Module 1 Flashcards
1
Q
Early Earth formed _______ basedd on analysis of slowly _______ _______.
A
- 4.5 BYA
- decaying radioisotopes
2
Q
Earth formed as a result of
A
nuclear fusions on the sun (formed from supernova event)
3
Q
Early Earth was _______, characterized by a ______ _____ under intense bombardment by steroids and other ther objets from space
A
- inhospitable
- molten surface
4
Q
The intense heat and the absence of liquid water indicate that Early Earth was certainly a _____ _____.
A
Sterile planet
5
Q
analyses of ____ ______ _____ indicate the presence of solid crust and liquid water on the Earth as early as 4.3 BYA.
A
Ancient zircon crystals
6
Q
Suggest biogenic origin
A
Carbon isotope ratios of graphite materials in zircon minerals
7
Q
Oldest known sedimentary rocks date to
A
3.86 BYA
8
Q
Sedimentary rocks indicates that
A
oceans were present at the time these rocks were formd
9
Q
Sedimentary rocks contained
A
- fossilized remains of what appear to be cells
- carbon with isotopic ratios that provide further evidence for ancient microbial life.
10
Q
4 requirements need to be fulfilled on the conditions of the Early Earth
A
- little or no free oxygen
- Abundant energy source
- Occurrence of chemical building blocks, dissolved inorganic minerals.
- Time
11
Q
Independently proposed. that organic molecules could form spontaneously from simpler raw materials when sufficient energy is supplid in a reducing (energy-rich, electron adding) environment.
A
Oparin and Haldane (1920s)
12
Q
created a “reducing atmosphere” of H2O, NH3, H2, CH4 in a spark chamber, after sparking they found that amino acids and other organic cmpounds ha formed.
A
Miller and Urey (1950s)
13
Q
Organic polymers can form _______ from monomer building blocks on some sad, clay, or rock surfaces.
A
spontaneously
14
Q
Models of how and where life started:
A
- Prebiotic broth hypothesis
- Bubble hypothesis
- Iron-sulfur world hypothesis
- deep-hot biosphere hypothesis
- exogenesis
- religious/christian belief
15
Q
life began from an”organic soup” in the oceans
A
Prebiotic broth hypothesis
16
Q
a variation on the prebiotic broth, with “oily bbbles” from an organic soup interacting with land surfaces at shallow seas or seashores.
A
Bubble hypothesis
17
Q
A variation on the prebiotic broth, wth “oily bubbles” from an organic oup interacting with land surfaces ate shallow seas or seashores
A
Bubble hypothesis
18
Q
life began from an “organic soup” interacting with mineral surfaces at hydrothermal vents in the ocean floor, with abundant iron and sulfur there impacting the early metabolism that developed
A
iron-sulfur world hypothesis
19
Q
life began in an “organic soup” deep within the Earth
A
deep-hot biosphere hypothesis
20
Q
earth was seeded with life from an extraterrestrial source
A
exogenesis
21
Q
life was creates by a divine creator
A
religious/christian belief
22
Q
A model for how the first cells could have originated and functioned
A
A. Protobionts that resemble living cells, the evolutionary precursor of prokaryotic cells
B. Genetic reproduction as crucial in the origin of true cells
23
Q
A. protobionts that resemble living cells, the evolutionary precurso of prokaryotic ell
A
- Microspheres, a type of protobiont, that form spontaneously when liquid water is added to abiotically produced polypeptides.
