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Evolution
Evolution
BASIC: change over time
BIOLOGY: change in the gene frequency of a
population over time
- individuals do not evolve
- changes in the population accumulate
and eventually lead to change
TYPES of Evolution
Microevolution: change in the gene pool
(genetic content) of a population
EX: normal variations
Macroevolution: change on a large scale
leading to new and different species
EARLY THEORIES
CONTRIBUTING TO DARWIN
Hutton: gradualism
- slow happenings of geology
Lyell - geologist - uniformitarianism
- geological systems are constant
Lamark: inheritance of acquired traits and use and
disuse
- individuals acquired traits would be passed
down to the next generation - USE AND DISUSE
EX: giraffe
blacksmith
- disproved: mice and tails
Linnaeus (classification)
Hutton (gradual geologic change)
Lamarck (species can change)
Malthus (population limits)
Cuvier (fossils, extinction)
Lyell (modern geology)
Darwin (evolution, natural selection)
Mendel (inheritance)
American Revolution
1750
Wallace (evolution, natural selection)
French Revolution
U.S. Civil War
1800
1850
1900
1795 Hutton proposes his theory of gradualism.
1798 Malthus publishes “Essay on the Principle of Population.”
1809 Lamarck publishes his theory of evolution.
1830 Lyell publishes Principles of Geology.
1831–1836 Darwin travels around the world on HMS Beagle.
1837 Darwin begins his notebooks on the origin of species.
1844 Darwin writes his essay on the origin of species.
1858 Wallace sends his theory to Darwin.
1859 The Origin of Species is published.
1865 Mendel publishes inheritance papers.
Figure 22.2
DARWIN
- HMS Beagle & Galapagos
- collected different species - noticed
similarities to other species on other islands
and South American species
CONCLUSION: new species could arise from
an ancestral form by the gradual
accumulation of adaptations to a different
environment
DESCENT WITH MODIFICATION
CLASSIC: FINCHES
- big beaks and little beaks
- big seeds in dry
- little seeds when wet
Driving force: Natural Selection and
Adaptation (survival of the fittest)
- those that survive get to breed and pass
on their traits
POINTS of Natural Selection
1. great potential for reproduction
2. populations remain stable in size
3. resources are limited in size
RESULT: competition for resorces
4. variation in population
5. variation mostly due to genetic recombination and
inheritance
RESULT: survival dependent on better suited
characteristics
RESULT: better characteristics get passed on to next
generation
THUS: Organisms are “shaped” into those that best fit the
environment
ARTIFICIAL SELECTION: analogous evidence
choose traits and breed them
- in the wild? Artificial selected traits revert
back to wild type
Terminal
bud
Lateral
buds
Brussels sprouts
Cabbage
Flower
cluster
Leaves
Cauliflower
Kale
Flower
and
stems
Broccoli
Stem
Wild mustard
Figure 22.10
Kohlrabi
KEY POINTS:
only populations evolve - cumulative
change over a period of time
only heritable traits are amplified or
diminished
Evidence for Evolution
Keep in Mind:
Theory and logic are not the same as evidence.
Real evidence only has one interpretation
Not all Truth is Factual.
