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A HISTORY OF LIFE Origin and Evolution of the Universe Entire universe arose about 15 billion years ago. The solar system started taking shape about 5 billion years ago. – PowerPoint PPT presentation

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Origin and Evolution of the Universe
  • Entire universe arose about 15 billion years ago.
  • The solar system started taking shape about 5
    billion years ago.
  • The sun ignites as condensed hydrogen gas atoms
    begin fusing to form helium.
  • The earth starts to coalesce and cool about 4.5
    billion years ago.
  • The early earth was rich in water, silica,
    metals, heavier molecules, and other rocky
  • Early oceans became salty as carbonates, Mg2,
    K, and other ions accumulated as acids (e.g.,
    H2CO3, HNO3, H2SO4) interacted with water and
    inorganic matter.  
  • Atmosphere arose as the earth formed and as
    out-gassing occurred from within the earth, CO
    (carbon monoxide), CO2, H2S (hydrogen sulfide),
    CH4 (methane), and NH3 (ammonia).  The
    characteristics of the early atmosphere is based,
    in part, on what planetary astronomers have
    discovered from other planets in the solar
  • Conditions on earth, before life began - Refer to
    Figures 18-6 and 18-7 on pages 380 and 382 in the
  • First protobiont appears about 3.5 billion years

Origins of Primeval Life
  • In the 1930s, Alexander I. Oparin from Russia and
    J. B. S. Haldane from England, proposed that life
    arose under certain conditions that allowed for
    abiotic formation of organic compounds. 
  • Oparin and Haldane assumed that three conditions
    had to exist
  • Anoxic atmosphere  (presence of free oxygen would
    tend to interfere with chemical reactions that
    transform simple organic molecules into complex
  • Precursor molecule supply had to be in abundance
  • A source of  Energy existed to start and keep the
    process going (electrical, chemical, light, etc.)

Stanley Millers Experiment
  • In 1953, Stanley Miller (in Urey's Lab) tried to
    replicate such conditions in the laboratory to
    see what would happen. 
  • In a sterile vessel containing no O2, Miller
    mixed a molecule supply (i.e., H2, CH4, H2O, and
    NH3), a source of energy (i.e., an electric spark
    - other folks have used UV light), and modulated
    the temperature from 0-100 C over the course of
    one week. 
  • At the end of the week, Miller collected samples
    of the "primordial soup" and analyzed it. 
  • Constituents of the soup did not contain life,
    but it did contain complex organic
    macromolecules, including amino acids,
    nucleosides, polyphosphates, and others.
  • Refer to Figures 18-8 and 18-9 on pages 384 in
    the textbook.

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  • The Protobiont the first living cell
  • How it formed, no one really knows. 
  • Some properties associated with living cells can
    arise from the interactions between organic
    macromolecules, water, and the environment. 
  • Most probably, the transition from a non-living
    complex system of macromolecules to a living
    organism somehow occurred by a yet undetermined
    means in accordance to the natural laws of
    chemistry and physics. 
  • Due to the relative complexity of a living cell,
    even a single-celled prokaryote, some scientists
    have ventured the hypothesis that life could not
    arise through abiotic (non-living) processes in
    the time scale (about 1 billion years) that it is
    thought to have occurred. 
  • The panspermia hypothesis suggests that life came
    to earth from some external source. 
  • The late Francis Crick, in his 1981 book, Life
    Itself, proposed that life was brought to earth
    by intelligent extraterrestrials. 
  • The recent suggestion that meteorites from Mars
    might contain fossilized remains of ancient
    organisms has continued to fuel the debate (refer
    to Figure 18-10 on pages 385 in the textbook). 

What happened after life began?
  • Early life forms were probably unicellular and
    resemble modern day prokaryotes.  After life got
    started, it probably existed in an anaerobic
    environment.  As more complex biochemical
    pathways evolved, such as photosynthesis, waste
    products produced of such processes (i.e.,
    oxygen) were toxic to existing organisms.
  • Geological Evidence
  • uranite - UO2 precipitates in stream beds.  Early
    atmosphere was probably lt 1 O2 .  Geologic
    record indicates uranite started to accumulate
    about 2 billion years ago.
  • iron oxide or rust suddenly starts to accumulate
    in rock that are 2-3 billion years old
  • Biochemical Evidence
  • Early attempts of cellular respiration, early
    stages of this process do not require oxygen
    (glycolysis, fermentation), but later stages
    require oxygen (oxidative respiration).