24
Q
- a type of protobiont, that form spontaneously when liquid water is added to abiotically
produced polypeptides - can grow, divide, and maintain internal chemistry different from their surroundings
- show that some spontaneous production and maintenance of organization is possible, but
are incomplete as a model for formation of the first cells
A
microspheres
25
____________ was crucial in the origin of true cells
genetic reproduction
26
RNA likely was first
RNA world Hypothesis
27
- can catalyze a variety of reactions, including some self-catalytic reactions
- can also store genetic information
28
- has shown that the RNA world hypothesis is feasible
– selection can act on
self-replicating RNA molecules in vitro
in vitro evolution of RNA
29
likely came later and had the selective advantage of greater stability
DNA
30
possible to imagine that certain RNA molecules once had the ability to catalyze their own synthesis; these earliest forms of life may have had little or no need for __________
DNA or protein
31
events hypothesized to precede the origin of cellular life
Prebiotic chemistry
Precellular life
Early Cellular life
LUCA
Evolutionary diversification
32
Prebiotic chemistry
33
Precellular life
RNA world
Protein synthesis
DNA
34
Early cellular life
Lipid bilayers
35
LUCA and Evolutionary diversification
Divergence of bacteria and archea
36
Under biological building blocks
Amino acids, Nucleosides, sugar
37
Under RNA world
Catalytic RNA, Self-replicating RNA
38
Uner protein synthesis
RNA-templated translation
39
Under DNA
Replication, Transcription
40
under Lipid bilayers
- Cellular compartments
- Early cells likely had high rates of HGT
41
Divergence of Bacteria and Archea
Component of DNA replicatiob, transcription, and translation all in place
42
The earliest self-replicating biological systems may have been based on ________
catalytic RNA
43
At some point
RNA enzymes evolved the capability to synthesize proteins, and proteins became the _________
main catalytic
molecules
44
required the evolution of DNA and RNA polymerases.
Conversion from RNA- to DNA-based genomes
45
- the site of electron transport and the evolution of this structure was
likely important for energy conservation
- in addition to containing and protecting biomolecules
Lipid bilayer
46
LUCA
Last universal common ancestor
47
- preceded the divergence of Bacteria and Archaea
- was a cellular organism that had a lipid bilayer and used DNA, RNA, and protein.
LUCA
48
may have allowed rapid transfer of beneficial genes among early
forms of life
Horizontal gene transfer (HGT)
49
a possible energy-conserving
scheme for primitive cells.
Formation of pyrite (FeS
2
) leads to H
2
production and S reduction, which fuels a
primitive ATPase.
50
leads to H
2
production and S reduction
Formation of pyite (FeS2)
51
fuels a
primitive ATPase
H
2
production and S reduction
52
plays only a
catalytic role
H
2
S
53
Origin of life (scientific standpoint)
1. the first evidence of life in the fossil record are isotopic carbon “fingerprints” in rocks
from ~3.8 bya
2. the first evidence of cells are microfossils of prokaryotic cells in fossils of stromatolites
dated to ~3.5 bya
3. the first cells were most likely anaerobic heterotrophs
4. the first photosynthetic organisms were likely the purple and green sulfur bacteria,
which use H2S as a hydrogen donor
54
the first evidence of life in the fossil record are
isotopic carbon “fingerprints” in rocks
from ~3.8 bya
55
the first evidence of cells are
microfossils of prokaryotic cells in fossils of stromatolites
dated to ~3.5 bya
56
are rocklike structures made up of layers of bacteria and sediment
stromatolites
57
the first cells were most likely
anaerobic heterotrophs
58
later, as organic molecules became scarcer, __________ were favored
photosynthetic organisms
59
first photosynthetic organisms were likely the _______ and __________,
which use H2S as a hydrogen donor
purple and green sulfur bacteria
60
- the energy-generating metabolism of primitive cells would have been exclusively anaerobic.
- During this era CO2 may have been the major source of carbon for cells (autotrophy)
because abiotic sources of organic carbon would quickly have become limiting as life
became more and more abundant on Earth.
- abiotic sources of fixed nitrogen would have become limiting on the early earth, and microbes
evolved the ability to use atmospheric N2 as a source of nitrogen (nitrogen fixation) as early as
3.2 billion years ago, as indicated by isotopic ratios of nitrogen found in ancient
sedimentary rocks.
Metabolic Diversification: Consequences for Earth’s Biosphere
61
hypothesis that also was supported by the
Tree of Life
H2 as a major
fuel for energy metabolism of early cells.