“Truth takes time.” – Irina Derevko
EVIDENCE OF EVOLUTION
1. Biogeography
- species of nearby areas populate those around it
- evolution of a species is going to be based on what
was near it
EX: South American species are going to be
more like North American than Australian
Evidence:
Fossil record
- present day species should have fossils of
other things like them
PROBLEMS:
- fossil record - HUGE GAPS
2. Comparative Anatomy:
-species that evolved from a common
ancestor should have similar anatomical
structures
HOMOLOGOUS STRUCTURES:
- same components but different variations
Vestigial Organs: remainders of past use
Homologous Structures
Human
Figure 22.14
Cat
Whale
Bat
3. Comparative Embryology:
“ontogeny recapitulates phylogeny”
ontogeny = development
phylogeny = past history
- means as the individual develops
embryological, the embryo shows the past
history or evolution of the species
EX: gill slits on human embryo
PROBLEM: embryological studies show
some of the greatest differences between
species
Comparative embryology
Pharyngeal
pouches
Post-anal
tail
Chick embryo
Figure 22.15
Human embryo
4. Molecular Biology
- comparison of DNA, RNA and proteins from
species to see similarities – closer the
molecule, the closer the relation
- Cytochrome C - cellular respiration
- very similar - all from one original source variations due to mutations
Microevolution:
STUDY OF MICROEVOLUTION =
POPULATION GENETICS
- study of genetic variation in a population
and how it changes from one generation to
another
Uses a MODERN SYNTHESIS approach
- studies populations as the units of
evolution (not individuals) using principles
from different fields of study
POPULATION: localized group belonging to
one species
SPECIES: group of populations whose
individuals have the potential to interbreed
and produce viable (fertile) offspring
Study of Population focus:
GENE POOL = total aggregate of genes in the
population
Generation
1
CW CW
genotype
CRCR
genotype
Plants mate
Generation
2
All CRCW
(all pink flowers)
50% CR
gametes
50% CW
gametes
Come together at random
Generation
3
25% CRCR
50% CRCW
50% CR
gametes
25% CWCW
50% CW
gametes
Come together at random
Generation
4
25% CRCR
50% CRCW
25% CWCW
Alleles segregate, and subsequent
generations also have three types
of flowers in the same proportions
Analyzed using HARDY WEINBERG
EQUATION
- focuses on frequencies of alleles AND
genotypes = genetic structure
- tells us if a population is evolving or not
- if there is NOT change in the frequencies =
NOT evolving
- if there IS change in the frequencies =
Evolving
PRINCIPLES OF HARDY WEINBERG
THEORUM:
- genetic frequencies of a population remain
the same unless acted on by an outside force
= HARDY WEINBERG EQUILIBRIUM
- reshuffling of alleles through reproduction
has no affect on frequencies UNDER
SPECIFIC CONDITIONS
USE HW Equation
p2 + 2pq + q2 = 1 - represents the possible
combinations and percent probabilities of
crosses
derived from p + q = 1
(amount of dominant + amount of recessive =
100%)
- why squared? how do you get homozygous
dominant?
Punnet square: Aa X Aa
- one way to get AA = 1/2 from father , 1/2 from
mother = 1/4
- aa = same
- heterozygous: Aa or aA - 2 ways = percent
probability x 2
p = dominant allele
q = recessive
Gametes for each generation are drawn at random from
the gene pool of the previous generation:
80% CR (p = 0.8)
20% CW (q = 0.2)
Sperm
CR
(80%)
CW
(20%)
p2
Eggs
CR
(80%)
pq
p2
16%
CRCW
(20%)
CW
64%
CRCR
16%
CRCW
qp
4%
CW CW
q2
If the gametes come together at random, the genotype
frequencies of this generation are in Hardy-Weinberg equilibrium:
64% CRCR, 32% CRCW, and 4% CWCW
Gametes of the next generation:
64% CR from
CRCR homozygotes
+
16% CR from
CRCW homozygotes
=
80% CR = 0.8 = p
4% CW from
CWCW homozygotes
+
16% CW from
CRCW heterozygotes
=
20% CW = 0.2 = q
With random mating, these gametes will result in the same
mix of plants in the next generation:
Figure 23.5
64% CRCR, 32% CRCW and 4% CWCW plants
Calculating the Frequency of a Gene
# of a Specific Allele/Total # of all Alleles
320 AA 160 Aa and 20 aa
Frequency of A = (640 + 160)/1000
Frequency of a = (160 + 40)/1000
WHY 160 for each? heterozygous
WHAT IF YOU ARE DOING A FIELD STUDY?
can’t tell homozygous dominant from a heterozygous
use the frequency of the homozygous recessive to calculate
probabilities
1. TAKE recessive phenotype
ex. 20 out of 500 = 0.04 = 4%
- represents frequency of q2
2. TAKE square root
= .2
3. use p + q = 1 equation to solve for p
p=1-q
p = 0.8
4. Plug frequencies of p and q into HW equation and solve.
WHEN DOES THIS APPLY?
