Precambrian:
4.6 billion years ago: formation of the earth
Hadean: 4600 - 4000 mya
Archaean: 4000 - 2500 mya
Proterozoic: 2500 - 541 mya
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Cambrian Explosion
Scientific American
Cambrian Period / System
540 - 485 mya
There are only four eons:
- Hadean: no eras
- Archaean: four eras
- Proterozoic: three eras
- Phanerzoic: three eras
How to remember the eons:
- Two eons: no life
- Two eons: life --
- one eon: early life; ends with ediacaran
- second eon: visible life; begins with Cambrian
Proterozoic EON (early life)
Proterozoic: "early life" EON
early life
Proterozoic -- "early life" -- three eras:
- early: palaeo-proterozoic
- middle: meso-proterozoic
- late: neo-proterozoic -- ENDS WITH THE EDIACARAN
Then at end of "early life" -- end of EDIACARAN -- all of a sudden -- explosion of life -- THE CAMBBRIAN PERIOD -- the first of six periods in the Paleozoic Era
Right at end of Proterozoic eon and beginning of Phanerozoic era -- abundant evidence of life. Ediacaran.
The Ediacaran marks the first widespread appearance of complex multicellular fauna following the end of the Cryogenian global glaciation known as the Snowball Earth.
But it was the Cambrian explosion that was most remarkable.
Three "dividing points" begin within a million years of each other:
1) classic point -- trilobites and corals
trilobites
reef builders -- corals
2) first appearance of a complex feeding burrow called Treptichnus pedium
first appearance: 542 mya
earliest widespread complex trace fossil
3) first appearance of a small, generally disarticulated, armoured form called "the small shelly fauna"
Phanerozoic EON (visible life)
Phanerozoic Eon: originally this was the eon of most interest to paleontologists but term fell out of favor. Paleontologists immediately went ot the "eras" and the "periods" (e.g., Paleozoic era and the first period, the Cambrian); the Mesozoic era and the three periods, Triassic, Jurassic, and Cretaceous
Paleozoic ERA -- age of fishes and reptiles
- Cambrian period
- Ordovician period
- Silurian period
- Devonian period
- Carboniferous period
- Permian period
Mesozoic ERA -- age of dinosaurs -- started with The Great Dying -- P-T ended 66 mya volcano, second greatest dying
- Triassic period
- Jurassic period
- Cretaceous period
Cenozoic (tertiary) ERA -- started with the second greatest dying, the K-P; currently age of mammals; now age of man
- Paleogene period
- Neogene period
- Quarternary period
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Cambrian Explosion
Three "dividing points" begin within a million years of each other:
1) classic point -- trilobites and corals
trilobites
reef builders -- corals
2) first appearance of a complex feeding burrow called Treptichnus pedium
3) first appearance of a small, generally disarticulated, armoured form called "the small shelly fauna"early skeletal fossils
somewhere between Ediacaran and Cambrian
Phanerozoic EON: originally eon of most interest to paleontologists but term falling out of favor.
Phanerozoic Eon: Visible Life
Three eras:
Paleozoic: explosion --> fishes -- reptiles --> dinosaurs
Mesozoic: age of dinosaurs
Cenozoic: us
Paleozoic:
begins with Cambrian explosion, then
Ordovician
Silurian
Devonian
Carboniferous
ends with Permian
Mesozoic: 250 mya -- 66 ma
Permian-Triassic: THE GREAT DYING
Triassic period
Jurassic period
Cretaceous period
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The Book Evolution, Steve Parker, Alice Roberts, c. 2015
560+ pages
- Chapter 1: earliest life; p. 22 - 53 (31 pages)
- Chapter 2: plants, p. 54 - beginning to present -- p. 97 (43 pages)
- Chapter 3: invertebrates, p. 98 - 171 (73 pages)
- Chapter 4: fishes and amphibians, p. 172 - 227 (155 pages)
- Chapter 5: reptiles, p. 228 - p. 369 (141 pages)
- Chapter 6: birds, pages 370 - 415 (45 pages)
- Chapter 7: mammals, pages 416 - 559 (143 pages)
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Cretaceous: tertiary extinction / boundary
Cretaceous-Paleogene extinction / boundary: K-P line
Tertiary: obsolete term; encompassed most of the Paleogene / Neogene periods
therefore, K-T (Cretaceous-Tertiary)
66 mya: extinction
all non-avian dinosaurs
most marine life
eliminated 80% of all life
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Trilobites
Paleozoic Era: the oldest era of the Phanerozoic EON
The trilobites first show up in the Cambrian Explosion -- completely die out at end of Permian -- so Trilobites DEFINE THE Paleozoic era -- had the six periods ... Cambrian to Permian
die out just before the Triassic (end of Mesozoic Era)
so, if you find a trilobite, you are in the Paleozoic Era -- first era of visible life, the Phanerozoic EON
Trilobites: seen in early Cambrian
ancestor unknown
many species evolved at beginning of the Paleozoic / Cambrian until they completely died out at end of Paleozoic/Permian
Paleozoic Era: bookends -- Cambrian / Permian
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Arthropods
Five classes (?)
