towards multicellularity
DESCRIPTION
Towards multicellularity. Four elements to make a multicelluar organism. Apoptosis. Information exchange. External s ecretion. Colonial organization. Bacteria. Paenibacillus forms colonies moves on hard s urfaces through jointly secreted lubricants communicates with other cells - PowerPoint PPT PresentationTRANSCRIPT
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Towards multicellularity
Colonial organization
Information exchange ApoptosisExternal
secretion
Four elements to make a multicelluar organism
Paenibacillus dendritiformis
BacteriaPaenibacillus
•forms colonies•moves on hard surfaces through jointly secreted lubricants•communicates with other cells•no apoptosis•no real cell differentiation
Myxococcus xanthus
Myxobacteria•form colonies of millions of cells•Some have coordinated movements•form biofilms•largest bacterial genomes (9 - 12 kB)•some produce fruiting bodies for the release of spores•no apoptosis•rudimentary cell differentiation
Why did Bacteria not evolve true multicellularity?Maybe their limits in genome size do not allow for higher order differentiation.
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Nanowires and electrical signalling
Geobacter sulfurreducens
Microbial electrical cell-cell communication via nanowires may
be widespread in nature.
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Colonial organization
Information exchangeApoptosis External
secretion
Four elements to make a multicelluar organism
Vascular plants
Brown algae Slime moulds
Fungi
Metazoa
Cell differentiation
Specialized cells reproduceHigh degree of cell differentiationReal tissuesOrgansNo central coordination
Early differentiation of germ lineHigh degree of cell differentiationReal tissuesOrgansCentral coordinationSpecialized cells reproduce
Cell differentiationNo real tissuesNo organs
Specialized cells reproduceCell differentiationReal tissuesNo organs
Facultative multicellularityRudimentary cell differentiationNo real tissuesNo organsMultiple origin of multicellularity in each of these groups
Multicellularity probably monophyletic
Stigmergy:indirect signalling by secretion
ChlorophytesFacultative multicellularityLimited cell differentiationNo real tissuesNo organs
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The multi-taxon genome initiative
Amoebozoa
Ichthyospora
Sphaeroforma arctica
Capsaspora
Nuclearia
Fungi
Metazoa
Choanoflagellata
Apusozoa
Ministeria
Pseudo-multicellular colonies
Nematostella
Single celled parasites of marine pulmonate snails
Some species form colonies
Chorallochytrium
Corallochytriumlimacisporum
Free living
Parasitic
Free living
True multicellularity
Single celled aquatic heterotroph
Single celled marine heterotroph
Parasitic
Single celled free living marine heterotroph Single celled terrestrial or
aquatic bacteriophages
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Tonian1000-850
Mesoproterozoicum1600-1000
PlantaeOomycota
Mycetozoa s.str.
Choanoflagellata
Microsporidia
Metazoa
Chytridiomycota
Zygomycota
Ascomycota(Saccharomyces cerevisiae)Basidiomycota
Lecanoromycetes
Plant pathogen
Arthropod pathogen
phagotroph
Saprotroph / mutualists
lichenized
Dicaria
Opistho-konta
Fungi
terrestrial
Multiple loss of flagellum
Phytophora infestans
Amphiacantha
Chytridium
Glomeromycota
Phycomyces
terrestrialUnikonta
Bikonta
Nuclearia simplex
Nuclearia
(Chromista)
Arbuscular mycorrhiza
Ektomycorrhiza
First Glomeromycota fossils
Ordovician490-440
Silurian440-410
Devonian410-355
Carboniferous 355-290
First lichens
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PDZ signal
PDZ signalwwguk
Generalized Metazoa
Ichthyospora
The MAGI genesGuanylate kinases regulate tight tissue junctions
Zebra fish
Single cell organismsParasites of marine fish, birds and mammalsSome species form pseudo- multicellular colonies
Ichthyospora
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A major invention: Metameria
Christiane Nüsslein-Volhard (1942-)
Arche Hox
EHG box Proto Hox Proto NKL
EHG box Extended Hox NKL Para HoxEarly Vertebrates
Early arthropods
All animals share a common gene family, the homeobox family, that controls metameric and embryonal development.
Trichoplax adhaerens
Early Metameria
Cnidaria
Walter Jacob Gehring (1939-)
In sponges and Ctenophora Hox genes haven’t been detected yet.
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Plants
Fungi
Metazoa
Homeotic genes: MADS-box
Homeotic genes
Homeotic genes: Hox-genes
Convergent evolution of genes that regulate ontogenetic development
Cnidaria
Metameria
Placozoa
From: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/H/HomeoboxGenes.html
Eleutheria dichotoma,Photo from Jacob and Schierwater
2007, Plos One 2: e694.