- study of a population for one generation
- study of next generation will show if the population
is evolving
- if change = evolution
CAUSES OF MICROEVOLUTION/REQUIREMENTS
FOR HW
- the causes of microevolution are the opposite for the
requirements for HW to be maintained
MICROEVOLUTION
1. GENETIC DRIFT
- change in the gene pool due to
chance
- smaller sample of individuals
Specific Types of Genetic Drift:
Bottle Neck Effect
- natural catastrophe reduces
population to a few individuals
- become parents of resulting
population
- can wipe out a certain trait
Founder Effect
- a few individuals start the
population
HW
1. Very large population
- allows for greater mixing
CWCW
CRCR
CRCR
Only 5 of
10 plants
leave
offspring
CRCW
CWCW
CRCR
CRCR
CRCW
CWCW
CRCR
CRCW
CRCW
CRCR
CWCW
CRCW
CRCR
CRCR
CRCW
Generation 1
p (frequency of CR) = 0.7
q (frequency of CW) = 0.3
Only 2 of
10 plants
leave
offspring
CRCR
CRCR
CRCR
CRCR
CRCR
CRCR
CRCR
CRCR
CRCW
CRCW
Generation 2
p = 0.5
q = 0.5
Figure 23.7
CRCR
CRCR
Generation 3
p = 1.0
q = 0.0
(a) Shaking just a few marbles through the
narrow neck of a bottle is analogous to a
drastic reduction in the size of a population
after some environmental disaster. By chance,
blue marbles are over-represented in the new
population and gold marbles are absent.
Figure 23.8 A
MICROEVOLUTION
2. Gene Flow individuals
move in or out of the
population introducing
or removing new alleles
HW
2. ISOLATION from
population
- no gain or loss of genes
MICROEVOLUTION
3. Mutations
- introduce new alleles
- rare - most are fatal or
have no effect
3. No mutations
HW
MICROEVOLUTION
4. Non-random matingmost animals choose
based on some
characteristic
- isolates favorable traits
Types:
Selective – specific trait is
favored
inbreeding - closely
related
assortive mating - similar
phenotype
HW
4. Random mating
- all traits treated equally
MICROEVOLUTION
5. Natural Selection
- best fit survive
HW
5. No natural selection
- all equal chance of
survival
MICROEVOLUTION AND VARIATION
MICROEVOLUTION IS DEPENDENT ON GENETIC VARIATION
Interspecies Variation
1. Quantitative: polygenic inheritance
- continuum of characteristics
EX height
2. Discrete: either/or trait
may be two traits or more
- if more = POLYMORPHISM
Interpopulace variation (geographic
variation)
Altitude
Latitude
Proximity of Other Species:
- mutualism
- predator
- competition
Heights of yarrow plants grown in common garden
EXPERIMENT
Researchers observed that the average size
Mean height (cm)
of yarrow plants (Achillea) growing on the slopes of the Sierra
Nevada mountains gradually decreases with increasing
elevation. To eliminate the effect of environmental differences
at different elevations, researchers collected seeds
from various altitudes and planted them in a common
garden. They then measured the heights of the
resulting plants.
Atitude (m)
RESULTS The average plant sizes in the common
garden were inversely correlated with the altitudes at
which the seeds were collected, although the height
differences were less than in the plants’ natural
environments.
CONCLUSION The lesser but still measurable clinal variation
in yarrow plants grown at a common elevation demonstrates the
role of genetic as well as environmental differences.
