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Astrobiology > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

What is the major reason we think life will be found elsewhere?

A

Statistics, the total number of possible exoplanets

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2
Q

Describe the likely first life (not LUCA)

A

single-celled prokaryotes based on RNA

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3
Q

Why do we want to find life as a global entity?

A

much less likely to be a contamination event

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4
Q

Vernadsky

A

geology and biology are fundamentally indistinguishable, the line between living and non-living is not very clear

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5
Q

Lovelock - Gaia hypothesis

A

once life is established, it would respond to the changing environment to ensure that it continues

living, self-regulating, homeostatic system

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6
Q

Miller and Urey

A

mimicked conditions on early Earth with electrodes and inorganic compounds

solution became cloudy with organic molecules, including amino acids

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7
Q

What is the predominant form of life on Earth?

A

prokaryotes

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8
Q

What would a methane-based solvent change about life?

A

may be based on silicon instead of carbon

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9
Q

What would a non-water solvent change about life?

A

upside-down lipid bilayer (hydrophobic exterior)

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10
Q

Why would life need constant habitats?

A

to maintain life

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11
Q

Why would life need variable habitats?

A

resources are not depleted, waste products do not build up, produces natural selection

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12
Q

What is the “life as a process” defn of life?

A

something that consumes energy to maintain its organization (lower entropy, build biomass)

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13
Q

What is the textbook defn of life?

A

a self-sustaining bounded local environment in disequilibrium with its environment

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14
Q

Why does life require “some” fidelity?

A

fidelity is required so life can continue and make more cells, mistakes are required to produce variety for evolution to act upon

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15
Q

Defn of metabolism

A

the sum of all the chemical reactions that occur within the cell

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16
Q

Describe anabolism

A

consuming energy to build things up

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17
Q

Describe catabolism. How is the way life performs this process different than non-life?

A

releasing energy by breaking things down, life can use a number of steps to control the release of energy and reduce the amount of energy wasted

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18
Q

Describe autopoiesis

A

self-creation powered by the controlled consumption of energy; the process of making more biomass

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19
Q

What are the two life-specific parts of reproduction?

A

start with raw materials and use anabolic reactions to form monomers, polymers, and a cell

have an evolutionary history

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20
Q

What is the unique chemistry of life on Earth?

A

nitrogen, carbon, oxygen, hydrogen, sulfur, phosphorus

Earth’s crust is mainly silicon

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21
Q

Types of life - Darwin life

A

emphasis on the capacity for organisms to adapt to their environment and change through time

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22
Q

Types of life - Haldane life

A

emphasis on metabolism and maintenance, if organisms are decreasing entropy and processing the chemical reactions that make up life

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23
Q

Types of life - Carl Woese life

A

he used the r16s (small subunit rRNA) gene to develop the phylogeny of life that moved us from 5 kingdoms to 3 domains

24
Q

Types of life - synthetic life

A

wetware; taking living cells and genetically modifying them

25
Q

Types of life - virtual life

A

software; AI or life contained within the machine

26
Q

Types of life - mechanical life

A

hardware; life that cannot build new versions of itself from raw materials

27
Q

Types of life - Paul Davies “dark life”

A

life that does not rely on sunlight for energy and instead uses chemicals such as hydrogen sulfide or ferrous iron

28
Q

Origin of life - Panspermia

A

Francis/Crick, life came from elsewhere, does not explain where that life came from

29
Q

Origin of life - Primordial Soup

A

dilute solutions on earths surface where life could use lightning or UV radiation from the sun as energy and the water and simple organic molecules brought by asteroids; requires cycles of freezing or desiccation

30
Q

Origin of life - Deep Sea Vents

A

hydrogen sulfide and other inorganic compounds that can serve as sources of energy; would also be hard to concentrate reactants and retain products; iron/sulfur chimney structures as catalysts

31
Q

Thermal beginning of life

A

thermophiles are at the root of the tree of life; may indicate support for deep sea vents or just that thermophiles are the most likely to survive the early bombardment of Earth

32
Q

8 steps for life (list)

A

source of energy, polymerization, formation of a membrane, info-polymers, RNA, DNA, statistically re-occurring of effective and efficient metabolites, proteins

33
Q

What are some compounds found on early Earth? What sort of atmosphere did we have?

A

hydrogen, nitrogen, carbon dioxide, ammonia, cyanide, formaldehyde, hydrogen sulfide

reducing atmosphere

34
Q

How much energy does the reaction of hydrogen and oxygen yield?

A

237.14kJ

35
Q

What are the three ways ATP can be produced?

A

electron acceptor chains, substrate level phosphorylation, electron pair bifurcation

36
Q

Describe LUCA

A

contains DNA and proteins; proto-cell with a cell membrane; small size

37
Q

Age of universe

A

14 BYA

38
Q

First elements

A

hydrogen and helium, combine for nuclear fusion in protostars

39
Q

Formation of earth

A

4.46 BYA, heavy elements closer to sun, lighter elements further away

40
Q

Age of first life, description

A

3.5-3.8 BYA, bacterial mats / stromatolites found in Australia

41
Q

Age of anoxic photosynthesis, description

A

3.4 BYA, used hydrogen sulfide before water

42
Q

Age of rock evidence for the release of oxygen

A

2.3-2.4 BYA, oxygen reacted with ferrous iron to make banded iron formations, allowed for aerobic respiration and multicellular life

43
Q

Age of first cyanobacteria

A

2.7 BYA

44
Q

Age of red/brown algae

A

1.2 BYA

45
Q

Why has increased complexity favored?

A

movement and increased specialization

46
Q

Evolutionary significance of stable environments

A

stabilizing selection with fewer extreme phenotypes, low diversity

47
Q

Evolutionary significance of changing environments

A

preference for extreme phenotypes, causes speciation and high diversity

48
Q

Meaning of inclusive fitness

A

the heredity of genes is the most important; even if you die, close relative may survive and pass on your genes

49
Q

Minimum temperature, adaptations

A

-10/-15*C, increased branched fatty acids and cholesterol in membranes

50
Q

Maximum temperature, adaptations

A

121*C, disulfide protein bonds, lipid monolayer and/or ether bonds, reverse gyrase

51
Q

Minimum pH, adaptations

A

below 0, use electrons from ferrous iron to balance protons in the environment

52
Q

Maximum pH, adaptations

A

around 11, use sodium pumps for ATP production

53
Q

Essay ? - Nelson Conrad 1999, three categories of life

A

physicists - use light/heat, chemists - use chemical energy, biologists - use other organisms

54
Q

Essay ? - Mariscal and Doolittle 2018, defining life

A

all defns of life suck, choose what you like best

55
Q

Essay ? - Jeffares et al 1998, RNA world

A

DNA - double stranded, deoxyribose sugars, thymine

Proteins - shorter reaction times, more functional groups, precise tertiary structure, small substrates

56
Q

Essay ? - Darwin’s pond

A

favor hydrolysis, cycles of desiccation or freezing

57
Q

Essay ? - Upper temperature limit

A

121*C, disulfide bonds, lipid monolayer and/or ether bonds, reverse gyrase

Astrobiology (5 decks)

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