26 Flashcards

1
Q

geologic events that alter environments

A

change the course of biological evolution

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2
Q

scientific evidence is accumulating that chemical and physical processes on early earth, aided by the emerging force of selection, produced very simple cells thru a sequence of 4 main stages:

A

1) abiotic synthesis of small organic molecules (ex: amino acids and nucleotides)
2) the joining of these small molecules (monomers) into polymers (ex: proteins and nucleic acids)
3) the packaging of these molecules into protobionts
4) the origin of self-replicating molecules that eventually made inheritance possible

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3
Q

protobionts

A

droplets with membranes that maintained an internal chemistry different from that of their surroundings

aggregates of abiolotically produced molecules surrounded by a membrane or membrane-like structure

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4
Q

earth and the other planets of the solar system formed about

A

4.6 billion years ago

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5
Q

how did earth and th eother planets of the solar system form

A

they condensed from a vast cloud of dust and rocks that surrounded the young sun

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6
Q

its unlikely that life could’ve originated or survived on earth for the first few hundred miliion years b/c

A

the planet was still being bombarded by huge chunks of rock and ice left over from the formation of the solar system. these collision generated enough heat to vaporize all the available water and prevent seas from forming. this phase stopped 3.9 bill years ago

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7
Q

oldest known rocks on earth’s surface

A

Issua in Greenland. 3.8 billion years old

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8
Q

atmospheric conditions of early Earth

A

thick w/ water vapor, along w/ various compounds released by volcanic eruptions, including nitrogen and its oxides, carbon dioxde, methane, ammonia, hydrogen, and hydrogen sulfide

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9
Q

as earth cooled,

A

the water vapor condensed into oceans, and much of the hydrogen quickly escaped into space

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10
Q

Oparin-Haldane hypothesis

A

1920s - postulated that earth’s early atmosphere had been a reducing (electron-adding) environment, which organic compounds could’ve formed from simple molecules

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11
Q

what provided the energy for the organic synthesis described by the Oparin-Haldane hypothesis?

A

lightning and intense UV radiation

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12
Q

haldane suggested that

A

the early oceans were a solution of organic molecule, a “primitive soup” from which life arose

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13
Q

it’s unclear whether young Earth’s atmosphere contained enough __ and __ to be reducing

A

methane and ammonia

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14
Q

growing evidence suggests that the early atmosphere was made up primarily of __ and __ and was neither __ nor __

A

nitrogen and carbon dioxxide;

reducing nor oxidizing (electron-removing)

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15
Q

it is likely that small “pockets” of the early atmosphere, perhaps near ___, were reducing

A

volcsubmanic openings

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16
Q

instead of forming in the atmosphere, the first organic compounds on earth may have been synthesized

A

near submerged volcanoes and deep-sea vents, weak points in earth’s crust where hot water and minerals gush into the ocean

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17
Q

submerged volcanoes and deep-sea vents are rich in

A

inorganic sulfur and iron compounds, which are important in ATP synthesis by present-day organisms

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18
Q

some of the organic compounds from which the first life on earth arose may have come from space b/c

A

among the meterorites that land on earth are carbonaceous chondrites

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19
Q

carbonaeceous chondrites

A

rocks that are 1-2% carbon compounds by mass

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20
Q

life is defined partly by 2 properties

A

accurate replication and metabolism

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21
Q

role of metabolism

A

it provides an elaborate enzymatic machinery necessary for the replication of DNA. it also provides a copious supply of nucleotide building blocks

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22
Q

protobionts exhibit

A

some of the properties associated w/ life, including simple reproduction and metabolism

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23
Q

laboratory experiments demonstrate that protobionts couldve formed spontaneously from

