Transcript The History of Life on Earth

The History of Life on Earth
As We Know It
The History of Earth
• Earth is ~ 4.5 billion years old
• Earth’s history is divided into four eons
– Hadean Eon: (Gk: Hades - the netherworld)
– Archean Eon: (Gk: Arche - ancient)
– Proterozoic Eon: (Gk: Protero - former)
– Phanaerozoic Eon (Gk: Phanero - visible,
apparent)
The History of Earth
• The most recent eon is divided into three eras
– Paleozoic Era (Gk: Paleo - ancient)
– Mesozoic Era (Gk: Meso - middle)
– Cenozoic Era (Gk: Ceno - recent)
The History of Earth
• eras of the modern eon are divided into
periods
– Paleozoic Era
• Cambrian Period
• Ordovician Period
• Silurian Period
• Devonian Period
• Carboniferous Period
• Permian Period
The History of Earth
• eras of the modern eon are divided into
periods
– Mesozoic Era
• Triassic Period
• Jurassic Period
• Cretaceous Period
– Cenozoic Era
• Tertiary Period
• Quaternary Period
Earth’s History: Changing Conditions
Table 22.1
Earth’s History: Changing Conditions
• atmospheric oxygen concentration has risen
from near 0 to ~21%
• See Figure 22.3
Earth’s History: Changing Conditions
• atmospheric oxygen concentration has risen
from near 0 to ~21%
• mean temperature has fluctuated significantly
• sea level has fluctuated significantly
• continents have entirely changed positions
• relatively gradual changes
rapid, climate-changing events
• “catastrophic” events have modified the
evolution of life
Log-log Oxygen levels
Figure 22.4
Changes
in
Earth’s
Mean
Temperature
in the
Modern Eon
Figure 22.5
Changes
in
Sea Level
in the
Modern Eon
Figure 22.2
Earth’s History: Changing Conditions
• atmospheric oxygen concentration has risen
from near 0 to ~21%
• mean temperature has fluctuated significantly
• sea level has fluctuated significantly
• continents have entirely changed positions
midCambrian
Continental
Drift
(~510 mya)
(forming
Gondwana)
Figure 22.9
Devonian Drift (400-350 mya)
Figure 22.11
Permian Drift (formation of Pangaea)
[~290-250 mya]
Figure 22.13
Cretaceous Continental Positions
(~100 mya)
Figure 22.15
“catastrophic” events have modified the
evolution of life
• Dramatic climate change
– End of Ordovician, Devonian, Permian,
Triassic, Cretaceous
• Volcanism
– End of Permian
– During Triassic, Cretaceous
• Meteorite collisions
– End of Triassic, End of Cretaceous
Figure 22.6
“catastrophic” events have modified the
evolution of life
• several mass extinctions have occurred
– repeatedly, up to 75% of species became
extinct
– afterward, new life forms proliferated and
became dominant - evolutionary radiation
Dating events in Earth’s history
• absolute dates are estimated from the decay of
radioactive elements
• relative ages are determined by the position in
a series of rock layers
– remains of dead organisms are mineralized
(fossilized) under the right conditions
• anaerobic
• undisturbed
• proper geochemistry
Dating events in Earth’s history
• absolute dates are estimated from the decay of
radioactive elements
half-lives of some radioactive isotopes
14C
- 5,700 years
40K - 1.3 x 106 years
238U - 4.5 x 109 years
Figure 22.1
Figure 22.8
Figure 22.7
changing faunas
Figure 22.17
The History of Life on Earth
• Earth’s past biotas are represented by
fossilized remains
~300,000 described species
• Earth’s different ages are characterized by
different types of fossils
• boundaries defining the eras and periods of the
modern eon represent changes in fossil
assemblages
The History of Life on Earth
• Fossils from successive ages reveal patterns
– particular fossil types are found in rocks of
the same age
– new types of organisms appear sequentially
in younger rock layers
– types of organisms in shallower (younger)
layers more closely resemble extant
organisms
– the appearance of new types of organisms
occurred at different rates through time
three dominant world faunas
Figure 22.17
The History of Life on Earth
• Fossils from successive ages reveal patterns
– three faunas dominated animal life over time
– size and complexity of organisms increased
with time
– predators became more efficient; defenses
became more effective
– extinction happened
• a typical species exists for ~10,000,000 years
• ~99% of species are extinct
The History of Life on Earth
• Fossils from successive ages reveal patterns
– few innovations
• novel structures are rare
• most diversity is variation on existing
body plans
The History of Life on Earth
• Fossils from successive ages reveal patterns
– microevolutionary change:
• change that modifies species
Sticklebacks - no predatory fish, short
spines
Figure 22.20
The History of Life on Earth
• Fossils from successive ages reveal patterns
– macroevolutionary change:
• change that produces new types of
organisms
The History of Life on Earth
• The history of Earth is characterized by
dramatic changes
– gradual structural and climatic changes
punctuated by catastrophic events
• The history of life on Earth is characterized by
increases in size, complexity, competition &
predation
Eon Era
Period
"Age"
Mesozoic
Paleozoic
Phanaerozoic
Cenozoic
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
Age
of the
Mammals
Age
of the
Reptiles
Age of the
Amphibians
Age of the
Fishes
Age of the
Invertebrates
Precambrian ~87% of
Geological Time Scale
Geologic
History
from a
Biologist’s
Point of View