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Origins of Life.ppt

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					     EVOLUTION
Theories on the Origin of Life
    Extraterrestrial Origin
This theory states that life originated on
   other Planets outside of our solar system,
   and was carried here on a meteorite or
   asteroid.
1. Intelligent life seeded the planet.
2. Organic molecules (1st bacterial cells)
   formed in space and were carried here by
   meteorites or asteroids.
             Creationism




Life was put here, on Earth, by divine forces.
• Because of the separation of church and
  state, we are not allowed to teach this in
  school.
• This is based on faith not fact.
• Relies on stories that have been passed
  down over the years.
           Origin from Non-Living
                   Matter

• Life arose from inanimate matter.
  Random events produced stable
  molecules that would reproduce
  themselves. Then Natural Selection
  favored changes that increased their
  rate of reproduction. This eventually
  lead to the first cell. Organic acids
  came together to form organisms.
    Definition of Evolution



• Evolution is the process of change
  through time.
• It is the process by which modern
  organisms have descended from
  ancient organisms.
       Evolutionary Theory



• Is the unifying principle for all the
  biological sciences.
• Provides an explanation for the
  differences in structure, function, and
  behavior among life forms.
• It includes the change in characteristics of
  populations through generations. Thus
  existing life forms have evolved from
  earlier life forms.
           Supporting Evidence
• Comparative Anatomy- this is the comparative
  study of certain organisms showing similarities in
  anatomical features.




• Comparative Embryology- comparison of early
  embryonic development among groups of organisms
  reveals similarities which suggest common ancestry.
More Supporting Evidence
 • Comparative Cytology- Organelles are
   structurally and functionally similar in
   most divergent organisms, suggesting that
   all living things are related to some
   degree.
 • Comparative Biochemistry- Many
   different organisms have similar proteins
   and enzymes, therefore their DNA must
   be similar.
 • Geologic Records- Fossils, the direct or
   indirect remains of organisms preserved
   in media, suggest links between modern
   and ancient forms, as well as, divergent
   pathways from common ancestors.
      Origins of Life
Early Theories on How
      Life Began:
     Spontaneous
    Generation and
Scientific Experiments
         Spontaneous Generation
ABIOGENESIS- creation without life.
Spontaneous Generation was the mistaken idea that
   life can arise from non-living materials. We
   now believe the cell theory. The cell theory
   states that all cells come from pre-existing
   cells.

•   Ancient Egyptians believed that eels and frogs
    came from the mud of the Nile.
•   Aristotle “active principle” responsible for life:
       fleas come from sweat
       mice come from garbage
       flies and maggots come from dead and
    decaying meat
             Scientists and
              Experiments
• Jan Baptista van Helmont- He was a supporter of the belief
  in Spontanous Generation. He experimented with wheat
  grains in a sweaty shirt. After 21 days wheat grains are gone
  and mice are present. The active ingredient was sweat.
• Francisco Redi- (mid 1600’s) discovered maggots came from
  flies not decaying meat. Questioning Spontaneous
  Generation.
• Anton Van Leeowenhoek- Was the first to use a microscope
  to see the first living cells. He called the small animals he
  observed “animacules”. Took pond water and boiled it. Then
  added hay. Organisms were found- hay was the active
  ingredient.
• John Needham- (1745) boiled flasks of broth, then sealed
  them. Days later microorganisms were found in the broth.
  Hypothesized that “animacules” came from the gravy.
• Lorenzo Spallenzini- challenged Needham. Boiled
  contents longer, and left one flask open and the
  others closed. Life was found in the open flask, and
  not in the closed flask. This experiment supported
  Redi’s in that it proved life can only come from
  existing life.
• Louis Pasteur- took microorganisms/spores in the air
  and used flask with long curved necks to demonstrate
  that it was exposure to the air that allowed for the
  microorganisms to get into the broth in the flask
  This experiment took place over one year. This
  finally, and conclusively, disproved Spontaneous
  generation.
         Primitive Life Forms
• Raw Materials- primitive Earth was very hot, consisting of
  inorganic substances in liquid, solid, and gaseous states,
  having a rich supply of energy.

