Download Evol unit: part 1

Chapter 15
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Fossils
Evidence of organisms that lived in
past times.
Because there are many methods of
formation, there are many types of
fossils. See pg 382 & 418
Fossil types
1.
2.
3.
4.
5.
6.
7.
Trace – marking left by animal; such as a
footprint.
Casts – minerals fill a space left by a
decayed organism.
Petrified – minerals penetrate and replace
parts of an organism.
Imprint – thin object imprint preserved in
hardened sediment.
Molds – organism buried in sediment
decays, leaving empty space.
Amber – entire organism trapped in
hardened tree sap.
Frozen – entire organism trapped and
quickly frozen in ice.
Paleontology: the scientific study of ancient
life using fossil evidence.
Geologic Time Scale
Formation of earth, estimated to be 4.6 billion years ago.
Era
Precambrian
Paleozoic
Mesozoic
Cenozoic
Period
cambrian
Ordovician
Silurian
Devonian
Carboniferous
Permian
Triassic
Jurassic
Cretaceous
Tertiary
Quaternary
# of years ago
3.5 billion
540 million
510 million
439 million
408 million
362 million
290 million
245 million
208 million
146 million
66 million
1.6 million
events
unicellular prok/euk
invertebrates
vertebrates
jawed fish/land plants
amphibians
seed plants/ reptile
conifers dominant
dinosaurs/mammal
flowering plants/birds
flowering plants dom
placental mammals
humans@200,000yrs
determining age of rocks
1.
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Relative dating
Geologic law: if rock layers have not
been disturbed…
The layers at the surface are younger
than the deeper layers.
Fossils in the top layers are younger
than those fossils in deeper layers.
Relative dating cannot be used to
determine actual age.
2.
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Radiometric dating
Utilizes radioactive isotopes to determine
specific age.
Radioactive isotopes decay over time
giving off radiation.
As radioactive decay continues, these
isotopes form new elements.
Radioactive isotopes have decay rates,
this rate can be used as a type of clock
called half-life.
Rock/fossil age can be estimated by
comparing the amount of radioactive
isotope present to the amount of new
element present in the sample item.
Examples of Radaiometeric dating
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Radioactive half-life=1 million years If a
rock contains equal amounts of the
radioactive isotope and the new element
to which it decays, the rock must be 1
million years old.
Fact: For very old rocks/fossils
potassium 40 is used; it decays to argon
40. Half-life=1.3 billion years.
For rocks/fossils less than 50,000 years
old carbon 14 is used; it decays to
nitrogen 14. Half-life=5,730 years.
Evolution
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Simply stated evolution is the change in
living things, or populations, over time.
A change in the gene pool of a population.
Theories of evolution
In 1809 Jean Baptiste de
Lamark was one of the
first to present a theory
of evolution.
It was based on two
principles :
 The use and disuse of
organs
 Inheritance of acquired
traits
 His ideas are flawed and
later his hypothesis is
rejected
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Others Who Influenced
Earth is ancient and changing
Evolutionary Thought
 James Hutton – 1785,
proposed that Earth is
shaped by geological
forces.
 Charles Lyell – 1833, wrote
principles of Geology and
stressed that scientists
must explain past events in
James Hutton
terms of processes that
they can actually observe,
like geological forces.
 Thomas Malthus – 1798, an
economist who predicted
Charles Lyell
that the human population
will grow faster than the
space and food supplies
needed to sustain it.
Thomas Malthus
Theories of Evolution
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Charles Darwin (18091882) he published his
book Origin of Species, on
how species change over
time…after 22 years of
reading, study, specimen
collection, observation and
experimentation.
In it he presented his
revolutionary new theory of
evolution which remains
the cornerstone of modern
evolutionary thought today.
Darwin's travels on the HMS Beagle took
him to the Galapagos Islands where he
noted similar animals to those on the
South American continent, but they were
not exactly alike. One example were the
finches he found on the different islands.
Darwin’s Principles
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Variation exists within species, and
some of this variation is heritable.
All organisms compete for limited
resources.
Organisms produce more offspring
than can survive, and many that do
survive do not reproduce.
