IV. PROKARYOTES – EUBACTERIA, cont
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Transcript IV. PROKARYOTES – EUBACTERIA, cont
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