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Today’s Plan: 2/25/11. Bellwork: Go over test/fly counts (30 mins) Amino Acid Sequence and Evolution Lab (30 mins) Begin Natural Selection Notes (the rest of class) Pack/Wrap-up (last few mins of class). Today’s Plan: 2/26/10. Bellwork: Finish Flies/Compile Class Data (30 mins) - PowerPoint PPT Presentation
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Today’s Plan: 2/25/11
Bellwork: Go over test/fly counts (30 mins)
Amino Acid Sequence and Evolution Lab (30 mins)
Begin Natural Selection Notes (the rest of class)
Pack/Wrap-up (last few mins of class)
Today’s Plan: 2/26/10
Bellwork: Finish Flies/Compile Class Data (30 mins)
Sexual Selection Video Pack/Wrap-up (last few mins of class)
Today’s Plan: 3/1/10
Bellwork: Go over lab/Do PTC (15 mins)
AP Lab 8: Population Genetics and Evolution-Part B Genetic Drift (20 mins)
Finish video Continue Notes-if time Pack/Wrap-up (last few mins of class)
Today’s Plan: 3/2/10
Bellwork: Settle in/Grab cards (5 mins)
Finish Lab (30 mins) Continue notes (25 mins) Pack/Wrap-up (last few mins of class)
Today’s Plan: 3/3/10
Finish Notes (30 mins) Restriction Mapping Exercise (the rest
of class) Pack/Wrap-up (last few mins of class)
Today’s Plan: 3/4/10
Bellwork: Finish Restriction Mapping (20 mins)
Finish Nat. Sel Notes (20 mins) HB fun week (the rest of class)
Today’s Plan: 3/5/10
HB Stations-the entire period!
Before Natural Selection Recall that Darwin wasn’t the 1st to think about how species have
changed over time Aristotle’s Scala Naturae grouped species with similar “affinities”
together Linnaeus came up with Binomial Nomenclature and did much
classifying based on physical similarity Cuvier noted that fossils of species differed significantly from more
modern forms (proposed the idea of Catastrophism-that changes happened b/c of catastrophic events, and not gradually)
Lamarck suggested that use/disuse and will could change an organism’s body to fit the environment (he thought that acquired traits were heritable)
Malthus also discussed population limits Darwin bred pigeons for various traits (artificial selection) Recall that besides thinking about species change, others before
Darwin worked with how the planet changed Hutton proposed that geologic features were the result of gradual
changes that are still occurring today Lyell took this a step further and proposed his principle of
Uniformitarianism-mechanisms of change are constant over time
Figure 24-1
Simple cells
Fungi
Green algae
Land plants
Invertebrates
Vertebrates
Humans
Aristotle proposed that species were organized into a sequence based on increased size and complexity, with humans at the top
Natural Selection Aka “Descent with Modification” was Darwin’s
proposal for how species change over time and was the result of careful ponderance over his Galapagos Island collections
Darwin’s main focus was on adaptations that allowed species to survive better in their environments-finches had beaks adapted to their food source
Recall that while Darwin came up with the idea first, Alfred Russel Wallace also had the same ideal later, with no knowledge of Darwin’s work
The term Natural Selection was coined by Darwin’s friend, T.H. Huxley, who was called “Darwin’s bulldog” because he staunchly defended Darwin’s hypothesis
Darwin’s Observations and Inferences Observations:
Members of a population vary greatly in their traits Traits are inherited from parents to offspring All species are capable of producing more offspring than their
environment can support Because of lack of resources, many offspring don’t survive
Inferences (Summary of Natural Selection’s Mechanism): Individuals whose inherited traits give them a higher
probability of surviving and reproducing in an environment tend to leave more offspring (have greater reproductive success)
This inequality means that favorable traits accumulate in populations over multiple generations
Remember: Populations evolve, individuals don’t Traits influenced by natural selection must be heritable Environments are moving targets, so there’s no “perfect” and
what’s good in one population isn’t necessarily good in another
Current Directly Observable Evidence for Natural Selection Predation and Coloration in Guppies
Pools of guppies w/high predation produce more drab colored males There are numerous examples of these “natural experiments” done by
scientists Drug-resistant HIV and other “superbugs”
It’s natural for some viruses or bacteria to be resistant, but when you treat, what’s all that’s left to reproduce?
