UNIT VIII
POPULATION GENETICS & CLASSIFICATION
• Big Campbell
Ch 22-28, 31
• Baby Campbell
Ch 13-17
I. INTRODUCTION TO EVOLUTION
• Evolution
o Change over time in the allele
frequency of organisms
o Descent with modification
• Natural Selection
o Populations of organisms can change
over the generations if individuals
having certain heritable traits leave
more offspring than others
o Differential reproductive success
• Evolutionary Adaptations
o A prevalence of inherited
characteristics that enhance
organisms’ survival and reproduction
November 24, 1859
II. A HISTORY OF EVOLUTIONARY THEORY
• Carolus Linnaeus (1707-1778)
o Taxonomy
• James Hutton (1726-1797)
o Gradualism
• Jean-Baptiste de Lamarck (17441829)
o Use & Disuse
o Inheritance of Acquired
Characteristics
II. A HISTORY OF EVOLUTIONARY THEORY, cont
• Thomas Malthus (1776-1834)
o Populations
• Charles Lyell (1792-1875)
o Uniformitarianism
• Gregor Mendel (1822-1884)
o
• Alfred Wallace (1823-1913)
o Independent development of
evolutionary theory
II. A HISTORY OF EVOLUTIONARY THEORY, cont
II. A HISTORY OF EVOLUTIONARY THEORY, cont
• Charles Darwin (1809-1882)
II. A HISTORY OF EVOLUTIONARY THEORY, cont
II. A HISTORY OF EVOLUTIONARY THEORY, cont
• Darwin’s Finches
o New species of finches arose from gradual accumulation of adaptations due to
variations in food supply, terrain
III. DARWIN’S CONCLUSIONS
• Descent with Modification
o Four Observations
Members of a population often vary
greatly in their traits.
Traits are inherited from parents to
offspring.
All species are capable of producing
more offspring that their
environment can support.
Owing to a lack of food or other
resources, many of these offspring
do not survive.
III. DARWIN’S CONCLUSIONS, cont
• Decent with Modification
o Two Inferences
 Individuals whose inherited
traits give them a higher
probability of surviving and
reproducing in a given
environment tend to leave
more offspring than other
individuals.
 This unequal ability of
individuals to survive and
reproduce will lead to the
accumulation of favorable
traits in the population over
generations.
IV. EVIDENCE FOR EVOLUTION
• Direct Observation
o Antibiotic/Drug
Resistance
o Coloration in Guppies
IV. EVIDENCE FOR EVOLUTION, cont
• Fossil Record
o Succession of forms
over time
o Transitional Links
o Vertebrate descent
IV. EVIDENCE FOR EVOLUTION, cont
• Homology
o Homologous structures
o Vestigial organs
 Snakes
 Cetaceans
 Flightless birds
o Convergent Evolution
 Independent evolution of similar
features in different lineages
 Analogous structures
IV. EVIDENCE FOR EVOLUTION, cont
• Biogeography
o Geographical
distribution of species
o Continental Drift
 Pangaea
o Islands are inhabited
by organisms most
closely resembling
nearest land mass
IV. EVIDENCE FOR EVOLUTION, cont
• Comparative
Embryology
o Pharyngeal
Pouches
 Gill slits
o Tail
IV. EVIDENCE FOR EVOLUTION, cont
• Molecular Biology
o Similarities in DNA,
proteins, genes, and gene
products
o Common genetic code
V. POPULATION GENETICS
• Population Genetics
 The study of genetic changes in
populations
• Population

• Species

• Gene pool
 Population’s genetic make-up
• Modern Synthesis/Neo-Darwinism
V. POPULATION GENETICS, cont
• Hardy-Weinberg Principle
– Predicts allele frequency in a
non-evolving population; that
is, a population in equilibrium
– Can be used to determine if
a population is evolving
– States that allele frequencies
in a population will remain
constant from generation to
generation if five conditions
are met
V. POPULATION GENETICS, cont
• Five Conditions for Hardy-Weinberg
Equilibrium
1)
2)
3)
4)
5)
• If any of these conditions are not met,
evolutionary change will occur
V. POPULATION GENETICS, cont
• Hardy-Weinberg Equation
 If p = frequency of one allele (A) and
 q = frequency of the other allele (a), then
p + q =
• Therefore,
p =
q =
•
•
•
•
Frequency of AA =
Frequency of aa =
Frequency of Aa =
Distribution of genotype frequencies in a population =
V. POPULATION GENETICS, cont
Hardy-Weinberg Practice Problems
1. If you know that you have 16% recessive fish (bb), . . .

q2=

q

Therefore, p =
• Calculate the frequency of each genotype using Hardy-Weinberg
p 2 + 2pq + q 2 = 1
 p2 =
 BB =
 2pq =
 Bb =
 bb =
V. POPULATION GENETICS, cont
• Hardy-Weinberg Practice Problems, cont
2. If in a population of 1,000, 90 show recessive phenotype (aa), use
Hardy-Weinberg to determine frequency of allele combinations.
