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HISTORY OF LIFE

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HISTORY OF LIFE Chapter 14 Some scientists still believed that bacteria and viruses spontaneously generated from the air Pasteur proved them wrong with his experiment ... – PowerPoint PPT presentation

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Title: HISTORY OF LIFE


1
HISTORY OF LIFE
  • Chapter 14

2
  • How old is the Earth?
  • What changes have occurred?
  • What is a Mass Extinction?
  • How do we know they happened?

3
Field Museum Trip
  • Important Questions
  • 2,4,9,16,21,24,27,32,43,52,59

4
The Record of Life
  • Ch. 14, Sec 1

5
Early History of Earth
  • 5 billion years ago our solar system was formed
    as a swirling mass of gas and dust
  • Gravity pulled this material together to form the
    sun
  • Remaining gas and debris circled the newly formed
    sun
  • Collisions between the space debris created the
    planets

6
  • Earth formed about 4.6 billion years ago, dated
    by studying the layers of rock that make up the
    planet
  • Young Earth was hot, there was no atmosphere to
    block UV rays from the sun
  • No oxygen to breath
  • A lot of carbon dioxide and water

7
  • Life originated in Earths oceans 3.9-3.4 billion
    years ago
  • Early life forms would have been very similar to
    bacteria

8
History in Rocks
  • Rocks provide information about Earths history
    including the history of life on Earth
  • Paleontologists study ancient life and fossils

9
  • Fossils are found in sedimentary rock
  • Organism gets buried in mud, sand, or clay after
    they die
  • More sediment gets layered over the organism,
    over time the minerals in the sediment replace
    the minerals in the skeleton

10
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11
Dating Fossils
  • Relative Dating (stratigraphy) layers of rocks
    have different ages, the youngest layers on
    top older fossils found in older layers of rock
  • Radiometric Dating atoms in the fossil break
    down at a certain rate, age of the fossil depends
    on the ratio of atoms to broken down atoms

12
Geologic Timescale
  • Begins with the formation of Earth and goes
    through present time
  • Scale is divided up by the kinds of organisms
    that lived during that time

13
  • Layers of rock match up with the Geological
    Timescale

14
Organization of the GTS
  • Broken down into 4 Eras, each era is further
    broken down into Periods
  • The eras and periods are characterized by
    specific events and specific organisms
  • Mass Extinction many organisms disappear from
    the GTS almost all at once

15
4 Eras
  • 1. Precambrian Era
  • Beginning of the GTS, longest era 87 of Earths
    history
  • Oldest rocks are from the Precambrian, oldest
    fossils too
  • First organisms were single celled

16
  • 2. Paleozoic Era
  • Cambrian Explosion occurred during the Cambrian
    Period
  • Enormous increased in diversity of life in oceans
  • Organisms with backbones emerged
  • Mass extinction occurred at the end of the
    Paleozoic Era killing off 90 marine life, 70
    land life

17
  • 3. Mesozoic Era
  • began 248 million years ago
  • Dinosaurs died out during another mass extinction
    making room for mammals
  • Meteor crash could have caused the mass extinction

18
  • 4. Cenozoic Era
  • Began 65 million years ago
  • Increased diversity in mammalian life
  • Modern humans appeared 200,000 years ago

19
  • As you move towards the bottom of the rock
    layers, you move back on the Geological Timescale
  • Similar fossils found on different continents
    because at several times in Earths history the
    continents were connected

20
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21
  • Pangea existed 250 million years ago
  • Plate Tectonics the surface of Earth is made up
    of plates that drift on top of a molten layer of
    rock
  • http//www.nature.nps.gov/geology/usgsnps/animate/
    PLATES_3.MPG
  • http//www.ucmp.berkeley.edu/geology/tecall1_4.mov

22
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23
The Origin of Life
  • Ch. 14, Sec. 2

24
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25
Spontaneous Generation
  • Pre-17th century it was believed that living
    things arose from nonliving things through a
    process called Spontaneous Generation

26
  • 6th century BC Greek philosophers propose life
    arose when sunlight was shined onto mud
  • Why?

27
  • 1600s It was believed that mice appeared from
    rotten grain
  • Why?