• Matter- water condensing and falling as rain, carried the
  dissolved and atmospheric gases and minerals into the seas,
  forming a hot, thin, soup.

• Energy sources- in addition to heat energy in the form of
  lightening, solar radiation, and radioactive materials in the
  rocks, provided an energy rich environment.
                     Synthesis
• Energy from the environment contributed to the formation
  of chemical bonds among the dissolved particles of the “hot,
  thin soup” of the seas.

• What was formed by the chemical bonds?

• This type of synthesis led to the formation of organic
  molecules such as simple sugars, amino acids, and nucleic
  acids.
EARLY THEORIES OF
   EVOLUTION
       Theories of Evolution
 Jean Baptiste Lamarck- 1809 French Biologist
• Proposed that life evolves or changes.
• Explained evolution as a process of adaptation.
• Law of Use and disuse. -New organs arise
  according to the needs of an organism, and their
  size is determined by the degree to which they
  are used.
• Inheritance of acquired characteristics.- Useful
  characteristics acquired by an individual during its
  lifetime can be passed on to its offspring.
• No evidence to support this theory.
 Theories cont….

August Weissman-
• Helped to disprove Lamarck’s theory
  of Inheritance of Acquired Traits.
• Conducted experiments involving the
  removal of the tails of mice over
  several generations.
• Found that the offspring of the tail-
  less mice did not pass on that
  characteristic to their offspring.
                 Theories cont…..

Hugo DeVries-
• Discovered mutations and proposed that it
  was these mutations that were the source
  of new traits that permitted evolution to
  occur.

• This was the one area, in Darwin’s theory,
  that was weak. Darwin’s theory did not
  account for the genetic basis for
  variations.
Charles Darwin- 19th century English Naturalist
• Proposed that evolution occurred as the result of Natural
   Selection.
• Overproduction- within a population more offspring are
   produced in each generation than can survive, because of
   limitations of space and food.
• Competition- individuals compete for the available food and
   opportunity to mate and reproduce.
• Variation- within each generation some individuals are better
   fitted to survive than others because of variations in
   characteristics.
• Survival of the Fittest- those individuals better fitted to
   survive are more likely to live long enough to reproduce.
• Transmission of Favorable Traits (Reproduction)- offspring of
   the fittest individuals will inherit the favorable variations that
   enabled their parents to survive and reproduce.
• Evolution of Species (Speciation)- accumulation of favorable
   variations will gradually lead to the appearance of new species
   better adapted to their environment.
• Weakness in Darwin’s Theory is that it does not account for
   genetic basis of variations. At the time, not much was known
   about the mechanisms of genetic inheritance.
    Natural Selection
• Natural selection is the process where inheritable
  traits that make it more likely for an organism to
  survive long enough to reproduce, become more
  common over successive generations of a
  population.
• It is a key mechanism of evolution.
• The Galapagos finches provide an excellent example
  of this process. Among the birds that ended up in arid
  environments, the ones with beaks better suited for
  eating cactus got more food. As a result, they were in
  better condition to mate. Similarly, those with beak
  shapes that were better suited to getting nectar from
  flowers or eating hard seeds in other environments
  were at an advantage there. In a very real sense,
  nature selected the best adapted varieties to survive
  and to reproduce. This process has come to be
  known as natural selection.
   The Peppered Moth Study
An Example of Natural Selection!
     Write similarities and
differences between these two
         organisms!
Both have the Scientific Name:
– Biston betularia
Both are the same moth, commonly called
  peppered moths. There is a story behind these
  two different color variations. Click to find out
  what happened!
Can you find the         • During the early
moth on the tree           1800’s in
trunk?                     Birmingham,
                           England there were
                           dark and cream
                           colored moths.
                           However, almost
                           all peppered moths
                           were cream colored
                           because the tree
                           trunks were light
                           colored.
        Would it be an advantage or
        disadvantage for the moth to be light?
Something was happening in the cities
      of England at this time,
    What could that have been?
        Industrial Revolution
•A greater number of factories were being
created, which meant more pollution!
WRITE:
•What do you think was happening to the
peppered moths as a result of
industrialism?
WHAT’S HAPPENING!
              • Around 1850, black-
                colored peppered
                moths started to
                become more common
                than cream, usually in
                heavily industrialized
                areas.
Why did the frequency of black
moths increase with the growing
          industries?
Darwin’s Theory of evolution
by natural selection suggests a
         hypothesis.
  White tree trunks were blackened
      by heavy pollution from
              factories.




