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Evolution (Chapters 17-20)
I. History of the Development of
the Theory of Evolution
A. Definitions
1. evolution = change in
the genetic makeup or
gene frequency of a
population over time
2. evolution = origin of
“new” organisms by
descent and modification
from previously existing
forms or species
B. Macroevolution vs
microevolution
1. microevolution – small
changes within a species
2. macroevolution – large
changes when one species
gives rise to a different
species or higher
taxonomic group
3. taxonomic levels:
C. Lamarck (1809) –
Inheritance of acquired
characteristics (Giraffe – not
correct)
D. Charles Darwin (1859) –
Origin of Species by means of
Natural Selection – developed
the theory of evolution
proposing that species
changed slowly (gradualism)
through time via natural
selection
1. natural selection =
differential reproduction
of genotypes: individuals
with some genotypes
produce more offspring
than those of others and if
successful in reproducing,
these characteristics
become more common;
nature favors those
characteristics that help a
species survive and
reproduce successfully
(survival and
reproduction of the “best
adapted”)
a. organisms have genetic
variations
b. organisms struggle to
exist
c. organisms differ in
“fitness”
2. Darwin’s voyage on the
Beagle – observations of
organisms on Galapagos
Islands (finches, tortoises,
etc.), influences of
Malthus (struggles for
existence and
competition) and Hutton
(slow, geological changes
– uniformitarianism)
3. Alfred Wallace also
proposed the mechanism
of “natural selection”
E. Evidence for the Theory of
Evolution by Natural
Selection
1. artificial selection –
animal and plant
breeding
2. fossils – remains of
prehistoric life
a. organisms have changed
through time
b. geologic column –
simpler organisms are
found in deeper strata,
more complex
organisms are found in
higher strata; disappear
of species and types of
organisms with
appearance of new
forms; transitional
forms; data of strata
and fossils via half-life;
changes in relative
abundance of types of
organisms
c. construction of fossil
genealogies and
evolutionary “trees”
3. comparative anatomy
a. similar organisms have
similar structures, but
these structures may be
used for a different
function (homologous):
bat’s wing, whale’s
flipper, cat’s foreleg,
horse’s front leg, human
arm). All of these
originate from the same
structure during
embryonic development
and have the same
bones, but each limb has
a different function and
the bones are modified
to fit that use) – reflect
adaptive radiation or
divergent evolution;
organisms have these
structures because they
have a “common
ancestor”)
b. vestigial organs and
structures – seem to
have lost their original
purpose or function
(appendix, hind limb
bones in some marine
mammals such as
whales and some snakes)
c. analogous structures –
have similar functions
but may be different in
their structures and
embryonic development
(bird’s wing, insect
wing) – may reflect –
may reflect convergent
evolution
4. Comparative
embryology
a. embryo contains
structures not found in
the adult (pharyngeal
slits and a “tail” in
vertebrate embryos),
implies a “common
ancestor”
b. new features may have
developed from
“remodeling” of
earlier features
(primitive vs
advanced)
c. early development:
protostomes (Mollusca,
Arthropoda) vs
deuterostomes
(Chordata and
Echinodermata);
coelomate vs
acoelomate vs
pseudocoelomate
animals
5. comparative
biochemistry
a. order of nitrogen bases
in similar segments of
DNA
b. order of amino acids in
proteins
6. biogeography – where
plants and animals live
and why
a. puzzles: Why did the
Galapagos islands have
more species of finches
than the mainland of S
America and how were
these groups related?
Why were marsupials
confined mostly to
Austrailia?
b. From ancestral
groups, new
populations could
spread , become
isolated, and through
natural selection
become new species
(adaptive radiation)
c. Islands have many
endemic species
(unique to that
location); mainland
species may have
migrated to islands,
become isolated,
adapted to different
conditions, and
eventually become new
species (Darwin’s
finches and tortoises)
II. Relationships between
evolution and natural selection
A. Natural selection is the
driving mechanism for
evolutionary change
B. Basic concepts linking
evolution and natural
selection
1. individuals of a species
vary
2. some variations are
genetic (mutations,
crossing over, random
assortment, etc.)
