Download howard overhead notes evolutionary biology

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AP Biology Notes: Evolutionary History &
Mechanisms chpt 22-26
Pre-cursor: Evolutionary Theory vs. “Intelligent
Design Theory”
A. Science is a tool not a god
1. as a “god” –“science has all the answers”
2. as a tool – limited by senses
GOD
B. Intelligent Design –
1. I Cor 1:18-21
2. Faith? Heb 11:1-3
a. There will never be scientific proof!!
3. age of Earth???????? Gen 1:1-3
C. Evolutionary Theory is not the Devil!
1. It is the best explanation of the data using
science as a tool
a. God? Science does NOT include God in its
evaluation because God is beyond the limitations of
science
Everythi
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2. Christians force the evolutionary theory into
the mold of anti-God – in reality it is a scientific
theory created by following the scientific method
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Evolutionary Biology
I. History
A. The Men
1. Linnaeus –Swedish naturalist --binomial
nomenclature – taxonomic system
2. Hutton – 1795 Scottish geologist – created
gradualism- profound change is produced by a slow,
continuous process (no instantaneous or miraculous
changes)
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3. Lamarck –1809 English –museum of natural
history fossils (he was WRONG, but 1st to say orgs
evolve)
a. 1st to create a theory of evolution
1) use/disuse –“if you don’t use it you lose it”
or if you use it a lot it becomes more pronounced
2) inheritance of acquired char. – some
change acquired during lifetime can be passed on to
offspring
3) natural transformation – offspring of each
generation slightly changed (more complex)
4. Cuvier – paleontology—study of fossils
a. catastrophism –each boundary between fossil
strata corresponded to a catastrophe of some kind
that resulted in extinctions
b. he established extinctions as fact
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5. Lyell – uniformitarianism (goes hand-in-hand
with gradualism)
a. uniformitarianism says geologic processes
that happened in the past are the same as are
happening now (same type & rate ---no catastrophes)
b. anti-catastrophism
6. Darwin (1809 – 1882) born the
same day as Abe Lincoln
a. 1831-36 – voyage on the HMS
Beagle as a naturalist (had a crappy
journey – seasick, caught Chaga’s disease) went to
the Galapagos Islands!!!
b. came back & married cousin 1839 married
into the Wedgewood China family $$$$$
c. 1859 - publishes book “On the Origins of
Species…” to explain how adaptations can lead to a
change in a pop over time
On the Origin of Species by Means of Natural
Selection, or the Preservation of Favoured Races
in the Struggle for Life.
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d. Darwin’s theory of natural selection
1) overproduction of offspring – always more
offspring are produced than can survive
2) variations occur between individuals in a
pop
3) limited envr. Resources creates a
a) “struggle for survival” – some variation
allows for one org to survive better than another
b) “survival of the fittest” – that org
passes these traits on to the offspring
4) inherited favorable char. become more
common
a) “descent with modification” – over TIME
variations can differentiate 1 group of orgs from
another
II. Modern theory of evolution (neo-Darwinism)
A. Terms
1. population –gp of interbreeding orgs of the
same species in the same geographic area
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2. species – orgs of the same kind that can mate
& have viable offspring
3. evolution –change over time
4. microevolution – pop change from 1 generation
to the next
5. macroevolution – patterns of changes in groups
of related species over broad periods of geologic
time
6. fossil – remains of orgs that were buried
quickly so that decomp was stopped/slowed – in
sedimentary rock
7. gene pool—all genes in a pop at any 1 time
B. Natural Selection
1. pops produce vast #’s of offspring
2. pop sizes remain stable
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3. envr. resources are limited – just because pops
grow larger doesn’t mean there’s more food, light,
water….
4. competition for survival – which org is best
able to get the limited resources
5. variation among individuals
6. most variations are heritable
7. survival of the fittest
8. evol. occurs as favorable traits accumulate in a
pop over time
C. Kinds of natural selection p.458
original pop
evolved pop
directiona
l selection
diversifying
selection
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1. stabilizing selection – eliminates individuals
w/extreme traits – the common traits are the best
adapted (gets rid of the extremes)
2. Directional Selection – favors individuals at 1
end of the spectrum (extreme traits) these traits
are best adapted
3. diversifying/disruptive selection – envr favors
the extremes of a trait
4. sexual selection – produces sexual dimorphism
a. sexual dimorphism- difs in
male & female secondary sex
characteristics (antlers, coloring,
plumage…)
b. male competition –
strength contests – winner gets
chance to mate
c. female choice- (intersexual
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selection) – females choose mate based on some
masculine characteristic (may reflect overall health
of male?)