The Fossil Record We can see trends in the evolution of species
Anatomical Features Similar patterns of fetal development Homology (forelimb picture) Vestigial structures
Biogeography Looking at what we think happened to the geographic features of the
planet to explain distribution of species (ex: how Pangea’s split allowed us to predict where we’d find certain types of fossils)
Molecular Similarity Studies of DNA sequence and amino acid sequence can be used to
construct “molecular clocks” that give us clues to which organisms diverged from one another, and tells us relatively how long ago the divergance occurred
Figure 24-11
M. tuberculosis
EVOLUTION OF DRUG RESISTANCE
Lung tissue
Bacteria with pointmutation in rpoB gene
1. Large population ofM. tuberculosis bacteria in patient’s lungs makes him sick.
2. Drug therapy begins killing most M. tuberculosis. Patient seems cured and drug therapy is ended. However, a few of the original bacteria had a pointmutation that made them resistant to the drug treatment.
3. The mutant cells proliferate, resulting in another major infection of the lungs. The patient becomes sick again.
4. A second round of drug therapy begins but is ineffective on the drug-resistant bacteria. The patient dies.
Figure 24-3
110 myo ammonite shell 50 myo bird tracks 20,000 y-old sloth dung
Figure 24-9
Turtle Human
Humerus
Radius and ulna
Carpals
Metacarpals
Phalanges
Horse Bird Bat Seal
Figure 24-8
Chick Human House cat
TailTailTail
Gill pouch Gill pouch Gill pouch
Figure 24-5 The human tailbone is a vestigial trait.
Humancoccyx
Capuchinmonkey tail
Goose bumps are a vestigial trait.
Erect hair on chimp (insulation, emotional display)
Human goose bumps
(used for balance, locomotion)
Figure 24-7
Aniridia (Human)
eyeless (Fruit fly)
Only six of the 60 amino acids in these sequences are different. The two sequences are 90% identical.
Amino acid sequence (single-letter abbreviations):Gene:
Figure 27-7
Tree thinking vs. Convergent evolution In many cases, evolutionary trees are
created in order to show how species evolved from common ancestors Sometimes, this happens b/c of adaptive
radiation-when organisms evolve in a variety of directions in order to exploit different aspects of the environment
Occasionally, organisms resemble each other, not because they’re related, but because some characteristics are advantageous regardless of their ancestry Ex: sugar gliders in Australia look like flying
squirrels
Figure 27-11
Hawaiian silverswords underwent adaptive radiation.
Hawaiian honeycreepers underwent adaptive radiation.
Star phylogeny (a large polytomy)
Adaptive radiations produce star phylogenies.
Rapidspeciation
Figure 24-15b
Bacteria ArchaeaGreenalgae
Landplants Invertebrates Vertebrates Fungi
Darwinian evolution produces a tree of life.
Common ancestor of all species living today
The branches on the tree represent populations through time. All of the species have evolved from a common ancestor. None is higher than any other
Sexual Selection This is a variation of natural selection where some
traits persist, not because they’re advantageous, but because they’re attractive
In some cases, the traits that evolve are disadvantageous, but continue to persist
Intersexual Selection is based on the “female choice” model-the opposite sex chooses a mate
Intrasexual Selection is based on competition within the sex for access to mates or resources that will attract mates
Causes sexual dimorphism (variation between sexes)
Figure 25-15
During the breeding season, males of the beetle Dynastes granti use their elongated horns to fight over females.
Males
Females
Scarlet tanagerBeetle Lion
Male scarlet tanagers use their brightcoloration in territorial and courtshipdisplays.
Male lions are larger than females lions andhave an elaborate ruff of fur called a mane.
Figure 25-14 Males compete to mate with females.
Variation in reproductive success is high in males.
Variation in reproductive success is relatively low in females.
