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Astrobiology: Exploring Other Worlds > Week 4: Life > Flashcards

Week 4: Life Flashcards

1
Q

What is the time period of Hadean earth?

A

4.6 - 4.0 billion years ago

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2
Q

Describe the hadean earth.

A

molten with extremely high surface temperatures
no thick atmosphere (only CO2, water vapor, hydrogen)

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3
Q

What is the time period of the late heavy bombardment?

A

4 - 3.8 billion years ago

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4
Q

Describe the late heavy bombardment.

A

period of frequent meteoric impacts
theorized that water got to earth from these meteors??

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5
Q

True or false: we can see evidence for the late heavy bombardment period in craters on the earth

A

false - not really
weathering and geologic activity over time have erased this evidence here
we see evidence in other planets / moons without these processes

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6
Q

What is geology?

A

science concerning the earth’s physical structure, history, and processes that act on it

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7
Q

What is the difference between erosion and weathering?

A

erosion involves little bits of rock being carried away by natural processes
weathering involves degrading and changing the shape of rocks without carrying bits of it away

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8
Q

What are two methods by which weathering is done?

A

temperature changes cause rocks to expand / contract
wind/rain/snow wear at rock surfaces

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9
Q

What are plate tectonics?

A

sections of earth’s crust collide, grind past, and slide over/under each other

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10
Q

What particles are emitted by a radioactive atom?

A

alpha particles
2 protons and 2 neutrons

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11
Q

What happens when the number of protons an atom has changes?

A

new element

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12
Q

What happens when the number of neutrons an atom has changes?

A

isotope of same element

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13
Q

What are the original and new isotopes of an element called?

A

original is parent isotope
new one is daughter isotope

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14
Q

True or false: radioactive substances delay at a constant rate

A

true - thats how we know half lives!!
the release of alpha particles is random, but on average the rate is steady

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15
Q

What is the significance of the jack hills zircon crystals?

A

oldest discovered rock on earth
age of 4.375 billion years
scientific analysis shows they were formed in the presence of water
indicates that 4.4 billion years ago there was solid rock and flowing water!!

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16
Q

What early conditions of earth do we think would have made it difficult for life to form?

A

no atmospheric protection from radiation
very high surface temperatures
no oxygen in atmosphere
atmosphere toxic to today’s life

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17
Q

Where do scientists theorize life started due to the harsh conditions of the hadean earth?

A

underground or underwater

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18
Q

What are the seven defining characteristics of life?

A

order
energy utilization
response to the environment
regulation
reproduction
growth and development
evolutionary adaptation

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19
Q

What is a phospholipid? What is important about their structure?

A

chain of fatty acids
has a water-loving (hydrophilic) head and a hydrophobic tail

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20
Q

How does the structure of phospholipids lead to the creation of membranes?

A

hydrophilic head and hydrophobic tail
naturally organize themselves into sheets so that tail does not touch water

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21
Q

What is a phospholipid bilayer?

A

membrane formed by phospholipids organizing to keep water away from tails

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22
Q

How is a vesicle formed?

A

phospholipid bilayer randomly loops in on itself and makes a round loop

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23
Q

How do clay bubbles impact phospholipids?

A

clay forms shells around air bubbles
phospholipids get inside of shell and form spherical micelles and liposomes

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24
Q

What is a micelle?

A

sphere formed by phospholipids organizing inside a clay shell around an air bubble

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25
Q

What is a liposome?

A

sphere with hollow inside formed by phospholipids organizing inside a clay shell around an air bubble
after the micelle

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26
Q

How does a semipermeable closed membrane form?

A

phospholipids create liposomes inside clay shells around air bubbles
when clay dissolves or breaks, you get a semipermeable closed membrane!!

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27
Q

By what processes do nucleobases get inside of semipermeable closed membranes?

A

evaporation, freezing, other processes

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28
Q

What happens when nucleobases get inside of semipermeable closed membranes?

A

in close contact with each other
formation of complex molecules like RNA

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29
Q

How do clay surfaces facilitate the formation of complex molecules like RNA?

A

attract nucleotides
close contact between nucleotides -> molecules
clay particles have organized molecular structures -> molecules are organized too

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30
Q

Where did the earliest organisms likely form? (more detailed answer than underground or underwater)

A

somewhere warm
geysers or hydrothermal vents

31
Q

By what type of evolution did the earliest life come from?

A

chemical evolution
later larger scale processes took over

32
Q

Describe the structure of RNA.

A

sugar-phosphate backbone
nucleobases adenine, cytosine, guanine, uracil

33
Q

Why is RNA important in the history of life formation?

A

maybe was the first organic molecule driving its self-replication!!

34
Q

True or false: RNA has all of the characteristics of life.

A

false
it has some of them, but not all
it wasn’t until DNA came around that all 7 characteristics could be regulated

35
Q

How does the earth have a magnetic field?

A

molten metal core!!!

36
Q

What impact does the earth’s magnetic field have on it?

A

protects the atmosphere from charged particles which could react with and destroy it
also protects life on earth from these particles

37
Q

What happens when a charged particle encounters a magnetic field line?

A

the particle spirals around the line and loses its potential to react with the atmosphere

38
Q

What is solar wind?

A

a sea of high energy particles emitted by sunlike stars

39
Q

In the earliest stages of the earth, how did water exist?

A

as steam!!
at some point it was able to exists as a stable liquid before the great heavy bombardment

40
Q

How do volcanic eruptions impact the presence of water in the early earth?