- insects
- arachnids
- crustaceans
- millipedes
- centipedes
account for 80% of all animal species on earth
trilobites: just one class of arthropods
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Ecdysozoa
Ecdysozoa: supergroup -- shed all skin as they grow -- CHITIN
Ecdysozans: include nematodes and velvet worms.
Common ancestor of the Ecdysozan is UNKNOWN.
Arthropods:
- chelicerata
- myriapods
- pancrustacea (includes insects)
- (trilobites)
Molluscs: 100,000 species known; at least twice that number waiting to be discovered.
Only arthopods have more species than molluscs.
Molluscs:
- slugs / snails (Gastropods: snails, slugs, conches, whelks, limpets -- largest group of molluscs -- 80% of all living species)
- shellfish: clams, scallops, oysters
- predatory: octopus, squid, cuttlefish
Date for the Ediacaran: neoproerozoic / late pre-Cambrian
so, Ediacaran: just before the Cambrian explosion
By middle Cambrian, most mollusc groups found in fossil record
So, Cambrian explosion: think molluscs -- slugs/snails; shellfish; predatory (octopus)
Gastropods: snails, slugs, conches, whelks, limpets -- largest group of molluscs -- 80% of all living species (of molluscs, I assume)
Then diagram:
Vertebrates: only 5% of all species.
Earliest fish:
appeared 480 mya
early ordovician
right after the Cambrian
Chordata
bilaterally symmetrical
no backbone, but a notochord
cartilage "backbone" providing structure
row of gill openings
tail beyond the anus
segmented muscles as repeated groups
Chordates: broke into two groups --
vertebrates
tunicates and cephalochordates
Some suggest because lobopods resemble onychophorans (velvet worms) -- the lobopods (Hallucigenic, e.g.) may be ancestors of onychophorans.
Lobopodian morphologies in the Cambrian - multiple life forms -- maybe experimenting.
Some suggest the Lobopodia should be placed in an unranked paraphyletic taxon, Panarthropoda, comprising three phyla:
arthropoda
tardigrada
onychophora
and genus Thelxiope
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Animalia
Phyla: 36.
36 phyla but nine phyla contain the majority of described, extant species
Nine/thirty-six major phyla:
mollusca
porifera
cnidaria
platyhelminthes
nematoda
annelida
arthorpoda
echinodermata
chordata
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Also: onychophora (see also lobopodia)
Ecdysozoa: molt, chitin
includes all animals that grow by ecdysis -- molting their exoskeleton
ecdysis: ancient Greek to take off; strip off.
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Figure 3: Invertebrates
Animalia
Brittanica:
Phylum Arthropoda:
four subphyla of extant forms
Chelicerta (spiders)
Crustacea
Hexapoda (insects)
Myriapoda (centipedes and millipedes)
One extinct subphylum: trilobitamorpha
Wiki: >20 classes in phylum Arthropoda
Classes include insecta and arachnida
Phylum: body plan.
Class: major division in a phylum
Phylum: onychophora -- velvet worms
Phylum: arthropoda -- animals with jointed legs
Class: chelicerata (includes horseshoe crabs)
Class: trilbita
Class: crustacea
Class: insecta
Class: Myriapoda
Interesting: -- Fortey -- British -- calls these divisions classes -- whereas, it seems, most others call the five classes subphyla -- and then with five subphyla there are > 20 classes of arthropods.