VI. MICROEVOLUTION
• A change in the gene
pool of a population
over a succession of
generations
• Five main causes:
Genetic Drift
Gene Flow
Natural Selection
Mutation
Non-random Mating
VI. MICROEVOLUTION, cont
• Genetic Drift
o Changes in the gene pool due to chance. More often seen in small population
sizes. Usually reduces genetic variability. There are two situations that can
drastically reduce population size:
 The Bottleneck Effect: type of genetic drift resulting from a reduction in
population (natural disaster) such that the surviving population is no longer
genetically representative of the original population
VI. MICROEVOLUTION, cont
• Genetic Drift
 Founder Effect
 Genetic drift attributed
to colonization by a
limited number of
individuals from a
parent population
 Gene pool is different
than source population
VI. MICROEVOLUTION, cont
• Gene Flow
 Genetic exchange due to the
migration of fertile individuals
or gametes between
populations – tends to reduce
differences between
populations
• Natural Selection
 Differential success in
reproduction; only form of
microevolution that adapts a
population to its environment
VI. MICROEVOLUTION, cont
• Mutations
 A change in an
organism’s DNA
(gametes; many
generations); original
source of genetic
variation (raw material
for natural selection)
• Nonrandom Mating
 Inbreeding and assortive
mating - both shift
frequencies of different
genotypes
VII. VARIATIONS IN POPULATION
• Polymorphism
 Coexistence of 2 or more
distinct forms of
individuals (morphs)
within the same
population
• Geographical Variation
 Differences in genetic
structure between
populations (cline)
VII. VARIATIONS IN POPULATION, cont
• Mutation and Recombination
• Diploidy
 2nd set of chromosomes
hides variation in the
heterozygote
• Balanced Polymorphism
 Heterozygote Advantage
 Frequency-Dependent
Selection
o Survival & reproduction of any
1 morph declines if it
becomes too common
o Parasite/host
VII. VARIATIONS IN POPULATION, cont
• Adaptive Evolution due
to Natural Selection
 Fitness - Contribution an
individual makes to the
gene pool of the next
generation
• Three ways in which
natural selection alters
variation
Directional
Diversifying
Stabilizing
VII. VARIATIONS IN POPULATION, cont
• Sexual Selection
 Can result in sexual
dimorphism - secondary
sex characteristic
distinction
 Intrasexual Selection
 Intersexual Selection
VIII. MACROEVOLUTION
• Origin of new taxonomic
groups
• Speciation
Anagenesis accumulation of heritable
changes transform
existing species into new
species
Cladogenesis - budding
of new species from a
parent species that
continues to exist (basis
of biological diversity)
VIII. MACROEVOLUTION, cont
• Biological Species Concept
 Described by Ernst Mayr in 1942
 A population or group of
populations whose members
have the potential to interbreed
and produce viable, fertile
offspring; in other words, similar
organisms that can make babies
that can make babies 
 Can be difficult to apply to certain
organisms . . .
VIII. MACROEVOLUTION, cont
• Reproductive
Isolation
o Prevent closely
related species
from
interbreeding
when their
ranges overlap.