The environment selects organisms
with beneficial traits Natural
Selection ( survival of the fittest)
Evidence of Evolution
1. Fossils:
 The fossil record gives us lots of evidence
that species have changed over time
Examples of extinct plants and animals
comes in many forms such as imprints
,molds ,casts, petrified fossils and even
insects trapped in amber .
2. Geographic Distribution of Living Species.
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The existence of similar
but unrelated species.
Example: Darwin found
entirely different species
of animals on South
America and Australia,
yet when he looked at
similar environments on
those continents, he
sometimes saw different
animals that had similar
anatomies and
behaviors. This led to
his theory of descent
with modification. P 383
3. Anatomical Evidence
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Homologous structures are
body parts found in different
organisms with the same
basic structure. Vary in
form, or function not
structure. These suggest a
common ancestry
Vestigial structures organs
that are so reduced in size
that they are just vestiges,
or traces, of homologous
organs in other species.
Suggest evolution from
organisms that used them.
Ex: shortened legs, toes,
appendixes in humans.
4. Embryological Evidence
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Embryonic cells
develop in the same
order and patterns
to produce the
tissues.
Similarities in
development of
embryos suggest a
common
evolutionary
relationship
Analogous Structures
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Wings of birds and
wings of insects have
the same function but
not the same structure
and are said to be
analogous . They have
no evolutionary
relationship.
Ch. 16 Origins of Variation
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Only genetic variations are passed from generation to
generation
Genetic recombination during meiosis is one source of variation
(gene shuffling can produce 8.4 million gene combinations)
Mutation is another important source
Artificial selection – breeding organisms with specific traits in
order to produce offspring with identical traits, used to improve
crops, livestock and pets.
Darwin hypothesized that if it happens artificially then it should
be happening naturally.
Mechanisms of Evolution
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Natural selection – occurs when organisms
having particular positive variations survive,
reproduce, and pass on the variations to the
next generation.
These adaptations can be structural,
anatomical, physiological processes and
behavior.
Structural adaptation example: mimicry –
enables one species to resemble another.
Physiological adaptations (can develop
rapidly) Example: antibiotic resistance –
bacteria
Members of a species that live in the same
area are members of a population.
Evolution occurs when there is a change in
the genetic makeup of a population.
Mechanisms of Evolution
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A gene pool is all the alleles of all genes in
all the individuals in a population.
The gene pool in a population will stay in
equilibrium unless something happens to
make it change. (Hardy-Weinberg Principle)
Relative frequency – of an allele is the
number of times that the allele occurs in a
gene pool, compared with the number of
times other alleles for the same gene occur.
For evolution to take place something must
upset the genetic equilibrium of a population
These processes include : natural selection,
migration, genetic drift, isolation, and
Before industrial revolution
The classic example of
Natural selection in
action was the change in
population densities of
light colored moths
during the industrial
revolution in England.
After industrial revolution
Darwin’s Hypotheses
Descent with Modification – Darwin proposed that
over long periods of time natural selection produces
organisms that have different structures, establish
different niches, or occupy different habitats.
 Each generation is modified due to which individuals
reproduce.
 Darwin also suggests that all living organisms are
related to one another called common descent.
Looking back over time, one will find:
 Tigers, panthers, and cheetahs share common
ancestors
 Felines, horses, dogs, and bats share common
ancestors
 Mammals, birds, reptiles, and fish share common
ancestors
 All species—living and extinct—share common
ancestors.
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Natural Selection on Polygenic trait
Three types of natural selection occur
1. Directional selection is gradual
environmental pressure to change.
2. Stabilizing selection eliminates the
extremes and reduces variation
3. Disruptive selection selects against the
average and favors the extremes
Directional selection
Stabilizing selection
disruptive selection
Mechanism for Change:
1. Migration
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Migration is the movement of
organisms into (immigration) and
out of (emigration) a population.
This either increases or decreases
the genes in a gene pool
2. Genetic Drift
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Genetic drift is the change in gene
frequency of a very small
population due to chance.
Individuals that carry a particular
allele may leave more descendants
than others, over time a series of
chance occurrences of this type
can cause an allele to become
common in a population
Founder Affect – when the
population that moved into a new
environment have particular alleles
that then start to present
themselves due to the environment
(chance not natural selection)
The mutations seen in this Amish child occur at
the rate of 1 in 14 as opposed to 1 in 1000 in
the general population due to chance
introduction in a small isolated population
3. Isolation
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Geographic isolation occurs when
a physical barrier separates
populations. Ex: Mountain, River,etc
Genetic isolation results when two
populations are unable to interbreed.