Which Moth is better adapted to its environment?
                   Explain why?
•Perhaps dark moths       •Light-colored moths
sitting on soot-          would have stood out
darkened bark             against a dark
escaped being eaten       background and
by birds because it       would have been
was too hard for the      easy prey for hungry
birds to see the dark     birds. Therefore,
moths against the         more dark moths
dark background.          survived.
          This is an example of Natural Selection!
• Natural Selection- is a gradual
  change in a species in response to
  the demands of its environment.
Do Now:
• Write how the peppered moth
  during the 1800’s was an example
  of natural selection in action!
  Charles Darwin
Background and Observations
              Background Info.
•   Darwin was born in England, Feb. 12, 1809.
•   Studied to become a physician, decided not to continue.
•   Studied to become a minister, decided not to continue.
•   Graduated college and at the age of 22, signed aboard the
    HMS Beagle, as ship’s Naturalist. His job, as naturalist, was
    to collect and study plant, animal, and geologic specimens
    form the journey around the world.
•   The voyage began in December of 1831 and lasted 5 years.
•   Darwin kept extensive journals of his observations, studies,
    and thoughts.
•   Darwin’s ideas on gradual change were influenced by the
    evidence presented by Charles Lyell. Lyell stated that
    gradual and observable geologic processes, such as erosion,
    could explain the physical features of the Earth today.
•   Darwin was also influenced by James Hutton, who in 1785
    proposed that the Earth was formed by geological changes
    that occurred over a very long period of time .
• Darwin’s most intriguing finds occurred on the
  Galapagos Islands.
• After returning home from his voyage, he
  continued to wonder about the things that he had
  seen.
• In 1838, he read an essay by Thomas Malthus, on
  human population. Malthus stated in his essay,
  that populations can grow much faster than the
  rate at which food supplies and other resources
  can be produced. Production of more individuals
  than the environment can support lead to a
  struggle for existence. This concept helped
  Darwin to propose a mechanism for evolutionary
  change.
• In 1844, Darwin outlined his ideas. In 1858, after
  another British naturalist, Alfred Wallace, came to
  the same conclusions about the basic mechanism
  for evolutionary change, Darwin published his book,
  The Origin of the Species by Means of Natural
  Selection.
      Darwin’s Observations
• There was an enormous number of species that
  inhabited the Earth.
• Patterns of Diversity- he asked why similar
  ecosystems were inhabited by different types of
  species (why the grasslands of England had
  rabbits, why the grasslands of Australia had
  kangaroos?).




• Darwin wondered why so many organisms that were
  once alive, were now preserved as fossil remains.
  Why did these organisms cease to exist? How
  were the fossils related to the living organisms?
• The Galapagos Islands- a small group of 16 islands 1000km
  off the west coast of Equador. Darwin noticed that even
  though the islands were relatively close together, they still
  had very different climates.
         The lowest were hot, dry, and barren
         The highest had more rainfall, vegetation, and
          more animal life.
• Darwin noticed that the characteristics of many plants and
  animals varied noticeably between the islands.
          Hood Island- tortoises had long necks, curved shells
  open around the legs, allowing the animal to get more access
  to the sparse vegetation.
          Isabella Island- tortoises had shorter necks, domed,
  curved shell, allowing for the animals to feed better on the
  more abundant vegetation that was close to the ground.
• Many specimens of finches were collected and differences
  were observed in the shapes and sizes of their beaks.
• After returning to England, Darwin began to wonder if the
  animals living on the islands were once members of the same
  species.
Supporting Observations For
  the Theory of Evolution
            Geologic Records

