Evolution
General Biology BI 04
Summer School Lecture Notes
Evolution
definition - change in gene
frequencies in populations over time
single, unifying theory in biology,
explains
origin of species,
diversity of organisms and their
relationships,
similarities and differences
among species,
adaptation to the environment
History of Evolutionary Theory
Ancient Greeks
Search for Natural Explanations
Plato
Essentialism, Eternal
harmony, Soul, Supernatural Creation
Aristotle
Purpose for every
organism, fixity of species, ladder of life
(scala naturae)
St. Augstine
nature has the potential to
produce and evolve
Middle Ages
Natural Theologians and
Creationism
Bishop Usher
Protestant Reformation and
Fundamentalism
Renaissance
Ray - catalogs/classifications
of species of plants and birds
Linne
Linnean Hierarchy (Kingdom,
Phylum, Class, Order ...)
Binomial epithet (genus
species: Homo sapiens or Homo sapiens)
Physicists, Astronomers break
with traditional beliefs (Galileo, Bacon, Descartes)
solar system debate - earth
versus sun as center of the universe
Kant - first ideas about the Big
Bang that created the solar system
1800's
Cuvier
dilemma of fossils, previous
ideas: fossils are examples of organisms growing out
of rocks, killed off by the Great flood
fossils, extinction,
catastrophism
Rise of Geology
Smith (principles of stratification), Lyell
and Hutton - uniformitarianism
Lamarck - introduces concept of change through
acquired inheritance, les sentiments interieur
Darwin
collected recent and extinct
specimens of organisms from all over the world during
voyages on the HMS Beagle
influenced by the fauna of
the Galapagos islands - Galapagos Tortoise, Galapagos Mockingbird and Galapagos Finches
studied materials back in
England
read Malthus' work on human
populations and famine
noticed the results of
artificial selection, sparked ideas about natural
selection
Accumulated evidence for
theory of evolution
geographic variation in
species, comparative anatomy, comparative
embryology, biogeography,
artificial selection,
classic example of the use of scientific method
and hypothetico-deductive method
1859 Linnean Society Meeting -
co-presentations of famous papers on evolution by
natural selection with Wallace
Wallace
studied animals of Malaysia
and surrounding archipelagos
read Malthus' work on human
populations and famine while being struck with
Malaria
1859 Linnean Society Meeting
- co-authors famous paper on evolution by natural
selection with Darwin
Darwin-Wallace theory of
evolution - basic tenets
evolution is change in
populations over time
mechanism of change is
natural selection, selects for most fit individuals
and against less fit
natural selection can occur
when
there is variation among individuals
some individuals are
better fit/adapted to their environment than
others
there are differences in
productivity, some individuals leave more
offspring behind in future generations than
others
evolution is gradual, takes
a long time, can't be observed in one person's
lifetime
Evidence for evolution
Emerging evidence - fossil
record and discovery of Archaeopteryx by Von Meyer,
missing link between birds and reptiles
Artificial
selection
domesticated
animals (e.g., dogs, cats, horses, cattle) and plants
comparative
anatomy - homology and vestigial organs
comparative
embryology
biogeography
taxonomy
Early 1900's - leads to the New
(neo-Darwinian) Synthesis
Mutationists
DeVries
Neo-Darwinian Synthesis -
Everyone gets together and explains how evolution
supports their ideas
Mathematicians
Hardy, Weinberg and the
Hardy-Weinberg Equilibrium
Fisher, Haldane, Wright
Pearson and statistics
Geneticists - Fruit Fly
Biologists
Morgan, Chetverikoff,
Dobzhansky
Evolutionists
Mayr and speciation
Paleontologists - Simpson
Botanists - Stebbins
Recent 1900's - leads to the
"Unfinished Synthesis"
1953: Watson and Crick -
discovery of DNA
Biochemical systematics
Immunology, Proteins, mtDNA,
cl DNA, nuclear DNA
DNA-DNA hybridization
Nei and genetic distances
PCR and genetic sequencing
Debate over whether natural
selection versus neutral evolution better explains change
in populations and leads to speciation
Study of adaptation-using
rigourous experimental testing versus idle-Darwininzing
Advances in paleontology -
debate over punctuated versus gradual equilibrium
Study of ancient DNA - molecular
paleontology
Hubble telescope and Big Bang
Advances in Embryology and
Development, links with genetics (hox genes turn on and
off developmental pathways)
New developments in systematics
and theory of taxonomy
Evidence for Evolution - Microevolution
Artificial
selection
dogs, cats,
horses, cattle, etc.
