EVOLUTION

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EVOLUTION

• Nancy G. Morris
• Volunteer State Community College

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Theory of Evolution

• The theory of evolution states that
• life arose from random non-living chemical
  processes that took place in the ancient oceans.
• mutations and natural selection have brought
  great change in organisms.
• Life has become more diverse and complex.

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THE ORIGIN OF LIFE

• Life on earth originated
• approximately 3.5 billion years ago.

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THE ORIGIN OF LIFE

• The theory states that abiotic chemical processes
  occurring on the early earth produced basic
  precursors leading to the building blocks of
  life.
• In 1953, Miller and Ureys classic experiment
  achieved synthesis of small organic molecules
  from abiotic compounds like those thought to
  exist on the early earth.

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THE ORIGIN OF LIFE

• Urey and Miller produced amino acids and other
  building blocks by electrically sparking
  atmospheric gases that probably existed on the
  early earth.

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Figure 20.1 A biotic synthesis of organic
molecules in model system
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THE ORIGIN OF LIFE

• An organic soup -- a mixture of all sorts of
  carbohydrate, amino acids, nucleotide, and lipid
  molecules --accumulated in the early oceans as
  atmospheric gases reacted.
• Energy was supplied by lightning and UV
  radiation from the sun.

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THE ORIGIN OF LIFE

• Laboratory simulations of early earth conditions
  have produced organic polymers such as
  polypeptides.
• Amino acids form polypeptides abiotically when
  water with amino acids drys on hot clay.

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THE ORIGIN OF LIFE

• Heterotrophic protocells probably came next.
• It is thought that these protocells had a cell
  membrane.
• Figure 20.4

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THE ORIGIN OF LIFE

• Protocells must have fed on the organic soup of
  the early oceans.
• Since there was no oxygen, we assume that the
  first cells were anaerobic fermenters.

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THE ORIGIN OF LIFE

• Once the protocell was capable of reproduction,
  it became a true cell, and biological evolution
  began.
• Many scientists think that these ancient cells
  had RNA for their genetic code and later cells
  had DNA.

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Classification 3 Domains

• Bacteria Archaea Eukaryotes
• Anaerobic Heterotrophs
• capable of division
• Anaerobic Heterotrophic Protocells
• Organic Soup

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Comparison of 5 and 6-Kingdom Systems
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HISTORY OF THE EVOLUTION

• The concept of evolution was formulated by Greek
  philosophers over 2000 years age.
• LeMarck (a French biologist early 1800s)
  proposed a theory of evolution based on acquired
  characteristics. (Figure 18.4)
• Charles Darwin (1860s) published his theory of
  evolution based on natural selection.

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Factors that Influence Evolution

• Continental Drift
• Figure 20.14 page 334
• Plate tectonics page 335
• The relationship of continents to one another has
  affected the biogeography of the earth.
• The mammalian diversity of our world is the
  result of isolated evolution on separate
  continents.

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Factors that Influence Evolution

• Mass Extensions
• Figure 20.16 page 336
• Meteorite impact
• Tectonic, oceanic, and climatic fluctuations

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Natural Selection (page 306)

• Natural selection is selection by the environment
  for genotypes that best adapt an organism to
  present conditions
• 1) Requires variation members of the population
  must be different form one another

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Natural Selection

• 2) Requires inheritance
• 3) Requires adaptation to environment
• 4) Differential reproduction individuals better
  adapted will survive, reproduce, and make up a
  greater proportion of the next generation

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Evolution

• the change in allele ratios over time
• Liquids have no shape of their own they assume
  the shape of the container. Plants and animals,
  in fact all living things, are affected by their
  environment, the container in which it exists.
  

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Evolution

• Fitting into the environment is called evolution.
• Evolution is never complete, however, due to the
  ever-changing nature of the earth.

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Natural Selection

• Darwin and Wallaces Theory
• Natural Selection means Survival of the best
  adapted.
• Nature is prolific. More individuals are produced
  than the environment can support -- thus
  competition.
• Individuals with mutations which are beneficial
  (cause better adaptation to the environment)
  have a better chance of surviving.

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ISOLATION OF POPULATIONS

• Darwins observations occurred on the Galapagos
  Islands
• When a small population becomes geographically
  isolated from the main population, the small
  population tends to evolve into a separate
  species (speciation) because gene flow has been
  cut off from the main population.

