Transcript Chap 19 PP

Biology
A Guide to the Natural World
Chapter 19 • Lecture Outline
A Slow Unfolding: The History of Life on Earth
Fifth Edition
David Krogh
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19.1 The Geological Timescale
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Earth’s Geological Timescale
• Earth’s 4.6 billion years of history are
measured in the geological timescale, which
is divided into broad eras and shorter
periods.
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Relative Lengths of Geological Eras
Mesozoic
Cenozoic
Paleozoic
Precambrian
88% of Earth’s
history was spent in
the Precambrian era
Era
Period
Million
years
ago
(Mya)
Notable events
Representative organisms
Major extinction events
Historic time
Quaternary
0.01
Extinction of many large mammals; modern humans appear
1.80
Early humans emerge (genus Homo)
Cenozoic
5
Grasses replace forests in drier areas
23
Tertiary
Rise of several modern mammals
35
Earliest whale fossils; first horses
56
First primate fossils
Extinction of dinosaurs
Cretaceous Extinction
Mesozoic
65
Cretaceous
Angiosperms replace gymnosperms in many habitats
146
Jurassic
First bird fossil (Archaeopteryx)
First flowering plants (Angiosperms)
Triassic Extinction
200
Triassic
Permian
First dinosaurs and mammals
Permian Extinction
251
First mammal-like reptiles
299
First reptiles
First gymnosperms
Paleozoic
Carboniferous
Devonian Extinction
359
First seed-bearing plants
Fish-to-tetrapod transition
Devonian
416
Early jawed fishes
First fossils of land animals
Silurian
444
Ordovician Extinction
First plant fossils
First fungus fossils
Ordovician
488
First fossil of chordate (ancestors of vertebrates)
Cambrian Explosion
Cambrian
Precambrian
542
635
First animal fossils
1,200
First multicellular life
2,000
First eukaryotic fossils
2,400
First substantial oxygen accumulation in atmosphere
3,400
Evidence of abundant bacterial and archaeal life
3,800
Possible evidence of earliest life on Earth
4,600
Earth is formed
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Figure 19.3
Earth’s Geological Timescale
• These timeframes are defined in large part
by the different life-forms that evolved
within them, as reflected in the fossil
record.
• Many of the transitions evident in the fossil
record came about because of major
extinction events
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Earth’s Geological Timescale
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Figure 19.4
Earth’s Geological Timescale
• Life is thought to have begun on Earth
about 3.8 billion years ago.
• From that time until perhaps 1.2 billion
years ago, all life was strictly microscopic
and single-celled.
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Earth’s Geological Timescale
• To judge by the fossil record, all the
animals and plants that exist today came
about in the last 16 percent of life’s 3.8
billion-year history.
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19.2 How Did Life Begin?
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How Did Life Begin?
• Life arose through a chemical process:
Simple elements and compounds available
on the early Earth came together to produce
more complex molecules.
• Ultimately, a group of these molecules
became capable of self-replication.
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Stanley Miller’s Experiment
• In a famous experiment conducted in 1953,
researcher Stanley Miller attempted to recreate, in a set of tubes and flasks, the
environmental conditions that he believed
existed on the early Earth.
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Stanley Miller’s Experiment
• Miller found that one variety of life’s
chemical building blocks, amino acids,
could be produced in these conditions in a
short period of time.
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Stanley Miller’s Experiment
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Figure 19.5
Replicator-first Model
• The replicator-first model of the origin of
life holds that the first life-form probably
was a single molecule, similar to today’s
DNA, which was capable of replicating
itself.
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Metabolism-first Model
• The metabolism-first model holds that life
probably originated through the initiation of
a self-sustaining chemical reaction that
involved a set of small, uncomplicated
molecules.
• Suggests a chemical reaction occurred
among an energy-yielding molecule and at
least two other simple molecules coming
together inside a “container” molecule
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Metabolism-first Model
• The initial reaction would have increased
the complexity of the original reaction and
would have brought about a net movement
of new materials into the container.