Some Genetic
Variation Maintained by Natural Selection
Sickle-Cell
Anemia
Disease affects shape of
hemoglobin molecule
Causes red blood cells
to assume irregular, elongated shapes
Molecules
form long, fibrous clumps that deform blood cell
Sickle-cell trait
Heterozygous, Ss
individuals
Produce few
sickle-shaped cells
Frequency of recessive
allele in various populations - geographic
distribution
Recessive allele
maintained at unusually high levels
Heterozygotes less
susceptible to malaria
Heterozygous women
more fertile than homozygotes
Environment acts to
maintain allele frequency
Selective force in
Africa is presence of malaria
Maintenance of
allele has adaptive value in Africa
No such selective
force in US black population
Selection acts to
eliminate allele in US
Peppered Moths and Industrial Melanism
European moth that rests
on trees during daytime
Prior to 1850 most had
light-colored wings
After 1850 most had
dark-colored wings
Possess dominant
allele
Allele rare in
populations until then
Observed dark tree
trunks in industrial areas
Dark moths less
conspicuous on their surfaces
Air pollution killed
light-colored lichens
Kettlewell hypothesis:
birds ate moths on trees
More dark moths
survived in polluted areas
More light moths
survived in unpolluted areas
Trends reversing due to
pollution controls
Lead Tolerance
Bent grasses grow on
lead mine refuse
Soils contain toxic
chemicals
Few plants survive
conditions
Comparison of plants in
pasture and mine refuse areas
Mine plants in
pasture soil survived but grew slowly
Mine plants in mine
soil grew well
Most pasture plants
in mine soil grew poorly if at all
Few exceptions that
grew well
Were of same
ancestral stock as mine plants
Genetic
predisposition to lead tolerance
Population change is
rapid when environment demands it
Adaptation
Documented cases of
adaptation exist as indicated above
More medical
examples
Darwinian
medicine - antibiotic resistance
(microorganisms, strains of the AIDS
virus)
Environment dictates
direction and extent of change
Evidence for Evolution - Macroevolution
The Fossil Record
Discovery of Archaeopteryx
Subsequent discoveries of
bipedal ancestors
Formation of fossils
Organisms buried in sediment
Calcium in bone and hard
tissue is mineralized
Imprints of dead organisms
Fossil bones
Example of sedimentary rocks -
Grand Canyon and other Canyons of the western US
Date of rocks reflects age
of fossils
Dating in Darwin`s day
solely by relative position
Recent dating uses more
accurate techniques
Measure rate of radioisotope
decay
Example - radioisotopes
and half-lives
Rate constant over time,
not affected by temperature or pressure
Fossils arrayed from oldest to
youngest
Provide evidence of
progressive evolutionary change
Examples
Hoofed mammals
Horse evolution
Human evolution
The Molecular Record
Progressive evolutionary
change implies a change within DNA
Result from accumulation
of genetic changes
Distant relatives have
greater number of differences
Comparison of DNA sequences
between organisms
Greater time since
divergence associated with more nucleotide
changes
Example: cytochrome c
Example: hemoglobin
Phylogenetic tree
Pattern of genetic
descent
Determined by comparing
nucleotide sequences
Often similar to
relationships predicted by anatomy
Homology
Structures derived from
common form, but functions are variable
Example: forelimbs of
mammals
Development
Evolutionary history
reflected in development of embryo
Embryo exhibits
characteristics of its ancestors` embryos
Example: human
development
Possess
fish-like gill slits early in development
Exhibit tail,
its vestige becomes coccyx
Possess fine fur
during fifth month
Example:Other
Vertebrate embryo comparisons
Vestigial Structures
Structures with no
apparent function resembling those of presumed
ancestors
Examples
Human ear muscles
Whale pelvic bones
Four-footed
"missing link" whales
Human vermiform
appendix
Convergent Evolution -
Unlikely that similarities result from coincidence
Community level
Different areas may
possess very distantly related communities
with similar appearance
Species level
Pleiosaur - fusiform
shape
Example: forms of
Australian marsupials
Examples: albinism
and blindness in cave-dwelling organisms
Systematics and
Classification and Comparative Anatomy
Patterns of imilarities
among organisms and their classification strongly
suggests evolutionary origins
Patterns of Distribution
Continent - Island
Organisms on islands
most closely resemble forms on nearest
continent
Forms not identical,
but diverged over time
Example: Galapagos
Finches, Hawaiian Honeycreepers
Continent
Biogeographic realms
Interesting resources on Evolution
versus Creationism debate
15 Answers to Creationist Nonsense
National Center for Science Education
Science and Creationism: A View from the
National Academy of Sciences
Talk/Origins Archive
Pope John Paul II's Message to Pontifical
Academy of Sciences on October 22, 1996
Microevolution
definition - evolution at the level
of populations within species, changes in gene frequencies in
populations
gene
frequencies in populations
frequency of homozygote dominant
individuals - f(AA) = number of homozygote dominant
individuals/total population size
frequency of heterozygote
individuals - f(Aa) = number of heterozygote
individuals/total population size
frequency of homozygote
recessive individuals - f (aa) = number of homozygote
recessive individuals/total population size
frequency of dominant alleles -
f(A) = total number of A alleles/total number of alleles
frequency of recessive alleles -
f(a) = total number of a alleles/total number of alleles
Hardy - Weinberg Eaquilibrium
definition - no changes in gene
frequencies when there are no agents (mutation,
migration, natural selection, assortative mating, genetic
drift) of evolution acting on a population
Derivation and some problems
| MATING |
FREQUENCY OF MATINGS |
OFFSPRING |
OFFSPRING |
OFFSPRING |
| |
|
AA
|
Aa
|
aa
|
AA x AA
(p2)(p2)
|
p4
|
p4
|
|
|
AA x Aa
(p2)(2pq)
|
2p3q
|
p3q
|
p3q
|
|
AA x aa
(p2)(q2)
|
p2q2
|
|
p2q2
|
|
| |
|
|
|
|
Aa x AA
(2pq)(p2)
|
2p3q
|
p3q
|
p3q
|
|
Aa x Aa
(2pq)(2pq)
|
4p2q2
|
p2q2
|
2p2q2
|
p2q2
|
Aa x aa
(2pq)(q2)
|
2pq3
|
|
pq3
|
pq3
|
| |
|
|
|
|
aa x AA
(q2)(p2)
|
p2q2
|
|
p2q2
|
|
aa x Aa
(q2)(2pq)
|
2pq3
|
|
pq3
|
pq3
|
aa x aa
(q2)(q2)
|
q4
|
|
|
q4
|
Offspring:
f(AA) = p4 + 2p3q
+ p2q2= p2 (p2+
2pq +q2)
f(Aa) = 2p3q + 4p2q2
+ 2pq3 = 2pq (p2 + 2pq +q2)
f(aa) = p2q2
+ 2pq3 + q4 = q2 (p2 + 2pq +q2)
Fundamentals:
f(A) = p
p + q = 1
f(AA) = p2
f(a) = q f(Aa) = 2pq
f(aa) = q2
(p2+ 2pq +q2
)= 1
Problems - Calculating gene
frequencies (from Strickberger 2000, page 519)
What are the gene
frequencies in the following population: p=freq
of T=? and q=freq of t =?