Figure 23.11
Sierra Nevada
Range
Great Basin
Plateau
Seed collection sites
GENERATION OF VARIATION:
1. Mutation - change in the DNA
- rare
- mostly harmful
- only those that matter
rate: 1 mutation per 100,000 genes per generation
1/1000chance – 99% lethal
- must be heritable
- role of mutagens
impact: page 437
2. sexual recombination
- shuffles the genes
Preserving Variation
- without variation, populations are more susceptible to disease
Preserving Variation;
1. Sexual Reproduction vs. Asexual
2. Diploidy
- one trait masks another
- mutation = lead to recessive defect
Dominance due to diploidy cancels defect
3. Balanced Polymorphism
- Maintaining a variety of traits - allows for survival of species
- Ex: finches and beak size
4. Heterozygote advantage: heterozygote better survivor maintains all frequencies
EX: sickle cell anemia
5. Hybrid vigor: mixing of traits produces stronger better plant
6. Frequency-dependent polymorphism- one trait is not necessarily
better - once its frequency gets 2 high , it drops
7. Sexual Dimorphism: difference in males and females
choosing a mate based of different physical characteristics:
- may connote fertility
- protective
- strength
TYPES OF NATURAL
SELECTION
- compare three types of individuals
two extremes and middle ground
correlate to polygenic trait
Stabilizing Selection: favors middle ground
- bird beaks
– human birth weight and size
Directional Selection: favors an extreme
- giraffe
Diversifying Selection: does not favor middle ground makes both extremes more frequent
- snails and shell color
Original population
Original
population
Evolved
population
(a) Directional selection shifts the overall
makeup of the population by favoring
variants at one extreme of the
distribution. In this case, darker mice are
favored because they live among dark
rocks and a darker fur color conceals them
from predators.
Fig 23.12 A–C
Phenotypes (fur color)
(b) Disruptive selection favors variants
at both ends of the distribution. These
mice have colonized a patchy habitat
made up of light and dark rocks, with the
result that mice of an intermediate color are
at a disadvantage.
(c) Stabilizing selection removes
extreme variants from the population
and preserves intermediate types. If
the environment consists of rocks of
an intermediate color, both light and
dark mice will be selected against.
NATURAL SELECTION: movement toward
perfection?
1. historical constraints
2. compromises
3. non-adaptive evolution
4. can only work with what’s present
BIOLOGICAL SPECIES CONCEPT
Species = group of populations whose members have
the potential to interbreed with one another in nature
to produce viable, fertile offspring, but who cannot
produce viable, fertile offspring with members of
others species
Qualifications:
- natural environment
-may not take into account morphological differences
- wolf, dog and coyote
- does not apply to species that do not reproduce
sexually
- does not explain gene flow between separate species
SPECIATION: formation of a new species
Modes of Speciation
Anagenesis – one species changing into a
different type – original is gone
Cladogenesis – one species diverting into two
or more with the original still present –
“branching”
Figure 24.2 (a) Anagenesis
(b) Cladogenesis
Species Barriers
TWO BASIC TYPES: prezygotic (prevent
fertilization) and postzygotic (prevent hybrid
from being fertile or reproductively
successful)
PREZYGOTIC BARRIERS
1. Habitat Isolation:
different places - can’t breed
2. Behavioral Isolation:
different courtship behaviors
different mate attractions
- fireflies
3. Temporal (time) Isolation:
breed during different times
- skunks
- flowers
4. Mechanical Isolation:
physically can’t breed “anatomically
incompatible”
5. Gametic Isolation:
gametes can’t fuse
- female’s reproductive tract may be inhospitable
to foreign sperm
sperm can’t fuse to egg
biochemical signals
- recognition proteins on surface of the egg allow
sperm to fuse
Prezygotic barriers impede mating or hinder fertilization if mating does occur
Habitat
isolation
Behavioral
isolation
Temporal
isolation
Individuals
of different
species
Mechanical
isolation
Mating
attempt
HABITAT ISOLATION
TEMPORAL ISOLATION
BEHAVIORAL ISOLATION
(b)
MECHANICAL ISOLATION
(g)
(d)
(e)
(f)
(a)
(c)
Figure 24.4
POSTZYGOTIC BARRIERS
1. Reduced Hybrid Viability - embryo fails to develop
- very weak offspring - die
2. Reduced Hybrid Fertility
- sterile: Mule (male donkey + female horse) or
Hinny (female donkey + male horse – less
successful)
male mules are sterile, females can sometimes
back breed with donkey or mule
- usually can’t back breed with parent species
3. Hybrid Breakdown
- reproduce for one generation
Gametic
isolation
Reduce
hybrid
fertility
Reduce
hybrid
viability
Hybrid
breakdown
Viable
fertile
offspring
Fertilization
REDUCED HYBRID
VIABILITY
GAMETIC ISOLATION
REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
(k)
(j)
(m)
(l)
(h)
(i)
MODES OF SPECIATION: how species are
formed
ALLOPATRIC (physical isolation) vs.