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The RNA World
• The discovery of RNA molecules, called
ribozymes provided evidence for an ancient
“RNA world” in which the only living
things were simple RNA molecules that
could bring about their own replication.
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Replicator vs. Metabolism-first
Model
• Both models assume the development of selfsustaining chemical reactions whose products
varied over time.
• Natural selection could then have acted on the
differing molecules, setting in motion the
evolution that would result in today’s diverse
living world.
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RNA-like Self-Replication
Animation 19.2: RNA-like Self-Replication
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19.3 The Tree of Life
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The Tree of Life
• Every living thing on Earth belongs to one
of three domains of life: Bacteria, Archaea,
or Eukarya.
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The Tree of Life
• All members of Domains Bacteria and
Archaea are single-celled microbes.
• No bacterial or archael cell has a nucleus,
which makes the bacteria and the archaea
prokaryotes.
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The Tree of Life
• In contrast, all organisms in Domain
Eukarya are composed of one or more cells
that have a nucleus, which means that all
members of this domain are eukaryotes.
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The Tree of Life
• Domain Eukarya is composed of four
kingdoms:
•
•
•
•
plants
animals
fungi
protists
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Domain Eukarya
Domain
Bacteria
Domain
Archaea
Kingdom
Protista
Kingdom
Plantae
Kingdom
Animalia
Kingdom
Fungi
amoebae
flowering
plants
grampositive
purple
bacteria
methane
producers
foraminifera
evergreens vertebrates
mushrooms
flagellates
ferns
salt
lovers
invertebrates
dinoflagellates
cyanobacteria
Domain
Bacteria
hot acid
lovers
Domain
Archaea
mosses
diatoms
yeast
Domain Eukarya
(Protists, Plants, Animals, Fungi)
Universal
ancestor
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Figure 19.6
The Tree of Life
• Life today can be conceptualized as
beginning with a universal ancestor that
produced an evolutionary line leading to
Domain Bacteria on the one hand and to
Domains Archaea and Eukarya on the other.
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The Tree of Life
• Separate evolutionary lines within domain
eukarya—lines collectively referred to as
protists—gave rise to the plant, animal, and
fungal kingdoms.
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19.4 A Long First Era:
The Precambrian
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The Precambrian
• The earliest evidence we have for life is a
chemical signature of it: carbon utilization,
as recorded in rocks found in Greenland
dated to about 3.8 billion years ago.
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The Precambrian
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Figure 19.7
The Precambrian
• The internal patterns of sedimentary rock
formations known as stromatolites, dating
from 3.4 billion years ago, tell us that life
was abundant by that point.
• All of this life was bacterial or archael, and
all of it appears to have existed in the
oceans.
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Notable Precambrian Events
• Photosynthesis was first performed by
bacteria beginning no later than 3.4 billion
years ago.
• This was a critical event because
photosynthesis provides the food that
supports almost all life on Earth.
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Notable Precambrian Events
• Oxygen came to exist in significant quantity
in Earth’s atmosphere through the activity
of the cyanobacteria, which produce oxygen
as a by-product of the photosynthesis they
carry out.
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Notable Precambrian Events
• Early eukaryotes benefited from the rise in
atmospheric oxygen after being invaded by,
and then continuing to live in symbiosis
with, bacteria that were able to metabolize
oxygen.
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Notable Precambrian Events
• A later bacterial invasion allowed one
variety of eukaryotes, the algae, to perform
photosynthesis.
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19.5 The Cambrian Explosion
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The Cambrian Explosion
• Living things began to diversify in form
about 635 Mya with the appearance of the
ancestors of modern animals.
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The Cambrian Explosion
• The fossil record indicates a tremendous,
rapid expansion in the number of animal
forms in a “Cambrian Explosion” that
began about 542 Mya.
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19.6 Plants Move onto Land
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The Movement onto the Land
• Plants, which evolved from green algae,
made a gradual transition to land in tandem
with their symbiotic partners, the fungi.