o Divided into 2
types
Prezygotic
Postzygotic
VIII. MACROEVOLUTION, cont
Prezygotic Reproductive Barriers
VIII. MACROEVOLUTION, cont
Postzygotic Reproductive
Barriers
VIII. MACROEVOLUTION, cont
• Speciation
o Fossil record shows evidence of bursts of many new
species, followed by periods of little chance
Known as punctuated equilibrium
o Other species appear to change more gradually
Gradualism fits model of evolution proposed by Darwin
VIII. MACROEVOLUTION, cont
• Modes of Speciation
 Based on how gene flow is
interrupted
 Allopatric
 Populations segregated by
a geographical barrier; can
result in adaptive radiation
(island species)
 Sympatric
 Reproductively isolated
subpopulation in the midst
of its parent population
(change in genome);
polyploidy in plants; cichlid
fishes
UNIT VIII, cont - CLASSIFICATION
I. EARLY EARTH
• Formation of Organic Molecules
o Oparin/Haldane Hypothesis
 Primitive Earth’s atmosphere was a
reducing environment
 No O2
 Early oceans were an organic “soup”
 Lightning & UV radiation provided
energy for complex organic
molecule formation
o Miller/Urey Experiment
 Tested Oparin/Haldane hypothesis
 Simulated atmosphere composed of
water, hydrogen, methane, ammonia
 All 20 amino acids, nitrogen bases,
ATP formed
 Hypothesis was supported
I. EARLY EARTH, cont
• Three Eons
 First two described as
Precambrian
o Archaean Eon
o Proterozoic Eon
 Present day = Phanerozoic eon
o Paleozoic era
o Mesozoic era
o Cenozic era
• Continental Drift
 Pangaea
 Gondwanaland & Laurasia
• Mass Extinctions
• Biogeography
 Study of past & present
distribution of species
I. EARLY EARTH, cont
II. PHYLOGENY
• Evolutionary
history of an
organism
• Phylogenetics the tracing of
evolutionary
relationships
• Linnaeus
• Binomial
nomenclature
• Taxon (taxa)
II. PHYLOGENY, cont
• Relationships may be
determined using
morphological and molecular
simlarities
 Homology vs. Analogy...
o Homology - likenesses
attributed to common
ancestry
o Analogy - likenesses
attributed to similar
ecological roles and
natural selection
 Convergent evolution
o Species from different
evolutionary branches
that resemble one
another due to similar
ecological roles
II. PHYLOGENY, cont
• Clade
 Refers to the set of species descended from
a particular ancestral species
 Relationships illustrated with a cladogram
o Branching diagram that depicts relationships
among taxa
o May illustrate derived character states among
taxa. Derived character states are traits not found
in ancestral species; indicate a close evolutionary
relationship among organisms
o Ingroup – Group of taxa being analyzed
o Outgroup – Used as a means of comparison;
closely related to, but not a part of, ingroup
o Parsimony – Also known as Occam’s Razor;
states that least complex explanation is most
likely
II. PHYLOGENY, cont
II. PHYLOGENY, cont
III. PROKARYOTES
III. PROKARYOTES, cont
Classification Methods
• Domain
 Archaea
 Bacteria
• Kingdom
 Archaebacteria
 Eubacteria
• Shape
 Cocci
 Bacilli
 Spirilla
• Gram Stain Reaction
 Positive
 Negative
IV. PROKARYOTES - EUBACTERIA
• Cell wall
 Peptidoglycan
 Gram Positive
 Gram Negative
• Capsule
 Adherence
 Protection
• Pili
 Adherence
 Conjugation
IV. PROKARYOTES – EUBACTERIA, cont
Motility
• Flagella
• Helical shape
 Spirochetes
• Slime
• Taxis
IV. PROKARYOTES – EUBACTERIA, cont
• Nucleoid region
• Plasmids
• Asexual reproduction
 Binary fission
• “Sexual reproduction”
 Transformation
 Transduction
 Conjugation
• Endospore
 Bacterial “hibernation”
IV. PROKARYOTES – EUBACTERIA, cont
Nutrition
• Photoautotrophs
 Photosynthetic
 Harness light to drive the synthesis
of organics
 Cyanobacteria
• Chemoautotrophs
 Oxidation of inorganics for energy
 Obtain carbon from CO2
• Photoheterotrophs
 Use light to generate ATP
 Must obtain carbon in an organic
form
• Chemoheterotrophs
 Consume organic molecules for both
energy and carbon
 Saprobes - decomposers
 Parasites
IV. PROKARYOTES – EUBACTERIA, cont
• Metabolism
o Nitrogen fixation
 Conversion of atmospheric
nitrogen (N2) to ammonium
(NH4+)
o Metabolic Cooperation
 Biofilms
o Oxygen relationships
 Obligate aerobes
 Facultative anaerobes
 Obligate anaerobes
