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HISTORY OF LIFE

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Title: HISTORY OF LIFE


1
HISTORY OF LIFE
  • Chapter 14

2
Take out notebook paper answer the following
questions with your lab partner
  • 1. How old do you think the planet Earth is?
    Explain.
  • 2. What physical changes have occurred on Earth
    during its history? What caused these changes?
  • 3. What is a Mass Extinction? What evidence do
    scientists have?

3
The Record of Life
  • Ch. 14 - Section 1 - pg. 369

4
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

5
  • 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

6
  • Life originated in Earths oceans 3.9-3.4 billion
    years ago
  • Early life forms would have been very similar to
    bacteria

7
Table 14.1 pg. 370
  • 4. Which of the following fossil types have you
    or your lab partner seen before? Explain when and
    where.
  • Read Paleontologists Detectives to the past on
    pgs. 370 371.
  • 5. Give 2 examples of evidence paleontologists
    can use to determine information about the past.
    EXPLAIN!!!

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

9
Figure 14.2 pg. 372
  • 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
Figure 14.3 pg. 373
  • 6. What are the chances that the Protoceratops
    death was not an accident? Explain your
    reasoning.
  • 7. What are 2 ways that the fossil in the Figure
    14.3 could have become exposed?

12
Dating Fossils
  • Relative Dating (stratigraphy) layers of rocks
    have different ages, the youngest layers on
    top older fossils found in older layers of rock,
    ex. stacks of newspapers.
  • 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.

13
Geologic Timescale Fig. 14.4 pgs. 374 375
  • 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

14
  • Layers of rock match up with the Geological
    Timescale

15
Organization of the G.T.S.
  • 8. List each Era from oldest to most recent and
    describe the types of organism found in each one.
  • 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

16
4 Eras
  • 1. Precambrian Era
  • Beginning of the GTS, longest era, 87 of Earths
    history
  • Oldest rocks and fossils are from the Precambrian
    Era
  • First organisms were single celled

17
  • 2. Paleozoic Era
  • Cambrian Explosion occurred
  • Enormous increase 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

18
  • 3. Mesozoic Era
  • began 248 million years ago
  • Dinosaurs died out during another mass extinction
    making room for mammals
  • Meteor crash most likely caused the mass
    extinction

19
  • 4. Cenozoic Era
  • Began 65 million years ago
  • Increased diversity in mammalian life
  • Modern humans appeared 200,000 years ago

20
  • 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

21
Thorium decays into lead. It takes 75,000 years
for half the amount of thorium in a sample to
decay into lead.
Half Life Total years passed Grams of Thorium Grams of Lead
0 0 15 0
1 75,000
2
3
4
22
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23
  • 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

24
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25
The Origin of Life
  • Ch. 14, Sec. 2

26
Spontaneous Generation
  • Pre-17th century it was believed that living
    things arose from nonliving things through a
    process called Spontaneous Generation

27
  • 6th century BC Greek philosophers propose life
    arose when sunlight was shined onto mud. Why?

28
  • 1600s It was believed that mice appeared from
    rotten grain. Why?

29
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

30
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31
  • 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

32
  • 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

33
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

34
  • By the 1800s scientists understood (thanks to
    the microscope invented a century ago) that
    microorganisms (bacteria viruses) caused people
    to get sick
  • But.

35
  • Some scientists still believed that bacteria and
    viruses spontaneously generated from the air
  • Pasteur proved them wrong with his experiment

36
  • 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!!!

37
  • Thanks to Pasteur.
  • Biogenesis living organisms come from other
    living organisms

38
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)

39
  • 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

40
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)

41
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42
Alternative Hypotheses
  • 1. Life (biomolecules) emerged in ice (Stanley
    Miller)
  • Within ice there are chemicals to create
    biomolecules microscopic pockets of water

43
  • 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

44
  • 2. Life (biomolecules) emerged in deep sea vents
  • Vents provide the heat chemicals that could
    cause chemical reactions to generate biomolecules

45
Formation of Protocells
  • Protocell Heating the amino acids can cause
    them to take on some life activities like growth
    and division

46
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

47
  • 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

48
  • 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

49
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50
  • 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)

51
Endosymbiotic Theory pg. 385 figure 14.15
  • Lynn Margulis hypothesis based on experiments
    and observations
  • Proposes that eukaryotes evolved through a
    symbiotic relationship of prokaryotes.
  • Ancient prokaryotes engulfed other prokaryotes
    and instead of digesting them they survived
    together.
  • Evidence 1.chloroplasts and mitochondria
    contain DNA and ribosomes that are similar to the
    DNA and ribosomes in prokaryotes and unlike DNA
    in eukaryotic cells. 2. Chloroplasts and
    mitochondria reproduce independently of cells
    that contain them.

52
  • This explains why mitochondria has its own DNA

53
Endosymbiosis
  • Endosymbiosishttp//highered.mcgraw-hill.com/sites
    /9834092339/student_view0/chapter4/animation_-_end
    osymbiosis.html
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