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Astrobiology: Exploring Other Worlds > Week 5: Emerging Complex Life and Intelligence > Flashcards

Week 5: Emerging Complex Life and Intelligence Flashcards

1
Q

What is the Proterozoic eon? What changes characterize its start?

A

2.5 billion - 541 million years ago
where fossil record begins
simple life proliferates + multicellular life emerges
rise of eukaryotic cells + aerobic respiration
begins with huronian glaciation - temperatures decrease and glaciers cover earth’s surface

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2
Q

What is the huronian glaciation?

A

2.4-2.1 billion years ago
first snowball earth
period of low temperatures and glaciers covering earth’s surface

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3
Q

What caused the huronian glaciation?

A

oxygen from photosynthesis dilutes greenhouse gases in atmosphere and decreases the greenhouse effect
feedback loop where snow + ice reflect sunlight and lead to more cooling, which leads to the formation of more snow and ice

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4
Q

How does aerobic comparison compare to anaerobic respiration?

A

requires oxygen
produces 18x more energy!! much more efficient

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5
Q

How did the rise of oxygen levels impact organisms using anaerobic respiration?

A

oxygen has oxidizing and corrosive effects
free oxygen reacts with molecules to produce free radicals, which can cause cell damage

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6
Q

True or false: aerobic respiration was first used by prokaryotic cells and allowed eukaryotic cells to develop.

A

false
eukaryotic cells started it

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7
Q

How did eukaryotic cells form in theory?

A

prokaryotes form symbiotic relationships with each other and eventually one absorbs the other
become chimeric cells
absorbed cells become membrane bound organelles

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8
Q

When did eukaryotic cells emerge?

A

2.1 - 1.6 billion years ago

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9
Q

How are eukaryotic cells stronger than prokaryotes?

A

able to adapt to a wider range of environments due to specialized organelles

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10
Q

How did the huronian glaciation period end?

A

volcanic activity revived greenhouse effect + warmed the planet

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11
Q

How did the end of the huronian glaciation period impact life on earth?

A

prokaryotic and eukaryotic life thrives and diversifies

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12
Q

When did multicellular life begin?

A

2 billion years after huronian glaciation period
575 million years ago

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13
Q

When did sexual reproduction emerge? How did it benefit life?

A

in Proterozoic era
allows mixing of genetic material -> increased genetic diversity
allows complex information to be passed on

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14
Q

How does the structure of DNA allow for sexual reproduction?

A

double helix with rungs made of paired nucleotides
pairs allow for replication

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15
Q

What nucleotides bond to which nucleotides?

A

cytosine bonds to guanine
adenine bonds to thymine

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16
Q

What is a genetic code?

A

sequence of base pairs (DNA)

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17
Q

What is a codon?

A

three base pairs (DNA)

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18
Q

What is a gene?

A

sequence of codons (DNA)

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19
Q

What is a genome?

A

set of genes

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20
Q

What is the purpose of genes?

A

instruct assembly of proteins

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21
Q

What is a chromosome?

A

condensed genome
used for sexual reproduction

22
Q

What is a gamete?

A

male/female reproductive cell
contain half of their organism’s chromosomes (make up a complete set when combined)

23
Q

True or false: sexual reproduction is less energy intensive than asexual reproduction.

A

false
it requires a lot more energy

24
Q

What is the Cryogenian glaciation?

A

720-635 million years ago
2nd snowball earth
glaciers covered earth
emergence of first multicellular organisms during this period

25
Q

what is the cambrian explosion?

A

20-25 million year period where “burst of evolutionary innovation” occurred

26
Q

What is the phanerozoic eon?

A

began with cambrian explosion

27
Q

What is a chordate? When did they emerge?

A

ancestors of vertebrates
during cambrian explosion

28
Q

True or false: genetically most organisms are very similar to each other

A

true
sequences of base pairs are different, but at the cellular level they are mostly the same

29
Q

What are hox genes?

A

code for proteins specific to certain species that regulate genetic expression
differentiate different species
determine what structures form in a developing embryo

30
Q

what motivated the evolution of hox genes?

A

mobility is good for survival
hox genes allow species to replicate previously evolved body plans instead of coming up with them freshly

31
Q

What is the ordovician period?

A

488 million years ago
plants begin to colonize land

32
Q

What is the carboniferous period?

A

359-299 million years ago
plant growth covers land and becomes modern day coal deposits
pangaea forms
oxygen levels reach peak concentrations

33
Q

What is a biosignature?

A

object, substance, or pattern that requires life in order to form

34
Q

Give three examples of potential biosignatures:

A

temporal variability of atmosphere composition (ex. oxygen)
change of planet surface reflectance due to biological life / activity
technosignatures indicating intelligent civilization

35
Q

What are the two main aspects of modern evolutionary biology?

A

studying lines of DNA and fossils

36
Q

What types of mutations are preserved by natural selection?

A

those that allow organisms to:
survive long enough to produce
produce offspring that are more likely to survive
hunt or scavenge more effectively
evade predators more effectively

37
Q

What two main environmental factors drive natural selection?

A

survival
competition for resources

38
Q

How have earth organisms adapted to the energy emitted by the sun?

A

sight has adapted to the wavelengths which the sun emits the most of (visible light wavelengths)

39
Q

true or false: by looking at the genomes of modern day species, we can accurately estimate a timeline for when species emerged

A

false
timeline part is not accurate

40
Q

What is LUCA?

A

last common universal ancestor
hypothetical organism with first genetic information that eventually led to all other life

41
Q

What three categories make up the tree of life?

A

bacteria
archaea
eukarya (includes plants and animals as small branches)

42
Q

What are mass extinction events?

A

events which apply natural selection forces to the whole planet at once
rapid decrease in biodiversity
spike in biodiversity caused by end of these events

43
Q

What is the KT extinction?

A

mass extinction event
66 million years ago
caused by asteroid
killed of dinosaurs :(

44
Q

how did mammals survive the KT extinction?

A

burrowing underground to avoid harsh surface conditions
omnivorous so they could continue to find food

45
Q

what are primates? When did they emerge?

A

mammals evolved for life in trees
65.5-55.8 million years ago
in early paleocene epoch

46
Q

What is the eocene epoch?

A

55.8-33.9 million years ago
emergence of early placental mammals

47
Q

When did the first human ancestor emerge?

A

7-5 million years ago

48
Q

True or false: the evolution of bipedalism happened gradually and linearly over time

A

false
it was not linear at all!!

49
Q

When did neanderthal humans exist?

A

400,000 - 40,000 years ago

50
Q

true or false: neanderthals coexisted with homo sapiens for a time

A

true
for about 5,000 years
probably some genetic mixing between the species

51
Q

What is EQ?

A

encephalization quotient
ratio of brain mass to body mass
correlatd with intelligence
humans have the highest (7.4-7.8)

Astrobiology: Exploring Other Worlds (6 decks)

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