• Absent students/make-up
• Chapter 22- go over quickly
• Lab results/complete and turn in
Evolution

 Evolution- change over time OR descent with modification
 Proposal that Earth’s species are descendants of ancestral
species that were very different from those alive today.
Pattern- data driven based on observations of the natural world.
Process- mechanisms produce diversity of living things.
How Did We Come to Evolution?

 Aristotle- 384-322 A.D.- opposed evolution, scale of
nature everything is fixed, from simplicity to complexity.
 Linnaeus (1707-1778) – developed naming system.
Grouped based on similar characteristics into general
categories, from the pattern of their creation.
 Cuvier (1769-1832) – paleontology, thought
catastrophism- boundaries due to catastrophes that
destroyed a species

 Hutton (1726-1797) – Proposed gradualism- said that
geologic changes took place through the cumulative
effect of slow continuous change
 Lyell (1797-1875) - Uniformatarianism which stated
that things don’t change over time
 Lamarck (1744-1829) – Believed in several lines of
descent called it inheritance of acquired
characteristics.

 Darwin (1840’s) – proposed the idea of natural
selection in which individuals with certain inherited
characteristics leave more offspring than individuals
with other characteristics.
 He called these ADAPTATIONS – characteristics of
organisms that enhance their survival and
reproduction in a specific environment.
Darwin never coined the term evolution rather:
“descent with modification”
3 Major Contributions from Darwin

 Organisms are related through descent from a
common ancestor that lived in the past – that
explains the unity of life.
 These descendants have accumulated diverse
modifications, or adaptations, that allow them to
survive and reproduce,
 Over long periods of time this descent with
modification has led to the rich diversity we have
today.
Darwin’s proposed mechanisms

 Artificial selection
Humans have modified a
variety of domesticated
plants and animals over
many generations by
selecting individuals with
the desired traits as
breeding stock
 Natural selection
1.
2.
3.
Organisms have heritable
traits that enable them to
reproduce at a higher rate
Overtime these traits
increase a match between
organism and environment.
If the environment changes
or if individuals move to a
new environment, a new
species could result in the
process.
Important points

 Individuals do not evolve – populations do.
 Natural selection can act only on heritable traits.
 Environmental factors vary from place to place and
from time to time.
Sounds Great- Where’s the Data?

4 major types of data:
1.
2.
3.
4.
Direct observation
Fossil record
Homology
Biogeography
1. Direct Observation

 Page 461 – Case Study
 Page 462 – Case Study
2. Homology

Homology

 Homologous structures – same structure different
function
 Vestigial structures – remnants of features that served a
function in the organism’s ancestors
 Molecular similarities
 Embryology
Tree

 Evolutionary tree- diagram that reflection
evolutional relationships among groups of
organisms
Different Cause of Resemblance

 Convergent evolution – independent evolution of
similar features in different lineages.
 Analogous- different structure, same function as a
result of convergent evolution
3. Fossil record

 Fossil record is NOT complete
 Can be used as indirect or direct evidence in some
situations.
4. Biogeography

 This relates to the geographic distribution of species.
Influenced by many factors
 Continental drift
 Endemic- species on island are found nowhere else in
world.
AP Biology

Quiz today!!!
Quiz

1. Describe the difference between direct and indirect
evidence supporting evolution.
2. Explain the difference between homologous and
analogous structures.
3. Explain natural selection and how natural selection
was developed.
Is the finch evolving?

Smallest unit of Evolution

 Individuals DO NOT evolve – populations do
 Natural selection acts on individuals meaning traits
affect its survival and reproductive success
 The effects of natural selection are only apparent in
changes within a population over time

 Microevolution – change in allele frequencies in a
population over time
 What affects change in allele frequency?
1. Natural selection
2. Genetic drift – events that alter frequency
3. Gene flow – transfer of alleles between
populations
Genetic variation

 Differences among individuals in the composition of
their genes or other DNA segments.
 Not all phenotypic variation is heritable only
Darwin and Mendel

 Discrete characters – determined by a single locus
 Quantitative characters- vary along a continum
Genetic Variation contd.