5. artificial selection – directional selection
carried out by humans
D. Evidence for Evolution
1. biogeography – study of the
distribution of orgs
a. related orgs live close to each
other
b. island species are related to
species on the nearest continent
2. Paleontology – study of the fossil
record
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a. provides evidence that the
variety of species that’s inhabited the
Earth has changed over time
1) strata – geological processes
form layers or strata of rock
2) each stratum has its own fossils
a) Law of Superposition- oldest
layer of rock is on the bottom – type of
RELATIVE DATING
b) Absolute dating – estimated
from amt/ratio of radioactive isotope in
specimen
3. Comparative Anatomy – allows
classification of orgs (taxonomy)
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a. Homologous structures – evolved
from common original structure
1) same structure different
function
2) divergent evolution – evolution
used 1 structure & modified it for dif.
purposes (ex forelimbs of mammals)
b. Analogous structures – evolved
from dif original structures, but due to
similar envr. have a similar function
1) convergent evolution – evolution
used multiple structures & modified
them for the same purpose (ex wings of
bats & birds)
c. parallel evolution – 2 related
species that have diverged then made
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similar evolutionary changes via dif paths
& reconverged
d. coevolution – one species evolves
in response to another species evolving
(predator/prey relationships)
e. vestigial structures – structures
that functioned in ancestral orgs but are
reduced in structure & function in
descendant
1) serve little or no purpose in
currently existing species – nat.
selection has selected for orgs w/in the
pop that have reduced or absent forms
of the structure (for metabolic
efficiency?) ex: muscles that move the
ears
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4. Embryology – reveals similar stages
in development among related species
a. similarities in ontogeny help
establish phylogeny
evolutionary relationships
“ontogeny recapitulates phylogeny”
5. Molecular Biology
a. DNA comparison or AA sequence
in like proteins—more closely related
species should have more similar dna or
more similar AA sequences. ----They’re
starting to use this to modify the
standard taxonomy of many orgs!
E. Population Genetics –
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1. Darwin’s explanation not well accepted until it
was combo’d with Mendelian genetics (early 1930’s) –
genetics explains the variations in populations
2. Variations in a pop caused by:
a. mutations
b. sexual reproduction – allows offspring to be
dif from parents (not clones), crossing over,
independent assortment of chromosomes, random
fertilization
c. diploidy – allows recessive genes to be
carried in pop
d. polymorphism – maintaining stable
frequencies of more than 1 phenotype in a pop
1) heterozyg. advantage- being heterozygous
for a trait is “better” than being homozyg.--heteroz for sickle cell anemia gives immunity to
malaria
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2) frequency-dependent variation- teetertotter effect over time – least common phenotype
becomes advantageous & thus
most common---- then
conditions change slightly &
what was MOST common
becomes least & back & forth
e. outbreeding – opposite of inbreeding
f. neutral variation – variation with no selective
advantage
3. changes in allele frequencies (gene
frequencies) caused by:
a. natural selection
(b. mutation – more commonly these are
harmful)
c. genetic drift – RANDOM changes in gene
frequencies
1) bottleneck effect – disasters (flood,
fire…) occur killing off most of a pop & by chance
certain alleles/genes will be over represented (&
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some entirely absent) *this usually decreases
variation in a pop
2) founder effect- small # of the pop
colonize a new area & are isolated *this usually
decreases variation in a pop
d. gene flow –genetic exchange due to
migration –
1) immigration – orgs entering a region
2) emigration – orgs exiting a region
e. non-random mating – choose mates based on
individual traits or nearness
1) inbreeding- mating w/relatives
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4. Hardy-Weinberg Equilibrium = genetic
equilibrium (no evolution)
*occurs when allele
frequencies in a pop
remain constant
*to study pops where
changes occur you must
have the “norm”
to
compare them to!
a. to have a HardyWeinburg equilibrium….
1. no natural
selection
2. no mutations
3. no gene flow
4. no genetic drift
5. random mating
6. LARGE pop
It would seem that almost no population would ever be in
equilibrium given these assumptions.
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However, in practice
A. mutation rates are small to negligible.
B. population size will still give a good fit to Hardy-Weinberg
even if the population is fairly small, say 100 individuals.
C. Also, since the equilibrium is established after one
generation, the population will come back to equilibrium
within one generation after being disturbed
p2+ 2pq + q2 = 1 (frequency of genotypes must add up to
1)
p + q = 1 (frequency of both alleles must add up to 1)
p = frequency of allele A (dominant)
q = frequency of allele a (recessive)
Roger Rabbit Lab!
