Evolution
• The process of biological change by which
descendants come to differ their ancestors.
• Evolution
• A Swedish botanist in the 1700’s who developed
a classification system for the organisms known
at this time
• Carolus Linnaeus
• A group of organisms so similar to one another
that they can reproduce and have fertile offspring
• species
• A French naturalist of the 1700’s who suggested
that species shared ancestors. He also rejected
that the Earth was only 6,000 years old
• Georges Louis Leclerc de Buffon
• Born in 1731, this was a respected English doctor
and poet. He proposed that all living things
descended from a common ancestor and that
more complex forms arose from less complex
forms.
• Erasmus Darwin
• In 1809, a French naturalist who proposed that all
organisms evolved toward perfection and
complexity. He did not believe in extinction, but
he did believe that organisms evolved.
• Jean- Baptiste Lamarck
• He proposed that changes in an environment
caused an organisms behavior to change, leading
to greater use or disuse of a structure or organ.
The organism would pass on these changes to
offspring.
• Lamarck
• The French zoologist who did not believe in
evolution but did believe in extinction. He
observed that each stratum, or rock layer, held
specific fossils.
• Georges Cuvier
• Traces of organisms that existed in the past.
• fossils
• A theory that states that natural disasters such as
floods and volcanic eruptions have happened
often during Earth’s long history
• catastrophism
• A Scottish geologist who proposed that the
changes he observed in landforms resulted from
slow changes over a long period of time
• James Hutton
• A belief that landforms change slowly over time
• gradualism
• The English geologist who wrote the book
Principles of Geology in the 1830’s. Charles
Darwin read this book and was inspired by it.
• Charles Lyell
• An expansion of gradualism that states that the
geologic processes that shape Earth are constant
through time. Essentially, the processes that
occur today, also happened in the past.
• Uniformitarianism
• What concepts about the Earth did Hutton and
Lyell agree upon?
• That changes occur gradually.
• What are the key differences between the
theories of gradualism and catastrophism?
• Gradualism emphasizes slow changes on Earth
over long periods of time, while catastrophism
emphasizes change through natural disasters.
• In 1831, what ship did Darwin take that enabled
him to travel around the world for 5 years
collecting specimens and making observations of
land?
• The HMS Beagle
• The differences in the physical traits of an
individual from those of other individuals in the
group to which it belongs.
• variation
• Variation that occurs among members of different
species.
• Interspecific variation
• Variation that occurs among individuals of the
same species
• Intraspecific variation
• A feature that allows an organism to better
survive in its environnment
• adaption
• What could account for fossils of marine
organisms being found on top of modern day
mountain ranges?
• Land that was once a marine environment could
be uplifted by Earth processes and becomes
terrestial.
• What accounts for the variation Darwin observed
among island species?
• The islands had different environments, and the
organisms had adaptations that enabled the
organism to live in those environments
• The process by which humans change a species
by breeding it for certain traits
• Artificial selection
• What is the selective agent in artificial selection?
• humans
• The ability of a trait to be passed down from one
generation to the next
• heritability
• What is the selective agent for traits in nature?
• The environment
• A mechanism by which individuals that have
inherited beneficial adaptations produce more
offspring on average than do other individuals
• Natural Selection
• Natural limits to population growth proposed by
economist Thomas Malthus
• Food, water, shelter, disease also limits growth
• All individuals of a species that live in an area
• population
• An aspect of evolution by which adaptations
arose over many generations
• Descent with modification
• What English naturalist independently developed
a theory similar to Darwin’s?
• Alfred Russel Wallace
• The four main principles to the theory of natural
selection are
• Variation
• Overproduction
• Adaptation
• Descent with modification
• A measure of the ability to survive and produce
more offspring relative to other members of the
population in a given environment.
• fitness
• Natural selection acts on ________ rather than
on genetic material itself.
• phenotypes
• What two ecologists observed an example of
natural selection among finches on the
Galapagos island?
• Peter and Rosemary Grant
• When scientists study fossils, they take into
account _______, ________,and________
• Age
• Location
• What the environment was like when the
organism it came from was alive.
• Darwin noted that island species most closely
resembled species on the nearest_________
• mainland
• The study of the distribution of organisms around
the world.