The survival of the fittest. . . Remember, fitness is relative, and
“struggle” isn’t always direct conflict. Depending on which traits are favored,
there are 3 ways in which natural selection can influence phenotypic variation Directional selection-one extreme phenotype is
favored Disruptive selection-both extreme phenotypes
are favored Stabilizing selection-average is favored
Figure 25-3
Before selection
Directional selection changes the average value ofa trait.
Normal distribution
For example, directional selection caused average bodysize to increase in a cliff swallow population.
During selection
After selection
Original population(N = 2880)
Survivors(N = 1027)
Change inaveragevalue
Highfitness
Lowfitness
Change inaveragevalue
Figure 25-4
Before selection
Stabilizing selection reduces the amount of variationin a trait.
Normal distribution
For example, very small and very large babies are themost likely to die, leaving a narrower distribution of birthweights.
During selection
After selection
Mortality
Reductionin variation
High fitnessLowfitness
Heavymortalityon extremes
Lowfitness
Figure 25-5
Before selection
Disruptive selection increases the amount of variationin a trait.
Normal distribution
For example, only juvenile black-bellied seedcrackers that had very long or very short beaks survived long enough tobreed.
During selection
After selection
Increase in variation
Low fitnessHigh
fitness
Only theextremessurvived
Only theextremessurvived
Highfitness
Evolution of Populations This is fueled by genetic variation
For individuals, can be quantified using average heterozygosity (average % of genes for which an individual is heterozygous)
For populations, you can directly compare individual karyotypes or gene sequences from each population Sometimes, the difference is dramatic, and sometimes
the difference is a cline (gradual difference) This often exists b/c of geographic variation (isolation)
Genetic Variation occurs for 2 reasons Sexual Reproduction Mutation is the ultimate source for most new genetic
variations. Often these mutations are neutral, but occasionaly, you get an adaptive mutation. The rates at which mutation occurs varies between species.
Hardy-Weinberg Useful for testing whether or not a
population is evolving This is a mathematical model:
p2+2pq+q2=1 p=frequency of the dominant allele q=frequency of the recessive allele
When a population is in Hardy-Weinberg equilibrium, the equation works, but when populations are evolving, it is an inequation.
Figure 24-10 If heritable variation…
… leads to differential success…
… then evolution results.
A1A1
A1A1
A1A1
A2A2
A2A2
A2A2A1A2
A1A2
A1A2
A1A2
A1A1 A1A2
A2A2
A1A1
Color varies among individuals primarily because of differences in their genotype
Birds find and eat many more dark-winged moths than light-winged moths
Allele frequencies have changed in the surviving moths
Figure 25-1-1
A NUMERICAL EXAMPLE OF THE HARDY-WEINBERG PRINCIPLE
Allele frequencies in parental generation:
Gene pool (gametes from parent generation)
A1 A1 A1 A1A2 A2 A2 A2
Allele A1
0.7 0.7 = 0.49 0.7 0.3 = 0.21
p p = p2
0.3 0.7 = 0.21 0.3 0.3 = 0.09
= q = 0.3
= p = 0.7
q p = pq q q = q2
Allele A2
q p = pq
1. Suppose allele frequenciesin the parental generation were0.7 and 0.3.
2. 70% of gametes in the gene
pool carry allele A1, and 30%
carry allele A2.
3. Pick two gametes at randomfrom the gene pool to formoffspring. You have a 70%
chance of picking allele A1 and a
30% chance of picking allele A2.0.21 + 0.21 = 0.42
Off
spri
ng
Figure 25-1-2
A NUMERICAL EXAMPLE OF THE HARDY-WEINBERG PRINCIPLE
Off
spri
ng
Frequency ofA1A1 genotype is
p2 = 0.49
Frequency ofA1A2 genotype is
2pq = 0.42
Frequency ofA2A2 genotype is
q2 = 0.49
Allele frequencies inoffspring gene pool p = frequency of allele A1 q = frequency of allele A2
12
(0.42) + 0.09 = 0.3q =
Genotype frequencies will be given by p2 : 2 p q : q2 as long as all Hardy-Weinberg assumptions are met.
