Transcript Evolution/Origin of Life

Evolution/Origin of Life
• What is life? Where does life come from?
• The Biogenesis/Abiogenesis Debate:
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Abiogenesis also known as Spontaneous Generation
Ancient Times (Aristotle): frogs from mud puddles
17th C (Jean Van Helmont): “mouse recipe”
Presence of the “active principle”
17th C (Francisco Redi): maggots from decaying meat
1st scientist to use a control
Gauze let air into the jar, and “caught” eggs on top
• 18th C (John Needham): boiled meat broth in loosely
sealed flasks
 Presence of “vegetative force”
• 18th C (Spallanzani); melted glass at top of flask
• 19th C (Pasteur): used swan-necked flasks to end the
Biogenesis/Abiogenesis Controversy
 Pasteur-Pouchet Debate
• Virchow : coined the term “biogenesis”
Origin of Life:
• Oparin’s Hypothesis (1936)
• 14.6 billion years ago (“Big Bang”)
 Sun formed from explosion of a small volume of matter and energy
• 4.6 billion years ago: Earth, other planets formed
 Heavy elements in the center of the earth (Fe, Mg)
 Lighter elements form primitive atmosphere (CHON)
 Evaporation of H2O; Clouds formed; Rained for millions of years;
Lightning
• Formation of the oceans
• Polymer formation in the oceans (“organic soup”)
 Heterotrophs (1st cells) dependent on food source in the ocean
(anaerobic)
 Autotrophs (2nd cells) independent; able to produce their own food
by photosynthesis (aerobic); release of O2 (formation of the Ozone
Layer)
• Stanley Miller (1953): proved Oparin’s
Hypothesis in his lab
 Substituted electricity for lightning
 Filled a vat with H2O, CH3, NH3
• Result: (2 weeks later) – amino acids
 Amino acids are in all living things – “building blocks of
proteins”
• Life came from chemical changes in the
ocean.
• Why is this explanation not considered to be
spontaneous generation?
 It took millions of years
 If lightning occurred…If it rained…If certain chemicals
were present…, then it is a possibility.
Evolution:
• Gradualism: A gradual
change in a species over
millions of years (Charles
Darwin)
• Punctuated Equilibrium:
periods of stability and
periods of drastic
changes within a species
(Stephen Jay Gould)
Proofs of Evolution:
• Fossils in sedimentary rocks
• Homologous Organs: same structure but different
function; examples: bird’s wing, horse’s front leg, whale’s
fin, human’s arm, bat’s wing
 Common ancestor
 Divergent evolution (Adaptive radiation): adapt to different
environments
• Analogous Organs: same function but different
structure: examples: bat’s wing, butterfly wing
 No common ancestor
 Convergent evolution (organisms come together in the same
environment)
• Vestigial Organs: organs with no apparent function;
examples: tone, wisdom teeth, ear muscles, appendix,
3rd eyelid, little toe, cave-dwelling fish with eyes
• DNA-RNA-ATP Similarities
• Similarities in Embryos
Charles Darwin (1809-1882)
• Naturalist on the Beagle (5 year voyage)
• Galapagos Islands (100 km. west of Ecuador)
 Variety of finches (13), tortoises, iguanas
• Influences on Darwin:
 Charles Lyell (Principles of Geology)
 Thomas Malthus (Essay on the Principle of Population)
• Work of Alfred Wallace
• 1859: On the Origin of Species
• Darwin’s Theory of Evolution:
 Overproduction of the species
 Observations of Thomas Malthus
 Constant struggle to survive
 Competition greatest among members of the same species
 Uniqueness (variety)
 Organisms produced sexually show a variety among offspring
 Natural Selection
 Nature/environment chooses which organisms will survive
 Survivors pass on genes
 “Survival of the Fittest”
LaMarck (1744-1829)
• Theory of Need
 Organisms have an inner need to change
• Theory of Use and Disuse
 Organs not used weaken and eventually disappear
• Inheritance of Acquired Traits
 Acquired abilities/traits are passed on to offspring
• Giraffe Story:
• How did giraffes get longer necks?
 Giraffes stretched their necks ---Led to longer necks---Organisms
change to survive in their environment (L)
 Variety of giraffes with different neck sizes---Nature or
environment determines which organisms will survive (D)
Natural Selection and Adaptation:
• A result of environmental change
• Story of English Peppered Moths:
 1800’s: 2 species of peppered moths in
Northern England (light – dark)
 Trees covered with light gray lichens
 What happened to the light-colored moths?
 What happened to the dark-colored moths?
 Industrial Revolution : soot on blackened tree bark
 What happened to the light-colored moths?
 What happened to the dark-colored moths?
Natural Selection Distribution Curves:
• Stabilizing Selection:
 Selection against the
extremes
 When individuals near the
center of the curve have
higher fitness than
individuals at either end
of the curve
 Intermediate phenotype
(average) favored
• Directional Selection:
 When individuals at one end
of the curve have higher
fitness than individuals in the
middle or at the other end
 Evolution causes an increase
in the number of individuals
with the trait at one end of the
curve
• Disruptive Selection:
 When individuals at the
upper and lower ends of the
curve have higher fitness
than individuals near the
middle of the curve
 Selection acts against
individuals of an intermediate
type (average)
Adaptation:
• The fitness of an organism for its
environment (able to survive and
reproduce)
• Structural: involves body parts
 Camouflage: hiding by blending in with
background
 Mimicry: copying body parts
 Monarch butterfly (bitter) and Viceroy butterfly
(good tasting); Viceroy survives possible predators
by copying Monarch
• Physiological: organism changes its metabolism to
survive
 Bacteria adjusts to different doses of penicillin
• Behavioral: organism changes its behavior to survive
 Courtship and mating behaviors
Mechanisms of Evolution:
• Gene Pool: all the genes for a population
• Genetic Equilibrium: all of the genes coming into a
population equal all of the genes coming out of the
population
(in=out)
• What causes changes in the genetic equilibrium?
 Mutations (DeVries), Genetic Drift (chance occurrence), Gene
Flow (immigration and emigration), Natural Selection
• Hardy-Weinberg Law (1908): A constant population
exists if there are no mutations, no genetic drift, no gene
flow (immigration or emigration), random mating, and a
large population
Speciation:
• Species: a group of interbreeding organisms that share
a gene pool
• Geographic Isolation: members of the same species
separated by a physical boundary (mountain, river)
Darwin’s finches
• Reproductive Isolation: formerly interbreeding
organisms prevented from reproducing (seasonal –
different breeding seasons)
Evolution vs. Creationism:
• A belief in a scientific explanation for the creation of life
vs. a literal interpretation of the Biblical story of Genesis
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1925 Scopes Trial (Tenn.)
John Scopes (a substitute biology teacher) violated Butler Act
Wm. Jennings Bryant (Prosecutor) – Clarence Darrow (Defense)
Scopes found guilty (fined $100)
Scopes Trial: