics in agriculture
    • Use full prescriptions
    • Vary prescriptions
4 17 12
  • Objective: To examine varieties of selection
  • Do Now:
    • With a partner, describe the differences between natural selection, artificial selection, and sexual selection. Provide an example of each.
  • Do later:
    • Read 13.13 and 13.17 in text
stabilizing selection
Stabilizing Selection
  • Selection that favors intermediate phenotypes

Stabilizing selection regulates birth weight

directional selection
Directional Selection
  • Selection that favors extreme phenotypes in one direction

Peppered moths

disruptive selection
Disruptive Selection
  • Selection that favors extreme phenotypes in both directions

Galapagos iguanas

practice time
Practice time!
  • With a partner, come up with an example of stabilizing and directional selection.
  • Challenge: Can you think of an example of disruptive selection?
popular misconceptions
Popular Misconceptions
  • Natural Selection does not createany traits.
    • It only selects on existing traits.

Where do new traits come from?

popular misconceptions1
Popular Misconceptions
  • Natural Selection is not goal oriented
    • Simpler organisms are older, but not less fit.
popular misconceptions2
Popular Misconceptions
  • Natural Selection is subject to constraints
    • Advantageous traits often come with trade-offs
4 20 12
  • Objective: To learn about hypotheses for the origin of cells
  • Do Now: In your notes, make a T chart to compare the conditions of early and modern Earth
  • Do Later: Read Ch. 15.1-3 in text
evidence for early life
Evidence for Early Life
  • Stromatolites – 3.5 billion years old
    • Oldest fossils
    • Single celled organisms
    • Grow in mats that harden into rock
cell theory
Cell Theory
  • Cell theory
    • All living things are composed of cells and their products
    • New cells arise from the division of older cells
    • Cells are the basic building blocks of life
    • Where did the first cells come from?
miller s experiment
Miller’s Experiment
  • Stanley Miller (1953)
    • Hydrogen gas (H2)
    • Ammonia (NH3)
    • Methane (CH4)
    • Water vapor
    • Spark
  • Product? Amino acids.
synthesis of nucleic acids
Synthesis of Nucleic Acids
  • Clay minerals catalyze the synthesis of DNA and RNA polymers


meteorite delivery
Meteorite Delivery
  • Murchison meteorite (1969)
    • Found in Victoria, Australia
    • Over 100 amino acids
      • L-amino acids
    • Nitrogenous bases (DNA/RNA)
    • Potential for extraterrestrial life
formation of protocells
Formation of Protocells
  • Lipids in water spontaneously arrange into vesicles
    • Hydrophobic effects
    • Can also be catalyzed by clay
chicken egg problem
Chicken-Egg Problem
  • DNA is needed to make proteins, and proteins are needed to make DNA
    • Which came first?
rna world
RNA World
  • 1989 – Discovery of catalytic RNA
    • RNA has a sequence of bases like DNA
    • RNA can catalyze reactions like proteins

Ribosomes contain RNA to help catalyze protein synthesis

prokaryotic life
Prokaryotic Life
  • Oldest species on earth are prokaryotes
    • No membrane bound organelles
eukaryotic life
Eukaryotic Life
  • Eukaryotic cells have membrane bound organelles
mitochondria and chloroplasts
Mitochondria and Chloroplasts
  • Mitochondria and chloroplasts have unusual properties
    • Double phospholipid membrane
    • Mitochondrial/Chloroplast DNA
endosymbiont theory
Endosymbiont Theory
  • Primitive prokaryotes became eukaryotic organelles