4. Three genotypes are possible.Calculate the frequencies of thesethree combinations of alleles.
5. When the offspring breed,imagine their gametes enteringa gene pool. Calculate thefrequencies of the two allelesin this gene pool.
6. The frequencies of A1 and A2
have not changed from parentalto offspring generation.Evolution has not occurred.
49% of offspring havethe A1 A1 genotype. All
will contribute A1 allelesto the new gene pool.
42% of offspring have the A1 A2Genotype. Half of their gameteswill carry the A1 allele and the
other half will carry the A2 allele.
9% of offspring havethe A2 A2 genotype. All
will contribute A2 allelesto the new gene pool.
(0.42) = 0.7p = 0.49 + 12
Conditions for Hardy-Weinberg
No mutation Random Mating No natural selection Large population size No gene flow Rarely do all of these conditions exist
at any given moment, but over time, populations tend to be in equilibrium
Altering Gene Frequencies Genetic Drift-caused by small population size or
random changes that make predicting gene frequency difficult. 2 examples: The founder effect-a small number of individuals are
isolated from the larger group and have to reestablish a gene pool
The bottleneck effect-catastrophic incidents drop population size quickly and dramatically
In either case, genetic variation is lost, and harmful alleles can persist
Gene Flow-occurs when genes transfer in and out of populations. Usually, this is negligible unless something causes any of the following factors to change dramatically: Immigration Emigration
Figure 25-6
Figure 25-8Lupines colonize sites and form populations.
Gene flow reduces genetic differences among populations.
Year 1: Seed establishes new population
Source population New population
Seed
Frequency of A1 = 0.90
Frequency of A2 = 0.10 Frequency of A2 = 0.50
Frequency of A1 = 0.50
A1A1
Frequency of A1 = 0.83
Frequency of A2 = 0.17 Frequency of A2 = 0.33
Frequency of A1 = 0.67
Year 2: Gene flow between source population and new population
Source population New population
A1A1A1A1 A1A1
A1A2 A1A2
A1A1A1A2
Geneflow
A1A1
A1A1 A1A1
A1A2A1A1
A1A2
A1A2
Initially, allele frequenciesare very different
Gene flow causes allelefrequencies to becomemore similar
Preserving Genetic Variation Diploidy-Since organisms get 2 copies of
each gene, recessive alleles can be preserved
Balancing Selection-occurs when natural selection maintains 2 forms of a trait in a population The heterozygote advantage-sickle cell disease
and malaria symptom resistance Frequency-Dependent selection-as a phenotype
becomes more common, it loses its advantage Neutral Variation-occurs when mutation has little
to no effect on phenotype or on reproductive success
Why isn’t there a “perfect” organism
Selection can only act on existing variations (and each intermediate step between phenotypes must be adaptive)
You can’t scrap ancestral anatomy to build something new (see above statement)
Adaptations are often compromises (multifunctionality means you have to choose a primary function. Ex: seals don’t have legs b/c they also swim)
Chance, natural selection, and the environment have to interact
Types of evolution
Microevolution-evolution of allele frequencies within gene pools
Macroevolution-patterns of evolution over long time spans (like the emergence of new species)
The Biological Species Concept
This is the classic definition of the term “species” put forth by Ernst Mayr
A species is a group of populations whose members interbreed in nature to produce fertile offspring
Species are held together by proximity and interbreeding
Making new species Requires Reproductive isolation-barriers
that prevent the production of viable offspring (remember that hybrids can exist, but are sterile: ligers, mules, etc)
Prezygotic barriers-block fertilization Blocking mating Blocking the successful completion of mating Preventing successful fertilization
Postzygotic barriers-prevent a hybrid from mating successfully
Types of Prezygotic Mechanisms
Habitat Isolation-2 species occupy different habitats
Temporal Isolation-species breed at different times
Behavioral Isolation-courtship rituals differ Mechanical Isolation-differences in
shape/form prevent mating Gametic Isolation-the gametes may not be
able to fuse
Types of postzygotic Mechanisms
Reduced Hybrid viability-parental genes prevent the hybrid’s survival
Reduced Hybrid Fertility-sterility due to inability to produce normal gametes
Hybrid Breakdown-Some hybrids can mate with one another, but their offspring are not viable
Limitations of Biological Species It’s hard to evaluate the reproductive isolation of
fossils, nor does it address species that reproduce asexually
Other species definitions Morphological species concept-characterizes species
by body shape and structure (can be applied to sexual and asexual reproducers, however this relies on subjective criteria)
Ecological species concept-characterizes a species based on its ecological niche (also can be applied to sexual and asexual reproducers, and emphasizes the role of disruptive selection in species definition)
Phylogenetic species concept-a species is defined by the smallest group of individuals that share a common ancestor (difficult to deterime the degree of difference required to separate one species from another)
Allopatric Speciation “other country” speciation-occurs when
species are geographically isolated Populations become divided and evolve
differently because of different environments, genetic drift, and different mutations
Remember that they’re not different species until they’re reproductively isolated. If the populations are put back together and can still mate, they’re not different species
Figure 26-5
DISPERSAL AND COLONIZATION CAN ISOLATE POPULATIONS.
VICARIANCE CAN ISOLATE POPULATIONS.
Island
Continent
RiverRiver ch
ang
esco
urse
1. Start with one continuouspopulation. Then, colonistsfloat to an island on a raft.
2. Island population beginsto diverge due to drift andselection.
3. Finish with two populationsisolated from one another.
1. Start with one continuouspopulation. Then a chanceevent occurs that changesthe landscape (river changescourse.)
2. Isolated populations begin to diverge due to drift andselection.
3. Finish with two populationsisolated from one another.
Sympatric Speciation “same country” speciation-occurs when organisms are
in the same area but speciate Can occur via several mechanisms:
Polyploidy-having an extra set of chromosomes Autopolyploid-more than 2 sets of chromosomes from a
single species (failure of cell division) Allopolyploid-caused by an extra set of chromosomes
via hybridization of 2 species (fertile when mating with one another only)
Habitat Differentiation-when a subpopulation exploits a resource that the rest of the population doesn’t
Sexual Selection-when different groups of females prefer different groups of males
Figure 26-7 Soapberry bugs use their beaks to reach seeds inside fruits.
Feedingon thefruit ofa nativespecies
Nonnative fruits are much smaller than native fruits.
Evidence for disruptive selection on beak length
Native plant(large fruit)
Nonnative plant(small fruit)
Feeding on the fruit ofa nonnativespecies
Short-beakedpopulationgrowing onnonnativeplants
Long-beaked populationgrowing on native plants
Figure 26-8
Tetraploid parent
Triploid zygote
Diploid gametesHaploid gametes
Diploid parent
Mating
Meiosis
Gametes
Meiosis
(Two copies ofeach chromosome)
(Four copies ofeach chromosome)
(Two copies ofeach chromosome)
(One copy ofeach chromosome)
(Three copies ofeach chromosome)
The gametes of a triploid individual rarely contain the same number ofeach type of chromosome. When gametes combine, offspring almostalways have an uneven (dysfunctional) number of chromosomes.
Hybrid Zones When allopatric species come back into
contact with one another, you get a hybrid zone
There are several possibilities for what can happen in a hybrid zone Reinforcement-occurs when hybrids are less fit
than the parent species Fusion-occurs when reproductive barriers are
weak and the species become increasingly alike Stability-occurs when the hybrids persist
Figure 26-11
Hybrids inherit species-specific mtDNA sequences from their mothers.
All individuals haveTownsend’s mtDNA
Hybrids have intermediate characteristics.