SYMPATRIC (intrinsic - change of genetic
info)
Figure 24.5 A, B
(a) Allopatric speciation. A (b) Sympatric speciation. A small
population becomes a new species
population forms a new
species while geographically without geographic separation.
isolated from its parent
population.
ALLOPATRIC:
1. Geographical barriers
- two groups get separated into different areas
- genetic drift
- natural selection leads to genetic differences
- geographical barrier may a difference of niche causes natural selection in one area that does not
occur in another
2.Isolation of a small group (founder effect)
3. Peripheral Isolate
- favors natural selection and genetic drift
3. Adaptive Radiation: species jumping from
one island to another - each time new group or colony grows may lead to natural selection or genetic drift
- all from a common ancestor
SYMPATRIC SPECIATION:
genetic isolation within the parent species
TYPES:
PLANT
polyploidism
- more than diploid
- faulty cell division that results in extra sets of chromosomes
1. AUTOPOLYPLOID: polyploidism - all chromosomes from the
same species
- in plants: can result in VIGOR - better and stronger traits
- results in a new species if the polyploidism is an even set
of chromosomes (4N) and there is self-fertilization
- can’t interbreed with normal parent species = 2n
2. ALLOPOLYPLOID: polyploidism - chromosome sets from
different species
- interbreeding = combined chromosomes
- usually sterile (odd numbers of chromosomes in gametes)
- can reproduce asexually
-
Failure of cell division
in a cell of a growing
diploid plant after
chromosome duplication
gives rise to a tetraploid
branch or other tissue.
Gametes produced
by flowers on this
branch will be diploid.
Offspring with tetraploid
karyotypes may be viable
and fertile—a new
biological species.
2n
2n = 6
4n = 12
Figure 24.8
4n
Unreduced gamete
with 4 chromosomes
Hybrid with
7 chromosomes
Species A
2n = 4
Unreduced gamete
with 7 chromosomes
Viable fertile hybrid
(allopolyploid)
Meiotic error;
chromosome
number not
reduced from
2n to n
2n = 10
Normal gamete
n=3
Species B
2n = 6
Figure 24.9
Normal gamete
n=3
ANIMAL:
1. reproductive isolation - dependent on specific
resources
- wasps and figs: specific figs - specific wasps
2. natural selection
3. mutation
GENETIC CHANGE CAN LEAD TO SPECIATION
- different environments = natural selection =
speciation
- reproductive isolation results as a secondary
effect
HOW MUCH CHANGE IS ENOUGH?
various - depends on what is changed
TEMPO OF CHANGE:
gradualism vs. punctuated equilibrium
gradualism = very small changes over a period of time
- not supported by fossil record
FOSSIL RECORD:
- shows stasis - no change for long periods of time then
disappear - replaced by something different
- little to no transition
POSSIBLE EXPLAINATION: changes that occurred are
not seen in the fossils because they were in the soft
tissues or were behavioral
-PUNCTUATED EQUILIBRIUM
- stayed same for long periods of time and then
underwent periods of rapid change for some
reason (presumably change in the
environment) - does not allow enough time for fossils to be
formed so there are none
Figure 24.13
Time
(a) Gradualism model. Species (b) Punctuated equilibrium
descended from a common
model. A new species
ancestor gradually diverge
changes most as it buds
more and more in their
from a parent species and
morphology as they acquire
then changes little for the
unique adaptations.
rest of its existence.
Possible mechanisms for Punctuated Equilibrium
1. polyploidy = only plants = still similar
2. exaption and natural selection: plasticity of traits
- can be used for one thing or another - may then give selective
advantage and lead to development of a different trait
EX: reptiles into birds
3. change in control genes of development (Homeotic Genes)
- in embryology: genes activate other genes (cascading effect)
that direct development - mutation here could result in change of
development
EX: allometric growth - how the body grows
- arms grow before legs - change could result in a different trait
or ability
Fig. 2 Representative skeletal phenotypes of newborns of the Hoxa13;Hoxd11-13;Gli3 allelic
series.
Rushikesh Sheth et al. Science 2012;338:1476-1480
Published by AAAS
Fig. 1 (A) Expression of Sox9 in E12.5 limbs of the Hoxa13;Gli3 allelic series.
