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Ch. 25 The History of Life on EarthObjective:
L.O. 1.9 TSIAT: evaluate evidence provided by data from many scientific disciplines that support biological evolution.L.O. 1.10 TSIAT: refine evidence based on data from many scientific disciplines that support biological evolution.L.O. 1.11 TSIAT: design a plan to answer scientific questions regarding how organisms have changed over time using information from morphology, biochemistry and geology.L.O. 1.12 TSIAT: connect scientific evidence from many scientific disciplines to support the modern concept of evolution.L.O. 1.13 TSIAT: construct and/or justify mathematical models, diagrams or simulations that represent processes of biological evolution.L.O. 1.14 TSIAT: pose scientific questions that correctly identify essential properties of shared, core life processes that provide insights into the history of life on Earth.L.O. 1.15 TSIAT: describe specific examples of conserved core biological processes and features shared by all domains or within one domain of life, and how these shared, conserved core processes and features support the concept of common ancestry for all organisms.L.O. 1.16 TSIAT: justify the scientific claim that organisms share many conserved core processes and features that evolved and are widely distributed among organisms today.L.O. 1.20 TSIAT: analyze data related to questions of speciation and extinction throughout the Earth’s history.L.O. 1.21 TSIAT: design a plan for collecting data to investigate the scientific claim that speciation and extinction have occurred throughout the Earth’s history.L.O. 1.27 TSIAT: describe a scientific hypothesis about the origin of life on Earth.L.O. 1.28 TSIAT: evaluate scientific questions based on hypotheses about the origin of life on Earth.L.O. 1.29 TSIAT: describe the reasons for revisions of scientific hypotheses of the origin of life on Earth.L.O. 1.30 TSIAT: evaluate scientific hypotheses about the origin of life on Earth.L.O. 1.31 TSIAT: evaluate the accuracy and legitimacy of data to answer scientific questions about the origin of life on Earth.L.O. 2.31 The student can connect concepts in and across domains to show that timing and coordination of specific events are necessary for normal development in an organism and that these events are regulated by multiple mechanisms.L.O. 2.32 TSIAT: use a graph or diagram to analyze situations or solve problems (quantitatively or qualitatively) that involve timing and coordination of events necessary for normal development in an organism.L.O. 2.33 TSIAT: justify scientific claims with scientific evidence to show that timing and coordination of several events are necessary for normal development in an organism and that these events are regulated by multiple mechanisms.L.O. 4.20 TSIAT: explain how the distribution of ecosystems changes over time by identifying large-scale events that have resulted in these changes in the past.L.O. 4.21 TSIAT: predict consequences of human actions on both local and global ecosystems.
Overview• Currently, the largest
fully terrestrial animal in Antarctica is a 5mm long fly.
• However, fossils on Antarctica show a history of tropical animals, including dinosaurs.
• An ever changing world give rise to new organisms, but what was the first organic being on Earth?
25.1 Conditions on Early Earth Made The Origin of Life Possible
• Life began in 4 stages:1. Abiotic synthesis of small organic molecules (amino
acids and nitrogen bases)2. The joining of these small molecules into
macromolecules (proteins and nucleic acids)3. The packaging of these molecules into protocells,
droplets with membranes that maintained an internal chemistry different from that of their surroundings.
4. The origin of self-replicating molecules making inheritance possible.
Synthesis of Organic Compounds
• Earth formed ~4.6 b.y.a.• Earth was hot.• Bombardment by rocks and ice (comets).• Early atmosphere likely contained:
– water vapor– chemicals from volcanic eruptions (N2 and its oxides,
CO2, methane, ammonia, H2, hydrogen sulfide)
• Earth cooled forming oceans
• In 1953, Stanley Miller and Harold Urey conducted lab experiments that showed that the abiotic synthesis of organic molecules in a reducing atmosphere is possible
• The first organic compounds may have been synthesized near volcanoes or deep-sea vents due to reducing properties.
EXPERIMENT“Atmosphere”
Electrode
Condenser
CH4
H 2NH
3
Water vapor
Cooled “rain”containingorganicmolecules
Cold water
Sample for chemical analysis
H2O “sea”
© 2011 Pearson Education, Inc.
Video: Tubeworms
© 2011 Pearson Education, Inc.
Video: Hydrothermal Vent
Macromolecules and Protocells• Dropping monomers on
hot “Earth” produces polymers (amino acids proteins; nucleotides RNA)
• Vesicles form when lipids are added to water.– Formation of lipid bilayer
• These vesicles absorb molecules near their surroundings (early proteins and RNA).