90 TT, 60 Tt, 50 tt =
200 individuals and 400 total genes (200 x 2)
freq(T) = (90x2) + 60
(1) divided by 400 = (180+60)/400 = .60
freq(t) = (50x2) + 60
(1) divided by 400 = (100+60)/400 = .40
Problems - Calculating the
HW Equilibrium frequencies
What are the HW EQ
frequencies in a population where 25% of the
population contains the recessive phenotype?
q2 = .25
q = .5
p = 1 - .5 = .5
Algebraic Frequencies
|
Expected Frequencies
|
p2
|
.5 (.5) = .25
|
2pq
|
2 (.5)(.5) = .50
|
q2
|
.5 (.5) = .25
|
Problems - Calculating the
HW Equilibrium frequencies
What are the HW Eq
frequencies for the following population of
plants with different colored flowers?
Is the population in HW
Equilibrium?
63 red (RR), 294 pink
(Rr) and 343 white (rr) = 700 plants, 1400 genes
or alleles
| Genotype |
Number
in RR |
Number
in Rr |
Number
in rr |
Total |
Frequency |
| R |
2x63=126 |
294 |
0 |
420 |
420/1400
= 0.3 |
| r |
0 |
294 |
686 |
980 |
980/1400
= 0.7 |
| Genotypes |
Algebraic Frequencies
(see
above)
|
Observed Frequencies
and
numbers
|
Expected Frequencies
and
numbers
|
RR
|
p2
|
63/700 = .09
|
p2 = (.3)(.3)
= .09
.09
(700) = 63
|
Rr
|
2pq
|
294/700 = .42
|
2pq = 2(.3)(.7) = .42
.42
(700) = 294
|
rr
|
q2
|
343/700 = .49
|
q2=
(.7)(.7)=.49
.49(700)
= 343
|
Problems - Is a population
in HW Equilibrium
Is the population below
in HW Equlibrium?
50 individuals (AA), 50
individuals (Aa), 50 individuals (aa), 300
alleles
| Genotype |
Number in RR |
Number in Rr |
Number in rr |
Total |
Frequency |
| A |
2x50=100 |
50 |
0 |
150 |
150/300 = 0.5 |
| a |
0 |
50 |
2x50=100 |
150 |
150/300 = 0.5 |
| Genotypes |
Algebraic Frequencies
(see
above)
|
Observed Frequencies
and
numbers
|
Expected Frequencies
and
numbers
|
AA
|
p2
|
50/150 = .33
|
p2 = (.5)(.5)
= .25
.25
(150) = 37.5
|
Aa
|
2pq
|
50/150 = .33
|
2pq = 2(.5)(.5) = .50
.50
(150) = 75
|
aa
|
q2
|
50/150 = .33
|
q2 = (.5)(.5)
= .25
.25
(150) = 37.5
|
Agents of evolution
Genetic Drift - random fluctuations of genes in
populations,
What causes drift
Factors - founder
population - small sample of population leaves
and colonizes new area
Example: Founder
effect - plant seeds on seabirds
Other Founder
Examples
Afrikaner
Population in South Africa (Dean
1972, Hayden 1981) 20 families are
descendants of current populationhigh
incidence of porphyria (problems with
barbiturates) and Huntington's
disease
Human
populations on Islands of Tristan de
Cunha - founded by 15 individuals -
high incidence of retinitis
pigmentosa (leads to blindness)
Kidd and
Cavalli-Sforza (1974) - cattle in
Iceland versus mainland Europe,
brought over by the Vikings, exhibit
different frequencies
Buri (1956)
- brown alleles
in Fruit Flies changed over a few
generations, each new generation was
started by a founder of 8 males and 8
females, lead to elimination and
fixation in different lines of flies
Factors - bottleneck
effect - population size is reduced by external
factors
Example: Bottleneck effect
Cheetah in Africa
Bonnel and
Selander (1974) - Northern Elephant Seal
populations depleted by overhunting,
exacerbated by harem system of mating,
leads to lack of genetic variation in
today's population
Migration - gene flow between
populations
Effects on populations
changes gene
frequencieshomogenizes populations (makes different
populations more similar to each other)
Examples from the literature
Glass and Li (1953) -
studied Rh alleles in humans (white and
African-Americans)
Mutation - old alleles change into new
alleles
Occurs at 2 levels - genic level
and chromosomal level
Chromosomal level mutations
Deletion - loss of a segment
Fusion - addition of a
