brief A history of life on earth The earth is ancient and how we know
isotope-dating Atmosphere, weather, positions of continents
Earth has changed over time The geological record The fossil record Continental drift Recent mammalian extinctions
The fossil record
Nicholaus Steno (1638-1686)
Law 1: In a sequence of sedimentary rocks, the layers of rocks were originally formed by lying horizontally. Law 2: In a sequence of sedimentary rocks, the oldest are lowest and the youngest are the highest.
Radioactive-isotopes Half-life = 14.3 days (31P) 3H = 12.3 years 14C = 5700 years (12C) 40K = 1.3 billion years (40Ar)
32P
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Radioisotope dating
The earth is ancient and changing:
Oxygen concentration Sea levels Temperature and humidity Meteors and comet impacts Continental Drift
Oxygen concentration increasing
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Sea levels have changed repeatedly.
* Indicates mass extinctions
of marine organisms
Hot-humid and colddry conditions have fluctuated.
Indicates when large areas of the earths surface was covered by glaciers
Meteorite and Comet Impacts
Pea-size meteoroids - 10 per hour Walnut-size - 1 per hour Grapefruit-size - 1 every 10 hours Basketball-size - 1 per month 1-km asteroid - 1 per 100,000 years 2-km asteroid - 1 per 500,000 years
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NY Times Jan. 3 2007
FREEHOLD TOWNSHIP, N.J., Whatever it was, the object that fell from the sky was not part of an airplane. That was all anyone knew for sure.It was dense with a rough metallic surface. The oblong object was only about two inches long - fitting into the palm of a hand - b ut weighed almost a pound. And it fell through the roof of a two-story house here Tuesday afternoon, shattering the tile floor of the second-floor bathroom and embedding itself in a wall.
Fig. 25-7
Pa
le o
ic zo
oMes zoic
Cenozoic
Humans
Colonization of land Animals Origin of solar system and Earth
1 Proterozoic
4 Archaean
rs ag 3 o
Bi
Prokaryotes
llio
2
ns
of
a ye
Multicellular eukaryotes Single-celled eukaryotes
Atmospheric oxygen
4
Precambrian Era
(4.5 b ya-543 mya)
White Island, New Zealand
Precambrian Era
(4.5 bya-543 mya)
Evolutionary milestone #1: Life arises
Primordial ooze
Precambrian Era
(4.5 bya-543 mya)
Evolutionary milestone #2: Cells form
Prokaryotic cell
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Precambrian Era
(4.5 b ya-543 mya)
Evolutionary milestone #3: Photosynthesis
Cyanobacteria: blue-green bacteria
Precambrian Era
(4.5 b ya-543 mya)
Precambrian Era
(4.5 b ya-543 mya)
Evolutionary milestone #4: Sex happens
Bacterial conjugation
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Precambrian Era
(4.5 b ya-543 mya)
Evolutionary milestone #5: Eukaryotes
Protist: single-celled eukaryotic organism
Precambrian Era
(4.5 b ya-543 mya)
Evolutionary milestone #6: Multicellularity
Volvox: multicellular protist
Some important dates
Precambrian era 4.5bya-543mya
Origin of earth to the Cambrian Explosion
Paleozoic era 543-251 mya
Buildup of many animal and plant forms. Colonization of terrestrial habitats. Ends with the earths greatest mass extinction.
Mesozoic era 251-65mya
Age of Dinosaurs. Evolution of owering plants. Ends with sudden extinction of dinosaurs.
Cenozoic era 65mya - present 12,000ya e xtinction of most large mammals in North and South America.
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Paleozoic Era: Cambrian period
(543 mya - 510 mya)
Cambrian Explosion 540 - 510 mya
After 3 billion years of life, most of the animal phyla we recognize today arose during a comparatively short period.
Compared to the pre-cambrian, these assemblages were complex
Why would so many animal forms evolve so suddenly?
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Fig. 25-4f
1 cm
Hallucigenia
Why a Cambrian Explosion?
1. Fossil record incomplete, diversification could have begun earlier. 2. Tens of millions of years still a very long time for evolution to take place. 3. Key innovations such as jointed appendages and jaws may have lead to escalation of biotic interactions and rapid co-evolution. Motile jawed predators select for defenses of prey (e.g. legs, shells, sensory capabilities).
Paleozoic Era (542-251mya) Six periods Cambrian (542-510mya): origin of animal phyla Ordovician (510-440mya): Colonization of land by plants and arthropods, diverse marine invertebrates Silurian (440-409mya): Diversication of early vascular plants Devonian (409-354mya): Diversication of bony shes. First tetrapods and insects Carboniferous (354-290): Extensive forests, rst seed plants, origin of reptiles Permian (290-245): Diversication of reptiles and insects. Largest mass extinction at end of period. 96% of marine animals went extinct. Many terrestrial extinctions as well
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Ordovician period
(510 m ya - 440 mya)
Paleozoic Era: Silurian period
(440 mya - 409 mya)
Euryoptids: predatory sea scorpions (NY)
Paleozoic Era: Devonian period
(409 mya - 354 mya)
Placoderm: plate-skinned fish
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Paleozoic Era: Carboniferous period
(354 mya - 290 mya)
Abundance of giant tree ferns
Paleozoic Era: Permian period
(290 mya - 245 mya)
Dimetrodon Pelycosaurs
Therapsid
Age of Dinosours
Mesozoic Era
Triassic period
(245 mya - 206 mya)
Jurassic period
(206 mya - 144 mya)
Cretaceous period
(144 mya - 65 mya)
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aka the Cretaceous-Tertiary boundary
K-T (65 boundary mya)
Fig. 25-14
20 Total extinction rate (families per million years):
800 700 Number of families:
15
600 500
10
400 300
5
200 100
Era Period
0 E 542 O
Paleozoic S D 359
C
P 299 251
Tr
Mesozoic J C 200 145
Cenozoic
0
P 65.5
N 0
488 444 416
Time (millions of years ago)
K-T boundary (65 mya)
Luis A lvarez, UC Berkeley
Worldwide iridium layer
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K-T boundary (65 mya)
K-T boundary (65 mya)
K-T boundary (65 mya)
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Cretatious/Tertiary boundary:
Dinosaurs did not go extinct (birds survived)
Mammals did not originate (many small mammals coexisted with dinosaurs)
Mesozoic mammals
Coexisted with dinosaurs for more than 100 million years. During the Mesozoic, largest mammals were about the size of house cats. Most mammals much smaller.
