origin and evolution of eukaryotes Flashcards
bacteria species examples
proteobacteria
gram positive
cyanobacteria
cytophaga
archaea species examples
methanobacterium
thermoproceus
methanoccoules
eukaryota species examples
fungi plants cilliates slime molds trichomonodas microspondia diplomondiads flagalletes animals
leca
last eucaryatic common ancestor
(limited genen sampling makes it hard to be accruatee)
was a complex cell with numerous organelles and 300 new gene families
luca
last universal common ancestor
bacteria
70 s ribosomes
binary fission
unicellular
circular dna
arose 4 bya
explore many chemical different environments (acidic, heat fluctuating, massive population)
large genetic variation (feeding and respiraiton methods)
archea
morphologically simlar to bacteria
biochemically and genetically different
eukarya
80-90 rivosomves membrane bound organelles can be multicellular histones mitosis and mesiosis cytoskeleon explore MORPHOLOGICAL space;
euglena
complex bacteria that was LECA
compare bacteria and human cell
paramecium has 40,000 genes
x2 of the pancreastic acinar cell
origin of eukaryote theories
- endosymbiosis
- autogeneous evolution
- hydrogen hypothesis
prokaryotes and respiration
compartementalize
respire oxygen
resporotray complexes are main source of oxygen
gram per gram prokaryotes respire faster than one cell eukaryote
what dont prokaryotes do
compartmentalize organelles
anerobic esporation
protection against oxygen toxiticity
increase speed of respiration
eukaryote energy per gene
1 cell of eukaryotes consume more oxygen per minute than a prokaryote, hence have a larger metabolic rate
endosymbiotic hypothesis
proposed by lynn margulis [also knowsn as SET]
multiple different endosymbiotic events gave rise to eukaryotes with multiple different endosymbioints such as
- mitochondria
- chlorplasts (from cyanobacteria)
false: cytokeleton and flagella didnt.
endysymbiosis hypothesis evidence
mitochondria/chlorplasta and bacteria have similar: circular dna ribosome size binar fishion structures dna processing
autogenous evolution theory
Tom Cavalier Smith: gradual evolution of unicellular cells into eukaryotes
- eukaryotes evolved autogenously by the loss of the cell wall driven by the evolution of phagotrophy
- mitchondria acquiisiton was LATE and qualitively unimportant
- mitchondria and chrloplasts evolved in compartmentalized plasmids in vesciles in plasama mebmrane; nucelus and cytosplasm formed by evolution
hydrogen hypothesis
bill martin; ‘non parasitic theory’
a singular endoysymbiotic event of 2 bacterial cells;
all eukaryotic traits evolved after the two prokaryotes merged
existence oef the ‘primitive phagocyte’ not true; only a host archeaon however
(hydrogen dependent archea bacteriam + methanogen eubacteriera—> eukaryote)
problems with SET
not always consistent
aerobic, heterotrophic prokaryotes enguledb y other cells by endocytosis; provided oxygen utliiation to anerobic host cells to source in oxygen environment and AID in ATP production
phagotrophy
invaginations of prokaryotes leading to compartmentalized functions
where can the AET be valid
origins of endoplasmic resticulum,
golgi apparatus
nucleur membrane
lysosomes
paradox of autogenous evolution
all complex life is eukaryotic; and it only arose once in 4 billion years
- all eukaryotes share universal traits
- prokaryotes show no tendency to evoleve into morpholoical complexity with any of these traits
therefore: if each of these traits evolved step by strep and each step has a selective advantage, why did none evolve in prokaryotes? (aka intermediates dont exist)
congruent evolution example
eyes; humans and octopus eyes are similar but evovled different
morphologically indepedent but SAME genes in common that create them
this is becasue SIGHT is an advantage
eukaryotic super groups
5-6; unicellular groups have most genetic diveristy; branch lengths seperating groups much shorter than bacteria within groups
suggests a ‘big bang’ after LECA
SAR
stramenophiles
alveolata
rhizaria
what is the black hole in biology
all eukaryotes share traits absent from prokaryotes
what traits do ONLY eukaryotes have
larger geneomes and cell volumes
dynamic cytoskeleton, motor proteins, flagella and cillia
nucleus, nucleur membrane, pore complexes, nuclelous and straight chromosomes
rericporcal sex, mitotisis and tubilin spindle
phagocytosis
seperation of transcription and translation
endomembrane systems like mitrochondria
‘big bang’ after all these traits evolved in leca
why do only eukaryotes have specific traits
selective bottle neck; great oxydation event 2.2. billion years ago;
only the best preadapted groups made it rhough this ‘selecive bottle neck’
- this fixed niches and led to fast evolution and explosive radiation into new forms
predictions of selective obottle neck
events such as snowball earth, oxygen, ocean temperature and anodic ocean stratificiation
- if selective; environmental contraits and biolgoically easy organisms should have been a polyphyletic radiation
polyphetic radiation
different bacteria groups SHOUDL have also given rise to complex life indepenently; traits lack common ancestor
paraphyletic radiation
semi dependent traits
monophyletic radiation
clade formation; traits of descenends all have same ancestry
leca big bang?