segmentInversion - reversal of a segment
Aneuploidy - loss or
addition of chromosomes due to non-disjunction during
meiosis
Genic level mutations -
exchanges or substitutions of nitrogenous bases (Purines
- A, G; Pyrimidines - C, T)
Transition
substitution of purine
for a purine - see bold text (G for A)
ATCG
- GTCG
substitution of
pyrimidine for a pyrimidine - see bold text (C
for T)
ATCG
- ACCG
Transversion
substitution of
pyrimidine for a purine or vice-versa - see bold
text
ATCG
- TTCG
Frameshift mutation - loss
or addition of a nitrogenous base in a gene sequence
addition - ATCG - AATCGloss
- ATCG - ACG, lost T
Consequences of mutations
Silent mutation - change
does not affect amino acid sequence of protein
production
Missense mutation -
alters amino acid sequence
Nonsense mutation -
turns off protein production
Summary of Examples from the
literature
3 Types of Studies of
Mutation in the Literature
1) Neutral mutations2)
Deleterious mutations3) Adaptive mutation
Assortative mating - non-random mating
Types
+ Assortative Mating: Inbreeding
- like x like individuals
- Assortative Mating:
Outbreeding - like x unlike individuals
Consequences of Inbreeding
1) Harmful - increase the
chances of 2 deleterious or lethal alleles coming
together
2) Harmless - occurs in many
species of plants that undergo selfing
Examples of Inbreeding from the
literature
Stone (1963), Dobzhansky (1963),
Mettler et al. (1963) - inbreeding depression in Fruit
Flies, numbers are % survival rates
| Species |
Distant cousins |
Closely related |
Sibling |
| 1 |
90 |
75 |
65.5 |
| 2 |
90.2 |
83.2 |
80.5 |
| 3 |
84.3 |
|
63.5 |
Crow et al. (1956) - incidence
of problems in human births
| Problem |
1st cousin |
2nd cousin |
unrelated |
| still birth |
.09 |
.06 |
.03 |
| infant death |
.14 |
.09 |
.07 |
Spuhler (1968) - human mating
preferences (tall females preferred tall males)
Anderson (1982) - widow birds
females showed preferences for males with longer tails
Moller (1989) - similar pattern
in Barn Swallows
Natural Selection
Natural Selection - survival of the
fittest
Conditions under which natural
selection can occur
genetic variation among
individualsdifferential survivaldifferential
reproductive success
Non-evolutionary variation
seasonal, age, sexual
Examples of genetic variation
among individuals
Individual variation - birds
(Harris' Sparrows, Ruddy Turnstones)
Polymorphism - Map
butterflies
Balanced Polymorphism
Heterozygote advantage
and sickle-cell anemia
Geographic variation
Well defined subspecies
or races - Fox Sparrows, Song Sparrows, Northern
Juncos
Clinal variation
Bergmann's rule
- animals in colder climates tend to be
larger, decrease ratio of surface to
body mass
(volume) and conserves heat
Allen's rule -
animals in colder climates tend to have
smaller extremities, decrease ratio of
surface to
body mass (volume) and conserves heat
Gloger's rule -
animals in the tropics tend to be more
colorful while organisms in colder
environments tend to be paler
Maintaining variation in
populations
recombination - mixing of
chromosomes and genes during meiosis
crossing over - eschange of
chromosome pieces during meiosis I (prophase I)
mutation - chromosome and
genic level mutations
heterosis - heterozygote
advantage as in sickle-cell anemia
What is the struggle in the
environment against?
Abiotic factors - physical
aspects of the environment
Climate - precipitation,
wind, humidity, temperature, etc.
Other - altitude,
daylength, water depth, water chemistry, tides,
etc.
Biotic factors - biological
aspects of the environment
parasitism, predation,
competition, etc.