III. Speciation – formation of a new
species (chpt 24)
A. speciation occurs via 2 means
1. allopatric speciation- a
geographic barrier separates 2 pops
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of the same species (rivers, mts,
desert)
a. genetic drift etc… allows for
variation & over time if enough
variation occurs then the 2 pops will
be unable to mate & have offspring--so a new species occurs
b. adaptive radiation –
new species branch off of parent
species
“rapid” evolution of many species
from 1 parent ancestor
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2. sympatric speciation – new
species form w/out
geographic/geologic barries
a. polyploidy speciation – mainly in
plants (generally detrimental in
humans & other animals) meiosis
mess up creates polyploidy gamete
polyploidy zygote
which can’t mate
w/original pop
b. hybridization – (mainly in
plants) – 2 dif but closely related
species mate along a geographic
boundary & create viable offspring--offspring have some variation that’s
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advantageous so hybrids develop along
geographic boundary
(whitetail deer
escape faster going down hill
mule deer escape faster going up
hill
hybrids – neither)
c. balanced polymorphism multiple variations of a particular
trait --- (ex. dif colors) 1 variation
works best in a slightly dif habitat
than another so orgs w/that
particular variation tend to stay
together & mate ultimately leading to
a new species
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B. Reproductive Isolation (no
physical barriers) – prevention of
breeding between species
1. prezygotic barriers – prevention
of fertilization or prevention of
mating
a. habitat isolation – orgs don’t
ever meet
b. behavioral isolation – orgs
don’t recognize mating behavior in
other species (elaborate courtship
rituals)
c. temporal iso. – species breed
at dif times of the day or during dif
seasons
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d. mechanical iso – anatomically
incompatible
e. gametic iso1) male gametes can’t survive
in female (internal fert)
2) female gametes don’t
chemically “recognize” male
gametes (protein ID)
2. postzygotic barriers – occurs
after fert
a. reduced hybrid viability –
zygote fails to develop
b. reduced hybrid fertility –
offspring are sterile
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c. hybrid breakdown – hybrids
are okay but the hybrids offspring
are not (due to a & b above)
IV. Origin of Life (chpt 26)
A. Earth & Atmosphere – formed
4.5 billion years ago (bya)
1. primordial atmos. – 1st existing
atmos – formed from gases vented
from Earth’s interior
a. consisted of – CO CO2 H2 N2
H2O HCl S HCN
(very little
O2 )
2. primordial seas – 1st existing sea
– as Earth cooled, gases condensed to
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create seas w/many minerals –
sometimes called “primordial soup”
3. complex molecules formed in
seas
a. E to catalyze reactions – came
from UV light, lightning, heat used to
catalyze rxns forming amino acids,
acetic acid…
b. 1920’s Oparin &
Haldane – theorized
that primordial atmos &
seas (w/out O2) allowed
all of these chem. rxns &
formations & since the seas & atmos
are dif today it no longer occurs
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c. 1953 Miller & Uray – tested
Oparin’s theory
1) created conditions of
primordial atmos in lab – H2O H2 CH4
NH3 - & were able to produce AA’s &
other organic cmpds w/heat &
electricity
4. polymers formed from
monomers through dehydration
synthesis (polymers formed by
removal of water)
non-living
a. proteinoids – abiotically
produced proteins – how?— by letting
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AA’s dry out on a hot substrate (like
a rock)
5. protobionts – aggregates/clumps
of abiotically produced molecules
a. precursors of cells
b. some had membranes that
enclosed an area where chem. rxns
occurred
???????And then a
miracle occurs ---otherwise known as
“spontaneous
generation”???
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Louis
Pasteur
read pp. 521-2 “Debate about origin
of life abounds”
p.517
6. primitive
prokaryotes formed –no
nucleus, heterotrophic
7. Autotrophic prokaryotes formed
(through mutation?) ex:
cyanobacteria
8. O2 & O3 layers formed –due to
autotrophic orgs – O2 atmos formed
then UV light converted O2 to O3
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blocking out the UV light & making
atmos more hospitable (& ending
abiotic syn of organic mlcls)
9. Eukaryotes formed via
endosymbiosis!
a. endosymbiotic theory – says
eukaryotes (w/nucleus) formed from
symbiotic relationships between
prokaryotes
b. evidence1) mitochondria & chloroplasts
have their own DNA
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2) ribosomes of mito. & chloro
are genetically
similar to
bacterial ribosomes
3) M & C – reproduce
independently inside the cell
via binary fission – like bacteria!
4) M & C have double
membranes – caused by
endocytosis
5) thylakoid membranes in C’s
are like membranes in
cyanobacteria
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V. History of Life
p.512-
A.
life originated 3.5 to 4
billion years ago (bya) -
1. oldest
fossils in Australia – similar to
bacteria today – they form
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stromatolites (fossilized bacteria
p.513)
2. prokaryotes dominated 3.5 –
2.0 bya
B. O2 accumulates 2.7 bya due to
autotrophic prokaryotes
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C. eukaryotes showed up 2.1 bya larger & more complex than
prokaryotes
D. multicellular eukaryotes 1.2 bya
E. animal diversity explosion 543 mya
F. plants, fungi, animals colonized
land 500 mya
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