IV. PROKARYOTES – EUBACTERIA, cont
Prokaryotic Ecology
• Decomposers
• Nitrogen Fixation
• Symbiosis
 Commensalism
 Mutualism
 Parasitism
IV. PROKARYOTES – EUBACTERIA, cont
Bacterial Pathogenesis
• Koch’s Postulates – Criteria for bacterial disease confirmation




• Opportunistic
 Normal residents of host; cause illness when defenses are weakened
• Exotoxins
 Bacterial proteins that can produce disease w/o the prokaryote present
(botulism)
• Endotoxins
 Components of gram negative membranes (Salmonella)
V. ORIGINS OF EUKARYOTIC CELLS
• Endosymbiotic Theory (AKA “Endosymbiont Theory”)
• Margulis
• Mitochondria and chloroplasts were formerly from small prokaryotes
living within larger cells
V. ORIGINS OF EUKARYOTIC CELLS
Support for Endosymbiotic Theory
• DNA structure
• Double membrane
• Replication of Mitochondria/Chloroplasts
• Ribosomes
• Similarities between chloroplast/mitochondrial DNA & specific bacterial genomes,
including cyanobacteria
• Enzymes
EUKARYOTES
VI. KINGDOM PROTISTA
•
•
•
•
Very diverse
All __________________
Mostly _________________
Classified according to eukaryotic
kingdom protist is most like, nutrition
 Animal-like
 Ingestive
 Protozoa
 Plant-like
 Photosynthetic
 Algae
 Fungus-like
 Absorptive
 Slime Molds
VI. KINGDOM PROTISTA, cont
Protist Phylogeny
VI. KINGDOM PROTISTA, cont
Protist Systematics
• Diplomonads
 Lack mitochondria, cell walls
 Giardia lamblia
 Trichomonas vaginalis
• Euglenoids
 Most are heterotrophic; may be
autotrophic
 Pellicle
 Flagellated
 Many have “eyespot”
 Euglena
 Trypanosoma
VI. KINGDOM PROTISTA - Systematics, cont
• Alveolates
 Contain small sacs called alveoli; may
help regulate water, ion concentration
 Dinoflagellates – phytoplankton, also
known as “spinning algae”
 Red Tides
 Ciliates – Paramecium, Stentor
 Apicomplexa - all parasitic; lack cilia,
flagella
 Plasmodium
 Toxoplasma
VI. KINGDOM PROTISTA - Systematics, cont
• Stramenopila
• Water molds (decomposers), mildews (parasitic),
algae (photosynthetic)
 Diatoms
 Photosynthetic; make up most of Earth’s
plankton
 Have glass-like silicon shells
 Brown Algae
 Golden Algae
VI. KINGDOM PROTISTA - Systematics, cont
• Foraminiferans
 Ca Carbonate shells
 Dead foraminiferans settle on ocean
floor; shells become chalk
 White Cliffs of Dover
• Rhodopyhta
 Red algae
 Mostly multicellular
• Chlorophyta
 Green Algae
 Volvox
 Spirogyra
 Chlamydomonas
 Unicellular; may be colonial
 Chloroplasts, cell walls of cellulose
 Gave rise to land plants
VI. KINGDOM PROTISTA - Systematics, cont
• Amoebozoa
 All have pseudopods
 Amoeba
May be parasitic
Entamoeba
histolytica
 Slime Molds
VII. KINGDOM FUNGI
VII. KINGDOM FUNGI, cont
Characteristics of Fungi
• Heterotrophic by absorption;
releases exoenzymes
 Decomposers (saprobes)
 Parasites
 Mutualistic symbionts
(lichens)
• Hyphae - body filaments
 Septate (cross walls)
 Coenocytic (no cross walls)
• Mycelium - network of hyphae
• Chitin cell walls
VII. KINGDOM FUNGI, cont
Life Cycle
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
VII. KINGDOM FUNGI, cont
Classification
• Phylum Chytridiomycota
 Most closely related to protists;
considered to be most primitive
member of Kingdom Fungi
 Aquatic fungi
• Phylum Zygomycota
 Food mold; Rhizopus
 Mycorrhizae
 Produce spores from zygote
surrounded by thick covering
called zygosporangium; may
remain dormant for months;
resistant to extreme conditons
VII. KINGDOM FUNGI - Classification, cont
• Phylum Ascomycota
 Sac fungi
 Yeasts, truffles, morels, Sordaria
 Produce sexual and asexual
spores
 Ascus – sexual spore
 Conidia – asexual spore
• Phylum Basidiomycota
 Club fungi
 Mushrooms, puffballs, bracket
fungi
 Basidiocarp – haploid hyphae fuse,
meiosis occurs, formation of
basidospores
VII. KINGDOM FUNGI, cont
Specialized Life Styles
• Molds
 Used to be classified as Deuteromycota or
“Imperfect Fungi”
 No known sexual stage
 Penicillium
• Yeasts
 Unicellular
 Reproduce asexually; budding
 Saccharomyces
• Lichens
 Mutualistic relationship with algae, cyanobacterium
 Sensitive to air pollution
• Mycorrhizae
 Mutualistic relationship found in 95% of all plants
 Increases absorptive surface of roots