• Earth has been estimated to be between 4.5-5 billion
  years old. (Determined through radioactive carbon
  dating).
• Fossil remains-the direct or indirect remains of
  organisms preserved in media such as tar, ice, rock, or
  amber.
• Fossils of prokaryotic life indicate that life existed
  over 3.4 billion years ago.
• Fossils can be found in the upper, and lower strata.
  These have been found to resemble each other,
  suggesting a connection between modern forms and
  older forms, as well as, divergent pathways from
  common ancestors.
Comparative Anatomy
•   Comparative studies of certain organisms indicate
    similarities in anatomical features.
•   Homologous structures- anatomical parts that are similar
    in structure and origin (development), but function
    differently. (Ex.- wing of bird, arm of man, foreleg of
    horse).
•   Homologous bones exist in the forelimbs of many
    different vertebrates such as birds, horses, man, bats,
    whales.
•   Analogous structures- are similar in appearance and
    function, but have developmental differences. (Ex.- wing
    of bird and wing of butterfly).
            Comparative Embryology
The study of embryonic developments among groups
    of organisms reveals similarities that suggest
    common ancestry.

1.   Early vertebrate embryos resemble each other.
2.   As development proceeds, the distinctive
     features of each species becomes apparent.
3.   All have gill slits, tail-bones (coccyx), segmented
     backbones, and are C-shaped.
       Comparative Cytology
According to the cell theory, the cell is the unifying
  structure for living things. Organelles such as the
  cell membrane, ribosomes, and mitochondria, are
  structurally and functionally similar in most
  divergent organisms. This suggests that all living
  things are related to some degree. The fewer the
  differences in these cell structures, the closer
  the relationship appears.
 Comparative Biochemistry
• Nucleic acids, their structure and
  function, are similar in living
  organisms.
• Many different organisms have
  similar proteins and enzymes.
• In order for this similarity to
  occur, their DNA must be similar.
• The greater their biochemical
  similarity, the closer the
  relationship among organisms,
  thus suggesting evolutionary
  relationships.
       Vestigial Structures
• These are structures that do not have
  any use, but are the remains of
  structures that were once functional in
  ancestral organisms.

• Some examples of vestigial organs are:
   Humans- appendix, coccyx, 3rd molars
   Horses- splint bones
   Whales- pelvic (hip) bones
Modern Theory of Evolution
       (continued)
    A Time Frame for Evolution
         Geographic Isolation
Geographic Isolation- favors speciation
  by segregating a small group of
  organisms from the main population.
  Changes in gene frequency are more
  likely to occur in a small population. In
  time, this isolated population may
  evolve into a separate species due to:
• Different initial gene frequencies than
  the main population.
• Different mutations occur within the
  main population and the isolated
  population.
• Different environmental factors, thus
  having different selection pressures
  on each population
• An example of this would be Darwin’s
  Finches, and Australia’s marsupials,
  and the Albert Squirrel.
                       Reproductive
                         Isolation
Reproductive Isolation- separated groups my become
  so divergent that even geographic barriers were
  removed, interbreeding could not take place. Thus
  the populations have become reproductively
  isolated and are now two separate species.
• These populations now have separate gene pools.
• Reproductive Isolation results from various
  isolating mechanisms that include: Geographic
  Isolation, Behavioral Isolation, or Temporal
  Isolation.
 A Time Frame for Evolution
Gradualism- Gradualism proposes that
  evolution is slow , gradual, and continuous.
  This viewpoint is supported by geologic
  fossils, which show slight changes in
  organisms between adjacent layers of
  sedimentary rocks.

• Species originate through gradual change
  of adaptations. There is one line of
  descent.
                   Time Frame (cont.)
Punctuated Equilibrium- Punctuated Equilibrium proposes that
   species have long periods of stability, interrupted by
   geologically brief periods of significant change, during which
   a new species may evolve.
• This was proposed by Niles Eldredge, and Stephen Gould in
   1972.
• Speciation occurs in relatively quickly, in rapid bursts,
   followed by long periods of genetic stability in between.
• Environmental changes (higher temps., and introduction of
   competitive species) lead to rapid changes in a small
   population’s gene pool that is reproductively isolated from
   the main population.
• Speciation happens relatively quickly- 10,000 years or less.
• Punctuated Equilibrium involves many lines of descent, it is
  a pattern of long, stable periods, interrupted by brief
  periods of more rapid change.

				
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