A

abiotically produced organic compounds

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24
Q

liposomes

A

small membrane-bounded droplets

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25
describe liposomes formation
they form when lipids or other organic molecules are added to water. the hydrophobic molecules in the mixture organize into a bilayer at the surface of the droplet, much like the lipid bilayer of a plasma membrane
26
b/c the liposome bilayer is selectively permeable,
liposomes undergo osmotic swelling or shrinking when placed in solutions of different solute concentrations
27
some liposomes store energy in the form of
a membrane potential -- a voltage across the surface
28
some liposomes can discharge their voltage in
nerve cell-like fashion
29
the 1st genetic material was
RNA, not DNA
30
RNA, which plays a central role in ______, can also carry out ______
protein synthesis; | a number of enzyme-like catalytic functions
31
ribozyme
enzyme-like RNA molecule that catalyzes reactions during RNA splicing
32
the best index fossils for correlating strata that are far apart are
the shells of marine organisms that were widespread
33
index fossils
similar fossils, the presence of which can be used to correlate the strata at one location with strata at another location
34
index fossils reveal that
at any particular location there are likely to gaps in the sequence
35
why is it likely that at any particular location there are likely to be gaps in the fossil sequence?
that location may have been above sea level during certain periods, and thus no sedimentation occurred; or some of the sedimentary layers that were deposited when the location was submerged may have eroded away
36
radiometric dating
a method paleontologists use for determining the ages of rocks and fossils on a scale of absolute time, based on the half-life of radioactive isotopes
37
half-life
the number of years it take for 50% of the original sample to decay
38
an isotope's half life is unaffected by
temp, pressure, and other environmental variables
39
the carbon in a living organism includes
the most common carbon isotope, carbon-12 ,as well as a radioactive isotope, carbon-14
40
what happens to an organism's carbon when it dies
organism stops accumulating carbon, and the carbon-14 that it contained at the time of death slowly decays and becomes another element, nitrogen-14
41
radiometric dating - we can determine the fossil's age by
measuring the ratio of carbon-14 to total carbon or to nitrogen-14 in a fossil
42
carbon-14, with a half life of ___, is useful for dating fossils up to ____
5,730 years | 75,000 years
43
5 kingdoms
``` monera protista plantae fungi animalia ```
44
whittaer distinuighsed 3 kingdoms of multicellular eukaryotes -- ___, ___, ___ -- partly on the criterion of ____
plantae, fungi, animalia | nutrition
45
most fungi are
decomposers that invade their food source, secreting digestive enzymes and absorbing the small organic molecules produced by digestion
46
three-domain system
the domains bacteria, archaea, and eukarya -- superkingdoms that are a taxonomic level higher than the kingdom level
47
the 3-domain system makes the kingdom ___ obsolete b/c
monera; it would have members in 2 diff domains
48
many microbiologists now divide each of the 2 prokaryotic domains into
multiple kingdoms based on phylogenetic analysis of molecular data
49
stromatolites
rocklike structures composed of many layers of bacteria and sediment
50
the oldest known fossils, dating from ____ years ago, are fossils of
3.5 billion; stromatolites
51
present-day stromatolites are found in
a few warm, shallow, salty bays
52
early in prokaryotic history, 2 main evolutionary branches, __ and __, diverged
bacteria and achaea
53
theres strong evidence that the electron transport mechanism actually oriignated
in organisms that lived before the last common ancestor of all present-day life
54
the earliest of the electron transport systems likely evolved before
there was any free oxygen in the environment and before the appearance of photosynthesis
55
considerable metabolic diveristy among prokaryotes living in various environments had already evolved more than __ years ago
3 billion
56
most subsequent evolution has been more __ than __
structural, metabolic
57
photosynthesis probably evolved very early in prokaryotic history, but
in metabolic versions that didnt split water and liberate oxygen
58
the only living photosynthetic prokaryotes that generate oxygen are
the cyanobacteria
59
most atmospheric O2 is of __ origin, from __
biological; from the water-splitting step of photosynthesis
60
when oxygenic photosynthesis first evolved,
the free Os it produced probably dissoved in the surrounding water until the seas and lakes became saturated with O2
61
in its ____ forms and in compounds such as hydrogen peroxide, oxygen attacks ___ and can ___
free and ionized; chemical bonds, inhibit enzymes and damage cells
62
increasing atmospheric concentration of O2 likely doomed ___
many prokaryotic groups
63
the oxygen evolution followed the evolution of
eukaryotic cells containing chloroplasts
64
the oldest fossils that are eukaryotic are about __ yrs old
2.1 billion years
65
name 3 internal structures that prokaryotes lack that are characteristic of eukaryotic cells
nuclear envelope, endoplasmic reticulum, Golgi apparatus
66
prokaryotes have no __, so they are unable to change shape of cells
cytoskeleton
67
the first eukaryotes may have been
predators of other cells
68
functions of cytoskeleton
1. surround and engulf other cells 2. shift internal structures from 1 part of cell to another 3. facilitates regular movement of chromosomes in mitosis and meiosis
69
mitosis made it possible to
reproduce the large genomes of eukaryotes
70
plastids
the general term for chloroplasts and related organelles, both photosynthetic and nonphotosynthetic
71
endosymbiont
cell that lives within another cell (host cell)
72
theory of endosymbiosis
proposes that mitochondria and plastids were formerly small prokaryotes living within larger cells
73
endosymbiosis
process that led to mitochondria and plastids
74
ancestors of mitochondria
aerobic heterotrophic prokaryotes that became endosymbionts
75
ancestors of plastids
photosynthetic prokaryotes that became endosymbionts
76
the ancestors of mitochondria and plastids gained entry to the host cell as
undigested prey or internal parasites
77
early host cells evolved a __ and __ that made it possible for them to engulf endosymbionts
cytoskeleton, endomembrane system
78
how was the relationship btwn endosymbionts and host cells mutually beneficial
heterotrophic host could use nutrients released from photosynthetic endosymbionts. anaerobic cells would have benefited from aerobic endosymbionts that turned the oxygen to advantage
79
all eukaryotes have __ but not all have __
mitochondria, plastids
80
serial endosymbiosis
a sequence of endosymbiotic events. supposes that mitochondria evolved before plastids
81
evidence supporting endosymbiotic origin of plastids and mitochondria (5)
1. inner membranes have enzymes and transport systems that are homologous to those found in the plasma membranes of living eukaryotes 2. replicate by splitting process similar to binary fission 3. contain single, circular DNA molecule that isn't associated w/ histones or other proteins 4. contain transfer RNAs, ribosomes, and other molecules needed to transcribe and translate DNA into proteins 5. similar in terms of size, nucleotide sequence, and sensitivity to certain antibiotics
82
SSU-rRNA
small-subunit ribosomal RNA. present in all organisms, good choice for studying the depest branches of the tree of life
83
comparisons of SSU-rRNA from mitochondria, plastids, and various living prokaryotes indicate that a group of bacteria called the __ are the closest relatives of mitochondria, and that cyanobacteria are the closest relatives of ___
alpha proteobacteria | cyanobacteria
84
over time, some of the genes originally present in mitochondria and plastids were
transferred to the nucleus, a process that may have been accomplished by transposable elements
85
the eukaryotic nuclear genome was derived from
parts of endosymbionts' genomes and from at least one other cell, the host cell
86
Orthologs
genes in different species that evolved from a common ancestral gene by speciation
87
mitochondria and plastids have provided clues to their origins b/c
they still carry small DNA molecules that have genes orthologous to prokaryotic genes
88
genetic annealing
produced the genome of eukaryotic cells. process in which horizontal gene transfers occurred btwn many diff bacterial and archaean lineages