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general bio 2024 > Lecture 15 > Flashcards

Lecture 15 Flashcards

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Biology 101 flashcards
1
Q

Theories on the origin of life on earth

A
  • I: Abiogenesis
  • II: Panspermia
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2
Q

Theory I: Abiogenesis

A
  • study of how life on earth might have emerged from non-life
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3
Q

Theory II: Panspermia

A
  • life exists and is distributed throughout the universe in the form of germs or spores
  • suggested that life might have come from space
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4
Q

origin of life

A

one of the great mysteries in the universe

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5
Q

currently accepted models for the origin of life

A
  • some chemical and physical processes on early Earth may have produced very simple cells through a sequence of stages
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6
Q

sequence of stages that produces cells (four main)

A
  1. the abiotic synthesis of small organic molecules (monomers)
  2. joining of monomers into polymers
  3. packaging of these molecules into protobionts
  4. the origin of self-replicating molecules that eventually made inheritance possible
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7
Q

protobionts

A
  • droplets
  • maintained a distinct internal chemistry different from that of their surroundings
  • similar to cells
  • aggregates of abiotically produced molecules surrounded by a membrane or membrane-like structure
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8
Q

abiotic synthesis of organic monomers

A
  • life could not have survived in the first million years after the earth’s formation
  • early earth provided the conditions for chemical evolution
  • life originated under very different conditions than those experimented today
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9
Q

how was the atmosphere of early earth?

A
  • reducing
  • thick with water vapors
  • has nitrogen, and its oxides, carbon dioxide, methane, ammonia, hydrogen and hydrogen sulfide
  • no oxygen/extremely low concentrations
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10
Q

what are the 4 requirements necessary for the creation of organic chemicals such as amino acids and hydrocarbons? (the primitive soup hypothesis)

A
  1. no free oxygen
  2. source of energy (volcanism, thunderstorms, bombardment by extraterrestrial objects, UV radiation)
  3. chemical building blocks (water, ions and dissolved gases)
  4. time (earth is about 4.6 billion years old)
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11
Q

The primitive soup theory

A
  • early oceans were a solution of organic molecules (primitive soup) from which life arose
  • UV radiation provided the energy to convert basic compunds like methane, ammonia and water into the first organic compounds in the oceans of the early earth
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12
Q

how was the primitive soup hypothesis tested?

A
  • creation of the conditions of early Earth in a laboratory (Oparin-Haldane hypothesis tested)
  • simple organic molecules (amino acids, sugars, lipids, nucleotide bases) formed from simpler raw inorganic materials (like methane, hydrogen and ammonia)
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13
Q

joining of monomers into polymers

A
  • all living cells contain an array of macromolecules, including enzymes, other proteins, and nucleic acids
  • laboratory similutations of early earth condition produces organic polymers
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14
Q

proteinoid

A
  • protein-like polymer that results from a mixture of amino acids subjected to such considerable heating
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15
Q

spontaneous formation of ribosomes

A
  • emergence of ribosome constituted a pivotal step in the evolution of life (4 billion years ago)
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16
Q

packaging of molecules into protobions

A
  • demonstrated the possibility of a rudimentary metabolism
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17
Q

what 2 properties is life defined by?

A
  • accurate replication
  • metabolism
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18
Q

what are some of the properties associated with life that probionts exhibit?

A
  • binary fission
  • homeostasis
  • catalytic activity
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19
Q

liposomes

A
  • droplets of abiotically produced organic compounds
  • form when lipids and other organic molecules are added to water
  • some can perform simple metabolic reactions
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20
Q

what happens to the hydrophobic molecules in the mixture? (liposomes)

A
  • form a bilayer at the droplet surface
  • like the lipid bilayer of a membrane
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21
Q

what happens because the liposome bilayer is selectively permeable?

A

liposomes undergo osmotic swelling or shrinking in different salt concentrations

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22
Q

what may have been the first genetic material?

A

RNA

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23
Q

what does RNA does?

A
  • carry information
  • cause chemical reactions (RNA enzymes)
  • catalyze protein formation
24
Q

Ribozymes (RNA enzymes)

A

may have catalyzed the synthesis of RNA, and processed RNA molecules

25
Q

what is more flexible: RNA or DNA?