A

they happened a lot and contained some water vapor

41
Q

How did the formation of oceans impact volcanic activity? How did this impact the atomic makeup of the atmosphere?

A

volcanoes are now lots of times underwater
reaction between volcanic gases and water prevent oxygen from existing freely in the atmosphere

42
Q

How did the rock cycle impact the makeup of the atmosphere in the early earth?

A

bonds oxygen to silicate rock
along with volcanic activity decreases presence of free oxygen in the atmosphere

43
Q

How do volcanic eruptions impact the makeup of the atmosphere?

A

decreases presence of free oxygen when eruptions are underwater
enriches atmosphere with ammonia, CO2, CO, H, methane, N, SO2, and water vapor

44
Q

What are the results of volcanic emissions on earth’s atmosphere? (not the oxygen thing)

A

atmosphere becomes thicker
protects the earth from solar radiation and insultates it

45
Q

How does the greenhouse effect work?

A

gases in the atmosphere absorb some of the solar energy that is bounced back from earth
heats the earth more than would be possible with just the sun and no atmosphere

46
Q

how does the presence of an atmosphere impact the formation of life?

A

atmosphere stabilizes temperature fluctuations from the earth’s rotation around the sun
protects life from crazy temperature changes

47
Q

What is ATP?

A

adenosine triphosphate
how all cells store energy
drives chemical reactions necessary for life

48
Q

What does the use of ATP in all cells indicate about the origins of life?

A

idea of a single common ancestor

49
Q

What is metabolism?

A

system of energy utilization essential for life

50
Q

How did the first living organisms on earth gain energy?

A

hydrogen sulfide from hydrothermal vents

51
Q

What is cyanobacteria? During what period did they originate and thrive?

A

first known life to photosynthesize
formed large biomats in ocean, mineral surfaces
3-2.5 billion years ago

52
Q

How were stromatolites formed?

A

layered fossils from 3.77 billion years ago
cyanobacteria form bio-mat layers on mineral surfaces in shallow waters
over time sediment / minerals are deposited on top of the cyanobacteria -> they grow upwards to find sunlight
when the remains of the cyanobacteria are gone this leaves a layered fossil

53
Q

What is the equation for photosynthesis?

A

6H2O + 6CO2 -> C6H12O6 + 6O2
powered by sunlight energy

54
Q

How did the presence of bacteria impact the atmosphere?

A

photosynthesize and release oxygen into atmosphere!

55
Q

Why did oxygen not become abundant in the atmosphere as soon as photosynthesis started?

A

early free oxygen bonded to rocks and seawater at first
it took about a billion years for oxygen to become abundant in atmosphere

56
Q

What caused the first mass extinction event?

A

increased oxygen levels from photosynthesizing organisms
life before this had evolved without oxygen, so the high levels of it were toxic to some life forms

57
Q

What era began after the first mass extinction event?

A

proterozoic era
emergence of complex life

58
Q

What are extremophiles?

A

organisms that thrive under extreme conditions which would kill normal organisms
mostly microbes or bacteria

59
Q

What are psychrophiles and cryophiles?

A

microbial extremophiles that thrive in temperatures below freezing

60
Q

How are psychrophiles and cryophiles able to live in their environments?

A

normally when water freezes and expands it bursts and kills cells
but these guys have a biological antifreeze!

61
Q

What are thermophiles?? Why are the conditions they live under usually uninhabitable?

A

organisms that thrive in temperatures above the boiling point of water
usually at that point, DNA starts to denature (unravel)

62
Q

What are xerophiles?

A

Organisms that can thrive under extreme dryness due to low metabolic rates

63
Q

What characterizes most extremophiles?

A

they are mostly single-celled organisms
exceptions exist, like tardigrades

64
Q

What is important about the miller-urey experiment?

A

replicated conditions of early earth in lab
complex molecules necessary for life such as amino acids formed naturally

65
Q

True or false: based on data from earth, we can estimate how likely it is for life to evolve on other planets

A

absolutely false
we have no idea

66
Q

Describe Titan. What characteristics of titan indicate its potential for life?

A

large moon of saturn
thick nitrogen atmosphere, active geology, abundant surface liquid (not water), warmed by hydrovolcanism
it if had biology, it would be entirely different from earth life

67
Q

Describe Europa.

A

moon of jupiter
may have liquid water below icy surface caused by warming from radioactive core

68
Q

Describe enceladus

A

moon of saturn
icy surface, but suspected to have salty underground liquid water (we have observed plumes of icy water vapor escaping from surface)

69
Q

What is the alternative explanation for the plumes of icy water vapor erupting from enceladus?

A

surface ice could just be melting away along cracks
might not be subsurface liquid water

70
Q

How do the size, mass, and distance from the sun of mars differ from earth?

A

smaller
less massive
50% further away from the sun

71
Q

Describe the atmosphere and surface conditions of mars.

A

very thin atmosphere made up of 96% CO2
- contains patches of methane shifting over time
cold surface temperatures
no surface water
weather, hydrological cycle

72
Q

What characteristics of mars make it seem potentially habitable?

A

weather
hydrological cycle
tectonics and volcanic activity in the past
ice glaciers below surface

73
Q

What does the methane in mars’s atmosphere tell us?

A

in patches that shift over time
two possible explanations:
- water-rock interactions
- microbes?!?!?!?

74
Q

True or false: the success rate of non-lunar missions has increased over time.

A

true :)

Astrobiology: Exploring Other Worlds (6 decks)

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