1 Chapter 18 Lecture Outline Copyright © McGraw-Hill Education. Permission required for reproduction or display. See separate PowerPoint slides for all.
Post on 21-Jan-2016
216 Views
Preview:
Transcript
1
Chapter 18Lecture Outline
Copyright © McGraw-Hill Education. Permission required for reproduction or display .
See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes.
A 50-million-year-old fossil of a unicorn fish – just one of the many different kinds of organisms that have
existed during the history of life on Earth 2
3
Chapter 18
The Origin and Historyof Life on Earth
Origin of Life on Earth
The Fossil Record
History of Life on Earth
Chapter Outline:
13.8 bya – Universe began with the Big Bang
4.6 bya – Our solar system began
The Earth is 4.55 billion years old
4 bya – Earth had cooled enough for outer layers to solidify and oceans to form
between 4 and 3.5 bya – Life emerged
4
Origin of Life on Earth
5
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
84 μm
(b) Modern cyanobacteria(a) Fossil prokaryote
112 μm
a: © Stanley M. Awramik/Biological Photo Service; b: © Michael Abbey/Visuals Unlimited
Origin of life – four overlapping stages
Nucleotides and amino acids produced prior to the existence of cells
Nucleotides and amino acids became polymerized to form DNA, RNA and proteins
Polymers became enclosed in membranes
Polymers enclosed in membranes acquired cellular properties
6
1.
2.
3.
4.
Stage 1: Origin of organic molecules
Conditions on primitive Earth may have been more conducive to spontaneous formation of organic molecules
Prebiotic or abiotic synthesis Little free oxygen gas so not oxidized Formed prebiotic soup (primordial soup)
Several hypotheses on where and how organic molecules originated
7
Reducing atmosphere hypothesis Based on geological data available at the time
Assumed an atmosphere rich in water vapor, H2, CH4, NH3 (and little O2)
Stanley Miller used a chamber apparatus to simulate this atmosphere and bolts of lightning
Formed precursor molecules – amino acids, sugars and nitrogenous bases
First attempt to apply scientific experiments to understand origin of life
Since 1950s, ideas about the early atmosphere of Earth have changed
Still, similar results 8
9
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
H2O
Electrical discharge Electrodes
To vacuum
Boiling water Trap
Sample containingorganic moleculessuch as amino acids
Precipitatingdroplets
Condenser
Cold water
Gases
NH3
CH4
H2
Extraterrestrial hypothesis Meteorites brought organic carbon to Earth
Including amino acids and nucleic acid bases
Opponents argue that most of this would be destroyed in the intense heat of collision
Deep-sea vent hypothesis Biologically important molecules may have been
formed in the temperature gradient between extremely hot vent water and cold ocean water
Supported by experiments and ancient fossils Complex biological communities found here that
derive energy from chemicals in the vent (not the sun)10
11
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cold H2O
H2O temperaturesuitable for organicchemistry
HotH2O
Hot H2S gas
Vent
Ocean floor
Crack inEarth’s crust
(a) Deep-sea vent hypothesis
12
BIOLOGY PRINCIPLE
Biology is an experimental science
By conducting experiments, Miller and Urey were able to demonstrate the feasibility of the synthesis of organic molecules prior to
the emergence of living cells.