Alphadon ( Cretaceous)
Cenozoic Era: Tertiary period (65 mya - present)
Indricotherium
Brontotherium Age of Mammals?
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Alfred Wegener (1880-1930) Continental Drift
1. 2. Shapes match: Continents look like jigsaw puzzle Plants and animals match: similar f ossils on different continents. Close matches between the coastlines of South America and Africa Rocks match: Same types of rock a t same age on different continents Ice matches: Striations from glaciers on southern continents about 300mya. No glaciers of this age in what are now northern continents. Conclusion: Northern continents were e quatorial at that time
3. 4.
Few believed S tegner He had no mechanism
Similar distributions of plants and animals in southern continents ~200 mya
Glossopteris plant
Fossil m esosaurus in Africa and SA Fossil platypus in SA
The mechanism: plate tectonics
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Fig. 25-12b
North American Plate Juan de F uca Plate Cocos Plate Pacific Plate South American Plate Caribbean Plate Arabian Plate
Eurasian P late
Philippine Plate Indian Plate
Nazca Plate
African Plate
Australian Plate
Scotia Plate
Antarctic Plate
(b) Major continental plates
Fig. 25-13
Present Cenozoic 65.5
ca eri Eurasia Am rth No Africa India South America Madagascar tralia s Au
Antarctica
Millions of years ago
Laurasia
Mesozoic
135
Gon dwan a
Fig. 25-13a
Present Millions of years ago Cenozoic
Paleozoic
251
a ae ng Pa
65.5
No
r th
Am
er
ic a
Eurasia Africa India
Madagascar
South America
Antarctica
Au
s tr
alia
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Fig. 25-13b
Laurasia
Mesozoic
135 Millions of years ago
Gon
dwa
na
Cenozoic Era: Quaternary period (1.8 m ya - present)
Epochs 1. Pleistocene 2. Holocene
(last 12,000years)
Paleozoic
251
Pa
ng
ae
a
Wooly mammoth
Juvenile giant ground sloth contemplates juvenile human
La B rea Tar Pits, Los Angeles
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What went extinct in western North America (partial list)?
Mammoths and mastodons (4 species) Ground sloths (4 species) Equids (horses - 3 species) Tapirs Camels American lion American cheetah Short-faced bear Giant saber-toothed cat (smilodon) Dire wolf Giant condor
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What caused pleistocene extinctions of large mammals?
Climate change? Could be, but climate had uctuated between glacial and interglacial periods many times without previous extinctions. Humans? Hunters using clovis points arrived in North America about 12-13 thousand years ago. As extinctions on other continents (e.g. Australia) also correlate with human arrival, this hypothesis seems likely.
Clovis points, a technological breakthrough that changed the world?
Why fewer extinctions in Africa where we still see many very large mammals?
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Deadly syncopation: human arrival and species loss
Europe: Mammoths and many other big mammals disappear gradually from 70-30,000 years ago. Australia 48-42,000 years ago: extinctions of many large mammals North and South America 13-10,000 years ago: extinctions of many large mammals Caribbean Islands 6000 years ago: extinction of pygmy ground sloths Madagascar 2000 years ago: Extinction of giant lemurs Pacic Islands 2000 years ago: Extinction of many large ightless birds New Zealand <1000years ago: Extinction of moas
Questions?
Some Important Dates
What major events occurred roughly at these times?
4.5 bya 3.6 bya 550 mya 250 mya 65 mya 12,000 years ago
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1.
What major events occurred roughly at these times?
4.5 mya Origin of Earth 3.6 mya Life originates 540 mya C ambrian Explosion 250 mya B oundary between Paleozoic and Mesozoic eras 65 mya Extinction of dinosaurs 12,000 years ago Extinction of many large mammals in North and South America.
When was the age of Dinosaurs?
a. b. c. d. 540-250 mya 250-65 mya 540-65 mya 65mya-12000ya
2. A major increase in the oxygen content of the atmosphere may have coincided with the origin of what type of prokaryote? a. b. c. d. e. Archaebacteria Blue-green algae Cyanobacteria Volvox Amoeba
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Fig 25-UN2
1
4
Bi lli on
2
a ye
a rs 3
go
s of
Prokaryotes
Fig 25-UN9
le Pa
oic oz
o- CenoMes zoic zoic
Origin of solar system and Earth
1
4
Proterozoic Archaean Bil go lio ns sa ar of ye 3 2
Fig 25-UN11
Pa
le
o oz
ic
oMes zoic
Cenozoic
Origin of solar system and Earth
1 Proterozoic Bi llio ns of 2
4 Archaean
ye ar go sa 3
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