Evolution
Earth’s History
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The Earth was formed about ______ _________________ years ago.
By 2.2 billion years ago, the Earth probably looked like it looks today
___________________ was not believed to be in abundant supply in Earth’s early atmosphere.
Oldest known cellular fossil (3.5 billion years old) traces back to a place in Australia.
Were probably _____________________________, photosynthetic unicellular prokaryotes
First prokaryotes were probably anaerobic – Why?
______________________ = a principle that states the same __________________ processes that occur
today occurred in the past.
These processes occur very ________________, requiring organisms to change as well (very slowly).
Origins of Life
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1 billion years of chemical change to form the first cells, followed by about 3.7 billion years of
biological change.
Types of Evolution
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______________________ ___________________ – the formation of organic molecules from inorganic
substance.
 ______________________ ___________ – Chemicals in the early ocean giving rise to organic,
and eventually, _______________ matter.
_________________ ______________________ – the changing of a species into something different by
the accumulation of small changes over time.
What was early Earth like?
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Earth was ___________!
Little or no ______________
Gases in atmosphere:
 Hydrogen cyanide (poison to you!)
 Hydrogen sulfide
 Carbon Dioxide
 Carbon Monoxide
 Nitrogen
 Water Vapor
pg. 1
How did Life Begin?
Miller - Urey Experiment
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_______________ and ____________ conducted
an experiment to determine if
__________________molecules could be formed
under the conditions of ______________Earth?
 They placed ____________ in a flask and
they added the _______________ that
simulated the early atmosphere.
 They _______________ the water and
______________________ it many times.
 Eventually this process produced
_______________ ___________.
Endosymbiotic Theory
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First proposed by Lynn Margulis in the 1960’s who was looking for an explanation for the
______________________ of ___________________________.
Proposed that similarities between prokaryotes and organelles, together with their appearance in the
fossil record, could best be explained by “____________________”.
Her hypothesis proposed that ________________________ are the result of endocytosis of
_______________ _________________ and __________________ are the result of endocytosis of
_________________________ __________________ entering primitive
_____________________________ cells.
In both cases large anaerobic bacteria would not be able to exist in an aerobic environment.
This arrangement became a ______________________ _______________________ relationship for
both cells (___________________________).
The result is a cell with a double-membrane bound organelle. The inner lipid bilayer would have been
the bacterial cell's plasma membrane, and the outer lipid bilayer came from the cell that engulfed it.
Evidence of Endosymbiosis
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They have their own _____________ (which is circular)
They have __________________ that are similar to prokaryotes
They have a double membrane and the inner membrane has ________________ similar to prokaryotes
They are roughly the ____________ ______________ as bacteria and are susceptible to the antibiotics
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They _____________________ their DNA and use the mRNA to synthesize some of their own proteins.
They can only be produced by ______________________ of pre-existing mitochondria and
chloroplasts.
pg. 2
Endosymbiotic theory
Evolution
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__________________________ is a theory on the origin of life?
 False – It is a theory explaining the origin of species
How old is the human species (Homo sapiens)?
 ~195,000 years old
What is the name of the theory that teaches that humans evolved from monkeys?
 _______ theory teaches that humans evolved from monkeys. Evolution indicates Humans and
modern monkeys share a _________________ _________________.
_______________________: the process by which all living organisms have developed and
________________ from earlier forms __________ ____________.
Evolution is Just a Theory
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pg. 3
______________________ _______________: a well-supported explanation of phenomena that
have occurred in the natural world that is confirmed through observation and experimentation.
Examples: Cell Theory, Theory of Plate Tectonics, and Theory of Evolution
Charles Darwin
Father of evolution
Darwin’s theory of evolution
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The Theory of Evolution is:
 an explanation as to why organisms are so ________________, but seem to be
__________________.
 an explanation as to how organisms undergo ___________________________
________________ over generations.
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Darwin joined the crew of the __________________________ in 1831 as a naturalist.
It was a five-year voyage that took him around the world.
The map below shows the route of the HMS beagle from England to South America, the Galapagos
Island, Australia, South Africa, and back to England
Wrote “On the Origin of Species By Means of Natural Selection”
 Published 1859, _______ years after his return home
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Darwin observed differences among island species.
