1. Ch. 25 The History of Life on Earth
Objective:
L.O. 1.9 TSIAT: evaluate evidence provided by data from many scientific disciplines that support biological evolution.
L.O TSIAT: refine evidence based on data from many scientific disciplines that support biological evolution.
L.O TSIAT: design a plan to answer scientific questions regarding how organisms have changed over time using information from morphology, biochemistry and geology.
L.O TSIAT: connect scientific evidence from many scientific disciplines to support the modern concept of evolution.
L.O TSIAT: construct and/or justify mathematical models, diagrams or simulations that represent processes of biological evolution.
L.O 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 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 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 TSIAT: analyze data related to questions of speciation and extinction throughout the Earth’s history.
L.O 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 TSIAT: describe a scientific hypothesis about the origin of life on Earth.
L.O TSIAT: evaluate scientific questions based on hypotheses about the origin of life on Earth.
L.O TSIAT: describe the reasons for revisions of scientific hypotheses of the origin of life on Earth.
L.O TSIAT: evaluate scientific hypotheses about the origin of life on Earth.
L.O TSIAT: evaluate the accuracy and legitimacy of data to answer scientific questions about the origin of life on Earth.
L.O 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 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 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 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 TSIAT: predict consequences of human actions on both local and global ecosystems.

2. 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?

3. 25.1 Conditions on Early Earth Made The Origin of Life Possible
Life began in 4 stages:
Abiotic synthesis of small organic molecules (amino acids and nitrogen bases)
The joining of these small molecules into macromolecules (proteins and nucleic acids)
The packaging of these molecules into protocells, droplets with membranes that maintained an internal chemistry different from that of their surroundings.
The origin of self-replicating molecules making inheritance possible.

4. 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

5. 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 H2
NH3
Water vapor
Cooled “rain” containing organic molecules
Cold water
Sample for chemical analysis
H2O “sea”

6. Video: Tubeworms
© 2011 Pearson Education, Inc.

7. Video: Hydrothermal Vent
© 2011 Pearson Education, Inc.

8. 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 plus
montmorillonite clay
Precursor
molecules only
an index of vesicle number
Relative turbidity,
20 m
(b) Reproduction
(c) Absorption of RNA
Vesicle
boundary
1 m
0.2
0.4 40 20 60

9. 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.

10. 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
Fossilized
stromatolite
Coccosteus
cuspidatus
4.5 cm
0.5 m
2.5 cm
Present
Rhomaleosaurus
victor
Tiktaalik
Hallucigenia
Dickinsonia
costata
Tappania
1 cm
1 m
100 mya
175
200
300
375
400
500
525
565
600
1,500
3,500
270
Figure 25.4

11. Animation: The Geologic Record Right-click slide / select “Play”
© 2011 Pearson Education, Inc.

12. 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
Fraction of parent
isotope remaining
Remaining
“parent”
Time (half-lives) 1 2 4 8 16

13. 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
OTHER
TETRA-
PODS
Temporal
fenestra
Hinge
†Dimetrodon
†Very late (non-
mammalian)
cynodonts
Mammals
Synapsids
Therapsids
Cynodonts
Reptiles
(including
dinosaurs and birds)
Key to skull bones
Articular
Quadrate
Squamosal
Dentary
Hinges
(partial view)
Early cynodont (260 mya)
Very late cynodont (195 mya)
Synapsid (300 mya)
Therapsid (280 mya)
Later cynodont (220 mya)

14. 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
Colonization
of land
Humans
Cenozoic
Meso-
zoic
Paleozoic 1 B i l o n s of y e a r g

15. 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

16. heterotrophic eukaryote Ancestral photosynthetic
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
Ancestral
prokaryote
Nuclear envelope
Nucleus
Endoplasmic
reticulum
Aerobic heterotrophic
Mitochondrion
heterotrophic eukaryote
Photosynthetic
Plastid
Ancestral photosynthetic
eukaryote

17. 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

18. 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.

19. 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.
65.5
135
251
Present
Cenozoic
North America
Eurasia
Africa
South
America
India
Antarctica
Madagascar
Australia
Mesozoic
Paleozoic
Millions of years ago
Laurasia
Gondwana
Pangaea
Juan de Fuca
Plate
North
American
Caribbean
Cocos Plate
Pacific
Nazca
South
Eurasian Plate
Philippine
Indian
African
Antarctic
Australian
Scotia Plate
Arabian

20. (families per million years):
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
542
488
444
Era
Period
416 E O S D
359
299 C
251 P Tr
200
65.5 J
Mesozoic N
Cenozoic Q
100
300
400
500
600
700
800
900
1,000
1,100
(families per million years):
Total extinction rate
Number of families:
Paleozoic
145
NORTH AMERICA
Yucatán
Peninsula
Chicxulub
crater

21. Consequences of mass extinctions
Loss of current diversity of life on Earth
Opens up the way for new life

22. Argyroxiphium sandwicense
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'I
5.1
million
years
O'AHU
3.7
LANAI
MOLOKA'I
1.3 million years
MAUI
HAWAI'I
0.4
Argyroxiphium sandwicense
Dubautia scabra
Dubautia linearis N

23. Effects of Developmental Genes
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
Human adult
Human fetus
Chimpanzee fetus
Gills

24. Changes in Spatial Pattern
Hox (homeotic) genes tell cells how to develop according to where it is located on the embryo.

25. 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 development
Hox gene 6
Hox gene 7
Hox gene 8
Ubx
About 400 mya
Drosophila
Artemia

26. 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
Ventral spines
Threespine stickleback
(Gasterosteus aculeatus)

27. 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
Pigmented
cells
Fluid-filled cavity
Cellular
fluid
(lens)
Cornea
Optic nerve
layer (retina)
Optic
nerve
Lens
Retina
(a)
(b)
(d)
(c)
(e)

28. 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.