13
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Stage 2: Organic polymers
Prebiotic synthesis of polymers was thought to be impossible in aqueous solutions Due to hydrolysis competing with polymerization
Experiments have shown formation of nucleic acid polymers and polypeptides on the negative silicate surface of clay
However, in 2004 Leman, Orgel and Ghadiri showed that polymers CAN also form in aqueous solutions Showed formation of peptides under mild conditions in water So polymer synthesis could have occurred in the prebiotic soup
Stage 3: Formation of boundaries
Protobiont An aggregate of prebiotically produced molecules
and macromolecules Has a boundary, such as a lipid bilayer, that allows it
to maintain an internal chemical environment distinct from that of its surroundings
15
Four characteristics of a protobiont:
1. Boundary separated external environment from internal contents
2. Polymers inside the protobiont contained information
3. Polymers inside the protobiont had enzymatic function
4. Protobionts capable of self-replication
16
Living cells may have evolved from
Coacervates Droplets that form spontaneously from the
association of charged polymers Enzymes trapped inside can perform primitive
metabolic functions
Liposomes Vesicles surrounded by a lipid layer Clay can catalyze formation of liposomes that
grow and divide Can enclose RNA
17
18
Stage 4: RNA world
Majority of scientists favor RNA as the first macromolecule of protobionts
Three key RNA functions:Ability to store information
Capacity for self-replication
Enzymatic function (ribozymes)
DNA and proteins cannot do all 3 functions
19
1.
2.
3.
Chemical selection
A chemical within a mixture has special properties that cause it to increase in number compared to other chemicals in the mixture
Hypothetical scenario with two steps:1. One of the RNA molecules mutates and has
enzymatic ability to attach nucleotides together Advantage of faster replication
2. Second mutation produces enzymatic ability to synthesize nucleotides No reliance on prebiotic synthesis
20
21
Advantages of DNA/RNA/protein world
Information storage DNA relieves RNA of informational role and allows
RNA to do other functions DNA is less likely to suffer mutations
Metabolism and other cellular functions Proteins have greater catalytic potential and efficiency Proteins can perform other tasks – cytoskeleton,
transport, etc.
22
Preserved remains of past life on Earth
Paleontologists study fossils
Many rocks with fossils are sedimentary Sediments pile up and become rock Organisms buried quickly, hard parts replaced by
minerals
Older rock is deeper and older organisms are deeper in the rock bed
23
The Fossil Record
24
Radioisotope dating
Fossils can be dated using elemental isotopes in accompanying rock
Half-life – length of time required for exactly one-half of original isotope to decay
Measure amount of a given isotope as well as the amount of the decay product
Usually igneous rock is dated
Expect fossil record to underestimate actual date species came into existence
25
26
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
00
Iso
top
e (%
)
1 2 3 4
100
75
50
25
Buildup of decay product
Decay of radioisotope
Time (half-lives)
(a) Decay of a radioisotope
RadioisotopeDecayproduct
Half-life(years)
Useful datingrange (years)
100–50,000Carbon-14
Potassium-40
Rubidium-87
Uranium-235
Uranium-238
100,000–4.5 billion
10million–4.5 billion
10million–4.5 billion
10million–4.5 billion
Nitrogen-14
Argon-40
Strontium-87
Lead-207
Lead-206
5,730
1.3 billion
47 billion
4.5 billion
710 million
(b) Radioisotopes that are useful for geological dating
27
Geological time scale Origin 4.55 bya to present
Four eons Hadean Archaean Proterozoic Phanerozoic
Each eon further divided into eras28
History of Life on Earth
Precambrian
29
30
31
Changes in living organisms are the result of Genetic changes Environmental changes
Can allow for new types of organisms Responsible for many extinctions
32
Major environmental changes
Temperature Atmospheric composition (amount of O2) Land masses shifting Flood Glaciation Volcanic eruptions Meteorite impacts