Inactivation of Cnox 3 in the hydrozoan Eleutheria
dichotoma produces multiple heads, for
instance head duplication and therefore a bilaterian
pattern
The evolution of Hox genes
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Tonian1000Super-
continent Rodinia
Cryogenian850
Rodinia breaks up.Largest
glaciations (snowball
earth)
Ediacaran630
Warmer period
interrupted by local ice ages
?
Metazoa
Charniodiscus
Dickinsonia Tribrachidium
Spriggina floundersi
ParvancorinaCyclomedusa
?
From Tonian to modern times
HorodyksiaMaybe a colonial benthic two tissued
metazoan
Meso-protero-zoicum
1600-1000
Parmia
Maybe a homonomous segmented metazoan
Photos from Fedonkin 2003
Biotracers of Porifera
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Early Ediacaran
630 Warmer period
Middle Ediacaran
600 Local ice ages
Avalon assemblages
580 Warmer period
Increase in atmospheric
O2 level
White sea and Nama
assemblages560
Warmer period
Cambrium540
Warmer period
Aspidella
Advanced Rangeomorpha and simpler ErniettomorphaProbably not related to any modern taxon
Charnia
Shallow water mobile animals related to
modern taxa
Immobile, deep-water filter feedersNo mouth or gut, no reproductive organs
Rangeomorpha were fractal organisms developing through simple branching patterns (like Fungi)
An early embryo
Kimberella, Mollusca: like
Chiton
Spriggina Arthropoda:Canadia,
Annelida
Tateana
Acri-tarch
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Porifera
ChoanoflagellataPlacozoa
Ctenophora
Cnidaria
Plathelminthes s. str.
Cycloneuralia(Nematoda, Priapulida)
Lophotrochozoa
Chordata
Mul
ticel
lula
rity,
Hox
box
„Bilateria”
Protostomia
Blastoporus becomes anus
Cho
anoc
ytes
Upp
er a
nd lo
wer
sid
e
ParaphyleticMultiple bilaterality
Gas
trula
, Mus
cle
cells
Metameria, Coelom
Ect
o-, E
ntod
erm
Cnidocytes, Rhopalia
Ner
vous
cel
ls, S
tato
cyst
Acoela
Xenoturbellida
Cryogenian850-680
Ediacaran680-540
Tonian1000-850
Cambrian540-490
Mesoproterozoicum1600-1000
Ambulacraria (Hemichordata, Echinodermata)
Chaetognatha
OnychophoraArthropoda
Gnathifera
Annelida s. l.Mollusca
Deuterostomia
EcdysozoaMetameriaPseudocoelom
Metameria, Coelom
Mes
oder
m
Pseudocoelom
No anus
No anus
No anusNo coelom
Lophophorata
Pseudocoelom, Anus, Metameria
Paraphyletic
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Ectoderm
Ciliate entoderm
Nervous cellsPorifera
Statocyst
PlacozoaInformation exchange via neurotransmitters
Trichoplax
A functional model of metazoan evolution
A hypothetical creeping animal of Gastrula organization
CtenophoraCnidaria
Acoela
Xeno-turbel-lida
Deuterostomia s. str. Lophotrochozoa Ecdysozoa
Mesogloa
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Cryogenian850-630
Ediacaran630-540
Cambrian540-490
Mass extinction
Onychophora
Trilobites
The molecular evidence
ChelicerataXiphosura, Arachnida
Pycnogonida
Pancrustacea
„Myriapoda”Diplopoda
Chilopoda
MyodocopaPodocopa
Remipedia
Ordovician490-440
Silurian440-410
Hexapoda
Branchiopoda
Maxillopoda
Malacostraca
Aysheaia
Beckwithia
typa
Aglaspida
Cephalocarida
Isopoda
Ostra-coda
Tardigrada
Panarthropoda(Tetraconata)
MandibulataXenocarida
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The Cambrian explosion
Cambrian 540-490
During the Cambrian atmospheric oxygen concentration increased to a level to allow for the development of hard skeletons. Probably all today’s phyla were already present.
First complicated food webs including higher predators appeared. This might have caused the disappearance of the Ediacaran fauna.
Waptia, Chelicerata? An early predator
Burgessochaeta, Polychaeta
An early predator
Ottoia, PriapulidaAn early predator
Chmatocrinus, CrinoideaThe earliest deuterostomes
Pikaia, ChordataOlenoides serratus,
Trilobites
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Ordovician 490-440 Silurian 440-410
Ice ageMass extinction
First primitive terrestrial fungi, vascular plants and animals (millipedes,
arachnids)
Eurypterus remipes,
Chelicerata
First Cephalopoda (Nautiloids) and Bivalvia. Rise of Brachiopoda and Bryozoa.
