Download Early Earth

History of Life on Earth
Chapter 25
Overview
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First Cells
Major Life events
Fossil Record
Geologic Time scale
Mass extinctions
Continental Drift
What was Early Earth like?
What do we really know about
the first living organism??
Can we take Darwin’s theory
all the way back to
the Origin of Life?
What were the major
milestones in the
Evolution of Life?
How long ago was that ?
Getting used to the geologic
time scale…
• We use
– Millions of years (MYA) and
– Billions (BYA) of years ago.
• One Million Years: If we give 10,000
years for all of recorded human history
– One million years equals 100 times all
human history.
– Enough time for 30,000 generations
Evolutionary
Clock
• Eras not to scale
• “Our” world, with
plants and
animals on land
is not very old
• Protists and
Bacteria / Archae
have been
around longer
and are more
diverse.
Fig 25-UN11
Origin of solar system
and Earth
4
1
Proterozoic
2
Archaean
3
Geologic Time
Scale Table 25.1
Know :
• Eons
– Phanerozoic
– Proterozoic
– Archaean
• 4 eras
– Their dates
– Major Animal and
Plant groups
– “Precambrian” Era
• Periods:
– Permian
– Cretaceous (K)
– Tertiary (T)
The three Eras and
the new groups that begin to
dominate on land
• Cenozoic – 65.5 MYA
– Mammals, birds flowering plants
• Mesozoic – 251 MYA
– Reptiles, conifers
• Paleozoic – 542 MYA
– Amphibians, insects, moss, ferns
• Precambrian (2 eons) – 4.6 BYA
– Origin of animal phyla
– Protists, bacteria
The three Eons and
the new groups that begin to
dominate on land
Eons:
• Phanerozoic – Present to 542 MYA
“Precambrian”:
• Proterozoic - 542- 2,500 MYA
– Origins of Eukaryotes
• Archaean – 2,500- 4,500 MYA
– bacteria, and oxygen atmosphere
Four Eras
• Eras do not have same amount of time
• Pace of evolution quickens with each
major branch or era .
• Recent organisms generally are more
complex – older ones simpler.
• Why ?
Key Events in the History of
Life on Earth
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4.6 BYA Formation of Earth
Origins of Biomolecules
Formation of Polymers
Origin of Protobionts; Self
replicating RNA-DNA; Metabolism;
Evolution
• 3.5 BYA Formation of first cell –
prokaryotes
Key Events in the History of
Life on Earth
• 2.7 BYA Origin of Oxygen generating
photosynthesis
• 1.5 BYA Origin of Eukaryote cells
• 1.2 BYA – 565 MYA Multicellularity
• 535 MYA Cambrian Explosion
• 500 MYA Colonization of land
Fig 25-UN8
1.2 bya:
First multicellular eukaryotes
2.1 bya:
First eukaryotes (single-celled)
535–525 mya:
Cambrian explosion
(great increase
in diversity of
animal forms)
3.5 billion years ago (bya):
First prokaryotes (single-celled)
Millions of years ago (mya)
500 mya:
Colonization
of land by
fungi, plants
and animals
Fig. 25-4
Present
Rhomaleosaurus victor,
a plesiosaur
Dimetrodon
Casts of
ammonites
Hallucigenia
Coccosteus cuspidatus
Dickinsonia
costata
Stromatolites
Tappania, a
unicellular
eukaryote
Fossilized
stromatolite
Early
Paleozoic
era
(Cambrian
period)
542
Late
Proterozoic
eon
Sponges
500
Arthropods
Molluscs
Annelids
Brachiopods
Chordates
Echinoderms
Cnidarians
Millions of years ago
Fig. 25-10
How did Life come into
being ?
Spontaneous generation ?
• Life from non-living matter.
– Mice from wet hay makes mice
• Refute for animals, and plants in
1600’s.
• Still thought to be the case for
microbes, until Pasteur.
Louis Pasteur
(1822-1895)
• Disproved
spontaneous
generation
• Showed that
biogenesis alone
accounted for new
cells
• Invented
Pasteurization
Biogenesis
• Life (whole organisms) comes from
reproduction of other preexisting life.
• Later, the cell theory will be similar
– all cells come from preexisting cells.
What about the first Cell?