intense genetic diversity and short branch lengths
all eukaryotic genes can be traced back to it unlike prokaryotic and archaeic genes
what are the eukaryotic supergroups
metazoa
ophisthokonta
amoebozoa
excavata
SAR
archae plastidida
environmental bottle neck
polyphyletic
different lifestyles led to changes
serial bottle neck
diverse endosymbiosis in different envrionemnts
restrictive bottle neck
rare change in cell to structure or pylogeny;
if bottle neck were restrictive due to biological contsraints;
what about bacterials trucutred prevented evolution into higher complexity?
leca; had mitochondria= supports mitcohondria acquissiton and eukarotic origin in SAME event
eukaryotes and competititors?
forms arising later must have been outcompeted to extinction by fully evolved eukaryotes;
if true there were no ecological and evolutionary eukaryotic interdmediates as always became extinct
(one reasons why prokayaryes not more complex?)
acheozoa
aagainst selective bottleneck;
they could be the missing ‘link’ as evolutionary eukaryotic intermediates
all possess organelles derived from mitchondria
post date leca
are ecological interdmieiesats; underwetn reductive evolution from more complex archea as incentive to dominante was lost
ring of life?
evidence suggests sukaryotic cell arose via stochastic endosymbiosis between two prokaryotes; search of natural seelection acts on cells over billions of years; does not intrinsigly cause complexity
examples of archeoxoa
parabasala
microsporindia
could archeons be the host cell
genetic evidence based on 29 sequnces of protreins
whats the closest relative to eukaryotes
lokiarcheota
lokiarcheota
found in loki’s castle in mid atlantic
are a complex archae that might bridge prokaryot-eukearyotic gap
domains of life
2, not 3?
hot cell for eukaryote was an archeon; phylogentic strucutres place eukaryotes as branching FROM achaea
as a cell within a cel l
example of bacteria in a bacteria
cyanobacteria
bioenergetic constraints of prokaryoates
- respire over cell membrane
- surface area to volume constraits
- respoiration effiency half with doubling dimensions
- dont internalize or compartmentalize
- oxygen making proteins different to eukaryotes
bioenergetic plus of eukaryotes
better oyxgen making proteins
need genes in mitchondria to control respiration as they grow larger
merge of 2 prokaryotes allows this
cyanobacteria and nitrogen fixing bacteria
internal membranes
no organnelle genome out parts
e.coli
a giant bacteria
respires across plasma membrane; area of biogenetic membrane is massive and nucleoids each govern each other bacterial volume of cytoplasm
exreme polyploid 9gene size)
issues with full geneomes and prokaryotic size
- without intracellular transport networks each egeneome has a fixed volume in the cytoplasm
- extreme polyploidy requires massive energy costs to express all genes; hence the energy ber gene is giant and small bacteria
- no energetic apactiy to support increase in size and complexity therefore of bacteria
- eukaryotes have larger power per haploid gene; hence larger metabolic rate
why is endosymbiosis neccessary?