(a) Self-assembly
Time (minutes)
Precursor molecules plusmontmorillonite clay
Precursor molecules onlyRe
lativ
e tu
rbid
ity,
an in
dex
of v
esic
le n
umbe
r
0
20 m
(b) Reproduction (c) Absorption of RNA
Vesicle boundary
1 m
0
0.2
0.4
4020 60
• RNA serves as instructions for protein synthesis as well as acts as enzymes.
• RNA molecules that were more stable or replicated more quickly would have left the most descendent RNA molecules.
• Copying errors occurred (mutations) leading to slight differences and thus natural selection.
25.2 The Fossil Record Documents The History of Life
• Fossils are only made in certain conditions, making the fossil record incomplete.– However, it can be seen how extinct species could
have given rise to current ones (sepciation).Dimetrodon
Stromatolites
Fossilizedstromatolite
Coccosteuscuspidatus
4.5 cm
0.5 m
2.5 cm
Present
Rhomaleosaurus victor
Tiktaalik
Hallucigenia
Dickinsonia costata
Tappania
1 cm
1 m
100 mya
175200
300
375400
5005255656001,500
3,500
270
Figure 25.4
© 2011 Pearson Education, Inc.
Animation: The Geologic Record Right-click slide / select “Play”
• Dating Fossils– Relative dating: older fossils are lower in the
Earth’s strata.– Absolute dating (exact age) uses radiometric
dating: use of half life’s of radioactive isotopes within the fossil.
Accumulating “daughter”
isotope
Frac
tion
of p
aren
t is
otop
e re
mai
ning
Remaining “parent” isotope
Time (half-lives)1 2 3 4
1 2
1 41 8 1 16
The Origin of New Groups of Organisms• Ex: mammals
– Mammals belong to the group of animals called tetrapods– Evolution of unique mammalian features can be traced through gradual
changes over time
OTHERTETRA-PODS
Temporal fenestra
Hinge
†Dimetrodon
†Very late (non-mammalian) cynodonts
Mammals
Synapsids
Therapsids
Cynodonts
Reptiles (including dinosaurs and birds)
Key to skull bones
ArticularQuadrate Squamosal
Dentary
Temporal fenestra
HingeHinge
Hinge
Hinges
Temporal fenestra(partial view)
Early cynodont (260 mya)
Very late cynodont (195 mya)
Synapsid (300 mya)
Therapsid (280 mya)
Later cynodont (220 mya)
25.3 Key Events in Life’s History Included The Origins of Single-celled and Multicellular Organisms and the Colonization of Land
Geologic Time Scale•Boundaries formed by major extinction events•3 Eons (Archaean, Proterozoic, Phanerozoic)•Phanerozoic (current eon) divided into Eras
– Paleozoic – age of trilobites to amphibians– Mesozoic – age of reptiles– Cenozoic – age of mammals
Origin of solar system and Earth
Prokaryotes
Atmospheric oxygen
Archaean
4
3
Proterozoic
2
Animals
Multicellular eukaryotes
Single-celled eukaryotes
Colonization of land
Humans
CenozoicMeso-
zoic
Paleozoic
1
Billions of years
ago
First Single-Celled Organisms• Stromatolites are rocks formed from
prokaryotes bind sediment together.– Thought to be 1st cells
• Cells began to photosynthesize, releasing O2 into the atmosphere.
Stromatolites
The First Eukaryotes•Formed 2.1 b.y.a. by the endosymbiont theory.
– Ancestral mitochondria and chloroplasts were their own type of prokaryotic cells.
– Mitochondria were up taken by protocells, then chloroplasts.
Plasma membrane
DNA
Cytoplasm
Ancestralprokaryote
Nuclear envelope
Nucleus Endoplasmic reticulum
Aerobic heterotrophicprokaryote
Mitochondrion
Ancestralheterotrophic eukaryote
Photosyntheticprokaryote
Mitochondrion
Plastid
Ancestral photosyntheticeukaryote
The Origin of Multicellularity• Formed ~1.5 b.y.a.• First multicellular
organism was algae.• After “snowball Earth”
(long ice age), the Cambrian explosion occurred creating all the phyla that currently exist and 1st predator-prey interactions.
Sponges
Cnidarians
Echinoderms
Chordates
Brachiopods
Annelids
Molluscs
Arthropods
Ediacaran Cambrian
PROTEROZOIC PALEOZOIC
Time (millions of years ago)
635 605 575 545 515 485 0
Colonization of Land
• Fungi, plants, and animals colonized land ~500 m.y.a.