• biogeography
• Fish , birds, reptiles, and mammals all have
_____ ____ as embryo’s
• Gill slits
• What does similar features of embryo’s in
different organisms suggest?
• Evolution from a distant common ancestor
• Features that are similar in structure but appear
in different organisms and have different
functions.
• Homologous structures
• Structures that perform a similar function but are
not similar in origin
• Analogous structures
• Provide an example of a homologous structure
• Human hand and bat wing
• Provide an example of an analogous structure
• Insect wings, bird wings
• Underdeveloped or unused features that are
remnants of organs or structures that had a
function in an early ancestor.
• Vestigial structure
• What type of structure would you call the stumplike limbs of a snake?
• vestigial
• Why are structures considered critical evidence of
evolution?
• They are homologous to full-size features and
evidence of common ancestry among organisms
that share them.
• Describe how some of the Galapagos finch
species, which traditionally were seed eaters,
evolved over generations to prefer insects over
seeds.
• On some islands, insects might have been more
abundant than seeds, or there might have been
less competition for insects than for seeds. The
feeding behavior must have been heritable to
become common in the population over time.
• How can a bat’s wing be considered both a
homologous structure and an analogous
structure?
• A bat wing is homologous to the forelimbs of
other vertebrates. It is analogous to the wing of
an insect because the wings are structurally
different even though they perform the same
function.
• The study of fossils or extinct organisms.
• Paleontology
• Why is the fossil record not complete?
• Most living things do not form into fossils when
they die. The remains are scattered by
scavengers.
• Has any fossil evidence ever been found that
contradicts evolution?
• No
• What genetic evidence supports evolution?
• All living things have DNA
• They all make the same proteins from the same
20 amino acids.
• DNA sequence comparisons can be used to show
probable evolutionary relationships between
species.
• How do pseudogenes support evolution?
• Pseudogenes are like vestigial structures. They
are genes that no longer function but are carried
along, or remain, in DNA. This provides evidence
that genes change over time.
• What type of genes control the development of
specific structures?
• How does this support evolution?
• Homeobox genes
• They indicate a very distant common ancestor
• How may protein comparisons support evolution?
• A unique set of proteins are found in specific
types of cells. DNA is coded to make proteins.
Cells from different species that make the same
proteins have similar DNA. This suggests that
they may come from a common ancestor.
• Genetic variation is stored in a population’s
________ ______.
• Gene pool
• The combined alleles of all of the individuals in a
population.
• Gene pool
• A measure of how common a certain allele is in
the population.
• Allele frequency
• Genetic variation comes from two main sources:
• Mutation and recombination
• A random change in the DNA of a gene.
• mutation
• A process in which new allele combinations form.
This happens primarily during Meiosis.
• recombination
• The crossing of two different species that share
common genes.
• hybridization
• A type of distribution in which the frequency is
highest near the mean value and decreases
toward each extreme end of the range.
• Normal distribution
• The observable change in the allele frequencies
of a population over time. This type of evolution
occurs on a small scale – within a single
population.
• microevolution
• Natural selection can change the distribution of a
trait along one of three paths:
• Directional, stabilizing, or disruptive selection.
• A type of selection that favors phenotypes at one
extreme of a trait’s range.
• Directional selection
• The intermediate phenotype is favored and
becomes more common in the population.
• Stabilizing selection
• This type of selection occurs when both extreme
phenotypes are favored, while individuals with
intermediate phenotypes are selected against by
something in nature.
• Disruptive selection
• If two similar populations do not have gene flow,
what happens to them over time?
• Lack of gene flow increases the chance that the
two populations will evolve into different species.
• Changes in allele frequencies due to chance.
• Genetic drift
• The movement of alleles from one population to
another.
• Gene flow
• Genetic drift that occurs after an event greatly
reduces the size of a population.
• The bottleneck effect
• Genetic drift that occurs after a small number of
individuals colonize a new area.
• Founder effect
• What model describes populations that are not
evolving?
• The Hardy-Weinberg Equilibrium
• What 5 conditions are necessary for a population
to stay in equilibrium? (To not evolve)
• 1. A very large population (no genetic drift)
• 2. No emigration or immigration (no gene flow)
• 3. No mutations (No new alleles)
• 4. Random mating (no sexual selection)
• 5. No natural selection (all traits must equally aid
in survival)
•
•
•
•
•
•
What five factors lead to evolution?