• Scientists think, first cell-like
structures came from non living
matter.
• What would be needed to make a cell
from scratch ?
Origin of life • Need to have biomolecules:
– Complex Carbohydrates
– Proteins
– Lipids
– Nucleic acids
• To make membranes,enzymes, DNA
and all the other cellular
components.
Where did biomolecules
come from?
• Today only living organisms make
biomolecules
“Arm Chair” science
• Still mostly untested hypotheses,
and conjecture.
• Trying to test hypotheses by making
artificial cells in labs.
Conditions on Earth 4 BYA
Oparin – Haldane 1920’s chemists
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•
•
•
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•
•
No free Oxygen – No Ozone layer
More uv radiation
Reducing (electron rich) atmosphere
More lightning
Meteorite bombardment
More volcanic activity
H20, Methane (CH4), Ammonia (NH3)
Energy rich
early earth
Urey & Miller - 1953
• Used Oparin / Haldane ideas of earth
earth conditions
• Made an apparatus to mimic early
earth conditions
• Let run and tested fluid for
compounds
• Found simple sugars, amino acids,
and other organic compounds.
Stanley
Miller
Significance:
Abiotic synthesis of
macromolecules
Ribozymes
• RNA self
replication
before
enzymes?
• RNA before
DNA
Hypothetical Protobionts
Not “facts” but working
hypotheses
• Lab experiments can only show what
could have happened
• Other thoughts:
– Deep sea vents – constant environment,
chemical energy
– Panspermia or microbes from
meteorites
• Most like our understanding will
change greatly in future.
Universal Common Ancestor
• Hypothetical
• Would be cell from which all modern life
has descended
• Have things that ALL living organisms
share:
– Phospholipid bilayer cell membrane
– Use DNA/ RNA for genes, and make proteins
from the genetic code
– Glycolysis, ATP in their metabolism
Fossil Record
• Fossil any preserved remnant or
impression of an organism that lived in
the past
• Most form in sedimentary rock, from
organisms buried in deposits of sand
and silt. Compressed by other layers.
• Also includes impressions in mud
• Most organic matter replaced with
minerals by Petrification
• Some fossils may retain organic matter
• Encased in ice, amber, peat, or dehydrated
• Pollen
Fossil Formation –
Radiometric “absolute” dating
Dating Fossils
• “Absolute” Radiometric dating: decay and
half-life of natural isotopes.
• Index dating – comparing index fossils in
strata
Brachiopod
index
fossils
Many changes in geologic
history due to Plate tectonics
Layers of the Earth
35 km (21 mi.) avg., 1,200˚C
Crust
100 km (60 mi.)
200 km (120 mi.)
Crust
Low-velocity zone
Mantle
Lithosphere
Solid
10 to 65km
2,900km
100 km
(1,800 mi.)
3,700˚C
Outer core
(liquid)
Core
200 km
5,200 km (3,100 mi.), 4,300˚C
Inner
core
(solid)
Asthenosphere
(depth unknown)
Plate tectonics
• The study of the movement of earth
structures in the crust.
• Internal forces from the core create heat
that keeps asthenosphere molten.
– Convection cells
– Mantle Plumes
Convection Cell in Mantle
Earth’s Layers - Crust
• Oceanic Crust
– only 3 miles thick
• Continental Crust
– up to 12-40 miles thick
• Oceans change shape much more than
continents.
• These land movements we call Plate
Tectonics, and cause earthquakes.
Plate
tectonicsDivergent
Areas
Lithosphere
Asthenosphere
Oceanic ridge at a divergent plate boundary
• Plates spread apart in Divergent
(constructive) making new crust
Fig. 10.6a
Slide
Convergent zones
• Plates move together and collide.
• An Oceanic Plate sinks under Continental
in a Subduction zone.