• Arthropods and tetrapods are the most widespread and diverse land animals– Tetrapods evolved from lobe-finned fishes ~365 m.y.a.
25.4 The Rise and Fall of Groups of Organisms Reflect Differences in Speciation and Extinction Rates
• Earth’s crust is broken into plates that are constantly in motion (moving 2cm/yr).
• This causes changes in habitats and climates on Earth over time (Antarctica used be near the equator). Move, adapt, or die.
Juan de FucaPlate
NorthAmerican Plate
CaribbeanPlate
Cocos Plate
PacificPlate
NazcaPlate
SouthAmericanPlate
Eurasian Plate
Philippine Plate
Indian Plate
African Plate
Antarctic Plate
Australian Plate
Scotia Plate
Arabian Plate
65.5
135
251
Pre
sen
t
Cen
ozo
ic
North Americ
a
Eurasia
AfricaSouthAmerica
India
Antarctica
MadagascarAustra
lia
Mes
ozo
icP
aleo
zoic
Mil
lio
ns
of
year
s ag
o
Laurasia
Gondwana
Pangaea
Mass Extinctions• Many species died on Earth around the same time
frames.– 5 mass extinctions have been recorded.– b/w Paleozoic and Mesozoic 96% marine life died! (volcano)– b/w Mesozoic and Cenozoic killed dinosaurs, etc. (meteor)
25
20
15
10
5
0
542 488 444
EraPeriod
416
E O S D
359 299
C
251
P Tr
200 65.5
J C
Mesozoic
P N
Cenozoic
0
0
Q
100
200
300
400
500
600
700
800
900
1,000
1,100
To
tal
exti
nct
ion
rat
e(f
amil
ies
per
mil
lio
n y
ears
):
Nu
mb
er o
f fa
mil
ies:
Paleozoic
145
NORTH AMERICA
YucatánPeninsula
Chicxulubcrater
Consequences of mass extinctions• Loss of current diversity of life on Earth• Opens up the way for new life
Adaptive Radiation• Many species adapted from 1 due to many new
environmental challenges.– Global: Extinction of dinosaurs mammal flourished– Regional: Hawaiian Islands newly created and bare for
organisms to diversify on.
Dubautia laxa
Dubautia waialealae
KAUA'I5.1
millionyears O'AHU
3.7millionyears
LANAI
MOLOKA'I1.3 million years
MAUI
HAWAI'I0.4
millionyears
Argyroxiphium sandwicense
Dubautia scabra Dubautia linearis
N
25.5 Major Changes in Body Form Can Result From Changes in The Sequences and Regulation of Developmental Genes
Effects of Developmental Genes• Current organisms are genetically similar to ancestors, but
developmental timing makes them physiologically different.– Ex: heterochrony between chimps and humans.– Ex: Paedomorphosis in salamanders (juvenile anatomy in adults)
Chimpanzee infant Chimpanzee adult
Chimpanzee adult
Human adultHuman fetus
Chimpanzee fetus
Gills
Changes in Spatial Pattern• Hox (homeotic) genes tell cells how to
develop according to where it is located on the embryo.
Changes in Genes• Changes in developmental genes can result in new
morphological forms– Probably from duplications– Ex: Specific changes in the Ubx gene have been identified
that can “turn off” leg developmentHox gene 6 Hox gene 7 Hox gene 8
Ubx
About 400 mya
Drosophila Artemia
Changes in Gene Regulation• Change in regulation, not sequence of DNA.
– Ex: threespine sticklebacks in lakes have fewer spines than their marine relatives
– The gene sequence remains the same, but the regulation of gene expression is different in the two groups of fish
Threespine stickleback(Gasterosteus aculeatus)
Ventral spines
25.6 Evolution is Not Goal Oriented• Evolutionary Novelties
– Human Eye: a complex organ … how did it evolve?
• Improve on given structure based on current function
• Start simple – photoreceptors that tell light from dark
• Cup photoreptors in round shape.
• Filter light through a pupil• Focus light with a lens• Protect eye with cornea
Pigmented cells(photoreceptors)
Epithelium
Nerve fibers
Pigmentedcells
Nerve fibers
Fluid-filled cavity
Epithelium
Cellularfluid(lens)
Cornea
Optic nerve
Pigmentedlayer (retina)
Opticnerve
Cornea
Lens
RetinaOptic nerve
(a) (b)
(d)(c)
(e)
Evolution is NOT Goal Oriented• Organisms don’t think “I need wings” and are
then able to make wings over generations.• Organisms use what they have that helps
them currently.