Individuals that look likeTownsend’s warblers buthave hermit mtDNA
Some individualshave Townsend’smtDNA, othershave hermitmtDNA
All individuals havehermit mtDNA
Townsend’s-hermithybrid
Townsend’s warbler
Hermit warbler
Present rangeof hermit warblers(in orange)
Pacific Ocean
Present hybridzones (where two ranges meet)
Present rangeof Townsend’swarblers(in red)
Speciation Rates Darwin originally believed that gradualism
existed (species change at a slow, steady rate over time)
From the fossil record, we now know that punctuated equilibrium exists (periods of equilibrium followed by periods of natural selection)
This can happen very rapidly, and as little as 1 gene can make a species reproductively isolated
Geologic Time
This is a time scale that uses the fossil record to trace the major events in the planet’s history
Dates are determined by dating fossils Relative Dating-accomplished via the law
of superposition Absolute Dating-accomplished via
radiometric dating
Figure 27-5
SeedsPollen Leaves
Sand and gravelBuried material from swamp
Bedrock
HOW FOSSILIZATION OCCURS1. A tree lives in aswampy habitat.The tree dropsleaves, pollen, andseeds into the mud,where decompositionis slow.
2. The tree falls.The trunk andbranches breakup as they rot.
3. Flooding bringsin sand and mud,burying the remainsof the tree.
4. Over millions ofyears, the mountainserode and the swampis filled with sediment.The habitat dries.
Earth’s History Earth is believed to have existed for 4.6
billion years Life on earth is believed to have originated
3.5 billion years ago. The first life forms were probably prokaryotes
There have been 5 mass extinctions over the history of the planet, and in each, the dominant group of organisms was replaced by another group
Figure 27-8a
The Precambrian (Hadean, Archaean, and Proterozoic Eons) included the origin of life, photosynthesis, and the oxygenatmosphere.
Format
ion o
f sola
r sys
tem
Moon fo
rms
Earth
form
atio
n com
plete
Liquid
wat
er o
n Ear
th
First o
cean
s; h
eavy
bom
bardm
ent
fr
om s
pace
ends
Orig
in o
f life
First e
viden
ce o
f photo
synth
etic
c
ells
First e
viden
ce o
f oxy
genic
p
hotosy
nthes
isFirs
t rock
s co
ntain
ing o
xygen
(i
n atm
ospher
e an
d oce
an)
First e
ukary
otic fo
ssils
First p
hotosy
nthet
ic e
ukary
otes
First r
ed a
lgae
; firs
t evi
dence
o
f sex
ual s
truct
ures
First l
ichen
-like
org
anis
m
First s
ponges; f
irst b
ilate
rally
s
ymm
etric
anim
als;
oce
an
com
plete
ly o
xygen
ated
Proterozoic Eon
Multicellularorganisms beginto diversify slowly
Most of Earth is coveredin ocean and ice.
All life is unicellular
Position of the continents unknown
Archaean EonHadean Eon
Millions of years ago (mya)
Figure 27-8b
Phanerozoic Eon: The Paleozoic Era included the origin early diversification of animals, land plants, and fungi.
First c
omb je
llies
, arth
ropods,
v
erte
brate
s, o
ther
phyl
a
Cambrian
Algae abundant,marineinvertebratesdiversify
Arthro
pods div
ersi
fy;
fi
rst e
chin
oderm
First b
ryozo
ans
(new
est
a
nimal
phyl
um)
First l
and p
lants
First m
ycorr
hizal
fungi (
Glo
mal
es)
First c
artil
agin
ous fis
h
First b
ony fis
h
First i
nsect
s
First f
ish w
ith ja
ws
First f
erns,
vas
cula
r pla
nts,
a
scom
ycet
e fu
ngi, lic
hens
on land
First t
ree-
size
d pla
nts
First w
inged
inse
cts
First t
etra
pods (a
mphib
ians)
First s
eed p
lants
First p
lants
with
leav
es
First r
eptil
es
First m
amm
al-li
ke re
ptiles
First b
asid
iom
ycet
e fu
ngi
First v
esse
ls
in
pla
nts
Ordovician Silurian DevonianCarboniferous
PermianMississippian Pennsylvanian M
ass
exti
nct
ion
Mas
sex
tin
ctio
n
Mas
sex
tin
ctio
n
Echinoderms(sea stars, seaurchins) diversify
Coralreefsexpand
First upland plantcommunities(evergreen forests),diversification of fish,emergence ofamphibians
Insects diversify,coal-forming swampsabundant, sharksabundant, radiationof amphibians
Coal-forming swampsdiminish; parts ofAntarctica forested
Supercontinent Pangeaassembles. Building ofAppalachian Mountains ends.Climate warm; little variation.