 Variation occurs between populations
 Geographic variations- differences in genetic
composition of geographically separate populations
Mutation

 New genes and new alleles originate by mutation
 Sexual reproduction results in genetic variation as
existing alleles and genes are arranged in new ways
 New alleles arise by mutation
Mutation rates

 Some organisms mutate faster than others
 Compare: sexual reproduction to HIV
 HIV- no DNA, RNA mutates faster (that is why a
single treatment is not effective)
 Sexual reproduction – crossing over, independent
assortment, fertilization
Hardy-Weinberg

 Population – a group of individuals of the same
species that live in the same area and interbreed to
produce fertile offspring
 Gene pool- the total alleles for the individuals in a
population
Hardy-Weinberg

 This principle states that the frequencies of alleles
and genotypes in a population will remain constant
from generation to generation if these conditions are
met:
1.
2.
3.
4.
5.
NO mutation
Random mating
No natural selection
Extremely large population size (genetic drift)
NO gene flow (immigration/emigration)
Hardy-Weinberg

p+q=1
p - the allelic frequency of P
q - the allelic frequency of p
Hardy-Weinberg

( p + q )( p + q ) = 1
Or
p2 + 2pq + q2 = 1
p2 – frequency of PP
2pq – frequency of Pp
q2- frequency of pp
H-W

400 total flowers in the population. 100 white flowers are
homozygous recessive genotype pp.
1. Determine the pp of the population?
Means: 100/400 = ¼ = _____
2. How can we calculate q and p?
q2 = ______
p+q=1
q = 0.25
q = ______
p=1-q
p = 1 – 0.5 = 0.5
H-W

500 wildflowers in the population 1000 total genes
CR CR – red (320)
CW CW – white (20)
CR CW - pink (160)
Lets find the allelic frequencies
CR
1. Find the # of CR in the pink flowers ____
2. Find the # of CR in the red flowers ___________
3. CR frequency = ______________________
H-W

500 wildflowers in the population 1000 total genes
CR CR – red (320)
CW CW – white (20)
CR CW - pink (160)
Find CW frequency
1. Find CW in the pink flowers _______
2. Find CW in the white flowers ______
3. Allele frequency ___________
Changes to H-W can alter allele
frequencies in population

 Nonradom mating- can affect the frequencies but
usually have no effect on allele frequencies in the
gene pool.
 Natural selection – Alleles are passed on to the next
generation in frequencies different from their relative
frequencies in the present population.
Changes to H-W can alter allele
frequencies in population

 Genetic drift – chance fluctuations in allele frequencies in
small populations
 Large populations allele frequencies do not change from
generation to generation by chance alone.
 The smaller the population the greater chance of
deviation
 Small populations fall into 2 groups
 Founder effect  Bottleneck effect

 Founder’s effect
 Bottleneck effect
When a smaller group
establishes a new
population whose gene
pool differs from the
source population
Sudden change in
environment, a severe
drop in population

 Gene flow – the transfer of alleles among
populations due to the migration of fertile
individuals or gametes
Three modes of Selection

1. Directional selection –
2. Stabilizing selection –
3. Disruptive selection -
AP Biology

 If you didn’t turn in your quiz last class please do so
now
 H-W quiz later in class period
 Chapter 24-25 today
 Study guides/lab finish
Sexual selection

 Sexual dimorphism – differences between sexes in
secondary sexual characteristics (size, coloration,
ornamentation)
 Intrasexual selection – direct competition among
individuals of one sex for mates of the opposite sex
(battles/patrol/rituals)
 Intersexual selection – mate choice, when memebers
of 1 sex (usually female) select mates.
Heterozygote Advantage

 Determined at genotype level
 Heterozygote advantage maintains genetic diversity
at the human gene
 Sickle cell SS – normal rbc’s
 Ss – Protected against malaria
 ss – sickle cell
Chapter 24