1. genetic drift
2. gene flow
3. mutation
4. sexual selection
5. natural selection
• If gene flow between two populations stops for
any reason, the populations are said to be
_____________.
• isolated
• This type of isolation occurs when members of
different populations can no longer mate
successfully with one another.
• Reproductive Isolation
• The best environments for any type of
fossilization include _________, _________, and
areas where sediment is continuously deposited,
such as __________, ___________, and
______________.
• Wetlands, bogs
• river mouths, lakebeds, and floodplains.
•
•
•
•
•
•
What processes may make a fossil?
Permineralization
Natural casts
Trace fossils
Amber preserved fossils
Preserved remains
• This type of fossilization occurs when minerals
carried by water are deposited around a hard
structure. They may also replace the hard
structure itself.
• permineralization
• This type of fossil records the activity of an
organism. They include nests, burrows, imprints
of leaves, and footprints.
• Trace fossils
• This type of fossil contains organisms that
became trapped in tree resin that hardens into
amber after the tree gets buried underground.
• Amber-preserved fossils
• Many fossils form in _________ ______, which is
made by many layers of small rock particles.
• Sedimentary rock
• Why are so few complete fossils discovered?
• Specific conditions and events are required for
fossilization to occur. Only a tiny fraction meet
these criteria. Rock cycling also destroys many
fossils.
• This method of dating estimates the time during
which an organism lived by comparing the
placement of fossils of that organism with the
placement of fossils in other layers of rock.
• Relative dating
• A dating technique that uses the natural decay
rate of unstable isotopes found in materials in
order to calculate the age of that material.
• Radiometric dating
• Atoms of an element that have the same number
of protons but a different number of neutrons.
• isotopes
• What are the three naturally occurring isotopes of
carbon? Describe them.
• C-12, C-13, C-14
• They all have six protons. They differ by their
number of neutrons. Carbon twelve has 6
neutrons, carbon thirteen has seven, and carbon
fourteen has eight neutrons.
• What are the three isotopes of hydrogen? Name
and describe them.
• Protium has one proton and no neutrons
• Deuterium has one proton and one neutron
• Tritium has one proton and two neutrons
• As an isotope for an element decays, it may
break down to form a different __________.
• element
• The decay rate for many radioactive isotopes has
been measured and is expressed as the isotope’s
___________.
• Half-life
• What effect do environmental conditions such as
temperature and pressure have on an element’s
half-life?
• None
• C-14 decays into ____________.
• N-14 in roughly 5730 years.
• Living organisms absorb carbon through eating
and breathing. Carbon 14 is constantly being
resupplied. What happens to carbon fourteen
when an organism dies?
• The intake of carbon stops but the decay of
carbon-14 continues.
• How do scientists determine the ago of the Earth?
• Meteorites formed in the solar system at about
the same time as the Earth. Uranium to lead
isotope ratios consistently estimate the age of the
solar system, and therefore the Earth, to be 4.5
billion years old.
• Why is a uranium isotope often used rather than
C-14 in radiometric dating to determine the age of
the Earth?
• Carbon has a very short half life. Uranium has a
half-life that may be used to measure in billions of
years.
• Explain the difference between relative dating and
absolute dating.
• Both relative dating and absolute dating are used
to find how old a site or fossil is. Relative dating
does not give specific dates, but dates a sample
in context with other samples. Absolute dating
gives a specific age of a sample within a margin
of error.
• When mountains form, the order of rock layers
can be disturbed. How could radiometric dating
be used to sort out the relative ages of such rock
layers?
• Disturbed rock strata may not be ordered
sequentially. Radiometric dating of different
layers can sort out the absolute ages of the rocks
and determine the correct sequence of the strata.
• Fossils of organisms that existed only during
specific spans of time over large geographic
areas. They provide an additional tool to
determine the age of fossils or the strata in which
they are found.
• Index fossils
• What characteristics must an index fossil have?
• Common, easy to identify, found widely around
the world, and only existed for a relatively brief
time.
• A representation of the history of the Earth that
marks major changes or events that have
occurred.
• The Geologic Time Scale
• What are the three basic units of time used by the
Geologic Time Scale?
