Transcript The History of Life

Chapter
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The History of Life
14.1 Fossil Evidence of Change
Land Environments
 Earth formed about 4.6 billion years ago.
 Gravity pulled the densest elements to the
center of the planet.
 After about 500 million years, a solid crust
formed on the surface.
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14.1 Fossil Evidence of Change
Atmosphere
 The gases that likely made up the atmosphere are
those that were expelled by volcanoes.
 Water vapor (H2O)
 Carbon dioxide (CO2)
 Sulfur dioxide (SO2)
 Carbon monoxide (CO)
 Hydrogen sulfide (H2S)
 Hydrogen cyanide (HCN)
 Nitrogen (N2)
 Hydrogen (H2)
• How do we know about these events and their
place in the geologic time scale?
Chapter
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The History of Life
14.1 Fossil Evidence of Change
Clues in Rocks
 A fossil is any preserved evidence of an
organism.
 Most organisms decompose before they
have a chance to become fossilized.
Chapter
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The History of Life
14.1 Fossil Evidence of Change
Chapter
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The History of Life
14.1 Fossil Evidence of Change
Fossil Formation
 Nearly all fossils are formed in
sedimentary rock.
 The sediments build up until they cover the
organism’s remains.
 Minerals replace the organic matter or fill the
empty pore spaces of the organism.
Chapter
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The History of Life
14.1 Fossil Evidence of Change
Dating fossils
 Relative dating is a
method used to
determine the age
of rocks by
comparing them
with those in other
layers.
Chapter
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14.1 Fossil Evidence of Change
Radiometric Dating
 Uses the decay of
radioactive
isotopes to
measure the age
of a rock
 Radioactive
isotopes that can
be
used for radiometric dating are found only in
igneous or metamorphic rocks.
SAY HELLO TO OTZI!
Chapter
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The History of Life
14.1 Fossil Evidence of Change
The Geologic Time Scale
 The geological time scale is a model that
expresses the major geological and
biological events in Earth’s history.
 The geologic time scale is divided into the
Precambrian time and the Phanerozoic eon.
 Eras of the Phanerozoic eon include the
Paleozoic, Mesozoic, and Cenozoic eras.
 Each era is divided into one or more
periods.
Chapter
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14.1 Fossil Evidence of Change
Precambrian
 Nearly 90 percent of Earth’s entire
history, stretching from the formation of
Earth to the beginning of the Paleozoic
era about 542 million years ago
 Autotrophic prokaryotes enriched the
atmosphere with oxygen.
Chapter
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14.1 Fossil Evidence of Change
The Paleozoic Era
 The ancestors of most major animal groups
diversified in what scientists call the
Cambrian explosion.
 Life in the oceans continued to evolve at the
end of the Cambrian period.
 Fish, land plants, and insects appeared
during the Ordovician and Silurian periods.
 The first tetrapods emerged in the Devonian.
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14.1 Fossil Evidence of Change
 A mass extinction ended the Paleozoic
era at the end of the Permian period.
 Between 60 and 75 percent of the species
alive went extinct.
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14.1 Fossil Evidence of Change
The Mesozoic Era
 Mammals and dinosaurs first appeared
late in the Triassic period, and flowering
plants evolved from nonflowering plants.
 Birds evolved from a group of predatory
dinosaurs in the middle of the Jurassic
period.
 About 65 million years ago, a meteorite
struck Earth.
Chapter
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14.1 Fossil Evidence of Change
The Cenozoic Era
 Mammals became the dominant land
animals.
 After the mass extinction at the end of the
Mesozoic era, mammals of all kinds began
to diversify.
Chapter
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The History of Life
14.2 The Origin of Life
Origins: Early Ideas
 Spontaneous generation is the idea that life arises
from nonlife.
 Francesco Redi, an Italian scientist, tested the idea
that flies arose spontaneously from rotting meat.
Chapter
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14.2 The Origin of Life
 The theory of biogenesis states that only living
organisms can produce other living organisms.
 Louis Pasteur designed an experiment to show
that biogenesis was true even for
microorganisms.
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14.2 The Origin of Life
Origins: Modern Ideas
 Simple organic molecule formation
 The primordial soup hypothesis was an
early hypothesis about the origin of life.
 Organic molecules could have been
synthesized from simple reactions.
 UV light from the Sun and electric
discharge in lightning might have been
the primary energy sources.
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14.2 The Origin of Life
 Stanley Miller and
Harold Urey were the
first to show that
simple organic
molecules could be
made from inorganic
compounds.
 Later, scientists found
that hydrogen cyanide
could be formed from
even simpler molecules
in simulated early Earth
environments.
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14.2 The Origin of Life
Making Proteins
 Life requires proteins.
 One possible mechanism for the formation of
proteins would be if amino acids were bound to a
clay particle.
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14.2 The Origin of Life
Genetic Code
 Some RNA sequences appear to have
changed very little through time.
 Many biologists consider RNA to have been
life’s first coding system.
 Other researchers have proposed that clay
crystals could have provided an initial
template for RNA replication.
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14.2 The Origin of Life
Cellular Evolution
 Scientists hypothesize that the first cells
were prokaryotes.
 Many scientists think that modern
prokaryotes called archaea are the closest
relatives of Earth’s first cells.
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14.2 The Origin of Life
Photosynthesizing Prokaryotes
 Archaea are autotrophic.
 They do not obtain their energy from the Sun.
 Archaea also do not need or produce
oxygen.
Chapter
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14.2 The Origin of Life
 Many scientists think that photosynthesizing
prokaryotes evolved not long after the
archaea.
 Prokaryotes, called cyanobacteria, have
been found in rocks as old as 3.5 billion
years.
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14.2 The Origin of Life
The Endosymbiont Theory
 The ancestors of eukaryotic cells lived in
association with prokaryotic cells.
 The relationship between the cells
became mutually beneficial, and the
prokaryotic symbionts became
organelles in eukaryotic cells.
 This theory explains the origin of
chloroplasts and mitochondria.
Chapter
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14.2 The Origin of Life
Chapter 15.115.2
Evolution
Early Theories of Evolution
 Lamarckian
 Lamarck