 Speciation – process by which one species splits into
two or more species.
 Speciation concept EMPHASIZES reproductive
isolation
 Reproductive isolation – biological barriers that
prevent members of two species
Reproductive isolation

 Prezygotic barriers – fertilization block
 Postzygotic barriers – fertilization occurs but may
prevent hybrid zygote from developing into a viable,
fertile adult
Prezygotic

 Habitat isolation – different habitats even if in same
geographic area
 Behavioral isolation – courtship behavior to attract mate
 Temporal isolation – breed at different times
 Mechanical – anatomically incompatible
 Gametic – gametes do not form a zygote
Postzygotic

 Reduced hybrid viability – genetic incompatibility,
may abort or produce frail offspring
 Reduced hybrid fertility – even if hybrid is vigorous,
hybrid may be infertile
 Hybrid breakdown – first-generation is viable and
fertile, but next generation is feeble or sterile
Speciation

 Allopatric speciation – geographic separation of
population restricts gene flow
 Geographic barriers (mountain ranges, glaciers, land
bridges, canyons etc)
Speciation

 Sympatric speciation – speciation occurs between
populations that live in the same geographic area.
 Note** reproductive barriers must exist for this to
occur.
 Example: polyploidy, habitat differentiation, sexual
selection,
Speciation

 Polyploidy – results in extra sets of chromosomes
 Autopolyploid – individual that has more than two
chromosome sets all derived from a single species
 Allopolyploid – when two different polyploids mate
How long does this take?

 Gradulaism – slow steady continuous change
 Punctuated equilibrium – rapid change followed by
stasis
AP Biology

 Quiz today last H-W quiz 
 Please turn in pGLO labs if you haven’t yet
 Email me H-W modeling lab
Chapter 25

 Macroevolution – broad pattern of evolution above
the species level
What scientists think…

1. Abiotic synthesis of small organic molecules
(monomers)
2. Joining of monomers into macromolecules
3. Packing of these molecules into protocells, (droplets
with membranes that maintained a distinct internal
chemistry
4. Origin or self-replicating molecules that eventually
made inheritance possible
How do we test these?

 Abiotic synthesis
 Oparian and Haldane
 Hypothesized the conditions on early Earth favored the
synthesis of organic compounds from inorganic
precursors
 Miler and Urey
 Tested the hypothesis, they “recreated” conditions on
Earth, discharged sparks (lightning) and gasses and
water vapor… Results – amino acids and other organic
molecules formed.
Protocells

 Protocells – self assemble
 Must have had reproduction capabilities and energy
processing (metabolism)
 These conditions likely produced vesicles (fluid filled
compartments bound by a membrane-like structure)
 Research has shown that given lipids and other
organic molecules, vesicles will self-assemble
RNA

 RNA may have been the first genetic material
 RNA catalyst called ribozymes can make short pieces
of RNA when supplied with nucleotide building
blocks
Fossil Record

 An incomplete chronicle of evolutionary change
 Radiometric dating – decay of isotopes
 Relative dating – where fossils are in strata
comparative dating
Eons

 History of Earth has been divided into 3 eons
 Archaean
 Proterozoic
 Phanerozoic
 Eras: Paleozoic, Mesozoic, Cenozoic
Evolution of photosynthesis

 Most atmospheric oxygen is of biological origin,
from the water-splitting step of photosynthesis
Endosymbiont theory

 Eukaryotic cells are more complex than prokaryotic
cells
 Endosymbiont theory – suggests that mitochondria
and plastids were small prokaryotes that began
living within larger cells
 Mutually beneficial for each cell
 Became increasingly interdependent
 Serial endosymbiosis – supposes that mitochondria
evolved before plastids
Plate tectonics

 Theory suggesting that continents drift movement is
continental drift (measured data)
 Pangaea
 Mass extinction
 Habitat destroyed, environmental changes
 Biological factors may change
 Global environmental change
Mass extinctions

