Topic 1: Evolution of life on earth Flashcards
what is abiogenesis
theory that life originated from inorganic/non-living substances
what is biogenesis
origin of life from organic, pre existing matter
approximately when did Earth form, what were the conditions
about 4.6 BYA
sterile and inhospitable
when was the hadean eon and what were the characteristics of it
4-4.6 BYA
- meteor bombardments, and water was present in form of vapor
- low biosignature
when was the Archaean eon and what were the characteristics of it
2.5-4 BYA
- stable oceans began forming, cyanobacteria and prokaryotes present
- anoxygenic photosynthesis
approximately when did microbial life appear on Earth
3.8 BYA
- evidence of some biosignature present
what are stromatolites
fossil evidence
- cyanobacteria on limestone, photosynthesize and create by product of oxygen
what are the microbial layers of stromatolites
green layer- diatoms/cyanobacteria
pink layer - purple sulfur bacteria
crystalline layer - sulfate reducing bacteria
black layer
what are the carbonate layers of stromatolites
top 1- primary layer
top 2- porous layer
top 3- compact layer
top 4- bottom layer
what are examples of microfossils
- clonial cyanpbacteria
- filamentous prokaryotes
-algae
what are examples of chemical biosignature
kerogen-> substances produced by the decay of living organism
- membrane lipids
what is the great oxidation event
when was it
2.1- 3 BYA
followed by the proliferation of cyanobacteria–> producing high by-products of oxygen which lead to highly oxic environments.
- microbes evolved to adapt to oxic environment
what is panspermia theory
theory that life was transported to earth following meteorites, asteroids, or comets.
what is spontaneous generation model and who proposed it
hypothetical process by which living organisms develop from non living matter
(aristotle)
what is the primordial/prebiotic soup model
oparin and haldane hypothesis
- primitive water bodies were full of inorganic material, the atmosphere was methane/ammonia dominated
- strong impact by lightening or UV caused formation of life
what is the Urey Miller experiment
replicated environment with methane, ammonia, water, and hydrogen
- used 50,000-60,000 voltage to replicate lightening
- resulted in 15-13 or 22 amino acids
what was the significance of the miller urey experiment
Inorganic materials can form organic molecules in the right conditions
- insight on prebiotic chemistry
describe differences between DNA and RNA
DNA– double stranded, no OH group
RNA- single stranded– OH group on ribose
what are the 3 key qualities of RNA that contribute to RNA world hypothesis
- capable of storing genetic info
- can catalyze chemical reactions
- recent studies show RNA can self replicate
what are limitations of RNA world hypothesis
RNA is more unstable than DNA
what are the strong and weak points on the theories that proteins came to form life first
- amino acids are synthesized under a variety of conditions
- can exhibit catalytic activity
- amino acids compose high diversity of information content
weak:
- lack of self replication
- proteins require DNA for function
what is the central dogma
flow of genetic info from DNA to RNA to make functional protein
- DNA replication
- Transcription (DNA-RNA)
- translation (RNA-protein)
what is the role of ribosomes in the central dogma
factories that translate code of DNA into functional unit (protein)
define gene expression
process by which DNA is converted into a functional product
what is the role of mRNA
relaying message in DNA to protein translation apparatus
what is a ribozyme
catalytic RNA molecules, break and form covalent bonds in RNA
what is evidence of endosymbiosis
(MADDR)
M- membranes (evidence of double membrane)
A- antibiotics (susceptibility to antibiotics)
D- Division (reproduction through binary fission
D- DNA (mitochondria/chloroplast has own DNA)
R- ribosomes (have its own ribosomes)
differentiate between eukaryotic cell and prokaryotic cells
eukaryotic: membrane bound nucleus with organelles
prokaryotic: unicellular lacking nucleus and organelles
what is LUCA
last universal common ancestor
- assumed single celled
what is a clade/monophyletic group
consists ancestral species and all its descendants
what is a paraphyletic group
consists of common ancestor but some (not all) its descendants
what is a polyphyletic group
species grouped by similarity, not from common ancestor
what is the difference between a cladogram and phylogram
cladogram- branches are uniform in length and are not proportional to the length of time of evolution
phylogram- different branch lengths that are proportional to the length of time of evolution
what is an outgroup
taxon that diverges from the tree prior to the last common ancestor of the taxa being studied
what is homology
sharing of traits via common ancestry
what is analogy
similar traits but independent origins
what is divergent evolution
group from same common ancestor evolve and accumulate differences
what is convergent evolution
organisms sharing analogous traits that are not inherited from a common ancestor
what is parallel evolution
independent evolution of similar traits from similar ancestral conditions
what are derived traits
traits that are not present in the common ancestor of all species of interest
what are ancestral traits
traits present in common ancestor of all species
what is evolution
the change of alleles frequencies in a set of organisms over time
what is microevolution
evolutionary changes that occur over relatively short periods of time within a population
what is macroevolution
evolution that results in relatively large changes over a long period of time
what processes give rise to new alleles
mutations and recombination
what causes changes in allele frequency
selection and genetic drift
define mutation
random changes in DNA sequence that accumulate in all DNA sequences over time
what is recombination
segments of DNA are broken and rejoined to create new combination of genetic material
what are environmental factors that influence mutations
sunlight
xrays and radiation
tobacco
chemicals
nitrites
what is single nucleotide polymorphism
changes a single nucleotide in a DNA sequence (point mutation)
what are indel mutations
insertion or deletion mutations that result in addition or removal of one or more nucleotides
result in frameshift mutations (shift in reading frame of DNA template)
what is transition mutation
changes from purines to purines (AG)
or pyrimidines to pyrimidines (CT)
what is transversion mutation
changes from purines (AG) to pyrimidines (TC) or vice versa
what is the frequency of error in a single round of replication
10^-6 to 10^7 per thousand bases
what is the most frequent to least frequently occurring mutation
missense> silent> nonsense
what is duplication mutation
a piece of DNA that has been copied more than one time
what is horizontal gene transfer
uptaking foreign DNA that is not in the organisms direct cellular lineage
what is transformation
competence– the uptake of free naked DNA from the environment
can be natural or artificial (requires calcium or lightening)
what is general transduction
allows for transfer of any gene through phage infection (taking DNA from phage cells)
what is specialized transduction
allows for transfer of selective genes and small region of a chromosome (also with phages)
what is the Pasteur experiment
disproved spontaneous generation
showed that a boiled nutrient broth did not give rise spontaneously to new life, but that if direct access to air was permitted, the broth decomposed, implying that small organisms (in modern terms, microbial spores) had fallen in and started to grow in the broth.