28
Francesco Redi (1626-1697)
  • Mid-17th century people believed flies were
    spontaneously generated from rotting meat
  • Redi was a scientist who noticed a life stage to
    the flies on the rotten meat
  • 1. Maggots
  • 2. Pupa
  • 3. Flies
  • He observed that the maggots appeared where flies
    had landed first

29
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30
  • Redi predicted that if the meat could be kept
    away from the flies, then there would be no
    maggots on the meat
  • He did not believe that flies spontaneously
    generated from meat!!!
  • So he set up his experiment

31
  • Control Group uncovered jar of meat, flies
    layed eggs, which hatched into maggots, which
    turned into more flies
  • Experimental Group covered jars of meat, flies
    have no chance to lay eggs, new flies do not
    appear

32
Louis Pasteur (1822-1895)
  • Finally disproved spontaneous generation once and
    for all! 200 years after Redis experiment
  • Pasteur set up an experiment where boiled broth
    was exposed to air, but microorganisms couldnt
    fall in

33
  • By the 1800s scientists understood (thanks to
    the microscope invented a century ago) that
    microorganisms (bacteria viruses) caused people
    to get sick
  • But.

34
  • Some scientists still believed that bacteria and
    viruses spontaneously generated from the air
  • Pasteur proved them wrong with his experiment

35
  • Boiled broth was exposed to air in a specially
    shaped flask over a period of time but nothing
    grew
  • Once the neck was broken off bacteria grew in the
    broth
  • Bacteria did not spontaneously grow from the
    air!!!

36
  • Thanks to Pasteur.
  • Biogenesis living organisms come from other
    living organisms

37
Modern Experiments on Origins
  • All elements found in organic compounds needed to
    form biomolecules existed on Earth since its
    formation
  • Early atmosphere contained Ammonia (NH3),
    Hydrogen Gas (H2), Water Vapor (H2O), Methane
    (CH4)

38
  • Under high temperature the gases might have
    formed simple organic compounds (contains Carbon)
    like amino acids
  • When Earth began to cool the organic compounds
    would have condensed with the water vapor and
    collected in lakes and seas

39
Stanley Miller Harold Urey (1953)
  • Recreated the conditions of early Earth in the
    lab on a smaller scale
  • Included chemicals present at the time and an
    energy source similar to what as present at the
    time
  • Able to generate amino acids (biomolecule)

40
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41
Alternative Hypotheses
  • 1. Life (biomolecules) emerged in ice (Stanley
    Miller)
  • Within ice there are chemicals to create
    biomolecules microscopic pockets of water

42
  • Water freezes forcing the chemicals to be close
    together which increases the chances of chemical
    reactions occurring
  • When the ice melts the biomolecules generated are
    released into oceans

43
  • 2. Life (biomolecules) emerged in deep sea vents
  • Vents provide the heat chemicals that could
    cause chemical reactions to generate biomolecules

44
Formation of Protocells
  • Protocell Heating the amino acids can cause
    them to take on some life activities like growth
    and division

45
First True Cells
  • No direct evidence of the first cells, scientist
    can only analyze data that we collect now
  • Early Earth had little oxygen, oldest fossils
    thought to be cells resemble the size shape of
    some living prokaryotes, the first cells had
    organic molecules to eat

46
  • Therefore.
  • The first cells were anaerobic, heterotrophic
    prokaryotes
  • Anaerobic respiration that doesnt require
    oxygen
  • Heterotrophic needs to eat other things in
    order to get the organic molecules needed for
    life

47
  • Next evolved
  • Autotrophs make their own food
  • Early autotrophs similar to present day
    Archaebacteria
  • Archaea prokaryote organisms that thrive under
    harsh conditions, make food through
    chemosynthesis
  • Chemosynthesis CO2 is the carbon source, energy
    comes from the use of inorganic chemicals

48
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49
  • Next evolved
  • Photosynthetic prokaryotes
  • Autotrophs now able to use sunlight energy to
    make food
  • Created oxygen for the atmosphere which allowed
    for an increase in diversity of life because now
    there was an ozone layer (provides protection
    from UV light)

50
Endosymbiotic Theory
  • Eukaryotic cells evolved from Prokaryotic cells
  • Symbiosis close, long term relationship between
    species
  • An ancient prokaryote engulfed another prokaryote
    and instead of digesting it they lived together

51
  • This explains why mitochondria has its own DNA
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