5 documented mass extinctions
1. Permian – volcanic eruptions divided Paleozoic and
Mesozoic eras. 96% species were extinct.
2. Cretaceous – meteorites, boundary between
Mesozoic and Cenozoic eras more than half species
went extinct (dinosaurs included)
Adaptive Radiation

 Occur when a few organisms make their way into
new areas, or when extinction opens up ecological
niches for surviving species
Evolution is not goal oriented

AP Biology

 Hardy- Weinberg quizzes – redo 
 Chapter 26 – Phylogeny
 TURN IN YOUR LABS – if you haven’t done so
 Study guides – review
 Blast Lab - intro
Chapter 26

 Phylogeny is the evolutionary history of a species or
groups of species
 Systematics – system used to classifying diversity
and determining the evolutionary relationships of
living and extinct organisms
 Taxonomy - determines how organisms are classified
and named.

 Linneaus developed a naming system :







Kingdom
Phylum
Class
Order
Family
Genus
Species
Clade- grouping
of organisms
which include
ancestral species
and all of its
descendants
Shared derived character – evolutionary novelty unique to a particular
clade
Shared ancestral character – originated in an ancestor of the clade
Example: Human s
shared derived- hair
shared ancestral – vertebrae
Scientists identify each of the following:
Outgroup – species or group of species that diverged before the lineage that
includes the species being studied
Ingroup – species being studied and their relatives
Naming systems

 5 kingdom naming system:
1. Monera (prokaryotes)
2. Protista (mainly unicellular eukaryotes)
3. Plantae
4. Fungi
5. Animalia

 Problems –
 As data comparisons came in they found organisms
that were grouped could be very different from each
other…
SO…
Scientists revised their system to a 3 domain system
Grouping of organisms

 Organisms are grouped into 3 major domains of life:
1. Archaea – diverse group of prokaryotes inhabiting
wide variety of environments
2. Bacteria – most prokaryotes including bacteria most
closely related to chloroplasts and mitochondria
3. Eukarya – includes all organisms with a true nuclei
(however plantae, Fungi, and Animalia are still
recognized)
AP BIO

 Blast lab next class – online already
 Today finishing up rest of unit
 Test March 6 
 See cabinet for sign ups for classes next year
(Honors Anat. and Phys.)
Prokaryotes vs Eukaryotes
 Prokaryotes







Most Unicellular
0.5-5 µm
Flagella
Internal foldings
Circular DNA
Binary Fision
Many shapes
 Spherical (cocci)
 Rod-shaped (bacilli)
 spiral (spirilla)

 Eukaryotes
 Unicellular and multicellular
 10-100 µm
Bacteria vs Archaea

 Cell wall of peptidoglycan
 Gram-staining – used to classify bacteria based on
amount of peptidoglycan
 Gram positive – lots of peptidoglycan (purple)
 Gram negative – less peptidoglycan (redish)

Prokaryotes

 Lack complex structures, but
have infoldings of plasma
membrane, for metabolism
 Lack true nucleus – nucleoid
 DNA – plasmids
 Divides via binary fission
 Conjugation – DNA is
transferred between two
prokaryotic cells
Metabolism

 Obligate aerobes – must use oxygen for cellular
respiration
 Obligate anaerobes – poisoned by oxygen, live via
fermentation
 Anaerobic respiration – substances other than oxygen
 Facultative anaerobes – use oxygen if present but can also
carry out fermentation or anaerobic respiration
Phylogeny

Archaea

 Extremophiles – lovers of extreme conditions
 Halophiles – salt lovers
 Thermophiles – heat lovers
 Methanogens – release methane
Bacteria

 Majority of prokaryotes
 Varied in structures and function
 Page 568-569 for more details
Protists

 Small eukaryotes
 Some have flagella
 Size ranges between 0.5 – 2 µm
 Have a nucleus
 Have membrane bound organelles (mitochondria
and golgi)