A

RNA

26
Q

RNA world hypothesis

A
  • RNA is the prime suspect for the earliest self-replication molecule because of its properties
27
Q

what jobs do biologist hypothesize that the RNA performed early in life’s history?

A
  • storing genetic information
  • copying itself
  • performing basic metabolic functions
28
Q

what did laboratory experiments demonstrate for RNA sequences?

A

RNA sequences can evolve under abiotic conditions

29
Q

what can single-stranted RNA molecules do unlike double-stranted DNA?

A
  • the molecules can assume a variety of three-dimensional shapes specified by their nucleotide sequences
30
Q

what do RNA molecules have?

A
  • a genotype (nucleotide sequence)
  • a phenotype (three-dimensional shape) that interact with surrounding molecules
31
Q

what can RNA sequences do under particular conditions?

A
  • are more stable
  • replicate faster with fewer errors
32
Q

what could make a protobiont differ from others? (with RNA that had fewer capabilities or without RNA)?

A
  • self-replicating
  • catalytic
33
Q

what would happen to a protobiont with self-replicating, catalytic RNA if it could split and pass on its RNA molecules to its daughter?

A

the daughter would have some of the properties of their parent

34
Q

what must the first protobionts have?

A
  • limited amounts of genetic information, specifying only a few properties
35
Q

what happens because the properties of the frist protobionts were heritable?

A

they could be acted on by natural selection

36
Q

deep sea vents

A
  • according to a new theory, deep sea vents have generated lipids and proteins and nucleotides , which may have given rise to the frist true cells
  • produce chemical gradients very similar to those used by almost all living organisms
37
Q

what did early organisms do with chemical gradients produced by deep sea vents?

A
  • exploited them
  • later on cells evolved to generate their own chemical gradient
38
Q

stromatolites

A
  • oldest known fossils
  • rocklike structures composed of layers of cyanobacteria and sediment
39
Q

how do microbialcommunites build stromatolites? (sediments)

A
  • traping fine sediments with a sticky film of mucus that each cell secretes, then binding the sediments grains together with calcium carbonate
40
Q

how to microbialcommunites build stromatolites? (framework)

A

cyanobacteria formings its own carbonate framework

41
Q

what can the magnetism of rocks provide?

A
  • dating information
  • magnetic reversals of the magnetic poles leave their record on rocks throughout the world
42
Q

how can the absolute ages of fossils be determined?

A

by radiometric dating

43
Q

how do we know how old things are?

A

fossils

44
Q

fossils

A

impressions of organisms from the past, preserved in rock

45
Q

sedimentary strata

A

reveal the relative ages of fossils

46
Q

how do scientists determine the origin of life?

A
  1. studying life on our own planet
  2. seeking out life or fossil life on other plantes or moons in our solar system
  3. trying to detect life in other solar systems
47
Q

studying life on our own planet

A
  • evidence from oldest rocks with fossil evidence of life on earth
48
Q

trying to detect in other solar systems

A
  • atmospheres of distant planets
  • looking for artificial radiation like radio signals that may be produced by advanced life
49
Q

from what did eukaryotic cells arose?

A
  • symbioses
  • genetic exchanges between prokaryotes
50
Q

cyanobacteria

A

photosynthetic prokaryotes that generate O2

51
Q

from what origin is most atmospheric oxygen from?

A

the process of photosynthesis

52
Q

on what did the increase of oxygen concentration had an enormous impact on?

A

anaerobic life on primitive earth

52
Q

what happened to organism that were sensitive to oxygen on primitive earth?

A

they died off

53
Q

heterotrophs

A
  • emerged because of the diversification of autotrophs
  • could live on molecules produced by the autotrophs
54
Q

why did the early protobionts must have used molecules present in the primitive soup?

A
  • growth
  • replication
55
Q

what replaced protobionts?

A

organisms that could produce all their needed compounds from molecules in their environment

56
Q

autotrophs

A
  • producing all required compunds for life
  • righ variety emerged
  • some could use light energy

general bio 2024 (22 decks)

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