 _____________________: difference in a physical trait of an individual compared to others in
the same group
 Galapagos tortoises that live in areas with tall plants have long necks and long legs
 Galapagos tortoises that live in areas with low plants have short necks and short legs
 Galapagos finches (Darwin’s finches) that live in areas with hard-shelled nuts have strong beaks
 Galapagos finches that live in areas with insects/fruit have long, thin beaks
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Darwin observed ______________and ____________________ _________________ supporting an
ancient Earth.
 Darwin found fossils of extinct animals that resemble modern animals
 Darwin found marine fossil shells high up in the Andes mountains
pg. 4
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Ancient organisms resemble modern organisms.
 _________________: preserved remains or traces of ancient organisms
 By studying fossils scientists have been able to infer why the ancient organism no longer exist.
Ideas That Shaped Darwin’s Thinking
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______________________ _______________________
How could a farmer use selective breeding to get cows with larger horns?
 In order for selective breeding to work you need natural variation.
 __________________ ___________________: individual organisms of the same species
can have different characteristics.
 Darwin called this process Artificial Selection.
 ______________________ _____________________: nature provides the variation and humans
select those they find useful.
pg. 5
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All of the different plants produced from wild mustard by ____________________
___________________________.
Darwin’s Theory of Evolution
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Darwin proposed Natural Selection as the mechanism of evolution.
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_________________ ____________________: the process by which organisms with variations
most suited to their environment survive and produce more offspring.
3 criteria for natural selection to occur:
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Natural Variation
Struggle for Existence
Survival of the Fittest
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__________________ ______________________
 There must be ____________________ among the individuals of a population (they have
________________characteristics).
 The traits must be _________________________.
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________________ _______ ____________________
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pg. 6
Species must ___________________ for limited resources and avoid predators.
__________________: the organism’s ability to survive and reproduce.
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__________________ ______ _______ ___________________
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Only the most “________” individuals will be able to ________________ and
__________________________ to pass on their adaptations.
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__________________________: any inherited characteristic that increases an organism’s fitness
(ability to survive and reproduce)
Evidence of Evolution
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Scientists must determine the age of the fossil to determine where the organism fits in the geologic time
scale.
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_________methods of determining ______________ _________
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pg. 7
___________________ _________________
 Where is it in the rock layer?
 Deeper layer = older fossil
 Can’t tell you exactly how old a fossil is, just that it is older or newer than another fossil
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___________________ _____________________ _________________
 By knowing the _________ _____ ___________ (half-life) of a radioactive element, the age of
an object can be determined.
 ____________________ is the time it takes for half of the radioactive element to decay…that
is…half of the element to change from parent to daughter.
 With each half-life, the amount of parent remaining is cut in half
 Half-life of carbon-14 is 5,710 years
Ideas That Shaped Darwin’s Thinking
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Geology
In Darwin’s time, most people believed the Earth was a few thousand years old.
Geologists began to gather evidence that the continents have been forming for ___________________
of years.
How did this information help Darwin form his theory of evolution?
Evidence of Evolution
Geographic Distribution of the Living Species
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______________ __________________ – similar organisms in _________________ locations were the
product of different lines of __________________________ _____________________.
pg. 8
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Animals found on different continents share similar features with other species but are more closely
related to other animals living in their habitat because of a shared ______________
____________________.
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Similar ecological conditions, similar pressures of natural selection
Continental Drift
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In 1912, _______________ ___________________ hypothesized about Continental Drift. He had an
idea that at one time 200 million years ago on different sides of the Atlantic, there were
___________________ animal fossils. Wegener compared the east side of South America to the west
side of Africa and found that they ________
together like puzzle pieces. Some other evidence he used was climate, rocks, and other
fossils. Though he was
criticized and rejected about
his theory at first, it was later
accepted 20 years after his
death in 1930.
Continental Drift is a hypothesis
that all continents were once
connected in a single large
landmass (___________________)
that broke apart 200 million years
and drifted slowly to their current
position.
pg. 9
pangaea
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Geologic Time Scale: a timeline of earth’s history.
 Major changes in fossils separate segments of time (periods).
 The end of each “Era” is usually a mass extinction.
 99% of all species that ever lived on Earth are extinct
pg. 10
Evidence of Evolution
Comparative Anatomy
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_________________________ ___________ ______________________
 Body structures shared by related species that have a ___________________
___________________ but ___________________ ____________________.
 Supports the theory that organisms evolved from a ______________ ______________________.
