History of Life on EarthHistory of Life on Earth
Chapter 25
Overview
• 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 What do we really know about the first living organism??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 systemand Earth
4
32
1
Paleozoic
Meso-
zoic
Ceno-zoic
Proterozoic ArchaeanBillions of years ago
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 andthe 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 andthe 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
• 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
Millions of years ago (mya)
1.2 bya:First multicellular eukaryotes
2.1 bya:First eukaryotes (single-celled)
3.5 billion years ago (bya):First prokaryotes (single-celled)
535–525 mya:Cambrian explosion(great increasein diversity ofanimal forms)
500 mya:Colonizationof land byfungi, plantsand animals
Pre
sen
t
500
2,00
0
1,50
0
1,00
0
3,00
0
2,50
0
3,50
0
4,00
0
Fig. 25-4Present
Dimetrodon
Coccosteus cuspidatus
Fossilizedstromatolite
Stromatolites Tappania, aunicellulareukaryote
Dickinsoniacostata
Hallucigenia
Casts ofammonites
Rhomaleosaurus victor, a plesiosaur
10
0 m
illi
on
ye
ars
ag
o2
00
17
53
00
27
04
00
37
55
00
52
55
65
60
03
, 500
1, 5
0 0
2.5 cm4.5 cm
1 cm
Fig. 25-10
Sp
on
ge
s
LateProterozoiceon
EarlyPaleozoicera(Cambrianperiod)
Cn
idar
ian
s
An
nel
ids
Bra
ch
iop
od
s
Ec
hin
od
erm
s
Ch
ord
ate
s
Mill
ion
s o
f y
ears
ag
o
500
542
Art
hro
po
ds
Mo
llus
cs
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 BYAOparin – Haldane 1920’s chemists
• 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 EarthLayers of the Earth
Mantle
Core
Crust
Low-velocity zone
Solid
Outer core(liquid)
Innercore(solid)
35 km (21 mi.) avg., 1,200˚C
2,900km(1,800 mi.)3,700˚C
5,200 km (3,100 mi.), 4,300˚C
10 to 65km
100 km
200 km
100 km (60 mi.)200 km (120 mi.)
Crust
Lithosphere
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 tectonics- Divergent
Areas
• Plates spread apart in Divergent (constructive) making new crust
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
Convergent plates
Slide 8
Fig. 10.6b, p. 215
Lithosphere
Trench Volcanic island arc
Asthenosphere
Risingmagma
Subductionzone
Trench and volcanic island arc at a convergentplate boundary
Fig. 25-12
(a) Cutaway view of Earth (b) Major continental plates
Innercore
Outercore
Crust
MantlePacificPlate
NazcaPlate
Juan de FucaPlate
Cocos Plate
CaribbeanPlate
ArabianPlate
AfricanPlate
Scotia Plate
NorthAmericanPlate
SouthAmericanPlate
AntarcticPlate
AustralianPlate
PhilippinePlate
IndianPlate
Eurasian Plate
Fig. 25-12b
(b) Major continental plates
PacificPlate
NazcaPlate
Juan de FucaPlate
Cocos Plate
CaribbeanPlate
ArabianPlate
AfricanPlate
Scotia Plate
NorthAmericanPlate
SouthAmericanPlate
AntarcticPlate
AustralianPlate
PhilippinePlate
IndianPlate
Eurasian Plate
Fig. 25-13
SouthAmerica
Pangaea
Mil
lio
ns
of
year
s ag
o
65.5
135
Mes
ozo
ic
251
Pal
eozo
ic
Gondwana
Laurasia
Eurasia
IndiaAfrica
AntarcticaAustralia
North Americ
a
Madagascar
Cen
ozo
ic
Present
• 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; Meso-
Cenozoic)
• Caused by a major change that affects many species at once.
Fig. 25-14
To
tal e
xtin
cti
on
ra
te(f
amili
es
pe
r m
illio
n y
ears
):
Time (millions of years ago)
Nu
mb
er o
f fa
mili
es:
CenozoicMesozoicPaleozoicE O S D C P Tr J
542
0
488 444 416 359 299 251 200 145
EraPeriod
5
C P N
65.5
0
0
200
100
300
400
500
600
700
800
15
10
20
Fig. 25-16
Pre
dat
or
gen
era
(pe
rcen
tag
e o
f m
arin
e g
en
era
)
Time (millions of years ago)
CenozoicMesozoicPaleozoicE O S D C P Tr J
542
0
488 444 416 359 299 251 200 145
EraPeriod C P N
65.5 0
10
20
30
40
50
Permian Mass Extinction
• 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
NORTHAMERICA
ChicxulubcraterYucatán
Peninsula
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
• 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
• 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 fuse- began 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
Very late cynodont (195 mya)
Later cynodont (220 mya)
Early cynodont (260 mya)
Therapsid (280 mya)
Synapsid (300 mya)
Temporalfenestra
Temporalfenestra
Temporalfenestra
EARLYTETRAPODS
Articular
Key
Quadrate
Dentary
Squamosal
Reptiles(includingdinosaurs and birds)
Dimetrodon
Very late cynodonts
Mammals
Sy
na
ps
ids
Th
era
ps
ids
Ea
rli er c
yn
od
on
ts
Fig. 25-7
Animals
Colonizationof land
Paleozoic
Meso-
zoic
Humans
Ceno-zoic
Origin of solarsystem andEarth
ProkaryotesProterozoic Archaean
Billions of years ago
1 4
32
Multicellulareukaryotes
Single-celledeukaryotes
Atmosphericoxygen
Fig. 25-17
Millions of years ago
Monotremes(5 species)
250 150 100200 50
ANCESTRALCYNODONT
0
Marsupials(324 species)
Eutherians(placentalmammals;5,010 species)
Ancestralmammal
Fig. 25-18
Close North American relative,the tarweed Carlquistia muirii
Argyroxiphium sandwicense
Dubautia linearisDubautia scabra
Dubautia waialealae
Dubautia laxa
HAWAII0.4
millionyears
OAHU3.7
millionyears
KAUAI5.1
millionyears
1.3millionyears
MOLOKAIMAUI
LANAI
Fig. 25-18a
HAWAII0.4
millionyears
OAHU3.7
millionyears
KAUAI5.1
millionyears
1.3millionyears
MOLOKAIMAUI
LANAI
Fig. 25-19
(a) Differential growth rates in a human
(b) Comparison of chimpanzee and human skull growth
NewbornAge (years)
Adult1552
Chimpanzee fetus Chimpanzee adult
Human fetus Human adult
Fig. 25-19a
(a) Differential growth rates in a human
NewbornAge (years)
Adult1552
Fig. 25-19b
(b) Comparison of chimpanzee and human skull growth
Chimpanzee fetus Chimpanzee adult
Human fetus Human adult
Fig. 25-20
Gills
Fig. 25-21
Vertebrates (with jaws)with four Hox clusters
Hypothetical earlyvertebrates (jawless)with two Hox clusters
Hypothetical vertebrateancestor (invertebrate)with a single Hox cluster
Second Hox duplication
First Hox duplication
Fig. 25-22
Hox gene 6 Hox gene 7 Hox gene 8
About 400 mya
Drosophila Artemia
Ubx
Fig 25-UN9
Origin of solar systemand Earth
4
32
1
PaleozoicMeso-
zoicCeno-zoic
Proterozoic Archaean
Billions of years ago
Fig 25-UN10
Flies andfleas
Moths andbutterflies
Caddisflies
Herbivory