3. more individuals are
produced through
reproduction than survive
4. individuals with some
traits are more likely to
survive than others
5. those that are more
successful in surviving
and reproducing will have
more offspring with those
particular traits
6. nature provides
“selective pressure”
favoring certain
genotypes and phenotypes
7. thus, organisms change
through time
8. as these changes
“accumulate” new species
may form or “evolve”
C. Examples of Natural
Selection in action
1. peppered moths in
England
2. resistance of plants to
toxic metals
3. resistance of insects to
pesticides
4. resistance of bacteria to
antibiotics
5. genetic variations in
human races or ethnic
groups
III. Population genetics and
evolution (Chapter 18)
A. Population - basic unit of
study in evolutionary change
1. population = all the
members of a species
occupying a particular
area at the same time and
freely interbreeding (part
of the same “gene pool”)
2. in the absence of
natural selection or
certain other influences,
the gene frequencies
within the gene pool
remain constant
3. different populations
may become isolated from
each other.
4. under environmental
influences (natural
selection), gene
frequencies may change,
leading to evolution and
formation of new species
B. Hardy Weinberg Law and
Equations provide a model
for examining evolutionary
change within a population
1. Law = In a large
population of diploid
organisms, the gene
frequencies will remain
constant and no evolution
will occur if 5 conditions
are met:
a. no mutation
b. no mating preferences
c. large population size
d. no gene flow –
immigration or
emigration
e. no selection
2. sexual reproduction by
itself can not produce
evolutionary change,
although it does “shuffle”
genes, producing genetic
variation
3. evolution can be
defined as: a change in
gene frequencies in a
population through time
4. if one or more of the
above conditions are not
met, gene frequencies
may change and hence
evolution can occur
5. using the HardyWeinberg equations to
determine gene
frequencies and genotype
frequencies
p2 + 2pq + q2 = 1
AA
Aa
aa
(genotypes and
phenotypes)
p + q =1
A
a
(gene or allele frequencies)
these only work for a
simple, Mendelian trait
example:
C. Causes of evolutionary
change
1. mutations – introduce
new genes and hence
genetic variation which
can be selected for or
against by nature (most
mutations are harmful)
2. mating preferences
(selective breeding and
artifical selection)
3. genetic drift – change in
the gene pool and hence
gene frequencies that
occurs when a small
group of individuals
forms a separate
population (i.e. founder
effect)
4. gene flow between
populations neighboring populations
may contribute genes to
another population
a. the closer the
populations, the
greater the changes of
gene flow
b. cline = character or
trait that shows a
gradient of variation
across an area
c. gene flow between
populations makes
them more similar, the
greater the distance
between populations,
the less the chance of
gene flow and the
greater the genetic
differences
5. natural selection –
nonrandom, differential
survival and reproduction
of genotypes from one
generation to the next,
does not always “act” in
the same manner on a
trait
a. stabilizing selection –
average phenotypes
have a selective
advantage over
extremes in either
direction
b. directional selection –
phenotypes of one
extreme are favored or
have an advantage
c. disruptive selection –
extremes of a range of
phenotypes are
favored relative to
intermediate forms,
may lead to two
distinct characteristics
and eventually
speciation
D. What promotes and
maintains genetic variability
in populations
1. heterozygote advantage
a. sickle cell anemia
b. hybrid offspring may
have superior traits
over their parents
2. genetic polymorphism –
the continued occurrence
in the same place at the
same time of two or more
genetic variants of the
same trait or set of traits
a. sexual differences
between males and
females (sexual
dimorphism), human
ABO blood type, etc.
3. rapid population
growth
4. decrease in selective
pressures (few predators,
reduced competition,
favorable environments
and habitats, etc.)
E.
What is a species?
1. species – one or more
populations of organisms
capable of interbreeding
with each other in nature
2. different species live in
reproductive isolation
from each other
3. reproductive isolating
mechanisms include:
a. prezygotic: habitat
isolation, temporal
isolation, behavioral
isolation, mechanical
isolation
b. postzygotic: gamete
isolation, zygote
mortality, offspring
sterility
4. all the members of the
same species share the
same gene pool.
5. species identification
and differentiation is
often based upon
morphological
differences. Type
specimens representing
species are preserved and
compared.