Types of selection
Directional Selection -
selection for a particular genotype
Examples from the literature
Ricker (1981) - Pink
Salmon decrease in size over time with fishing
Kettlewell (1954) -
Pepper Moths
Wood (1981) - DDT
resistance and insects
Antonovics (1971) -
plants and heavy metal resistance near mines
Hirschberg and McIntosh
(1983) - weed resistance to herbicides (triazine)
Boag and Grant (1981) - Galapagos Finches (during drought, body size of
birds increased)
Stabilizing Selection -
selection against extreme individuals and for the average
phenotype
Examples from the literature
Bumpus (1899) - House
Sparrows near Woods Hole, MA
Karn and Penrose (1951) -
birth weight in human babies
Rendel (1953) - duck eggs
parallel human birth weight results
Hecht (1952) - lizard size
affected by predation versus territorial defense
Mason (1964) - milkweed
butterflies (less variable males performed most of
the matings)
Disruptive Selection - selection
for extreme phenotypes and agains the average phenotype
Examples from the literature
All cases of Batesian
mimicry
Ford (1975) - multiple
phenotypes of the Swallowtail Butterfly
Thoday and Gibson (1962)
- laboratory example, selected for extreme Fruit
Flies
Remington (1954) - field
study of the Sulfur Butterfly (orange-winged
versus white-winged morphs)
Other Types of Natural Selection
Frequency Dependent
All cases of Batesian
mimicry - too many mimics spoils the program and
predators find outAll cases of Mullerian mimicry
- the more the merrier, more toxic mimics of each
other - the faster the predators find out
Clark (1962) - when
morphs reach a certain level in the population
they are selected against by fish predation
Ehrman (1968) - rare
male Fruit Fly achieves the most matings
Sexual selection
first described by
Darwin as a mechanism that leads to sexual dimorphism in a speciescould be due to
female mate choicecould be due to result of male
versus male interactionsother (e.g., exploitation
of different feeding niches)
Species and Speciation
Species concepts
Biological Species Concept:
Species are groups of interbreeding natural populations
that are reproductively isolated from other such
populations.
emphasis: reproductive
isolation
problems: universal
application - unisexual species, paleospecies and the
temporal dimension
Ecological Species Concept: A
species is a lineage (or closely related set of lineages)
which occupies an adaptive zone minimally different from
that of any other lineage in its range and which evolves
separately from all otherlineages outside its range.
emphasis: natural selection,
co-adapted genes and ecological niche
problems: ignores other
agents responsible for evolution
Cladistic/Phylogenetic Species
Concept: A species is the smallest diagnosable cluster of
individual organisms within which there is a parental
pattern of ancestry and descent.
emphasis: diagnostic
characters
problems: elevating too many
subspecies to species level
Pluralistic Concept -
combination of the above, criteria are applied
differently to different species' situations
Speciation - origin of new species
Allopatric speciation:
differentiation of geographically isolated populations
into species
Geographical or Continental Speciation
Example: North American Orioles
Mengel's (1964) species
groups of North American Warblers
Nashville Group
Connecticut Group
Black-throated Green
Group
Yellow-rumped Group
| Yellow-rumped
Warbler - Audubon's Warbler
|
Rocky
Mountains |
| Yellow-rumped
Warbler - Myrtle Warbler
|
boreal
US and Canada |
| Grace's Warbler |
sw US |
| Virginia's
Warbler |
se US |
Rising (1983)
Meadowlarks
Orioles
Northern Flickers
| Yellow-shafted
Flicker |
eastern
North America |
| Red-shafted
Flicker |
western
North America |
Buntings
Grosbeaks
Salamanders in
California - invasion of species into California
from Oregon, split by mountain ranges to form
ring species, southern populations are incapable
of breeding with northern populations and are
considered separate species
Quantum Model - peripheral
isolates become founder populations
Archipelago = Island Speciation
Bock (1970) -
Hawaiian Honeycreepers
Darwin (1859) - Darwin's Finches
Carson (1992) - Hawaiian Drosophila
Sympatric speciation: splitting
of populations in a common area into species
Instantaneous
Polyploidy
autopolyploidy - results from members of
the same species
failure of
chromosomes to separate during meiosis in
males and females, results in tetraploid
(4N) individuals
allopolyploidy - results from members of
different speciesExample: plant hybridization
Lewis and Lewis
(1955) - plant genus Clarkia primitive
species, 2N are 7 and 8 chromosomesadvanced
species, 2N are 18, 16, 15 chromosomes
(probably 4N)
In each case,
polyploid individuals are capable of breeding
with each other but not backcrossing with
parents -due to chromosome # problems
Other examples
Tragopgon weeds
in the Pacific northwestern US
Wheat used for
bread - allopolyploid between cultivated
wheat and wild grass
Gradual model - multiple
niche polymorphism
Boiler and Bush (1973) -
host switching by parasites
Tauber and Tauber (1989)
- lacewing insects: C. carnea feeds on deciduous
trees, C. downsei feeds on conifers
Bush (1969) - Rhagoletis
Fruit Fly species - rapid host shift from
Hawthorn trees to Apple, Cherry, Pear, etc.
occurred over last 100 years
Isolating
Mechanisms - keep species apart
Prezygotic Isolating Mechanisms
Ecological isolation - Same
area, but different habits and habitats
Thamnophis garter snakes
separated by habitat preferences
aquatic species
terrestrial species
Temporal isolation - Breeding
periods at different times
Spotted Skunks
Eastern species breeds
in late winter
Western species breeds
in late summer
Three species of Dendrobium
orchids breed in rainforest on different days
Behavioral or Ethological
isolation - Species specific mating rituals
Stein (1960's) - Empidonax
flycatchers
Trail's Flycatcher
divided into Willow and Alder Flycatchers based on song
differences also
includes Acadian, Least, Yellow-bellied Flycatchers
Fish
Crow and American Crow
Lanyon (1957, 1962) - Eastern and Western Meadowlarks in the United States
Pitocchelli (1990) -
Mourning and MacGillivray's Warblers
Sex Pheromones in insects
and mammals
Hawaiian Drosophila
Fireflies - different signal
patterns for different species
Cricket song and female
choice
Mechanical isolation - General
structural differences in genitalia or other structures
prevent interbreeding
Dufour (1844) - lock and key
relationship of male and female genitalia in some
insects
Dodson (1967) - orchid
species: flowers of some species mimic female insects
of certain bees and wasps, encourages
pseudo-copulation and pollination
Gametic Isolation - Prevention
of gamete fusion, Sperm not attracted to eggs of other
species, Sperm incapable of penetrating eggs
Postzygotic Isolating Mechanisms
3 types
Hybrid inviability - embryos
die early
Hybrid sterility - adults
are somatically vigorous but can not reproduce
Hybrid breakdown - adults
are somatically vigorous and can reproduce but future
offspring fail to reproduce
Macroevolution - evolution above the
species level
How do higher taxa (categories above
the species level - genera, families, orders, phyla, et.)