The origin of eukaryotes and the origin of
membrane-bound organelles
  • Lynn Margulis (1967) has been a strong advocate
    for the Endosymbiont hypothesis.
  • This hypothesis proposes that mitochondria and
    chloroplasts became incorporated into cytoplasm
    of eukaryotes through the symbiosis of larger
    cells with with bacteria (mitochondria and
    flagella) and cyanobacteria (chloroplasts) -
    refer to Figure 18-16 on page 392 in the
  • Prokaryotes, mitochondria, and chloroplasts
    possess similar genomes each type contain a
    naked circular loop of DNA.
  • ribosomes produced by prokaryotes, mitochondria,
    and chloroplasts are similar in size and
    structure and smaller than those found in the
    cytoplasm of eukaryotic cells
  • inner membranes of mitochondria and chloroplasts
    are similar to the plasma membranes of bacteria.
  • mitochondria, chloroplasts, and prokaryotes
    reproduce asexually through binary fission.
  • antibiotics that inhibit protein synthesis in
    bacteria also do the same to mitochondria and
    chloroplasts but not to inhibit protein synthesis
    mediated by the nucleus

Early Eukaryotes
  • About 2.5 billion years ago, a billion years
    after the origin of the first protobionts,
    eukaryotes evolved and proliferate. 
  • We would recognize many of these forms as being
    similar to modern day amoebae, protozoa, and
    unicellular green algae. 
  • Multicellular life forms do not appear in the
    fossil record until about 0.6 bya during a period
    of vast change on the face of life.

Cambrian explosion - "Life's Big Bang" occurred
about 600 million years ago
  • Evidence of this preserved as fossils in the
    Burgess Shale in British Columbia, Canada.
  • Animal Phyla in the Burgess Shale include 
    Porifera, Brachiopoda, Arthropoda, Echinodermata,
    Hemichordata, and Chordata (each phylum
    represents a different body plan).
  • Other phyla present in fossil record are extinct.

Major evolutionary trends
  • Over the past 600 million years there has been an
    explosion of animal, plant, and fungal diversity.
  • A transition from being unicellular, filamentous,
    or forming small colonies of cells toward
    becoming multicellular.
  • greater complexity
  • development of organs and organ systems
  • changes in reproductive strategies
  • development of adaptations to exist in and
    exploit a terrestrial environment
  • greater interdependence/more interactions among
    different species

SCALE (Keep in mind that these times are
  • Midnight - first protobiont or life forms come
    into existence (approx. 3.5 billion years ago) or
    midnight.  Prokaryotes rule!  Evolution of
    photosynthesis eventually leads to accumulation
    of  toxic levels of oxygen -  leads to mass
  • 1017 a.m. - first eukaryotes (e.g., unicellular
    organisms - protozoan-like).
  • 818 p.m. - trilobites and other aquatic
    multicellular organisms appear in earth's oceans
    (Cambrian explosion).
  • 834 p.m. - first vertebrates (e.g., marine and
    fresh-water fish).
  • 915 p.m. - land plants first appear.
  • 936 p.m. - winged insects take to the land and
  • 1034 p.m.- mass extinction.
  • 1118 p.m. - dinosaurs rule.
  • 1119 p.m. mass extinction (approximately 75 of
    all life goes extinct).
  • 1133 p.m. (approximately 65 mya) - adaptive
    radiation of birds and mammals.
  • 1159 p.m. - Humans arrive on the scene (200,000
    years ago).
  • 115956 p.m.- Birth of human civilization.