6. tests for evaluating a
“species”
a. reproductive isolation
b. behavioral differences
c. differences in protein
structure (order of
amino acids)
d. differences in DNA
(order of nitrogen
bases)
F. Speciation – How are new
species formed?
1. allopatric speciation –
population becomes
physically separated from
the rest of the species and
becomes so different that
members can no longer
interbreed with the
original group, and
therefore become a “new
species”
a. islands – Hawaiian
honeycreepers,
Darwin’s finches
b. Pleistocene glaciations
– warblers
c. Squirrel species on
opposite sides of the
Grand Canyon
d. Often leads to adaptive
radiation and/or
divergent evolution
2. sympatric speciation –
formation of a new
species within a
population (usually
involves a drastic change
in the chromosome
number so individuals
can no longer freely
interbreed)
a. polyploidy –
irregularities in
meiosis (common in
plants)
3. How quickly do new
species and/or groups of
organisms form?
a. Darwinian view – slow,
gradual (Gradualism)
b. Alternative view –
Punctuated
Equilibrium –
evolutionary change is
variable – sometimes
fast, sometimes slow:
evolutionary
breakthroughs or
traits that offer
significant advantages
often occur in small
populations, these then
spread quickly and
may have little chance
for fossilization since
they may only exist for
short periods of
geological time
(postulated to possibly
explain gaps in the
fossil record or lack of
certain transitional
forms)
IV. Origin of Life and Patterns in
Evolution (Chapter 19)
A. Origin of Life???
1. necessary conditions on
pre-biotic earth
a. long periods of time
b. absence or low
concentrations of
molecular oxygen (O2),
oxygen decomposes
organic molecules as
they form under most
natural conditions
(reducing atmosphere
rather than an
oxidizing atmosphere)
c. molecules present: H2,
H2O, CH4, NH3, CO2,
CO, etc.
2. biochemical evolution
and chemical selection
a. formation of simple,
organic chemicals
(amino acids) from
inorganic chemicals
with the addition of
appropriate energy
sources (heat,
radiation,
radioactivity,
lightning, etc.) and
under a reducing
atmosphere (Oparin’s
hypothesis and
Miller’s experiment)
b. monomers 
polymers: dehydration
synthesis of monomers
to make polymers
(protenoids) with ironnickel sulfides and clay
particles acting as
inorganic catalysts
c. formation of
aggregates – spheres
with membrane like
poperties
(phospholipids) and
organic molecules
inside (proteins, etc);
reactions begin to
occur inside
d. “chemical selection”
favors activity and
longevity (chemical
reactions with
catalysts)
e. energy metabolism
may have relied upon
molecules such as
ATP, GTP, CTP, UTP,
etc  “protocell”
f. anaerobic
fermentation may have
been the first
“metabolic” pathway
g. heterotrophs 
autotrophs
h. anaerobic
fermentation and
chemosynthesis 
photosynthesis  O2
 aerobic respiration
i. origin of DNA
(chemical code of
life)??? Proteins 
RNA  DNA (reverse
transcription, RNA
genes)
3. prokaryotes
(heterotrophs first, then
autotrophs), bacteria then
blue green bacteria
4. prokaryotes 
eukaryotes
(endosymbiont theory)
B. History of Life on Earth
(fossil records)
1. earth = 4.5-5 billion
years old
2. first primitive life
forms (2.8-3.5 billion
years ago)
3. eukaryotes (1.8 billion
years ago)
4. Eras – Cenozoic,
Mesozoic, Paleozoic, and
Archeozoic are divided
into Periods (Cretaceous,
Jurassic, Triassic, etc. are
divided into Epochs
(Holocene, Pleistocene,
Pliocene, Miocene, etc.)