– Causes Earthquakes, volcanoes
• When Continental plates collide neither
subducts, both deform, mountains
Trench
Volcanic island arc
Convergent plates
Rising
magma
Subduction
zone
Lithosphere
Asthenosphere
Trench and volcanic island arc at a convergent
plate boundary
Fig. 10.6b, p. 215
Slide 8
Fig. 25-12
North
American
Plate
Crust
Juan de Fuca
Plate
Eurasian Plate
Caribbean
Plate
Philippine
Plate
Arabian
Plate
Mantle
Pacific
Plate
Outer
core
Inner
core
(a) Cutaway view of Earth
Indian
Plate
Cocos Plate
Nazca
Plate
South
American
Plate
African
Plate
Scotia Plate
(b) Major continental plates
Antarctic
Plate
Australian
Plate
Fig. 25-12b
North
American
Plate
Juan de Fuca
Plate
Eurasian Plate
Caribbean
Plate
Philippine
Plate
Arabian
Plate
Indian
Plate
Cocos Plate
Pacific
Plate
Nazca
Plate
South
American
Plate
Scotia Plate
(b) Major continental plates
African
Plate
Antarctic
Plate
Australian
Plate
Fig. 25-13
Cenozoic
Present
Eurasia
Africa
65.5
South
America
India
Madagascar
251
Mesozoic
135
Paleozoic
Millions of years ago
Antarctica
• 10 MYA India (previously an
island) hits Asia
• 50 MYA. Australia becomes
completely isolated
• 65.5 MYA NA and Europe
still touched
• 135 MYA Pangea broke up
into Laurasia and
Gondwanaland
• 251 MYA Pangea all land
masses touched
Mass extinctions
• Mark borders of Eras:
– 251 Permian (Paleo-Mesozoic)
– 65.5 Cretaceous (K/T boundary; MesoCenozoic)
• Caused by a major change that affects
many species at once.
Fig. 25-14
800
700
15
600
500
10
400
300
5
200
100
0
Era
Period
542
E
O
Paleozoic
S
D
488 444 416
359
C
Tr
P
299
251
Mesozoic
C
J
200
145
Time (millions of years ago)
Cenozoic
P
65.5
N
0
0
Number of families:
Total extinction rate
(families per million years):
20
Predator genera
(percentage of marine genera)
Fig. 25-16
50
40
30
20
10
0
Paleozoic
Mesozoic
Era
D
C
P
C
E
O S
J
Tr
Period
359
488 444 416
542
299 251
200
145
Time (millions of years ago)
Cenozoic
P
65.5
N
0
Permian Mass Extinction
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90% marine & 80% insect species gone
251 MYA
Took place in about 5 MY
2 Possible causes:
– Pangaea forming
– Extreme volcanism- Global warming, climate change.
• Drop in sea level, loss of shoreline & intertidal,
• More severe continental weather
• Isolated species come together and compete,
causing extinctions
• Paleozoic to Mesozoic boundary
Cretaceous extinctions
• 65.5 MYA
• Wiped out 50 % marine species, on land
many families of plants and the Dinosaurs.
• Mesozoic to Cenozoic boundary.
• Climate cooled and shallow seas
retreated.
• Mammals and angiosperms around earlier,
but survived and radiated out to dominant
now empty niches
• Many diverse lineages from algae to
dinosaurs disappeared at once.
Fig. 25-15
NORTH
AMERICA
Yucatán
Peninsula
Chicxulub
crater
Alvarez-Impact theory
Chicxulub Crater- sonar image
Impact hypothesis
• Anomalous Iridium layer marks boundary
layer – element common in meteorites
• Chicxulub Crater
• Explains large water scarring in NA.
• Global winter lasting years, collapsed food
chains. Ignite tremendous wildfires, acid
rain.
• Some lineages were dying out before
impact.
• Probably a final and sudden blow coming
at a time of change, with continental drift,
climate change.
Conditions that favor
fossilization:
• Having Hard parts – shells, bones,cysts
• Get buried, trapped
– Marine species
– Marsh, flooding areas
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•
•
•
Abundant species (with many individuals)
Long lived species (as a species)
Avoid eroding away
Get discovered
Limitations of Fossils
record
• Has to die in right place under the right
conditions. Most things don’t get into the
fossil record
• Biased: Highly favors hard parts,
abundant, long lived species organisms.
• Lots of missing organisms
• Hard to find, only certain areas highly
researched (NA. Europe)
Earth’s
history as
a clock
Major events
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•
•
•
•
Origin of prokaryote cell
Formation oxygen atmosphere
Origin of eukaryote cell
Multi-Origins of multicellularity
Cambrian explosion of animal phyla
What we do know:
• Earth is old, about 4.6 BYA
• Oldest fossils appear to be
filamentous bacteria at about 3.5
BYA.