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MASS EXTINCTIONS

• The fossil record shows that evolution is most
  rapid following a mass extinction.
• Mammals and birds evolved rapidly after
  dinosaurs extinction 65 million years ago.

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THE PACE OF EVOLUTION

• Darwin thought evolution proceeded gradually.
• Stephen Gould and other modern paleontologists
  think that evolution tends to occur in spurts --
  especially after a mass extinction.
• Gould believes that evolution is often rapid,
  then a new species remains constant for long
  periods until the next major environmental change
  spurs another burst of evolution.

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THE PACE OF EVOLUTION

• Biologists know of some species that have changed
  very little over many millions of years because
  they are so well adapted to their niche or their
  way of life.
• Horse shoe crab

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Evolutionary Evidences

• The hypothesis that organisms share a common
  descent is supported by many lines of evidence
• Artificial selection
• Fossil record
• Comparative anatomy (Figure 18.16)
• Comparative embryology
• (Figure 18.17)
• Comparison of DNA

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Homologous structuresanatomical signs of
evolution Figure 18.16 page 296
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Artificial Selection

• All breeds of dog have evolved from a wolf
  ancestor through artificial selection by
  humankind over the last 10,000 years.
• Cabbage, broccoli, cauliflower, brussel sprouts
  all have been derived from a common ancestor by
  humankind in just a few thousand years.

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FOSSIL RECORD

• The oldest fossils are of the simplest organisms.
• Fossil evidence for the evolution of vertebrates
  is more complete than for soft-bodied animals.
• Strong fossil evidence for transitional forms
  like Archaeopteryx

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Comparative Anatomy

• The bone types in the limbs of amphibians,
  reptiles, birds, and mammals is very similar.
• This suggests common ancestry.

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COMPARATIVE EMBRYOLOGY

• All vertebrate animals are similar in their
  early embryonic development.
• They all have a notochord, tail, and gill pouches
  in their early development.
• In humans, the notochord is replaced by backbone,
  the tail degenerates, and gill pouches become the
  Eustachian tube, tonsils, and glands in the
  neck region.

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COMPARISON OF DNA

• Chimpanzees and humans have a DNA similarity of
  99.
• Humans and cows would have less DNA similarity.
• Humans and jellyfish would have still fewer genes
  in common.
• The degree of DNA similarity between two
  organisms indicates how closely related they are.

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VESTIGAL STRUCTURES

• The appendix, coccyx, and embryonic tail are
  vestigial structures in humans.
• Nonfunctional eyes in cave fish are vestigial.
• Vestigial pelvic bones are present in the body of
  the python.

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VERTEBRATE EVOLUTION

• The ancestor of the vertebrates was a small
  fishlike animal with a notochord that lived in
  the seas about 500 million years ago.
• The first fishes were jawless. Today the only
  surviving jawless fishes are lamprey.

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VERTEBRATE EVOLUTION

• Some of the jawless fishes evolved into jawed
  fishes .
• The early jawed fishes evolved into
• cartilaginous fishes
• bony fishes

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VERTEBRATE EVOLUTION

• Today there are many bony fishes.
• Cartilaginous fishes include sharks, skates, and
  rays.
• Some of the early lobe-finned fishes evolved into
  the first amphibians.

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VERTEBRATE EVOLUTION

• Amphibians today include frogs, toads, and
  salamanders.
• Some of the early amphibians evolved into the
  first reptiles.
• Today reptiles include snakes, lizards,
  turtles, crocodiles, and alligators.

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VERTEBRATE EVOLUTION

• The reptiles are better adapted to dry land
  living because of their waste-proof eggs and
  scaly skin.
• Some of the early reptiles evolved into the first
  birds and mammals.

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VERTEBRATE EVOLUTION

• Archaeopteryx was the first bird according to the
  fossil record.
• It had these reptilian features
• teeth in beak
• claws
• long reptilian tail vertebrae

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VERTEBRATE EVOLUTION

• Archaeopteryx was a bird because it had feathers.
• Early mammals were shrew-like animals.
• When dinosaurs became extinct, birds and mammals
  expanded into many diverse species.

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HOMINID EVOLUTION

• Hominids are primates which walk upright.
• The first hominids we have fossils of is Lucy
  Australopithecus afarebnsis from Africa.

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Hominid Evolution

• Homo habilis used stone tools.
• Homo erecutus used fire.
• Homo sapiens neanderthalensis lived during the
  Ice Age. They were hardy, muscular hunters who
  buried their dead.

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