33
34
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Era
s
GondwanaE
on
s
0
PA
LE
OZ
OIC
PR
OT
ER
OZ
OIC
PH
AN
ER
OZ
OIC
CE
NO
ZO
ICM
ES
OZ
OIC
PacificOcean
Australia
Asia
IndianOcean
Europe
Africa
NorthAmerica
AtlanticOcean
SouthAmerica
Antarctica
Cenozoic period (modern Earth)
Laurasia
Millionsof yearsago (mya)
65
248
PacificOcean
Mesozoic period
Tethys OceanPangaeaPanthalassicOcean
Paleozoic period (Pangaea)
PanthalassicOceanRodinia
PanafricanOcean
543
750
Pre-Paleozoic period
Tethys Ocean
Mass extinctions
5 large mass extinctions
Near end of Ordovician, Devonian, Permian, Triassic, and Cretaceous periods
Boundaries between geologic time periods are often based on these events
Rapid extinction of many modern species due to human activities is sometimes referred to as the sixth mass extinction
35
Prokaryotic cells arose during Archaeon Eon
Archaeon Eon – when diverse microbial life flourished in primordial oceans
First known fossils 3.5 bya
First cells prokaryotic
All life forms prokaryotic during Archaeon Eon
Hardly any free oxygen so organisms were anaerobic
Biologists are undecided about whether heterotrophs or autotrophs came first
36
Stromatolites
Autotrophic cyanobacteria
Form stromatolites – layered structure of calcium carbonate
Cyanobacteria produce oxygen as a waste product of photosynthesis
Spelled doom for many prokaryotic groups that were anaerobic
Allowed the evolution of aerobic species
37
38
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(a) Fossil stromatolite (b) Modern stromatolitesa: © Dirk Wiersma/SPL/Photo Researchers, Inc.; b: © Roger Garwood & Trish Ainslie/Corbis
The origin of eukaryotic cells is hypothesized to involve a union between bacterial
and archaeal cells
Origin of first eukaryotic cell matter of debate
In modern eukaryotes, DNA found in nucleus, mitochondria and chloroplasts
Examine properties of this DNA and modern prokaryotes
Nuclear genome – both bacteria and archaea contributed substantially Symbiotic relationship – two species live in direct contact Endosymbiotic – one organism lives inside another
Data support this origin
EVOLUTIONARY CONNECTIONS
EVOLUTIONARY CONNECTIONS
EVOLUTIONARY CONNECTIONS
Proterozoic Eon
Multicellular eukaryotes arise 1.5 bya
Two possible origins Individuals form a colony Single cell divides and stays stuck together
Volvocine green algae display variations in the degree of multicellularity
42
43
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Flagella
(a) Chlamydomonas reinhardtii,a unicellular alga
3 μm 10 μm 30 μm 100 μm
(d) Volvox aureus, composedof about 1,000 to 2,000 cells,has 2 cell types, somatic andreproductive
(c) Pleodorina californica,composed of 64 to 128 cells,has 2 cell types, somatic andreproductive
(b) Gonium pectorale, composedof 16 identical cells
a: Courtesy of Dr. Barbara Surek, Culture Collection of Algae at the University of Cologne (CCAC); b: © Bill Bourland/micro*scope; c-d: © Dr. Cristian A. Solari, Department of Ecology and Evolutionary Biology, University of Arizona
BIOLOGY PRINCIPLE
New properties emerge fromcomplex interactions
The formation of different cell types is an emergent property of multicellularity.
44
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Multicellular animals emerge toward the end of the eon
First animals were invertebrates Bilateral symmetry facilitates locomotion
45
46
Left
Right
Anterior
Posterior
Mouth
50 µm
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© We thank Prof. Jun-yuan Chen for permission to use this image
Phanerozoic Eon
Proliferation of multicellular eukaryotic life extensive (543 mya to today)
Paleozoic Era
Mesozoic Era
Cenozoic Era
47
Phanerozoic Eon – Paleozoic Era
543-248 mya
Cambrian period
Ordovician period
Silurian period
Devonian period
Carboniferous period
Permian period
48
Phanerozoic Eon – Paleozoic Era – Cambrian Period
543-490 mya
Warm and wet with no ice at poles
Cambrian explosion – abrupt increase in diversity of animal species Cause unknown – shell evolution, atmospheric
oxygen, “arms race”?