Ex: they reproduce at different
times, have differences in courtship
rituals or other reproductive
stategies.
4. Mutation
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Many mutations are harmful (lethal)
but when a mutation gives an
organism an advantage it is retained
(phenotype changed) in the gene
pool and changes the frequency of
alleles in the population.
Speciation
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Speciation is the evolution of an
organism into a new species.
A niche is the place and “profession”
of a species (its job in its habitat)
It is difficult for two species to
occupy the same niche, competition
is bound to favor one over the other.
Speciation from Isolating
Mechanisms
Geographic isolation: occurs when
a physical barrier separates populations
Behavioral isolations: occurs when
two population of organism have different
courtship or mating rituals.
Temporal isolation: occurs when two
populations have two different mating
seasons
Patterns of Evolution
1. Divergent Evolution
Divergent evolution is the process by
which organisms become less alike
This can result in speciation.
1.5 It can also lead to adaptive radiation,
where species adapt to a variety of
habitats and evolve into diverse forms
occupying different niches.
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2. Convergent Evolution
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Convergent evolution occurs when distantly
related organisms develop similar characteristics
due to influence of similar environments and
natural selection.
A good example of convergent evolution is
marine mammals and fish
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Convergent evolution can
often lead to mimicry-when
one organism evolves to
resemble another.
These animals have a selective
advantage
3. Coevolution
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Two different species evolve in
response to changes in each other
over time.
Example: flowers that attract a
specific type of pollinator.
Biochemical Evidence of
Evolution
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The more closely
related organisms
are, the more
similar their
biochemical
makeup is.
Similar chemistry
and structure of
chromosomes in
Eukaryotes
Cytochrome c is an example of a protein that can be used to
check if an organism is closely related to another organism.
Ch.17 Models for Rate of Evolution
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Gradualism – a slow gradual change
in a species over a long period of
time. (Think millions into billions of
years)
Punctuated Equilibrium – patterns of
long, stable periods interrupted by
brief periods of more rapid change.
(Think hundreds of thousands even
millions of years)
Speciation rates
Loxodonta
africana
Elephas
maximus
0
1
2
Elephas
3
4
Mammuthus
primigenius
Loxodonta
Mammuthus
5
Primelephas
6
Ancestral species
about 55 million years ago
Related Topics
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Extinction – disappearance of a species
from all portions of its geographical range.
Causes: natural selection, abiotic change
and /or food web collapse.
Microevolution – change of allele
frequency; genetic variation due to
processes such as selection, mutation,
genetic drift or migration.
Macroevolution – evolutionary change at
or greater than the species level;
formation of new species, new genera and
so on.
Earth’s Early History (Hypothesis)
a.
b.
c.
d.
Early Earth’s atmosphere had hydrogen
cyanide, carbon dioxide, carbon monoxide,
nitrogen, hydrogen sulfide, and water, very
caustic environment.
4 billion years ago first solid rocks and
volcanic activity, no oceans still too hot.
3.8 billion years ago cooled enough for water
to remain liquid, this is when early life
appeared.
First organic molecules – Miller, Urey –
experiments produced organic compounds
even cytosine and uracil.
e. Evolution of RNA and DNA – science is
still working on this puzzle but have
made surprising discoveries (viruses
could be source of nucleus, choloroplasts
and mitochondrion from bacteria –
Margulis) RNA before DNA.
f. Free Oxygen – photosynthetic bacteria
became common in shallow seas of the
Precambrian Era, they produced oxygen
which combined with Iron causing the
oceans to rust. This O accumulated and
caused the formation of the ozone layer.
2
Origin of Eukaryotic Cells
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Endosymbiotic theory- smaller
prokaryotes began living inside
larger cells causing a symbiotic
relation such as the mitochondria
and the chloroplast. (lynn Margulis)
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Nucleic Acid
comparisons (DNA
fingerprinting) - the
more closely related
two organisms are,
the more similar is
their DNA, e.g.
identical twins
Chlorophyll is the
same basic molecule
in all photosynthetic
organisms