  • Mammals- share characteristics with other mammals
    such as  vertebrate with a spinal chord,
    skeleton, skull housing a large brain, ability to
    give birth to live offspring, mammary glands,
    hair or fur, and common ancestry.
  • Humans differ from other mammals
  • Teeth
  • canines - for tearing and piercing (most
  • incisors - nip and cut food (rodents)
  • premolars with cusps - grinding and crushing
  • molars with cusps - grinding and crushing
  • Early and more primitive mammals have 66 teeth
    modern mammals have 44 humans have 32.
  • The incidence of Wisdom teeth appear to be
    diminishing (natural selection?) in human
    populations (in Central Europe, one or more
    wisdom teeth are missing in 19 of population. 
    Wisdom teeth or third molars are common among
    Native Americans, but not among Africans).
  • Offspring have an extended period of learning.
  • Humans have an overall larger brain size.
  • Humans possess behavioral flexibility

  • Change in overall skeletal structure and mode of
    locomotion - bipedalism (able to move on 2
    appendages for extended periods of time with
    minimum energy loss) -refer to Figure 17-21 and
    1725 on page 368 and 371 in the textbook .
  • Modification of hands - humans can cup hands and
    possess a opposable thumb - refer to Figure 17-23
    on page 370 in the textbook
  • Less reliance on sense of smell and more reliance
    on sense of daytime and color vision, and depth
  • Change in dentition - primates moved from eating
    insects to more fruits and vegetables to becoming
    omnivorous - adaptation of teeth is probably
    caused by natural selection, so that the kinds of
    teeth best able to accommodate a particular diet
    become enhanced over time - refer to Figure 17-23
    on page 369 in the textbook.
  • Brain expansion - more elaborate.
  • Gorilla 600 cm3
  • Humans 1350 cm3
  • Higher intelligence may have resulted from tool
    making, need for better memory, or to increase
    ability to anticipate jumps (from branch to
    branch) or throws (weapons and spears). 
  • Behavioral and cultural evolution- ability to
    learn and mimic behavior.  ex. language.

  • Biogeographic Origin of Humans ?Africa.
  • The movement to different types of environments
    may have influenced cultural evolution. 
  • Cultural evolution tends to be Lamarckian because
    changes can be acquired and passed on. 
  • Examples are language, tool making, technology,
    and domestication of plants and animals. 
  • The transition from humans making a living as
    hunter/gathers to an agriculturally-based
    civilization started about 12-14,000 years ago,
    based on archeological evidence.

  • Mitochondrial "Eve" determined through lineage
    coalescence all human descending from a very
    small population _at_ 150,000 to 200,000 years ago. 
  • These dates are inferred based on the fact that
    mitochondrial DNA is maternally inherited and on
    assumption that mutations in this DNA happen at
    consistent rate. 
  • Thus far the fossil evidence from South Eastern
    Africa tends to support these findings.

The family tree for primates
  • Prosimians - lemuroids lemurs, lorises, etc.
  • Tarsioids - tarsioids tarsiers
  • Anthropoids - ceboids new world monkeys
  • Cercopithecoids - old world monkeys prehensile
  • Hylobatids - gibbons, siamang
  • Pongids - orangutan, gorilla, chimps
  • Hominids - humans and their most recent ancestors

Humans and Chimpanzees
  • Morphologically humans and apes are distinct from
    one another. 
  • Based on molecular data, isozyme polymorphisms
    and sequences of mitochondrial and genomic DNA,
    humans and apes, in particular, chimpanzees are
    quite similar. 
  • The A, B, and O blood type system for humans and
    chimpanzees are the same.
  • Humans and chimpanzees share 52 of the same
    gene alleles. 
  • Nucleic acid differences are even less, 1.1
    percent difference. 
  • Should humans be classified as Pan sapiens
    instead of Homo sapiens, or should chimpanzees be
    called Homo troglodytes instead of Pan
  • Was the common ancestor to humans and chimpanzees
    separated by the Great Rift Valley in Africa,
    leading to allopatric speciation? 
  • Humans probably evolved in response to changing
    environmental conditions as forests gave way to
    savannas.  Some evidence supports this
    hypothesis, but it is far from conclusive.

Did Humans Arise from Apes?
Are human descended from apes?
  • The answer is NO! Based on scientific data, it
    appears that humans and apes share a common
    ancestor whose lineage diverged 15-20 million
    years ago.
  • Apes and humans probably share a common ancestor.
  • The common ancestor may have been ape-like, but
    it was not an actual ape in the modern sense.
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