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_________________________ ____________________
 These are remnants of organs that were ____________ _____________________, but they serve
________________or ______ ____________________presently (wisdom teeth, appendix,
tonsils, Darwin’s bump, and tailbone).
pg. 11
Comparative Embryology
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Closely related organisms look more ___________________in the early stages of
_______________________ ____________________________.
Comparative Biochemistry
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Genetics
 All living things have the _________same ________________ ___________.
 A group of 3 DNA nucleotides will code for the same amino acid in all organisms.
 ________________ __________________ organisms have a ________________ _________ sequence.
Influences on Darwin
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Jean Baptiste Lamarck (1809)
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proposed first hypothesis of evolution
“_____________________ _______________ _________________” – Organisms “willed” themselves
to change by using or not using certain body parts.
“_________ _____ ______________” – Organisms acquired traits during their life by the use or disuse
of organs. These new traits could then be passed on to offspring.
“__________________________ _____ _________________ ___________” –Traits acquired during
life were passed on to offspring.
Lamarck’s ideas turned out to be _______________, but he was the _________ to propose a testable means
by which ____________________ ____________ could occur. It just turned out that when his ideas were
tested experimentally, the results disproved his hypothesis.
pg. 12
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Thomas Malthus (1798)
 If left unchecked, _______________ _________________________will grow beyond the
space and food needed to sustain it.
 Believed it would __________________ the likelihood of war, famine, and disease.
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James Hutton (1785) and Charles Lyell (1833)
_____________________ who helped scientists realize that Earth is millions of years old, and the
processes that __________________ ______________in the past are the _____________ processes that
operate in the present.
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Alfred Russell Wallace (1858)
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Developed a theory of evolution very _________________ to that of Charles Darwin
Worked in the East Indies where he made some new discoveries about species there
Wrote to Darwin speculating on evolution by Natural Selection based on his studies of
plants and animals
 ____________________Darwin to ________________ his book, On the Origin of
Species, in 1859 – _______ years after his voyage on the Beagle.
Common Descent with Modification
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Darwin proposed that organisms ____________________ from common ancestors
Idea that organisms change with time, _____________________ from a common form
Caused evolution of _____________ ____________________
pg. 13
Common Descent
Adaptive Radiation
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_______________ ____________________: When a ______________ species evolves into
_________________ different species over time.
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All organisms share a __________________ _______________:
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All living organisms __________________from a _________________ common ancestor that
lived billions of years ago.
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Over time, that organism evolves in different ways to give to rise to _______ of the modern
living organisms.
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Organisms are _________________ __________________ if they share a recent common
ancestor.
Patterns of Evolution
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How are new species formed during adaptive radiation?
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_______________________: The formation of a _________species through
_________________________.
 Populations must be _______________________ _____________________ from each other
 Populations can be isolated by ___________________, _________________, or
________________.
Speciation can result when members of a population become isolated from one another
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Speciation is the creation of _________ different species from _________.
Populations become ___________________ isolated when there is _____ gene flow between them due
to some type of separation.
___________ __________is the exchange of genes between populations through sexual reproduction.
pg. 14
Mechanisms of Speciation
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Natural Speciation by Isolation of Small Populations
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Geographical Isolation
 Geographical _________________ __________________ two populations
 Mountain ranges
 Deep canyons
 Bodies of water
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Ecological Isolation
 Organisms of _________ populations require __________________ habitats
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Reproductive Isolation
 the ___________________of a species _____ ___________ successfully with related
species due to geographical, behavioral, physiological, or genetic barriers or
differences
Modes of Speciation
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Allopatric Speciation (Geographic Isolation)
 A _________________ barrier arises and ________________ gene flow between populations.
 Speciation occurs when the members of the divergent populations _______ longer interbreed.
Sympatric Speciation (Reproductive Isolation)
 A new species may form within the home range of an existing species
(there is _____ __________________ __________________)
 May be:
 Temporal
 Mechanical
 Behavioral
Speciation through Isolation
_____________________ Isolation - type of reproductive isolation due to the _____________________
to physically mate.
_____________________ Isolation – type of reproductive isolation due to ______________________ at
_______________________ times.
______________________ Isolation – reproductive isolation due to _______________ in mating or
courtship behavior even though they ________ physically interbreed.
Parapatric Speciation (Reproductive Isolation)
 Populations are ________ isolated by a ________________ _______________ and are “beside”
each other; nothing is stopping the individuals in the entire population from mixing and mating.
It just _______________ happen.
