test 3 lecture 16 Flashcards
what does abiogenesis or biopoiesis or Ool mean
the natural process of life arising from non-living matter, such as simple organic compounds
before the first cells could evolve , what fundamental conditions were needed
essentail elements
continual source of energy
temperature range permitting liquid water
why were essential elements needed for origins of life
to compose organic molecules
why was a continual source of energy needed for origins of life
life requires continual input of energy, which ultimately is dissipated as heat
why was temperature range permitting liquid water needed for origins of life
metabolic reactions cease at temps that are either too high or too low
when was the solar system formed
4.6 billion years ago
what made up the early atmosphere
primarily of CO2
what makes up the atmosphere now
CO2, N2, and O2
how do we have the compounds in the atmosphere now
contributions from living organisms
heavy metals created from bursting stars
how did temp affect the atmosphere
atmospheric gases absorb light and convert the energy to heat, raising the temp of the surface and atmosphere
what could have caused the green house effect
early atmosphere had high CO2 making it very hot
what kept the atmosphere temp down in the beginning of time
CO2 rose temp but with microbial consumption of CO2 and produce N2 and O2 kept temp down
possibly causing ice age
when was the hadean eaon
4.5 to 3.8 billion years ago
what happened during the hadean eon
repeated bombardment of meteorite
cycles of vaporizing ocean, cooling and condensation
when was the archean eon
3.8 to 2.5 billion years ago
what is significant during the archean eon
earths crust become solid
marked first period of stable oceans
earliest geological evidence for life from rock strata
what is the key ingredient of life during early earth’s existence
liquid over range of temps and dissolves inorganic and organic material
what is stromatolites
the earliest forms of life (bacterial communities) for which we have clear fossil evidence
how are stromatolites formed
layers of phototrophic microbial communities grew and died
what are the different layers of stromatolites
outside: oxygenic phototrophs (diatoms, cyanobacteria)
inside: sulfate reducing bacteria
what do stromatolites not reveal
they are deformed and dont reveal cell structures
what are the 4 geological evidences for early life
stromatolites
microfossils
biosignatures/ biological signatures
oxidation state
what is the most convincing evidence of early microbial life
microfossils
what is in a microfossil
minerals precipitated and filled in the form of ancient microbial cells
how can you tell how old a microfossil is
radioisotope decay
how far back do microfossils go back
2.0 to 3.2 billion years ago
what do they say about microfossils that are older than 2.0 billion years
metamorphic rock
microfossil interpretation controversial
what are biosignatures
chemical indicators of life
what are isotope ratios
ratios between certain isotopes of a given element can be altered by biological activity
what is cyanobacterial hopanoids
steroid like membrane molecules that are particularly durable and may last within rock formations for hundred of millions of years
how are elements are defined
number of protons in their nucleus
protons+neutrons= atomic weight
what are isotopes
elements with different numbers of neutrons
what type of elements have at least two stable isotopes with lightest being the most abundant
most environmentally relevant
H C N O S Cl
what is special about 2-methylhopanoids
both oxygenic and anoxygenic phototrophs have them
may be able to identify biological material but may not be good biomarker for differentiating among different types of cyanobacteria
what was the oxidation state like in early life
entry of O2 into earth’s biosphere arose gradually in the oceans
fluctuated with cycles of aerobic and anaerobic metabolism
what does molecular phylogeny mean
genetic relatedness
what are clades
branching groups of related organisms
what is a monophyletic group
a group of species that share a common ancestor
what is a phylogeny
the full description of branching divergence of a species
populations of organisms diverge from each other through several fundamental mechanisms such as
random mutations
natural selection
reductive evolution
what are random mutations
dna changes through rare mistakes as the chromosome replicates
what is natural selection
in a given environment, natural selection favors organisms that produce more offspring
what is reductive evolution
in the absence of selection for a trait, the genes encoding the trait accumulate mutations without affecting the organisms reproductive success
leads to loss or mutation of DNA encoding unselected traits
what is a molecular clock
the temporal info contained in a macromolecular sequence
what is maximum parsimony
the best fit tree is defined as the one requiring the fewest mutations to fit the data
what is maximum likelihood
the probability that such a tree would have produced the observed DNA sequences
what is horizontal gene transfer
acquisition of a piece of DNA from another cell
what is vertical gene transfer
the transmission of an entire genome from parent to offspring
what are informational genes
encode products essential for transcription and translation
what are operational genes
encode products that govern metabolism, stress response, and pathogenicty