Note: e.g., chelicerata is a subphylum
This is interesting: Fortey's jargon -- five major classes within phylum Arthropoda -- but it appears he takes largest class in each subphylum --
SUB-PHYLUM CLASS
Trilobitomorpha Trilobites (extinct)
Myriapoda
Chelicerata Arachnids
Horseshoe crabs
Hexapoda Insecta
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p. 42: velvet worm beginning to look as ancient as the horseshoe crab!!!
Best known onychophoran (velvet worms) from the Cambrian; Burgess Shale, BC, Canada
1977: Hallucigenia
Tardigrade --onychophoran -- arthropod -- velvet worm -- Aysheiai (extinct genus of soft-bodied lobopodian) -- on one really knows yet.
Back to onychophorans: extant velvet worms; then Aysheaia pedunculata (1911)
then hallucignia
So where does the story go from here? Seems to be two story lines: evidence of oldest animal and survivors ofall the mass extinction events.
p. 43: Fortey still comparing Aysheiai and Peripatus (velvet worms) --
Kerygmachela -- p. 45. Where do these all fit in tree of life??
Chitin would make articulated hinged joints a requirement; so closely related arthopods.
But velvet worms did not have chitin and hinges not possible; so we had teh non-articulated onychophoran and the articulated onychophorans (?).
Bottom line: Arthropods and Peripatus (genus of velvet worms) --- common ancestor.
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Phanerzoic EON
Five major extinctions
In fact, there were dozens, but folks like to keep it manageable and five is a nice, small round number.
Three: Cambrian to Permian, Paleozoic
Two: Mesozoic
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All those critters that appeared during the Cambrian -- most were by the end of the Paleozoic.
First extinction, but #2 in severity -- Ordovicia - Silurian -- 85% of marine species lost; not much on land to begin with.
Second extinction, relatively minor, Devonian (END of Devonian) -- almost only marine animals affected.
Third extinction, and this is the biggie -- the end of the Permian -- 96% of all marine species; 70% of all terrestrial species lost; "we" came close to losing it all!!!
Fourth extinction: end Triassic -- not much known about it -- again, mostly marine but land also hit hard; so two close together? third and fourth extinctions?
Fifth extinction -- end Cretaceous -- 65 mya -- loss of non-avian dinosaurs; allowed mammals to proliferate.
[Note: the 3rd extinction was preceded by a smaller -- but also huge CAPITANIAN extinction - the Capitanian is the latest subdivision of the Guadupian epoch which is the middle of the three epochs in the Permian.]
Sponges may have appears as long ago as 560 mya -- Ediacara fauna -- right before the Cambrian explosion, 540 - 550 mya.
Animal
porifera (sponges) -- one branch
eumetazoa -- the other branch
Dickinsonia; late pre-Cambrian; possible Placozoan
maybe a halway stage between sponges and Eumetazoa, animals with true tissues and specialized cells.
New discovery (2016): GK-PID.
This is so cool. Richard Dawkins was right on the cusp with sponges and then in 2016 -- the enzyme that connected the dots.
Placozoans:
should analysis be correct -- see wiki, also.
Trichoplax adhaevens -- wuld be the oldest branch of multicellular animals -- a relic of the Ediacara fauna -- or even the pre-Ediacaran fauna.
Some say only one living placozoan species -- others say three genera.
Phylum: Placozoa -- "flat animal"
Three named species:
**** Tricoplax adhaerens **** -- said to be the world's simplest animal -- just a blog of cells
Hoilungia honkongensis
Polyplacotoma mediterranen
p. 201 - bony, juawless fish -- Bone: distinctive proof that all chordates descended from a common ancestor.
First bone probably dates from the late Cambrian!!
The story of AMPHIOXUS -- pp. 201 - 202. Lancelet at wiki.
Gills --> transformed --> moveable parts that became struts and levers of jaws -- the story of a Swede, Erik Stensio!!!! p. 203.
Jaws: two arches --
--- the mandibular arch -- forms the jaws themselves;
-- the hyoid arch -- acts as a support for the mandibular arch.
p. 204 -- moves to amphibians --
Unab le to come up with living species of amphibian surviving from the base of the tree of life. It is Fortey's major missing survivor. Today's amphibians all descended from a common ancestor long afger tetrapods crawled out of hte water. Most of them evolved after the great Permian Period mass extinction.