Rushikesh Sheth et al. Science 2012;338:1476-1480
Published by AAAS
Fig. 5 Vertebrate limb evolution and distal Hox gene function.
Rushikesh Sheth et al. Science 2012;338:1476-1480
Published by AAAS
4. Chronology of development: time for
development to occur
ex. humans and chimps - humans brains
grow for longer periods of time - prolonged
juvenile characteristic
Phylogenic Systematics
PHYLOGENIC - evolutionary history
SYSTEMATICS - study of biological diversity in
evolutionary context
- study of biological diversity using evolutionary
history
Basis of Phylogenic Studies
Geology and the Fossil Record
Formation of Fossils
- stratification of earth
- oldest layers at bottom of strata
- sedimentation
- animals/plants die - become part of strata
1 Rivers carry sediment to the
ocean. Sedimentary rock layers
containing fossils form on the
ocean floor.
2 Over time, new strata are
deposited, containing fossils
from each time period.
3 As sea levels change and the seafloor
is pushed upward, sedimentary rocks are
exposed. Erosion reveals strata and fossils.
Younger stratum
with more recent
fossils
Older stratum
with older fossils
Types of Fossils
- hard parts of organisms remain
- organic substances replaced with mineral
- organic substance decays - leaves space - cast
- preservation of organic
- pressed between layers and kept from air
- no decomposition by bacteria or fungi - amber
- ice
(c) Leaf fossil, about 40 million years old
(b) Petrified tree in Arizona, about
190 million years old
(a) Dinosaur bones being excavated
from sandstone
(d) Casts of ammonites,
about 375 million
years old
(f) Insects
preserved
whole in
amber
Figure 25.4a–g
(g) Tusks of a 23,000-year-old mammoth,
frozen whole in Siberian ice
(e) Boy standing in a 150-million-year-old
dinosaur track in Colorado
Dating Fossils
- relative vs. absolute
RELATIVE
- geologic time scale
- older, younger, after, before
- based on strata in rock
- different layers –
ERAS of SIGNIFICANCE
- Cambrian - explosion of animals
Absolute Dating
- not “errorless”
- given in years
RADIOMETRIC DATING:
- Half-Life - time it takes for half the atoms in a
radioactive sample to decay into a more stable atom
- measure the amount of isotopes in a fossil and work
backwards
EX: Carbon 14 - half life - 5600
-dating: look at amount of carbon 14 in a sample
and move backwards
- use larger half-lives of different compounds to
date older specimens
Ratio of parent isotope
to daughter isotope
Accumulating
“daughter”
isotope
1
2
Remaining
“parent”
isotope
1
14
18
2
Time (half-lives)
3
1 16
4
- Racemization: conversion of amino acids from
biological form (L) to non-biological (D)
(enantiomers)
- biological systems only make L
- convert to D
- not accurate - rate changes with
temperature
GEOLOGY AFFECTING PHYLOGENY
CONTINENTAL DRIFT - PANGEA
- plate tectonics
- shifting of plates
- bring together and separate species
geographically
Phylogenic Patterns
- adaptation and radiation
- major catastrophe = mass extinction
- sudden changes = more adaptation =
more speciation
- ADAPTIVE ZONE - set of new living
conditions and resources that presents new
possibilities
Mass Extinction
- trace mass extinctions using fossil record -
-
when lots die - leave more fossils - if extinct don’t show up in the next layers
Predation
loss of habitat
Volcanoes
global warming
Meteors
-
impact hypothesis
Use of Phylogenic Information
- develop PHYLOGENIC TREES
- diagram to trace evolutionary relationships
AS BEST AS THEY CAN BE DETERMINED
- relate species based on common
characteristics
 basis of TAXONOMY = classification
Taxonomic Hierarchy
Hierarchy: Each level = taxon - classification level
Domain - largest grouping
Kingdom
Phylum
Class
Order
Family
Genus
Species- smallest grouping
- subspecies
- variety
Scientific Names
Scientific Name = Genus species
Binomial - two names