49
Phanerozoic Eon – Paleozoic Era – Cambrian Period
All existing major types of marine invertebrates plus many others that no longer exist
Although new species have arisen since, no major reorganizations of body plans
First vertebrates 520 mya
50
Phanerozoic Eon – Paleozoic Era – Ordovician Period
490-443 mya
Warm temperatures and atmosphere very moist
Diverse group of marine invertebrates including trilobites and brachiopods
Primitive land plants and arthropods first invade land
Toward end, abrupt climate change (large glaciers) resulting in mass extinction
Over 60% of marine invertebrates became extinct
51
52
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
2 cm
3 cm
(b) Brachiopod
(a) Trilobite
a: © Francois Gohier/Photo Researchers, Inc.; b: © DK Limited/Corbis
Phanerozoic Eon – Paleozoic Era – Silurian Period
443-417 mya
Relatively stable climate
Glaciers largely melted
No new major invertebrates
Significant new vertebrates and plants
53
Phanerozoic Eon – Paleozoic Era – Silurian Period
Many new fish
Coral reefs appeared
Large colonization by terrestrial plants and animals Evolved adaptations to prevent drying out
Spiders and centipedes
Earliest vascular plants54
Phanerozoic Eon – Paleozoic Era – Devonian Period
417-354 mya
Generally dry across north but southern hemisphere mostly covered by cool, temperate oceans
Major increase in number of terrestrial species
Ferns, horsetails and seed plants (gymnosperms) emerge
55
Phanerozoic Eon – Paleozoic Era – Devonian Period
Insects emerge
Tetrapods – amphibians emerge
Invertebrates flourish in the oceans
The Age of Fishes
Near end, prolonged series of extinctions eliminate many marine species
56
Phanerozoic Eon – Paleozoic Era – Carboniferous Period
354-290 mya
Rich coal deposits formed
Cooler, land covered by forested swamps
Plants and animals further diversified Very large plants and trees prevalent First flying insects Amphibians prevalent Amniotic egg emerges - reptiles
57
58
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Psaronius
© Ken Lucas/Visuals Unlimited
Phanerozoic Eon – Paleozoic Era – Permian Period
290-248 mya
Continental drift formed supercontinent Pangaea
Interior regions dry with seasonal fluctuations
Forest shift to gymnosperms
59
Phanerozoic Eon – Paleozoic Era – Permian Period
Amphibians prevalent but reptiles became dominant
First mammal-like reptiles appeared
At the end, largest known mass extinction event
90-95% of all marine species and large proportion of terrestrial species eliminated
Glaciations or volcanic eruptions blamed
60
Phanerozoic Eon – Mesozoic Era
Permian extinction marks boundary between Paleozoic and Mesozoic eras
The Age of Dinosaurs
Consistently hot climate, dry terrestrial environments, little if any ice at poles
61
Phanerozoic Eon – Mesozoic Era – Triassic Period
248-206 mya
Reptiles plentiful
First dinosaurs
First true mammals
Gymnosperms dominant land plant
Volcanic eruptions led to global warming and mass extinctions near the end
62
63
Phanerozoic Eon – Mesozoic Era – Jurassic Period
206-144 mya
Gymnosperms continued to be dominant
Dinosaurs dominant land animal Some attained enormous size
First known bird
Mammals present but not prevalent
64
65
Phanerozoic Eon – Mesozoic Era – Cretaceous Period
144-65 mya
Dinosaurs still dominant on land
Earliest flowering plants, angiosperms
Another mass extinction at the end of the period
Dinosaurs and many other species died out
Large meteorite/asteroid or volcanic eruptions blamed
66
Phanerozoic Eon – Cenozoic Era
Spans most recent 65 million years
Tropical conditions replaced by a colder, drier climate
Sometimes called The Age of Mammals
Amazing diversification of birds, fish, insects, and flowering plants
67
Phanerozoic Eon – Cenozoic Era – Tertiary Period
65-1.8 mya
Mammals that survived expanded rapidly
Birds and terrestrial insects diversified
Angiosperms become the dominant land plant
Fish diversified, sharks become abundant
Whales appeared
Hominids appeared about 7 mya
68
Phanerozoic Eon – Cenozoic Era – Quaternary Period
1.8 mya to present
Periodic ice ages cover much of Europe and North America
Widespread extinction of many species
Certain hominids become more human-like
Homo sapiens appear 130,000 years ago
69
top related