62
Bacteria and Archaea use _________ as an
_______ in energy metabolism and
are also autotrophs.
H2, electron donor
63
_____________ may have been one
of the earliest __________
Elemental sulfur (S), electron acceptors
64
Other early microorganisms may have used H2 and CO2 to produce _______________
acetate or methane
65
Other early microorganisms may have used H2 and CO2 to produce acetate or methane . Such
metabolism is called _____________ driven by H2
chemolithotrophic metabolism
66
chemolithotrophic metabolism driven by H2, would likely have
supported the production of large amounts of organic compounds from __________
autotrophic CO2
fixation
67
a heavy sounding term for nonphotosynthetic cells/organisms that do not use oxygen as terminal electron acceptor in respiration
anaerobic heterotrophs
68
allowed phototrophs to diversify extensively.
The ability to use solar radiation as an energy source
69
The origin of ____________ and the _________
in Earth’s atmosphere caused the greatest
change ever in the history of our biosphere and set the stage for the evolution of even newer forms of
life that evolved to exploit the energy available from O2 respiration.
oxygenic photosynthesis, rise of O2
70
were likely the first photosynthetic organisms
Cyanobacteria
71
contain microfossils
that appear remarkably similar to modern species of
phototrophic bacteria
Ancient stromatolites
72
most of Earth’s iron would have been
present in reduced forms (Fe0 and Fe2+) and large amounts of
iron would have been dissolved in Earth’s anoxic oceans.
In the absence of O2
73
Molecular and chemical evidence indicates that ________ first appeared on Earth several hundred million
years before significant levels of O2 appeared
oxygenic
photosynthesis
74
enough to initiate what has come to
be called the Great Oxidation Event
By 2.4
bya, O2
levels had risen to one part per million
75
led to banded iron formations
metabolism of cyanobacteria yielded O2 that oxidized
reduced minerals containing Fe2+ to iron oxides containing Fe3+
76
laminated sedimentary rocks
formed in deposits of iron- and silica-rich materials and an
indication of the release of O2
into the oceans
banded iron formations
77
As O2 accumulated on Earth, the atmosphere gradually changed from _______
anoxic to oxic
78
Microbes that evolved the capacity to respire O2
gained a tremendous energetic advantage because of the high reduction potential of the ______ couple
O2/H2O
79
The formation of the __________ soon after oxygenation of the atmosphere provided protection from
UV radiation and allowed life to expand to regions at and near the Earth’s surface
ozone layer (O3
)
80
- origins of cellular life
- formation of the crust and oceans
- formation of earth
Hadean (sterile earth)
81
- Origins of cyanobacteria and oxygenic photosynthesis
- Origins of anoxygenic photosynthesis
- Divergence of bacteria and archeae
Archaean
82
- Start of the Great oxidation event
- Ozone shield forming
- Evidence for multicellular eukaryotes
- Start of cambrian explosion
Proterozoic
83
- Origin of first animals
- Extinction of dinosaurs
Phanerozoic
84
Rank of eon based on atmospheric oxygen present: (1 as the highest)
1. Phanerozoic
2. Proterozoic
3. Archaean
4. Hadean
85
the oxygenation of the atmosphere
from cyanobacterial metabolism was ___________, occurring over a period of about 2 billion
years.
a gradual
process
86
model for
how at least some of the eukaryotic cell
organelles came to exist
Endosymbiotic theory
87
Endosymbiotic mitochondria were beneficial to the early eukaryotic cells because __________
they increased the cell’s
respiratory capacity.
88
became the ancestors of all living Eukarya
early mitochondria-containing cells
89
A second endosymbiotic event had a major impact on the evolution of life.