“species” - specific epithet
Domain Eukarya
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class Mammalia
Order Carnivora
Suborder Caniformia
Family Canidae
Species Canis lupus
Subspecies Canis lupus familiaris
As you classify an organism you make a
PHYLOGENIC TREE
- shows the taxonomic hierarchy
- each branch is a taxon
Bacteria, Oak, Amoeba, Starfish, Fish, Horse, Wolf, Dog
Taxonomic Trees usually represent Phylogenic
Trees
- shows evolutionary trends
- closer they are on the tree = closer
evolutionary history
Cladograms
Cladogram: depiction of patterns of shared
characteristics among taxa
Clade: group of species that includes an
ancestral species and all its descendants
Cladistics: the study of resemblances among
clades
Species
Genus
Panthera
Order
Family
Panthera
Mephitis
Canis
Canis
Lutra lutra
pardus
mephitis
familiaris
lupus
(European
(leopard) (striped skunk)
(domestic dog) (wolf)
otter)
Felidae
Mephitis
Lutra
Mustelidae
Carnivora
Canis
Canidae
TYPES OF PHYLOGENIC BRANCHES
1. Monophyletic: all descendents from a
common ancestor
E
D
J
H
G
F
C
K
I
B
A
(a) Monophyletic. In this tree, grouping 1,
consisting of the seven species B–H, is a
monophyletic group, or clade. A monophyletic group is made up of an
ancestral species (species B in this case)
and all of its descendant species. Only
monophyletic groups qualify as
legitimate taxa derived from cladistics.
2. Polyphyletic: same taxon, but different
ancestors
D
E
G
J
H
I
F
C
K
B
A
(c) Polyphyletic. Grouping 3 also fails the
cladistic test. It is polyphyletic, which
means that it lacks the common ancestor
of (A) the species in the group. Furthermore, a valid taxon that includes the
extant species G, H, J, and K would
necessarily also contain D and E, which
are also descended from A.
3. Paraphyletic: separate branch
G
E
D
C
J
H
K
I
F
B
A
(b) Paraphyletic. Grouping 2 does not
meet the cladistic criterion: It is
paraphyletic, which means that it
consists of an ancestor (A in this case)
and some, but not all, of that ancestor’s
descendants. (Grouping 2 includes the
descendants I, J, and K, but excludes
B–H, which also descended from A.)
all based on comparative science
HOWEVER: may have similarities and not
really be related
- analogous structures
- look / function the same - different
lineage
- differs from homologous structures
- different form, same lineage
FINDING PHYLOGENIC RELATIONSHIPS
1. Comparative anatomy
2. Molecular biology
a. protein comparison
amino acid sequences compared
- similar sequence = similar gene =
common ancestor
- more similar = more closely related =
more recent divergence on tree
Human
Human
Mushroom
0
Mushroom
Tulip
30%
0
Tulip
(a) Percentage differences between sequences
40%
40%
0
25%
15%
15%
15%
20%
10%
5%
5%
Tree 1: More likely
(b) Comparison of possible trees
Tree 2: Less likely
b. DNA and RNA comparison
DNA-DNA hybridization
- take single strand of DNA from one species and a
single strand from another - put together - amount of similarity will determine how closely two
species are related
Restriction Maps:
- restriction enzymes, electrophoresis - compare
bands of species - more similar = more related
- usually compare mitochondrial DNA (mtDNA)
DNA Sequence Analysis:
-compare actual nucleotide sequences
- use rRNA - little change
Lamprey
Tuna
Turtle
Leopard
Salamander
Lancelet
(outgroup)
CHARACTERS
TAXA
Hair
0
0
0
0
0
1
Amniotic (shelled) egg
0
0
0
0
1
1
Four walking legs
0
0
0
1
1
1
Hinged jaws
0
0
1
1
1
1
Vertebral column (backbone)
0
1
1
1
1
1
Turtle
(a) Character table. A 0 indicates that a character is absent; a 1
indicates that a character is present.
Leopard
Hair
Salamander
Amniotic egg
Tuna
Four walking legs
Lamprey
Hinged jaws
Lancelet (outgroup)
Vertebral column
(b) Cladogram. Analyzing the distribution of these
derived characters can provide insight into vertebrate
phylogeny.