5. Cambrian Period
during the Paleozoic 570
million years ago, a huge
explosion and diversity of
fossil types appeared with
major animal groups
(Arthropoda, Mollusca,
Echinodermata)
a. before that time, only
very few simple fossils
existed
6. Evolution of kingdoms
and phyla
Plantae
a. Monera  Protista 
Fungi
Animalia
Protista 
invertebrates
(animals with a
backbone) 
vertebrates
b. Protista 
Protostomes
(Arthropoda,
Mollusca, Annelida)
 Deuterostomes
(Echinodermata,
Chordata)
d. vertebrates: fish 
amphibians  reptiles 
birds
mammals
c. plants: protista 
chlorophyta (green
algae)  simple land
plants that reproduce
with spores
(Lycophyta, Bryophyta
- mosses)  land
plants with spores,
leaves, roots, and
stems (Pterophyta –
ferns)  higher plants
that reproduce with
seeds (Gingophyta),
cones and seeds
(Coniferophyta –
conifers, i.e. redwoods,
pines, cedars, junipers)
and flowers and seeds
(Anthophyta – oak,
tulip, rose, grass, etc.)
V. Taxonomy = Classification of
Living Organisms (Chapter 20)
A. Binomial nomenclature =
all living organisms are
assigned a two part name
consisting of the genus and
species written in latin
1. dog = Canis familiaris
2. wolf = Canis lupus
3. human = Homo sapiens
B. Organisms are placed into
taxa (groups) based upon cell
structure, complexity,
morphology, structures, and
possible evolutionary
relationships
C. Eight levels of
classification
1. eight categories
hierarchy
2. domains
3. kingdoms
D. Taxonomy (classification)
and evolutionary
relationships
1. evolutionary
systematics –
classification should
reflect both geneology
(common ancestry) and
genetic relationships
(shared genetic traits and
characteristics)
2. cladistics – taxa
(groups) should be
monophyletic containing
a common ancestor and
its descendants;
polyphyletic taxa with
several ancestors should
be broken up.
a. clade = common
ancestor and all the
groups descended from
it using a specific
characteristic
b. monophyletic – one
evolutionary “line”
c. polyphyletic – made up
of several evolutionary
“lines”
d. compares ancestral
(conservative) versus
derived or later
characteristics
e. utilizes cladograms to
show relationships
E.
Molecular systematics
1. compares order of
amino acids in specific
proteins (cytochrome C in
the electron transport
chain)
2. compares order of
nitrogen bases in specific
RNA (rRNA) and DNA
molecules (mtDNA)
3. molecular clocks can be
developed that utilize
changes in molecular
structure and/or mutation
rates to postulate
evolutionary rates of
change (5.1% change in
nucleic acid difference to
2.5 million years)
Human Evolution – Chapter 21
I. Classification of Humans
A. Kingdom
B. Phylum
C. Class
D. Order
E. Family
F. Genus
G. Species
II. Primates
A. Major characteristics
1. Mobile forelimbs and hind
limbs
2. binocular vision with
flattened face
3. reduced reproductive rate
– single birth
4. opposable thumb and in
some cases – big toes,
grasping “hands”
5. expanded, complex brain
with emphasis on learned
behavior
B. Prosimians vs anthropoids
1. prosimians – lemurs and
tarsiers
2. anthropoids – New World
monkeys, Old world
monkeys, hominoids – apes
and humans
a. Proconsul – ancestral
hominid (size of
baboon, brain = 165
cc)
b. Hominids = skeletal
features – spine, pelvis,
and limb bones; jaw
shape, brain size differ
from apes
c. Humans are most
similar in DNA and
other skeletal features
to apes
III. Evolution of Hominids
A. Australopithecines – evolved
and diversified in Africa
(gracile vs robust)
1. Australopithecus afarensis
(Lucy) – walked upright,
small brain (400 cc), sexual
dimorphism (males vs
females were distinct)
2. gracile forms (slight of
frame) are believed to be
more primitive to robust
forms (massive jaws,
stronger upper body)
3. Australopithecus africanus
and A. robustus (brain =
500cc)
B. Evolution of Humans
1. Genus Homo: main
features – brain size is
600cc or greater, jaw
similar to humans, face is
smaller and more flat than
humans, tool manufacture
and use seems evident
2. Homo habilis (brain = 775
cc)
3. Homo ergaster and H.
erectus (brain = 900cc)
4. Homo sapiens (modern
humans)
a. appeared 300,000 years
ago
b. multiregional continuity
vs out of Africa
hypothesis
c. Homo neanderthalensis
- archaic modern
human, 50,000 years
ago)
d. Cromagnon (Homo
sapiens) – brain size
(1300cc), 100,000 years
ago