Peripatric Specation (Geographic Isolation)
 Extreme case of geographic isolation where only a ________ individuals are
____________________, perhaps by some sort of disaster that kills off all but a few of the
isolated population.
pg. 15
Geographical Isolation
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Geographical Isolation is the separation of two
populations by a physical barrier.
Caused by the geographical barriers
A form of reproductive isolation
Darwin’s finches are a main example
Reproductive Isolation
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Reproductive isolation is the separation of two
populations in such a way they cannot
interbreed and produce a fertile offspring.
Caused by behavioral barriers, temporal
barriers, and geographical barriers
The major cause of speciation
One example is temporal isolation of redlegged and yellow-legged frogs.
Patterns of Evolution
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Convergent Evolution
___________________ organisms evolve _________________ adaptations because they live in
_________________ environments
pg. 16
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Sharks and dolphins do _______ share a recent common ancestor.
They have similar characteristics because they ____________ a similar environment.
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Does NOT support Evolution!
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______________________Structures
Body parts in different species that is similar in function but _________ in structure
Structures evolved in response to a similar environmental challenge.
Supports ____________________ evolution
Analogous Structures
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Coevolution
 The evolution of ________ or ________ species, each adapting to ________________ in the
other
 Occurs when species ____________________ closely with each other.
 Ex: Cheetah and Gazelles have co-evolved to become the fastest and second fastest land
animals
Rates of Evolution
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Punctuated Equilibrium:
Species do not evolve for _________ periods of time and then go through ___________ period of
_____________evolution.
What causes the period of rapid evolution?
___________ ________________________: Many species die out in a short time.
_________________________: A group of individuals get isolated from the main population.
pg. 17
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Punctuated Equilibrium
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Gradualism
Organisms have evolved at a __________ and ________________rate.
This theory is in contrast with punctuated equilibrium.
Evolution as Genetic Change
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Evolution, in genetic terms, is a _______________ in the allele frequency of a population over time.
 ___________ ____________: the combined genetic information of all the members of a
population
 __________________ ______________________: the number of times that an allele occurs in
a gene pool compare to the total number of alleles
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Natural selection affects polygenic traits differently than single gene traits.
Single-Gene Trait
 Controlled by one gene that has two alleles
 Two distinct phenotypes
 Ex: Tall or Short Pea Plants
pg. 18
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Polygenic Trait
 Controlled by more than one gene
with many alleles
 Many possible genotypes and
phenotypes
 Ex: Human Height
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Natural selection can affect the distributions of polygenic phenotypes in any of 3 ways:
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Directional Selection
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Stabilizing Selection
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When individuals at one end of the curve
have higher fitness than individuals in the
middle or other end.
Entire ______________ _____________
Favors _______ of the extreme variations
Individual in the center of the curve have
higher fitness than those at the ends of the
curve.
Center remains __________ but
_____________ entire graph
Favors ___________ individuals
Ex: weight of human infants
Disruptive Selection:
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pg. 19
When individuals at each end of the curve
have higher fitness than those in the middle
Favors _________
________________variations
Creates _______ distinct phenotypes (can
lead to speciation)
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Genetic Drift: ______________ change in allele frequency of a _____________population due to
_______________.
 Does ________ increase the overall fitness of the population
 More likely to occur in ______________populations.
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Genetic Equilibrium: when the allele frequencies in a population remain __________________over
time.
 The population is __________ evolving
Hardy-Weinberg Principle
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A population will not evolve if the following conditions are met:
 Random Mating
 Large Population
 No Migration
 No mutations
 No natural selection
Modern Classification is based on Evolution
pg. 20
Cladograms
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A ______________________ is a diagram used to show evolutionary relationships.
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Cladograms
 show ________________________ between organisms
 Are assembled using evidences of evolution
 Can be changed with new data
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Clade
 A group of _____________________, such as a species, whose members share
_____________________ features derived from a _________________
________________________.
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Derived character: trait shared by clade members.
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Node: where a branch splits in two
How to read a cladogram
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This diagram shows a relationship between 4 relatives. These relatives share a common ancestor at the
root of the tree.
Note that this diagram is also a timeline. The older organism is at the bottom of the tree.
The four descendants at the top of the tree are DIFFERENT species. This is called SPECIATION
pg. 21
Cladistics is classification based on Ancestry
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_______________________ is the evolutionary history for a group of species.
 shown with branching tree diagrams
pg. 22
pg. 23