size;
small cell; retains control of respiration= favoured by selection
large cell= loses control of respiration and dies
giant cell= needs polyploidy to control respireation
but eukaryotes have endosymbiosints; who supporte large host genome size
what does nick lane argue
all eukaryotes arose from common ancestor and prokaryotes dont evolve to morphological complexity
how does the mitonchrida cause the energy change to be permissive not presectiptive in eukaryotes
- reductive evolution and specializion of endosymbiont;
- exterme genomic assymetry
- mitcondrial genome allows expansion of biogenertic membrane
- overcomes energy contraints in prokaryotic genome cell to allow host cell to expand by 20000
why did eukaryotic genome size increase
- genes and intron addition of endosymbiont caused high mutation rate;
mutations masked by cell fusion and genome duplication resulting in a protosexual cell
therefore eukaryotic basal traits the saem and massive biogenetic expansion/release from geneome size contraits=
protosexual cell cycle and accumulation of eukaryotic traits
what do the bioenergetic changes in eukaryotes explain
unique origins of eukaryotes
absense of evolutionary intermediates
eovltuion fo sex in eukaryotes
when did eukaryotes origin
1 common ancestor 4 billio ears ago
common traits in eukaryotes and leca
intron positions
nuclear pore complex srcutre
synagamy and 2 step
(common ancestry therefore most parimony explanation as opposed to convergent evolution or lateral gene transfer)
why was it unlikely that prokaryotes developed repeatadably into eukaryotes, and were just outcompeted to extinction
- radiations exlore morphological space, not metabolic
- animals and plants are large and vulnerable to extinction
- no prokaryotes driven to extinction
- diverse morphological simple eukaryotes also exist
- extinction too esay to explain all complex life on earth sharing one common ancestor
- achezoa have lsot mitcondria by reductive evolution to mitosomes and hydrogenosomes
- likehoold of prokaryotes evolving up is 1 in 10^3000
- heaving selection against prokayotes to evolve to greater complexity
why do prokaryotes show no tendency to tlve to greater morphological complexity
a. chemical complexity exists (chromosome variation, itnernal membranes, parasitic)
b. dont accumulate all traits at once
c. streamlend for small genoems for fast replication; hence continous loss of uneeded genes by lateral gene transfer
d. accumulation of genes in eukaryotes reduce selection of smal purying popoulation
= hence dont want to explore morphologicla space
eukaryogenesis
cross of prokaryote to eukaryote
how did eukaryotes origin
symbiosisb etween prokaryotes
mitcondria ((universal in eukaryotes and a singular event; d-proteobacteria probably the ancestor) + host cell (tpe of archeon but unclear)
how did eukaryotic cells accumulate
endosymbiosis
tree of life not branching, but unbranching trunk
repricocal sex and cll fusion
must have been rapdi in small population
instabiliity ould hav eprevented specialization
large stable population after LECA evolved then into eukaryotic supergroups
how do mitcondria solve the eukaryotic origins
enable bioengertic membrane to cinrease
enable expansion of host cell genome
cause high mutation rate which casues cell fusion and sex
energy per gene variations
mean metabolic rate per cell: 0.49 pW in bacteria
mean metabolic rate per cell: 2286 pw in eukaryotes
= respire at same rate but eukaryotes produce learger eneger per gram; not restrained to expand by energetic limitations
why can only endosymbiosis fashion giant nuclear sizes
- mitochondrial geneome is lost adn transferrred to nucleas
- fastes replicators are simple= hence comeptition amogn individuals to remain endosymbiotic by simplicity
- eukaryotes have genomic assymetry as many tiny mitchondrias sustain many genomes; cell division therefore disperes gene
- gene loss is slow and functions are lost to save host cell atp synthesis
what do mitconrida do for eukaryotes
- oxidative phosphorylation for incrsae respiration rate
- plasmids cant enable caling as they cant replicate; mitchondria can
- reductive evolution for maximixed function
- hence reduced need for cell wall; allows cell fusion and growht with mroe easy
origin of sex in eukaryotes
- no evolutionary eukaryotic intermediates
- common ancestory; important to duplicate genome
hence INTRON positions present in LECA; therefore INTRONS cause mutations that forced sex and cell fusion