• Eras, Periods, and Epochs.
• A segment of the geologic time scale that lasts for
tens to hundreds of millions of years and consists
of two or more periods.
• Eras
• The most commonly used units of time on the
geologic time scale, lasting tens of millions of
years. Each is associated with a particular type
of rock system.
• Period
• The smallest units of geologic time and last
several million years.
• Epochs
• Paleozoic means _____________.
• Mesozoic means _____________.
• Cenozoic means _____________.
• Ancient life
• Middle life
• Recent life
• Within the eras, the boundaries between many of
the geologic periods are defined by ____
________.
• Mass extinctions.
• The largest adaptive radiations tend to follow
____ __________.
• Mass extinctions
• Why do adaptive radiations often occur after
mass extinctions?
• Mass extinctions create the opportunity for
organisms to disperse across a wider range of
habitats or environments. Over generations,
populations evolve adaptations to the conditions
of these environments.
• The most common index fossils are shells of
invertebrates. Give two reasons why this is so.
• Invertebrates have been common throughout
much of Earth’s history, and some had shells that
are more easily fossilized than soft parts. Many
shelled invertebrates lived in the ocean, where
the conditions for preservation are better.
• Scientists have inferred that there have been at
least five mass extinctions in Earth’s history. How
would fossil evidence support this inference?
• Abrupt changes in the fossil record support this
inference, where species found in older rock
layers are not found in younger rock layers. Less
species diversity in a younger layer may also
indicate a mass extinction. After catastrophic
events, there may also be boundary layers of
changed sedimentation.
• French physicist Henri Becquerel discovered
radioactivity in 1896, after geologists had
developed the geologic time scale. How did
Becquerel’s discovery help later geologists as
they refined the time scale?
• Prior to Becquerel’s discovery, geologists relied
exclusively on the relative dating of rock layers.
Discovering radioactivity led to the development
of radiometric dating, which offers absolute ages,
rather than just the relative ages of rock layers.
• Scientists disagree over details of the origin of the
Earth. What two key points do they agree on?
• 1. Earth is billions of years old.
• 2. the conditions of our planet and its
atmosphere today are very different from an early
earth.
• What gases made up the Earth’s atmosphere 3
billion years ago?
• Ammonia, water vapor, methane, and carbon
dioxide.
• Roughly how long ago did oxygen become
abundant in the atmosphere?
• 2 billion years ago
• What two hypotheses propose to explain how life
began on earth?
• The Miller-Urey experiment and the Meteorite
hypothesis
• What was the significance of the Miller-Urey
experiment?
• In 1953, Miller and Urey passed electricity
through gases and produced organic molecules
such as amino acids and nucleotides.
• How is the Meteorite hypothesis different from the
Miller-Urey experiment?
• In 1969, a meteorite fell in Australia from space.
It contained more than 90 amino acids. This
suggests that life could have formed in space, or
on Earth.
• Describe the iron-sulfide bubble hypothesis.
• In the 1990’s, biologists William Martin and
Michael Russell noted that hot iron sulfide rising
from below the ocean floor combines with the
cooler ocean water to form chimney-like
structures made of many compartments. The
walls of those compartments acted as the first cell
membranes.
• Describe the lipid membrane hypothesis.
• Lipid molecules spontaneously form membraneenclosed spheres, called liposomes. In 1992
biochemist Harold Morowitz tested the idea that
at some point liposomes were formed with a
double, or bilayer, lipid membrane. The
liposomes then formed around organic molecules.
• A hypothesis that has gained much support in
recent years proposes that ________, rather than
DNA, was the genetic material that stored
information in living things on early Earth.
• RNA
• _______ can copy itself, chop itself into pieces,
and from these pieces make even more _______.
• RNA, RNA
• Unlike RNA, DNA needs _______ to replicate
itself.
• enzymes
• What evidence supports the hypothesis that RNA
was the genetic material that stored information in
living things on an early Earth?
• 1. short chains of RNA will form from inorganic
materials in a test tube.
• 2. If zinc is added as a catalyst, longer chains will
grow.
• 3. RNA will fold into different shapes depending
upon its sequence of nucleotides. This means it
can perform more functions than DNA.
• Why may RNA have been replaced by DNA?
• RNA does not catalyze reactions as well as
proteins.