Theory (1744-1824)
believed living things:
changed over time
adapted to their environment
3 Hypotheses
 1.
A desire to change

An inborn urge to better themselves

Ex. Birds desired to fly → wings
 2.
Use and Disuse

Organism could alter body shape by using
their bodies in new ways

Ex. Snakes, giraffes
 3.
Passing on of traits

If an animal acquired a trait during its
lifetime, it could pass the change on to its
offspring

Ex. Weightlifter’s muscles
 All
of the above are fallacies associated
with evolution
Charles Darwin
1809-1892
1831 traveled around the world and
collected plant and animal species on
the HMS Beagle
 Published
On the Origin of Species by
Means of Natural Selection in 1859
The Galápagos Islands
 Darwin began to collect mockingbirds,
finches, and other animals on the four
islands.
 He noticed that the different islands
seemed to have their own, slightly
different varieties of animals.
Darwin Continued His Studies
 Darwin hypothesized that new species
could appear gradually through small
changes in ancestral species.
 Darwin inferred that if humans could
change species by artificial selection,
then perhaps the same process could
work in nature.
 Artificial
selection: the process of
directed breeding to produce offspring
with desirable traits
Natural Selection
 The
theory that organisms best adapted
to the environment will out compete
those who aren’t and will survive
4 Basic Principles
1. Individuals in a population show
variations
2. Variations can be inherited
3. Organisms have more offspring than can
survive on available resources
4. Variations that increase reproductive
success will have a greater chance of
being passed on
 Darwin’s theory of natural selection is
NOT synonymous with evolution.
 It is a means of explaining how evolution
works.
Evolution
 Evolution:
cumulative changes in groups
of organisms through time
 Groups
evolve, not individuals
Theory of Evolution
 Theory
of Evolution: all organisms on Earth
have descended from a common
ancestor
Support for Evolution
1. The fossil record
 Fossils provide a record of species that lived long
ago.
 Fossils show that ancient species share similarities
with species that now live on Earth.
Glyptodont
Armadillo
Archaeopteryx
Tikaatalik
Distinct scales on it’s back.
Fish-like features on
posterior portion of it’s
body. Reptilian anterior
features.
Ambulocetus natan – Could walk and swim; related to modern whales
Darwinius masillae – “Ida” – Short limbs close to body, fingernails,
grasping hands. Lemur-like but also containing ape-like features.
Discovered by paleontologists
from the University of Michigan
Support for Evolution
2. Comparative Anatomy
 Homologous
structures: anatomically
similar structures inherited from a common
ancestor
 The
structures may
move in different
ways, but they share
similar construction
 Ex.
Bird wings and reptile limbs
Vestigial Structures
 Structures that are the
reduced forms of
functional structures in
other organisms.
 Evolutionary theory
predicts that features of ancestors that
no longer have a function for that
species will become smaller over time
until they are lost.
 Other
examples?
Kiwi Bird
 Analogous structures
can be used for the
same purpose and can
be superficially similar in
construction, but are
not
inherited from a
common ancestor.
 Show
that functionally similar features can
evolve independently in similar
environments
3. Comparative Embryology
 Vertebrate embryos exhibit homologous
structures during certain phases of
development but become totally
different structures in the adult forms.
4. Comparative Biochemistry
 Common ancestry
can be seen in
DNA and amino
acid sequences
5. Geographic Distribution
 The distribution of plants and animals that
Darwin saw first suggested evolution to
Darwin.
Rabbit
Mara
 Patterns of migration were critical to
Darwin when he was developing his
theory.
 Evolution is intimately linked with climate
and geological forces.
Types of Adaptation
 An adaptation is a trait shaped by