Warm shallow seas Warm greenhouse phase (high CO2 level)
Trilobites Arthropoda Bryozoa
Cephalopoda
ConodontsBirkenia, Agnatha
Cooksonia grade land plants
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Ordovician490-440
Silurian440-410
Devonian410-355
Charophytes
Em
bryo
phyt
es
Marchantiopsida
Bryophyta
Aglaophyton Rhynia
Trac
heop
hyte
s
Lycopodiaceae
Isoetales
Drepanophycales
Psilophyton
Sphenopsida
Pterydophyta
Seed plants
Cambrian540-490
?
First land plants
?
Molecular data put the divergence of Bryophytes and Tracheophytes to the end of the Proterozoic (540 to 700 mya).
Parafunaria sinensis
Chara Lunularia cruciata
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Devonian 410-355
Stomata of Rhynia Pterychthyodes, Placoderna
Rather warm, zoned climate Rather warm, zoned climate Southern glaciation, mass extinction
Moresnetia zalesskyi
Kampecaris forfarensis , Myriapoda
Niedźwiedzki et al. 2010)
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Carboniferous 355-300
Ice ageMass extinction
Warm and wet climateHigh oxygen concentration
Breyeria harlemensis Paleodictyoptera
Euproops rotundatus Xiphosura
Delitzshala bitterfeldensis
Homoptera
Equisetum
Lepidodendron source of today’s coal
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Carboniferous 355-300
Ice ageMass extinction
Warm and wet climateHigh oxygen concentration
Synapsid reptiles Diapsid reptiles
Temporal fenestra
Heterodont HomodontAnapsid reptilesHomoodont
Archeothyrisfirst primitive Synapsid
Petrolacosaurusfirst primitive Diapsid
heterodont
Hylonomusa first primitive
Anapsid
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Carboniferous 355-290
Permian290-250
Trias250-205
Jurassic205-140
Cretaceous140-65
Pelycosauria
Therapsida
Mammalia
Am
nion
Sarco-pterygia
Mesosauria
Testudines ??
Crocodylia
Pterosauria
Dinosauria
Aves
Euryapsida
Squamates
Rhyncho-cephalida
Synapsid cranion
Diapsid cranion
Lepidosauromorpha
Archosauromorpha
Anapsida Testudines ?
Anapsid cranion
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Permian 300-250
Ice ageMass extinction Warmer and arid Arid Mass
extinction
Anapsid reptiles
Mesosaurus, Permian primitive anapsid aquatic reptile
Milleretta, Permian primitive anapsid terrestrial reptile
Aldabra tortoise
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Dimetrodon, Permian primitive synapsid Pelycosaur
Pelycosaur → Therapsida → Theriodontia (mammal like)
Proburnetia, Permian primitive synapsid Therapsid
Annatherapsidus petri , Permian synapsid Theriodont
Permian 300-250
Ice ageMass extinction Warmer and arid Arid Mass
extinction
Synapsid reptiles
Mammal like teeth
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Permian 300-250
Ice ageMass extinction Warmer and arid Arid Mass
extinction
Diapsid reptiles
Tuatara, Lepidosauria
Pterodactylus kochii, Archosauromorpha
Ichthyosaurus, Lepidosauria
LepidosauromorphaSquamata, Tuatara
ArchosauromorphaPterosauria, Dinosauria
Ichthyosauria
Thecodont dentition
Acrodont and pleurodont dentition
Terrestrisuchs, Crocodylomorpha
Endothermy?Scale derived thermoregulating body cover?
Thermoreg-ulating body cover
Crocodylomorpha
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Today’s reading
Ediacara fauna and the origin of Metazoa: http://www.peripatus.gen.nz/paleontology/Ediacara.html
http://www.ucmp.berkeley.edu/vendian/critters.htmlThe Burgess shale: http://www.gpc.edu/~pgore/geology/geo102/burgess/burgess.htm
http://www.palaeos.com/Paleozoic/Cambrian/Cambrian.htmThe history of life: http://www.palaeos.com/The tree of life: http://www.tolweb.org/tree/The virtual fossil museum: http://www.fossilmuseum.net/
On the cambrian explosion: http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1578734
Metazoan phylogeny: the state of art.:http://icb.oxfordjournals.org/cgi/content/full/46/2/93
Dunn C. W. et al. (2008) Broad phylogenomic sampling improves resolution of the animal tree of life. Nature 452: 745-750. Srivastava M. et a. 2008. The Trichoplax genome and the nature of placozoans. Nature 453: 855-960..