evolve?
Timing - tempo of evolution
above the species level
Gradualism - long time
Punctuated equilibrium -
short spurts of evolution followed by stasis
Origin of evolutionary novelties
- how do new features evolve
Allometry - different
parts of the body have different growth rates, leads to shape changes
Heterochrony - timing of
growth changes in different parts of the body, some
parts grow while others do not or grow later:
Example: Ground-dwelling
versus tree-dwelling salamanders, Tree-dwelling
species have shorter feet, growth of the feet was
controlled by turning off genes involved in
growth
Example: Paedomorphosis
- incorporation of adult sexual features into
larval or immature forms, sexual organs continue
to develop while the rest of the body does not
Example:Neoteny - retain
traits of immature stages in the adult
Homeotic changes or
mutations - gross aberrations in development and
growth patterns, growth of body parts and position of
body parts found inHox genes, mutations could result
where cells lose positional information
Example - antennapedia
mutation in Drosophila - leg grows in place of an
antenna
Interesting trends in
macroevolution
Horse Evolution: woodland
browser to grazer on the open savanna
4 toes and clipping
teeth to one toe and grinding teeth
Human Evoltuion: arboreal
tree climber - edge species (knuckle walker) -
bipedal movement on the savanna
Evoltuion of the vetebrate
jaw - from gill arches
Evolution of the mammalian
ear - from jaw and skull bones
Evolution of size -
titanotheres
All of the above examples -
due to chance, random changes in the environment, not
goal-directed
Fossil - term coined by Agricola
in the 16th century, derived from fossilis - to dig up
Modern Definition of fossils
Stahl (1985) - "Every
trace of the physical existence of an extinct
organism is considered a fossil and
regarded as potentially
helpful in determining the history of an ancestral
line."
Examples of fossils
fossilized bone, animal body
parts, plant parts, etc.
imprints of organisms or
their body parts
footprints
burrows
corprolites - fossil feces
eggshells and nest imprints
wounds or other damage
caused by predators are left on some organisms
fossil remains in the
intestines of organisms
gastroliths - fossil gizzard
stones in some reptiles
fossil insects in amber
Processes of fossil formation
sedimentation - organisms
die near shorelines or wet areas, become buried in
mud and covered by silt and sediments
cold storage: frozen fossils
- frozen in ice (Wooly Mammoth, ICE MAN)
petrification
mineralization -
minerals seep into tissues or hollow spaces of
bones (silica or calcium carbonate
amber = chemically altered
resin of ancient trees
bogs - aseptic preservation
in water hostile to bacteria and other organisms
tar pits - organisms caught
and drown in tar pits, become covered over
waxy hydrocarbon covering
caused by oil flows
mummification
lava flow catches an
organism
dessication or sandstorms in
the desert
Limitations of the fossil record
bias towards organism
preserved by sedimentation, living near water
Dating Fossils
Radiometric dating - decay
of radioactive materials (decay at a constant rate)
Carbon 14 method - ratio of
C14/C12, c14 has a half life of approximately 5,600
years, used for rocks approximately 50,000 years old
Uranium (U238 isotope) -Lead
(PB 206) method - calculate the ratio of
lead/uranium, 1/2 life of 4.5 billion
years, used to age rocks
in billions of years
The moving crust - plate
tectonics
crust floats/moves over the
mantle
lava floats up to the
surface and moves plates/continents apart
2 adjoining plates
slides past each other (Pacific plate carrying
section of California northward along the San
Andreas fault)
2 plates collide, one
plates goes under the other (Pacific plate
plunges into the mantle where it meets the North
American
plate at the
Aleutian Islands, causes volcanic activity
and uplifting or mountain building - Aleutian
Islands, Andes
Mountains where
Pacific plate meets and plunges under the
American plate in South America)
Major land masses
Pangea - oldest, all
continents connected
Laurasia - split of
Pangea, this contained the northern
continents
Gondwanaland - split
of Pangea, this contained the southern
continents
Systematics -study of evolutionary relationships of
organisms
Taxonomy - Science of biological
classification of organisms
Goals of Taxonomists
1) Reveal evolutionary
relationships between organisms
2) Describe pattern of
evolutionary relationships from primitive to advanced
3) Find ancestors along with
input from paleontology
4) Constantly re-evaluate
previous classifications
Current System: The Taxonomic/Linnaen Hierarchy for a Biological Classification
Characteristics of the
system
System Is Hierarchical
Binomial Classification
What is a classification?