Cladograms
 Follow the rule of Maximum Parsimony –
simplest is best
 Plesiomorphic Traits – common in all
branches – can’t be used to make a new
clade
 Apomorphic Traits – derived, novel, new
traits - form a new clade
 Synapomorphic Traits – shared, derived
trait in clades (common branch)
Apomorphy for
tetrapods
Plesiomophy for
vertebrates
How to Make a Cladogram
How to #2
MAJOR LINEAGES OF LIFE:
Original: Plants and Animals
Plants, animals, fungi
Plant, animals, fungi, bacteria
TRADITIONAL FIVE KINGDOM APPROACH
P, A, F, Protista, Monerans
Splitting of Groups based on biochemical
information
Eight Kingdom Approach
split the monerans based on metabolism
Bacteria
Archaea - old bacteria
split protista into three groups based on
structure and feeding methods
THREE DOMAIN APPROACH
- isolates bacteria, archae and eukarya into
separate groups
- emphasizes evolutionary relationships and
biochemical differences
- further fragments protista based on feeding
and structure
Figure 26.22
Domain Archaea
Universal ancestor
Domain Eukarya
Domain Bacteria
Figure 26.21
Plants
Fungi
Animals
Bilaterally symmetrical animals (annelids,
arthropods, molluscs, echinoderms, vertebrates)
Cnidarians (jellies, coral)
Sponges
Choanoflagellates
Club fungi
Sac fungi
Arbuscular mycorrhizal fungi
Zygote fungi
Chytrids
Amoebozoans (amoebas, slime molds)
Angiosperms
Gymnosperms
Seedless vascular plants (ferns)
Bryophytes (mosses, liverworts, hornworts)
Charophyceans
Chlorophytes
Red algae
Cercozoans, radiolarians
Stramenopiles (water molds, diatoms, golden algae, brown algae)
Alveolates (dinoflagellates, apicomplexans, ciliates)
Euglenozoans
Diplomonads, parabasalids
Euryarchaeotes, crenarchaeotes, nanoarchaeotes
Korarchaeotes
Gram-positive bacteria
Cyanobacteria
Spirochetes
Chlamydias
Proteobacteria
3 Domains
PREBIOTIC EVOLUTION
"This chapter is the most speculative of the unit,
for its main subject is the origin of life on a
young Earth, and no fossil record of that
seminal episode exists."
- Campbell, page 490, 5th Edition
Origin of Life
Formation of the earth
THE YOUNG EARTH
- little atmospheric oxygen
- high UV
- lightning
- volcanoes
- conducive to chemical reactions
- energy
- no oxygen to oxidize products and break
them down
Hot mixture of chemicals
- formed amino acids and nucleic acids
- formed proteins, RNA, and DNA
- formed simple cells (Protobionts)
- formation of heredity
- cells became more complicated
Glucose-phosphate
20 m
Glucose-phosphate
Phosphorylase
Starch
Amylase
Phosphate
Maltose
Maltose
(a) Simple reproduction. This liposome is “giving birth” to smaller
liposomes (LM).
(b) Simple metabolism. If enzymes—in this case,
phosphorylase and amylase—are included in the
solution from which the droplets self-assemble,
some liposomes can carry out simple metabolic
reactions and export the products.
Miller/Urey Experiment
- simulated primitive earth using the information
from their time travel experiment where they
actually went back in time and determined
what the earth was like
- methane, water, ammonia, H2, and electricity
- excluded CO, CO2, N2 and O2
FOUND: produced amino acids
change components and even produce all
amino acids, nucleotides and ATP
ABIOTIC FORMATION OF
PROTEINS
- in labs = Yes
- control
- concentrated
- role of clay - catalyze synthesis
Formation of Simple Cells = PROTOBIONTS
- aggregates of abiotically reproduced
molecules
- separate internal environments
- may have metabolic activity if an enzyme is
present
- may aggregate – “grow” and split - like oil
drops
Formation of Nucleic Acids
- abiotic generation of nucleotides
- self assemble
- self replicate - require a lot of nucleotides
(concentration)
- RNA can act as ribozyme to catalyze reactions
- build proteins
- build other RNAs
- each could change and have a molecular
selective advantage
- then ….