Supercontinent of Laurentiato the north and Gondwanato the south. Climate mild.
Climate cold;extensive icein Gondwana.
Supercontinent of Gondwanaforms. Oceans cover much ofNorth America. Climate notwell known.
Laurentia
Gondwana
Pangea
GondwanaGondwana
Figure 27-8c
Phanerozoic Eon: The Mesozoic Era is sometimes called the Age of Reptiles.
First n
ecta
r-drin
king in
sect
s
Triasssic
Gymnosperms become dominantland plants; extensive deserts
Mas
sex
tin
ctio
n
First d
inosa
urs
First m
amm
als
First t
yran
nosaurid
din
osaur
First a
ngiosp
erm
(flo
wer
ing p
lant)
First b
ird (A
rchae
optery
x)Firs
t cen
tric
diato
ms
First w
ater
lilie
s
First m
agnolia
-fam
ily p
lants
First b
ee; f
irst a
nt
First p
lace
ntal m
amm
als
Mas
sex
tin
ctio
n
Jurassic Mas
sex
tin
ctio
n
Cretaceous
Gymnosperms continueto dominate land
Dinosaurs diversify Flowering plants diversify
Pangea intact. Interiorof Pangea arid. Climatevery warm.
Pangea begins to break apart;interior of continent still arid.
Gondwana begins to breakapart; interior less arid.
India separated from Madagascar,moves north; Rocky Mountainsform. Climate mild, temperate.
Pan
gea
Pan
gea Gondwana
Figure 27-8d
Phanerozoic Eon: The Cenozoic Era is nicknamed the Age of Mammals.
First h
orses
Paleogene
Continents continue to drift apart.Collision of India with Eurasia begins.Australia moves north from Antarctica.Palms in Greenland and Patagonia.
First p
rimat
es
First f
ully a
quatic
whal
es
First a
pes
Old
est p
ollen fr
om
d
aisy
-fam
ily p
lants
Earlie
st h
omin
ins
Homo
s
apie
ns
Paleocene Eocene Oligocene
Neogene
Miocene Pliocene Pleistocene
Diversification of grazing mammalsDiversification of angiospermsand pollinating insects
Diversification ofmammalian orders
Strong drying trend inAfrica and other continents;grasslands form. Alps andHimalayas begin to rise.
Continents close to presentposition. Beginning ofAntarctic ice cap. Openingof Red Sea.
North and South Americajoined by land bridge.Uplift of the Sierra Nevada.Worldwide glaciation.
Figure 27-5
SeedsPollen Leaves
Sand and gravelBuried material from swamp
Bedrock
HOW FOSSILIZATION OCCURS1. A tree lives in aswampy habitat.The tree dropsleaves, pollen, andseeds into the mud,where decompositionis slow.
2. The tree falls.The trunk andbranches breakup as they rot.
3. Flooding bringsin sand and mud,burying the remainsof the tree.
4. Over millions ofyears, the mountainserode and the swampis filled with sediment.The habitat dries.
Major events in Earth’s History: The earth cools 1st life forms Accumulation of
atmospheric oxygen
1st eukaryotes Multicellular
organisms
Animals evolved Plants and fungi
colonized land Land became
colonized by other organisms
Where would life come from? Recall that Miller and Urey tested Oparin’s primordial
soup hypothesis and were able to create biochemicals Lab experiments since then have been able to form
polymers in conditions similar to early earth RNA was probably the 1st genetic material
These have been shown to be produced abiotically in the lab
Recall that Ribozymes exist as well. Protobionts can self-assemble
These are aggregates of abiotically produced molecules that form “membranes” and often can sustain chemical reactions (like a metabolism)
What about Eukaryotic cells? One current hypothesis, the
endosymbiant hypothesis tries to explain this Mitochondria have their own DNA,
resemble bacteria, and replicate themselves for cell division
This suggests that once the 1st primitive cells evolved, they “swallowed” other cells. It is believed that they could have become dependent on one another to carry out parts of their metabolism