natural selection that increases an
organism’s reproductive success.
 Fitness is a measure of the relative
contribution an individual trait makes to
the next generation.
Usually measured by number of
healthy offspring
Camouflage: allows an organism to
blend in with its environment
 Allows organisms
to become almost
invisible to
predators
Leafy sea dragon
Camouflage
Mimicry
 One species evolves to resemble another
species.
Western coral snake
California king snake
Consequences of Adaptations
 Some features of an organism might be
consequences of other evolved
characteristics.
 They do not increase reproductive
success.
 Features likely arose as an unavoidable
consequence of prior evolutionary
change.
Chapter 15.3
 Biologist
now know that natural selection is
not the only mechanism of evolution
 Inheritable
variation may come from any
of the following:
 1.
Genetic drift
 2. Gene flow
 3. Mutation
 4. Non-random mating
 5. Natural selection
Genetic Drift: when the same
genes are combined in different ways
to produce different results
 Due to chance with independent
assortment
 In
smaller populations, the effects of
genetic drift become more pronounced,
and the chance of losing an allele
becomes greater.
Founder Effect
 Occurs when a small sample of a
population settles in a location
separated from the rest of the
population
 Alleles that were uncommon in the
original population might be common in
the new population.
 Ex.
Blue People of the Appalachian
Mountains
Bottleneck
 Occurs when a population declines to
a very low number and then rebounds
 The
rebound group has traits that are
most similar to the smallest group
Gene Flow:
 Increases genetic variation as individuals
move in and out of a population
Mutations: Random changes in the
genetic code
Nonrandom Mating
Promotes inbreeding and could lead to a
change in allelic proportions favoring
individuals that are homozygous for
particular traits
Natural Selection
 Acts to select
the individuals
that are best
adapted for
survival and
reproduction
 Stabilizing selection eliminates extreme
expressions of a trait when the average
expression leads to higher fitness.
 Ex.
Babies who have too low birth weights
are less likely to survive
 Directional selection when an extreme
trait makes organisms more fit it
becomes more common.
 Ex.
Body color of the peppered moth
found in England
 Originally,
brown
most were white, now most are
 Disruptive selection a process that splits
a population into two groups.
 Tends
to remove individuals with average
traits but retains the extreme traits to
better suit them for their environment
 Ex.
Same snake species found in two
areas
Speciation
Speciation: The development of new
species through evolution
A population must diverge and then be
reproductively isolated
 Two
Types of Speciation:
 1. Allopatric speciation
 2. Sympatric speciation
Allopatric Speciation
 A physical barrier divides one
population into two or more
populations.
Abert squirrel
Kaibab
squirrel
Sympatric Speciation
 A species evolves into a new species
without a physical barrier.
 The ancestor species and the new
species live side by side during the
speciation process but cannot
reproduce.
Patterns of Evolution
 Speciation
takes a very long time
(compared to a human life) but there is
evidence that it occurs:
 Adaptive
Radiation
 Coevolution
Adaptive Radiation (divergent evolution)
 Can occur in a relatively short time when
one species
gives rise to
many different
species
 Follows large-scale extinction events
Coevolution
 The relationship between two species
might be so close that the evolution of
one species affects the evolution of the
other species.
 Mutualism
Convergent
Evolution
 Unrelated species
evolve similar
traits even
though they live
in different parts
of the world.
Rate of Speciation
 Evolution proceeds in small, gradual
steps according to a theory called
gradualism.
 Punctuated equilibrium explains rapid
spurts of genetic change causing
species to diverge quickly.