Classification is a system
with categories that contain similar organisms which
descended from a common ancestor, reflects a
phylogeny or genealogy, reconstruction of
relationships among taxa and groups they belong to
A classification is also
considered to be a monophyletic group of taxa
Composed of Categories
Examples
Kingdom, Phylum,
Class, Order, Family, Genus, Species
Categories are arranged into a hierarchy with most
inclusive group at top and least inclusive at the bottom, For each category
there are many taxa (in parentheses) that organisms belong to, Below is
an example of the classification for humans)
Example
Kingdom (Animalia)
Phylum
(Chordata)
Class
(Mammalia)
Order
(Primates)
Family
(Hominidae)
Genus
(Homo)
Species
(Homo sapiens)
Taxon - formal name for each
category
Examples
Animalia, Chordata,
Mammalia, Primates, Hominidae, Homo, Homo
sapiens
Printing conventions
Genus capitalized, species
not capitalized
Both genus and species
italicized or underlined
All other taxonomic unit
names capitalized, but no distinctive print style
How are classifications produced
Homology
Fundamental concept to
evolution and classification
Definition - a structure
possessed by members of 2 or more taxa that was
shared by a common ancestor
Examples
Individual bones
of the vertebrate forelimb - humerus,
radius, ulna, carpals, metacarpals,
digits (or phalanges) - each are
homologous structures found in many
vertebrates
bones of the
pelvic girdle of vertebrates (illium,
ischium, pubis)
Chitinous
exoskeleton of arthropods
Feathers of
birds
Hair and mammary
glands of mammals
Types of characters used in
taxonomic research
Qualitative characters
(qualities of an organism's phenotype)
Behavioral characters
Quantitative characters
(measurements)
Biochemical genetics
Immune responses
(antigenic distances), allozymes, nuclear
DNA, mtDNA, clDNA, other
Assess character state
primitive - reveals
evidence of the ancestral condition
derived - reveals
evidence of recent modification
Schools of Taxonomy
Phenetics
use of mathematical
measures of similarity - produces a similarity
matrix between taxa
| Taxa |
A |
B |
C |
| A |
- |
.7 |
.2 |
| B |
|
- |
.2 |
| C |
|
|
- |
uses as many characters
as possible (don't worry about convergence)
produce dendrogram
depicting relationships, uses various clustering
algorithms, based on the similarity matrix
Example - Schnell (1970)
produced classification of Charadriiform birds
based on external and skeletal measurements
problems - too much
emphasis on total similarity, can not handle
convergent or parallel traits
Cladistics or Phylogenetic
Systematics
uses homologous
characters and rigorous character analysis
primitive characters
= pleisiomorphic
derived characters -
apomorphic
determined by
character polarization - finding out which
one is primitive versus derived
Methods - compare
with the fossil record, outgroup comparisons, other
use of shared, derived
characters (synapomorphies) that define groups,
produce cladograms
Example - vertebrate evolution
Evolutionary classification
(being replaced with Cladistics)
mix of both
philosophies, use homologous characters and
emphasize overall similarity, emphasizes the
amount of morphological change during
construction of phylogenetic relationships
uses shared derived
characters, uses overall similarity in assessing
taxonomic rank
problems - character
weighting plays an influential role in defining
taxa
Origins
Summary of major events
| Timing |
Event |
| 11 - 20 BYA |
Big bang |
| 4.5 BYA |
Origin of the earth |
| 3.5 BYA |
Appearance of the first
prokaryotic organisms |
| 2.1 BYA |
Appearance of the first
eukaryotic organisms |
| 540 MYA |
Cambrian Explosion |
| 5 MYA |
Ape-like
ancestors of humans |
Origin of the Universe
Cosmology - study of the origin
of the universe
Big Bang - Big Bang - single
origin, expanding universe, time has a single
beginning and the universe will eventually end in a
single collapse, 11 - 20 BYA - big bang (all matter
is condensed into a small area, followed by an
explosion Immediately after explosion - fusions of
small atoms into larger atoms 10 BYA - galaxies form,
stars are formed and are burning, some explode into
supernova Hale-Bopp - one example of a piece of the
big bang floating around the universe
Oscillating Universe -
series of big bangs, time has no beginning and no
end, time is infinite, universe oscillates between
expansions contractions (big crunch), contractions
caused by gravity which can reverse expansion of
matter
Steady State - unchanging
universe except that as hydrogen diminishes in supply
it is replaced by hydrogen from an unknown source,
at higher levels - old galaxies
are replaced by new galaxies
Origin of the Planets and
Solar Systems
Collision theory - a
second star nearly collided with our sun and its
gravity pulled out materials from the sun which
eventually became the protoplanets Dust cloud or condensation theory
- large condensing mass of material in the center
of a cloud became the sun, peripheral masses
never reached critical temperatures to becomes
suns, instead became protoplanets
Earth Formed 4.5 Billion
Years Ago
5 BYA - origin of our
solar system and the Milky Way Galaxy
Particles revolve around
a proto-sun
Dust condenses
asteroid belts
planetessimals - collide
and compress
4 BYA - planets form and
revolve around the sun
Earth's atmosphere -
dominated by hydrogen, methane, water, ammonia,
nitrogen, carbon monoxide
Where did oxygen
come from?
