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 Urey 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

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

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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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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.

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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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Current Classification Schemes
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HISTORY OF THE EVOLUTION CONCEPT

• 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.
• Charles Darwin (1860s) published his theory of
  evolution based on natural selection.

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Mechanisms of Evolution

• Natural selection
• Mutation
• Isolation of Populations
• Mass Extinctions

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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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Continental Drift
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MASS EXTINCTIONS

• The fossil record shows that speciation
  (evolution) is most rapid following a mass
  extinction.
• Mammals and birds evolved rapidly into many
  different species after the dinosaurs were wiped
  out 65 million years ago.
• Humankind might not be here today had the
  dinosaurs not become extinct.

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THE PACE OF EVOLUTION

• Darwin thought evolution proceeded gradually.
• Stephen Gould and some 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.

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Evolutionary Evidences

• Artificial selection
• Fossil record
• Comparative anatomy
• Comparative embryology
• Comparison of DNA
• Vestigial structures

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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

• Fossils of the simplest organisms are the oldest.
• Fossil evidence for the evolution of vertebrates
  is more complete than for soft-bodied animals.
• Fossil evidence for transitional forms like
  Archaeopteryx is strong.
• Fossil evidence for human evolution is compelling.

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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
  vestigal structures in humans.
• Nonfunctional eyes in cave fish are vestigal.
• 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 hominid we have fossils of is Lucy
  Australopithecus afarensis 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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Major episodes
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Earths Inhabitants