Arose of Chloroplasts
90
- arose from the
incorporation of a cyanobacterium-like cell into the cytoplasm of a eukaryotic lineage, and this
endosymbiotic event triggered the origin of photosynthesis within Eukarya
- the 3rd Domain of life
Chloroplast
91
have descended from the lineage of cells that
acquired endosymbiotic chloroplasts
All phototrophic eukaryotes, including plants and algae
92
Atmospheric oxygen is intimately associated with the endosymbiotic
origins of organelles, being _______ by the ancestor of the mitochondrion and being ________ by the
ancestor of the chloroplast.
consumed, produced
93
These endosymbiotic events diversified the metabolism of early eukaryotic cells, with ___________
providing aerobic respiration and _____________ providing the ability to exploit sunlight for energy.
mitochondria
94
Providing aerobic respiration
Mitochondria
95
Providing ability to exploit sunlight for energy
Chloroplast
96
set the stage for the diversification of Eukarya into the forms we know
today.
Endosymbiotic origin of organelles
97
Eukaryotic models for the origin of eukaryotes
1. Serial endosymbiosis hypothesis
2. Hydrogen hypothesis
98
- proposes that the
eukaryotic ancestor diverged from the archaeal line and possessed
a nucleus and other features of eukaryotic cells prior to
endosymbiosis with the bacterial ancestor of the mitochondrion
- A later
endosymbiosis with the cyanobacterial ancestor of the chloroplast gave rise to
the eukaryotic ancestor of all plants and all other photosynthetic eukaryote
serial endosymbiosis hypothesis
99
- proposes that the eukaryotic cell evolved from a
symbiotic relationship between H2-producing cells of Bacteria and H2-consuming
cells of Archaea.
- The bacterial partner was eventually engulfed by its archaeal
partner and evolved over time into the mitochondrion.
- The nucleus and other
features of the eukaryotic cell evolved after establishment of endosymbiosis. - A later
endosymbiosis with the cyanobacterial ancestor of the chloroplast gave rise to the
eukaryotic ancestor of all plants and all other photosynthetic eukaryotes
hydrogen hypothesis
100
5 mass extinction events during Paleozoic era
1. Ordovician period (488-444 MYA)
2. Devonian period (416-359 MYA)
3. Permian period ended with the 3rd mass extinction event (251 MYA)
4. Triassic period (ended with the 4th MEE, 00MYA)
5. Cretaceous period (ended with the 5th MEE, 65 MYA)
101
Cenozoic Era
65MYA to present
102
has been marked by many ice ages, the rise of humans, and mass
extinctions
Neogene
103
most of these mass extinctions may have been caused by the ________
ice
age climate, humans, or both
104
the current mass extinction event (we are in one
now, the sixth extinction) is mostly caused by
humans
105
What lines of reasoning support the hypothesis that the first self-replicating systems were based on RNA molecules?
RNA is unique because it can both store genetic information like DNA and act as a catalyst like proteins (ribozymes). This dual function supports the "RNA world" hypothesis, suggesting RNA could have been the first self-replicating molecule before DNA and proteins evolved.
106
Why is the origin of cyanobacteria considered a critical step in evolution
Cyanobacteria were the first organisms to perform oxygenic photosynthesis, releasing oxygen as a byproduct. This led to the Great Oxidation Event around 2.4 billion years ago, transforming Earth's atmosphere and enabling the evolution of aerobic respiration and more complex life forms.
107
What kinds of evidence support the three domain concept of life?
Comparative analysis of small subunit ribosomal RNA (16S/18S rRNA) reveals fundamental genetic differences that separate all life into three domains: Bacteria, Archaea, and Eukarya. Other molecular and biochemical features also support this division, such as membrane composition and gene expression mechanisms.
108
In what ways has microbial metabolism altered Earth's biosphere? How might life on earth be different if oxygenic photosynthesis had not evolved?
Microbial metabolism has shaped Earth's geochemistry by cycling elements (carbon, nitrogen, sulfur) and producing gases like oxygen and methane. Oxygenic photosynthesis, mainly by cyanobacteria, led to atmospheric oxygen, making aerobic respiration possible. Without it, Earth would likely still be anaerobic, limiting the evolution of complex multicellular life.