– Formed layers like today’s stromatolites
• Bacteria predated eukaryotes
Early
Prokaryote
Fossils
Figure 26.4
Endosymbiosis Fig. 26.13
Endosymbiosis Theory
• Descendant of Archae develops eukaryote
type membrane system and nucleus
• Eukaryote cell engulfs bacteria that
survive in the cell and develop into
plastids and mitochondria
• We’ll review evidence later in eukaryote
chapter.
• 2.1 BYA
Endosymbiosis –
membrane layers
Coral
• Living example of
endosymbiotic
relationships
Earliest Multicellular
organisms
• 1.5 MYA
Cambrian
Explosion
• Most animal
appear at
same time
phyla in 20 MY
• Long fusebegan earlier
Systematics
• Taxonomy is naming, & organizing
organisms, both living and dead, into
groups.
• Systematics, use evolutionary
relationships as the classification
hierarchies.
Systematics debates:
• Biggest debates, and changes will be
at higher levels of classification.
• Shows scientists interest levels.
– Most lower level groups figured out.
– Question the origins of these groups
– Rely heavily on comparative gene
sequences.
Debates in Evolution
• Most lay people think the big debate is
around the origins of humans from apes.
• Most scientists see this area as pretty
clear, with details to be worked out by
specialists.
• Origins of Domains, Kingdoms the big
questions in evolutionary science today.
Five Kingdoms
A Changing View of Diversity
Prokaryote Diversity
Eukaryote Diversity
Fig. 25-6
Synapsid (300 mya)
Temporal
fenestra
Key
Articular
Quadrate
Dentary
Squamosal
Therapsid (280 mya)
Reptiles
(including
dinosaurs and birds)
Temporal
fenestra
Early cynodont (260 mya)
Later cynodont (220 mya)
Very late cynodont (195 mya)
Dimetrodon
Therapsids
Temporal
fenestra
EARLY
TETRAPODS
Very late cynodonts
Mammals
Fig. 25-7
Humans
Colonization
of land
Animals
Origin of solar
system and
Earth
4
1
Proterozoic
2
Archaean
3
Multicellular
eukaryotes
Single-celled
eukaryotes
Atmospheric
oxygen
Prokaryotes
Fig. 25-17
Ancestral
mammal
Monotremes
(5 species)
ANCESTRAL
CYNODONT
Marsupials
(324 species)
Eutherians
(placental
mammals;
5,010 species)
250
200
100
150
Millions of years ago
50
0
Fig. 25-18
Close North American relative,
the tarweed Carlquistia muirii
Dubautia laxa
KAUAI
5.1
million
years
MOLOKAI
OAHU
3.7 LANAI
million
years
1.3
MAUI million
years
Argyroxiphium sandwicense
HAWAII
0.4
million
years
Dubautia waialealae
Dubautia scabra
Dubautia linearis
Fig. 25-18a
KAUAI
5.1
million
years
MOLOKAI
OAHU
3.7
million
years
1.3
MAUI million
years
LANAI
HAWAII
0.4
million
years
Fig. 25-19
Newborn
2
5
Age (years)
15
Adult
(a) Differential growth rates in a human
Chimpanzee fetus
Chimpanzee adult
Human fetus
Human adult
(b) Comparison of chimpanzee and human skull growth
Fig. 25-19a
Newborn
2
5
Age (years)
15
(a) Differential growth rates in a human
Adult
Fig. 25-19b
Chimpanzee fetus
Chimpanzee adult
Human fetus
Human adult
(b) Comparison of chimpanzee and human skull growth
Fig. 25-20
Gills
Fig. 25-21
Hypothetical vertebrate
ancestor (invertebrate)
with a single Hox cluster
First Hox
duplication
Hypothetical early
vertebrates (jawless)
with two Hox clusters
Second Hox
duplication
Vertebrates (with jaws)
with four Hox clusters
Fig. 25-22
Hox gene 6
Hox gene 7
Hox gene 8
Ubx
About 400 mya
Drosophila
Artemia
Fig 25-UN9
Origin of solar system
and Earth
4
1
Proterozoic Archaean
2
3
Fig 25-UN10
Flies and
fleas
Caddisflies
Herbivory
Moths and
butterflies