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1

geologic events that alter environments

change the course of biological evolution

2

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:

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

3

protobionts

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

4

earth and the other planets of the solar system formed about

4.6 billion years ago

5

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

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

6

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

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

7

oldest known rocks on earth's surface

Issua in Greenland. 3.8 billion years old

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atmospheric conditions of early Earth

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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as earth cooled,

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

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Oparin-Haldane hypothesis

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

lightning and intense UV radiation

12

haldane suggested that

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

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

methane and ammonia

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

nitrogen and carbon dioxxide;
reducing nor oxidizing (electron-removing)

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

volcsubmanic openings

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

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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submerged volcanoes and deep-sea vents are rich in

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

18

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

among the meterorites that land on earth are carbonaceous chondrites

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carbonaeceous chondrites

rocks that are 1-2% carbon compounds by mass

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life is defined partly by 2 properties

accurate replication and metabolism

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role of metabolism

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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protobionts exhibit

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

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laboratory experiments demonstrate that protobionts couldve formed spontaneously from

abiotically produced organic compounds

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liposomes

small membrane-bounded droplets

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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

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b/c the liposome bilayer is selectively permeable,

liposomes undergo osmotic swelling or shrinking when placed in solutions of different solute concentrations

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some liposomes store energy in the form of

a membrane potential -- a voltage across the surface

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some liposomes can discharge their voltage in

nerve cell-like fashion

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the 1st genetic material was

RNA, not DNA

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RNA, which plays a central role in ______, can also carry out ______

protein synthesis;
a number of enzyme-like catalytic functions

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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

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index fossils

similar fossils, the presence of which can be used to correlate the strata at one location with strata at another location

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index fossils reveal that

at any particular location there are likely to gaps in the sequence

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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

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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

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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

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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

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carbon-14, with a half life of ___, is useful for dating fossils up to ____

5,730 years
75,000 years

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5 kingdoms

monera
protista
plantae
fungi
animalia

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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

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three-domain system

the domains bacteria, archaea, and eukarya -- superkingdoms that are a taxonomic level higher than the kingdom level

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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

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stromatolites

rocklike structures composed of many layers of bacteria and sediment

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the oldest known fossils, dating from ____ years ago, are fossils of

3.5 billion; stromatolites

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present-day stromatolites are found in

a few warm, shallow, salty bays

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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

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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

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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

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name 3 internal structures that prokaryotes lack that are characteristic of eukaryotic cells

nuclear envelope, endoplasmic reticulum, Golgi apparatus

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prokaryotes have no __, so they are unable to change shape of cells

cytoskeleton

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the first eukaryotes may have been

predators of other cells

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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

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mitosis made it possible to

reproduce the large genomes of eukaryotes

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plastids

the general term for chloroplasts and related organelles, both photosynthetic and nonphotosynthetic

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endosymbiont

cell that lives within another cell (host cell)

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theory of endosymbiosis

proposes that mitochondria and plastids were formerly small prokaryotes living within larger cells

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endosymbiosis

process that led to mitochondria and plastids

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ancestors of mitochondria

aerobic heterotrophic prokaryotes that became endosymbionts

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ancestors of plastids

photosynthetic prokaryotes that became endosymbionts

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the ancestors of mitochondria and plastids gained entry to the host cell as

undigested prey or internal parasites

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early host cells evolved a __ and __ that made it possible for them to engulf endosymbionts

cytoskeleton, endomembrane system

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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

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all eukaryotes have __ but not all have __

mitochondria, plastids

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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

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genetic annealing

produced the genome of eukaryotic cells. process in which horizontal gene transfers occurred btwn many diff bacterial and archaean lineages