- UV
irradiation of water in the upper
atmosphere, split water into
hydrogen and oxygen
- 2 - 3 BYA,
appearance of first autotrophs -
blue-green algae
Earth as it is today
The moving crust - plate
tectonics
crust floats/moves over the
mantle
lava floats up to the
surface and moves plates/continents apart
2 adjoining plates slides
past each other (Pacific plate carrying section of
California northward along the San Andreas fault)
2 plates collide, one plates
goes under the other (Pacific plate plunges into the
mantle where it meets the North American plate at the
Aleutian Islands, causes volcanic activity and
uplifting or mountain building - Aleutian Islands,
Andes Mountains where Pacific plate meets and plunges
under the American plate in South America)
Major land masses
Pangea - oldest, all continents connected
Laurasia - split of Pangea, this contained the northern continents
Gondwanaland - split of Pangea, this contained the southern continents
Origin of Life - Early Ideas
1) Spontaneous generation - life
from inanimate materials
2) Experimentation
Redi - showed that animals could
not arise from inanimate materials using dead fish
Pasteur - showed that
microorganisms could not arise from inanimate materials
Origin of Life 5 Hypothetical Stages -
Hypothetical Sequence
1) Formation of organic molecules
from inorganic materials - abiotic synthesis of organic
compounds
(Oparin - Haldane model,
confirmed by Miller-Urey experiments)
reducing atmosphere, energy,
water = environment
Panspermia - organic molecules
could have come from outer space, Murchison meteorite
contained amino acids that did not originate on earth,
all amino acids were very similar to ones produced in the
Miller-Ureyexperiments
2) Polymerization of organic
molecules to make more complex compounds
dehydration synthesis needs
energy and concentrating organic compounds - cyanic
condensing agents (cyanamide, cyanogen, cyanic acid,
etc..) produce peptide bonds in aqueous solutions, could
have occurred on clays
anhydrous production - heat can
remove water in the absence of condensing agents
3) Formation of a barrier to
separate inside of proto-cell from outside, could have formed
through membranous droplets or vesicles
Types
coacervates - colloidal
particles separate out of solution into droplets
under certain conditions (temperature, pH, etc.),
electrically charged water molecules become tightly
bound to charged molecules and or charged particles,
water molecules form a film-like barrier, separates
internal chemistry of the droplet from the outside
(Oparin 1957, 1971)
proteinoids - dry amino
acids can be polymerized, forming protein-like
molecules (proteinoids) when heated and allowed to
cool in water, coolling water can produce
microspheres which separate out of solution,
microspheres have two-layered boundary which is
osmotically active, are gram - when stained, internal
chemistry of the droplet from the outside, can
undergo processes similar to fission and budding
under certain conditions (Fox 1965, 1980)
liposomes - protocells with
a phospholipid bilayer membrane, under certain
conditions (addition of proteins, etc.) boundary
becomes increasingly selectively permeable
Importance to evolution of life
selective permeability
isolation of external and
internal environment
small size increases
probability of chain reactions inside the cell
(products of one reaction can be the reactants of
another)
membranes could have
incorporated peptides which acted as channels or
pumps for other molecules, moving them in and out of
the droplet
4) Production of enzymes necessary
for energy in chemical reactions that take place inside a
cell but proteins are made from instructions from RNA which
receive instructions from DNA (transcription and translation)
- where did the catalysts come from? First - need a
self-replicating system
Probable answers: 1) rRNA
replicates itself and controls chemical reactions without
help of other proteins, RNA world, based on work by Cech
(1987), found that rRNA could make copies of itself
without the help from proteins
Probable answers: 2) proteins or
protein-nucleic acid combinations
5) Evolution of metabolism
pattern, based on comparative
studies, indicates that anaerobic metabolism preceded
aerobic metabolism,
reactions that break down high
energy carbon compounds similar to anaerobic glycolysis
may have been primitive percursors, had to occur under
anaerobic conditions because there was little oxygen in
the atmosphere, predetermined by the abundance of small
molecules available, later pathways evolved to handle
larger molecules, eventually gave rise to the Krebs cycle
some protocells switched to reduction reactions with
CO2 using H2S
and later H2O as electron sources, released
them from a dependence on organic compounds as a source of energy, although
still heterotrophs - this transition could have lead to the evolution of
photosynthesis, photosynthesis creates an aerobic environment and organisms
that have produced their own sugars which could be made available to other
organisms, provides opportunity for evolution of the Krebs cycle and create
more energy from the breakdown of glucose in advanced heterotrophs
Experimental Recreation of Origins
Miller and Urey hypothetically
repeated process
Miller and Urey Apparatus
Similar atmosphere over liquid
water
Temperature 100%C with sparks of energy
Methane formed carbon compounds
Formaldehyde, hydrogen cyanide
Further combined into formic acid, urea
Later experiments produced carbon compounds
Amino acids: glycine, alanine, valine, proline, glutamic, aspartic acids
Adenine produced, one of the bases found in DNA and RNA
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Pitocchelli. All rights reserved. The contents of this page are
the intellectual property of Dr. Jay
Pitocchelli for distribution to
students enrolled in General Biology BI 04 at Saint Anselm
College. These pages may not be copied, photocopied, reproduced,
translated, or published in any electronic or machine-readable
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