So, amphibians evolved twice.
So, great question / essay for students: following each of the 5 great mass extinctions, what resulted?
Only one "ancestor" -- from the Permian age fossil "ancestor" -- all frogs, toads, newts, salamanders, and relatives from one ancestor: all are in one group -- Lissamphibia.
Reptiles:
turtles
tuataras
a few lizards
crocs / alligators
Reptilian survivor:
The tuatara (sphenodon) superficially unchanged since the Triassic -- New Zealand -- two species of Sphenodon. Tuatara at wiki.
First fossils recognized as reptiles: CARBONIFEROUS -- remote second cousins of the tuataras (New Zealand)
Bay of Funday -- p. 210
Hylonomus
reptiles: "egg-laying animals." -- p. 211
Most did not survive the Cretaceous extinction but some did (the Cretaceous extinction event that wiped out the dinosaurs.
Huge extinct turtle: Archelon -- end of Cretaceous.
Carboneferous (Mississippian, Pennsylvanian)
20-million year gap: Romer's Gap; wiki entry here.
360 mya - 290 mya (70 million years)
After the gap -- wide diversity of fauna -- must have been a major radiation of species
Earliest Tetrapods seen in Devonian -- fish iwth legs.
After Romer's gap -- true land-based tetrapods.
East Kirkton, Scotland, world's oldest-known vertebrate terrestrial community.
Temnospondyls: first appears here; amphibian (one time thought to be reptilian)
Lepospondyls also present (legless amphibia; resembled sharks)
most striking: reptile-like animals also diapsids.
Crocs and alligators; p. 213
Chapter 8: Heat In The Blood
Shelled eggs required three new membranes (and ample yolk(.
Three new membranes:
chorion
amnion
allatois
Mammals dispensed with the shell -- developed tissue (PLACENTA) that could interact directly with the three new membranes.
Monotremes: egg-laying mammals.
Echidnas
Platypus
Echidnus -- four species in Australia and New Guinea
The last species to be discovere dint he NG highlands: 1961 -- a grand total of five species in all.
Many reptilian traits, including their body temp of 31 - 33°C, the lowest operating temp in Mammalia.
Echidan and relatives lived during age of Dinosaurs.
10-cm long Megazostradon -- mammal -- traces back to Triassic. Wiki entry here.
First seen 200 mya -- mid-Jurassic.
Mammals pretty much began due to richness of insect niche!!
The trick of "internal fire" -- p. 230 -- Birds and Mammals.
Lianas
Epiphytes
Having found a mammal survivor -- the echidna -- now the author looks for an avian survivor -- p. 230 --
Andes, Ecuador --
Avian survivor -- p. 234
Tinamous (plural) -- singular tinamou --
most primitive living bird
Tinamous and ratites = Palaeognatha: "old jaws"
Molecular studies:
tinamous and ratites: in a single group
--> Kiwis
--> the rest
Now conventional: birds descended from lightly-built therapod dinosaurs with relatively long arms.
Feathers likely colorful.
The dodo was not a ratite. The dodo was a giant, flightless dove.
Archaeopteryx --> tinamou somewhere in here -->
Birds survived the Cretaceous extinction which eliminated all their non-avian relatives.
Living birds, could be argues, are the most successful living vertebrates -- perching birds (passerines) more than twice as many species as the most diverse of the mammal groups -- the rodents.
Warm Blood
Warm blood unites creatures with fur and creatures with feathers.
Birds as a whole: survivors.
"Remember: of the major groups, amphibians alone -- according to Fortey -- have no example of a survivor.]
Enantiornithines -- p. 241.
p. 245 .. hmmmm? Fortey -- amphibians -- no survivor found.
The Mallorcan midwife toad (Alytes muletensis] "a living fossil" -- wiki entry here.
Earlier in the book he seemed to equate "living fossil" with survivor --p. 245.
Chapter 9
Islands, Ice
Beginss about 100,000 years ago;
glacial
our own species emerged.
City of Las Palmas on the Mediterranean island of Mallorca.
The Mallorcan midwife toad also called a ferreret.
Balearic Islands: in the Mediterranean off Spain --
Mallorca
Menorca
Ibiza
Formentera
Possible that the ferreret is at the junction between frogs and toads.
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