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The Movement onto the Land
• Fungi fossils exist from about 460 Mya, but
they are thought to have come onto land
sometime before 500 Mya.
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Adaptations of Plants to the Land
• Major transitions in plant life came with the
development of a water-retaining covering
(the cuticle), embryos that matured inside
parent plants, and a “vascular” or fluidtransport system.
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Adaptations of Plants to the Land
• Later plants went on to develop seeds,
which can be thought of as packages
containing an embryo and food for it,
encased in a tough outer covering.
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Adaptations of Plants to the Land
• The living descendants of the first seed
plants are the gymnosperms, represented by
today’s conifers.
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Evolution of Plants
Bryophytes
mosses
ferns
conifers
flowering plants
Cenozoic
Present
Seedless
vascular plants Gymnosperms Angiosperms
flowers
300
500
Animalia
Fungi
Plantae
Protista
vascular
tissue
Archaea
400
Bacteria
seeds
Paleozoic
Millions of years ago
200
Mesozoic
100
movement
onto land
green algae
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Figure 19.12
Evolution of Plants
• The flowering plants, called angiosperms,
developed between 180 and 140 Mya and
eventually succeeded the gymnosperms as
the most dominant plants on Earth.
• Today, angiosperms include many food
crops, cactus, and tree varieties.
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Evolution of Plants
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Figure 19.13
19.7 Animals Move onto Land
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The First to Take Flight
• The first land animals were arthropods; a
centipede-like creature laid down the oldest
terrestrial animal tracks we know of.
• Insects, a variety of arthropod, soon
followed in great abundance.
• The arthropods were the only land animals
for millions of years thereafter.
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Vertebrates onto Land
• One group of fish, the lobe-finned fishes,
gave rise to the four-limbed vertebrates,
called tetrapods, that moved onto land
between 380 and 370 Mya.
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Vertebrates onto Land
(a) Lobe-finned fish
(b) Tetrapod-like fish
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(c) Amphibian
Figure 19.14
Evolutionary Lines of Land
Vertebrates
• Early tetrapods gave rise to amphibians—
represented by today’s frogs and
salamanders—that in turn gave rise to
reptiles.
• All mammals then evolved from reptiles.
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Evolutionary Lines of Land
Vertebrates
• Birds are the living descendents of the
reptile branch that included the dinosaurs.
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Evolutionary Lines of Land
Vertebrates
• Amphibians inhabit two worlds, water and
land, in keeping with their close
evolutionary relationship with animals that
lived strictly in water.
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Evolutionary Lines of Land
Vertebrates
• Reptiles evolved a protective amniotic egg
that allowed their offspring to develop away
from water, freeing reptiles to migrate
inland.
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Evolutionary Lines of Land
Vertebrates
• Mammals appeared as a group of small,
insect-eating animals about 220 Mya.
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Evolution of Terrestrial Vertebrates
Lobe-finned Amphibians Reptiles
fish
Mammals
Birds
Cenozoic
Dinosaurs
Present
100
Mesozoic
hair
300
amniotic
egg
600
ancestral
vertebrates
vertebrates
500
amphioxus
jawed fish
sea squirts
movement
onto land
acorn worms
400
Paleozoic
Millions of years ago
200
mammary
glands
invertebrate ancestors
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Figure 19.6
Evolutionary Lines of Land
Vertebrates
• Contemporary research indicates that all of
today’s basic forms of animals—all of the
modern mammalian orders—had evolved
by 75 Mya, some 10 million years prior to
the demise of the dinosaurs in the
Cretaceous Extinction.
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Evolutionary Lines of Land
Vertebrates
• Another round of mammalian speciation
began about 10 million years after the
dinosaurs died out.
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The Primate Mammals
• The order of mammals called primates has
fossils that date from 55 Mya.
• It is characterized by large, front-facing
eyes, limbs with an opposable first digit,
and a tree-dwelling existence.
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The Primate Mammals
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Figure 19.17
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