• It does not store as much information as DNA.
• Natural selection may have preferred DNA over
RNA because it is more stable and less likely to
either make a miscopy or mutate.
• Explain the phrase….the RNA world.
• There are several hypotheses about how RNA
could have led to life. Laboratory experiments in
which RNA molecules survive and self-replicate
support the idea of early cells being based on
RNA.
• RNA is hypothesized to be the earliest form of
genetic material because it can store information,
catalyze its own replication, and catalyze other
reactions. Which two of these functions can DNA
not do? Which two can proteins not do?
• DNA cannot catalyze its own replication or
catalyze other reactions. Proteins cannot store
information or catalyze their own replication.
• Single celled organisms changed Earth’s early
surface by depositing _____________.
• minerals
• How did the single celled organisms of an early
Earth change the atmosphere?
• They gave off oxygen as a by-product of
photosynthesis.
• The first prokaryotes would have been _______,
living without oxygen.
• anaerobic
• Scientists have found evidence that _______
________ evolved more than 3.5 billion years
ago.
• Photosynthetic life
• Domed, rocky structures made of layers of
cyanobacteria and sediment.
• stromatolites
• How are stromatolites evidence of Earth’s early
life?
• Stromatolite fossils can be as old as 3.5 billion
years, which means that we know of at least one
life form (cyanobacteria) that was alive at that
time. Also, cyanobacteria, being photosynthetic,
may have helped pave the way for aerobic life
forms.
• The fossil record shows that eukaryotic
organisms had evolved by ___ ________ years
ago.
• 1.5 billion
• Eukaryotic cells were all _________ on an early
earth.
• aerobic
• All cells in multicellular organisms today are
_________.
• eukaryotic
• In the 1970’s, Biologist Lynn Margulis of the
University of Massachusetts proposed the theory
of _______________, which is a relationship in
which one organism lives within the body of
another, and both benefit.
• endosymbiosis
• This theory suggests that early mitochondria and
chloroplasts were once simple prokaryotic cells
that were taken up by larger prokaryotes around
1.5 billion years ago.
• endosymbiosis
• What differentiates other organelles from
mitochondria and chloroplasts?
• They have their own DNA and ribosomes.
• How does sexual reproduction increase diversity
among living things?
• Through gamete production and crossing-over,
sexual reproduction provides genetic variation.
• How does sexual reproduction increase the
chances that some individuals will survive
changed environmental conditions?
• In a sexually reproductive population, there is
more mixing and combining of traits than in an
asexual population. Rather than depending on
mutation alone to create a trait that can be
advantageous, recombination of alleles can yield
new traits relatively quickly, possibly allowing a
population to adopt to new environmental
conditions more rapidly.
• For photosynthetic organisms to become more
common than those that get energy from eating
organic molecules, what environmental conditions
must have changed?
• In order for photosynthetic organisms to evolve
and thrive, there must have been increased levels
of sunlight and plenty of carbon dioxide in the
atmosphere and oceans.
• According to the theory of endosymbiosis,
mitochondria were once independent organisms.
Do you think it’s possible that mitochondria might
now be able to exist independently if removed
from a cell? Describe how you could investigate
this.
• Mitochondria would survive on their own if they
were in a nutrient rich environment. One test
would be to try to raise excised mitochondria in a
cell culture, with normal eukaryotic cells as a
control.
• Why would it have been advantageous to be
multicellular rather than unicellular?
• Cells that cooperate could compete more
effectively for energy. Increased dependence on
neighboring cells would have led the cells to
function as a colony.
• Multicellular organisms first appeared during the
___________ era.
• Paleozoic
• The __________ era began 248 million years ago
and ended 65 million years ago. This age was
called the age of reptiles because the dinosaurs
roamed Earth during this era.
• Mesozoic
• What are the three periods into which the
Mesozoic is divided?
• The triassic, the jurassic, and the cretaceous
• The earliest ancestors of modern humans
evolved near the end of the _________.
However, Homo sapiens, anatomically modern
humans, did not appear until about _______
years ago.
• Tertiary, 100,000
• The oldest living primate group are the
_________.
• Prosimians
• _____________, the humanlike primates, are
further subdivided into the New World Monkeys,
Old World Monkeys, and hominoids.
• Anthropoids