the macroevolutionary puzzle chapter 19. asteroid impacts many past catastrophic impacts altered the...
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Asteroid Impacts
• Many past catastrophic impacts
altered the course of evolution
• K–T boundary
• 2.3 million years ago in southern
Pacific Ocean
Macroevolution
The large-scale patterns, trends, and rates of change among
families and other more inclusive groups of species
Fossils
• Recognizable evidence of ancient life
• What do fossils tell us?– Each species is a mosaic of ancestral and
novel traits
– All species that ever evolved are related to one another by way of descent
Stratification
• Fossils are found in sedimentary
rock
• This type of rock is formed in layers
• In general, layers closest to the top
were formed most recently
Fossilization
• Organism becomes buried in ash or sediments
• Organic remains become infused with metal and mineral ions
• Carbon 14 dating
Figure 19.6Page 309
Radiometric Dating
after two half-lives
after one half-lives
parent isotope innewly formed rock
Figure 19.5Page 309
Geologic Time Scale
• Boundaries based on transitions in fossil record
Cambrian period
Proterozoic eon2,500myaArchean eon and earlier
Ordovician period
Silurian period
Devonian period
570
505
435
410
Carboniferous period
Permian period
Cretaceous period
Tertiary period
Quaternary period
370
290
210
205
138
65
1
Cambrian period
Jurassic period
Triassic period
Paleozoic era
Mesozoic era
Cenozoic era
Phanerozoic eon
Figure 19.4 (2)Page 308
Record Is Incomplete
• Fossils have been found for about 250,000 species
• Most species weren’t preserved
• Record is biased toward the most accessible regions
Continental Drift
• Idea that the continents were once joined and have since “drifted” apart
• Initially based on the shapes
• Wegener refined the hypothesis and named the theoretical supercontinent Pangea
Evidence of Movement
• Wegener cited evidence from glacial deposits and fossils
• Magnetic orientations in ancient rocks do not align with the magnetic poles
• Discovery of seafloor spreading provided a possible mechanism
Plate Tectonics
• Earth’s crust is fractured into plates
• Movement of plates driven by upwelling of molten rock
Pacific
plate
Nazca
plate
North
American
plate
South
American
plate
Eurasian
plate
African
plate
Somali
plate
Pacific
plate
Indo-
Australian
plate
Antarctic plate
Figure 19.8bPage 311
Comparative Morphology
• Comparing body forms and structures of
major lineages
• Guiding principle:
– When it comes to introducing change in
morphology, evolution tends to follow the
path of least resistance
Morphological Divergence
• Change from body form of a common ancestor
• Produces homologous structures
1
1
1
1
1
1
2
2
2
2
2
2
2
3
3
3
3
3
3
3
4
4
4
4
4
5
5
5
5
early reptile
pterosaur
chicken
bat
porpoise
penguin
human
Figure 19.10Page 312
Morphological Convergence
• Individuals of different lineages evolve in similar ways under similar environmental pressures
• Produces analogous structures that serve similar functions
Comparative Development
• Each animal or plant proceeds through a
series of changes in form
• Similarities in these stages may be clues
to evolutionary relationships
• Mutations that disrupt a key stage of
development are selected against
Altering Developmental Programs
• Some mutations shift a step in a
way that natural selection favors
• Small changes at key steps may
bring about major differences
• Insertion of transposons or gene
mutations
Development of Larkspurs
• Two closely related species have different petal morphology
• They attract different pollinators
front viewside view
D. decorum flower
front viewside view
D. nudicaule flower
Figure 19.12Page 314
Development of Larkspurs
• Petal difference arises from a change in the rate of petal development
00 10 20 40
2
4
6
Pet
al le
ng
th (
mill
imet
ers)
Days (after onset of meiosis)
D. decorum
D. nudicaule
Figure 19.12Page 314
Similar Vertebrate Embryos
• Alterations that disrupted early development have been selected against
FISH REPTILE BIRD MAMMAL
Figure 19.13aPage 315
Similar Vertebrate Embryos
Adult shark
Early human embryo
Two-chambered heart
Aortic arches
Certain veins
Figure 19.13bPage 315
Developmental Changes
• Changes in the onset, rate, or time of
completion of development steps can
cause allometric changes
• Adult forms that retain juvenile
features
Comparative Biochemistry
• Kinds and numbers of biochemical traits that species share is a clue to how closely they are related
• Can compare DNA, RNA, or proteins
• More similarity means species are more closely related
Comparing Proteins
• Compare amino acid sequence of proteins
produced by the same gene
• Human cytochrome c (a protein)
– Identical amino acids in chimpanzee protein
– Chicken protein differs by 18 amino acids
– Yeast protein differs by 56
Sequence Conservation
• Cytochrome c functions in electron
transport
• Deficits in this vital protein would be
lethal
• Long sequences are identical in wheat,
yeast, and a primate
Nucleic Acid Comparison
• Use single-stranded DNA or RNA
• Hybrid molecules are created, then heated
• The more heat required to break hybrid, the more closely related the species
Molecular Clock
• Assumption: “Ticks” (neutral mutations) occur at a constant rate
• Count the number of differences to estimate time of divergence
Taxonomy
• Field of biology concerned with
identifying, naming, and classifying
species
• Somewhat subjective
• Information about species can be
interpreted differently
Binomial System
• Devised by Carl von Linne
• Each species has a two-part
Latin name
• First part is generic
• Second part is specific name
Higher Taxa
• Kingdom
• Phylum
• Class
• Order
• Family
• Inclusive groupings meant to reflect relationships among species
Phylogeny
• The scientific study of evolutionary relationships among species
• Practical applications– Allows predictions about the needs or
weaknesses of one species on the basis of its known relationship to another
Examples of Classification
Kingdom
Genus
Species
Family
Order
Class
Phylum
Plantae
Zea
Z. mays
Poaceae
Poales
Monocotyledonae
Anthophyta
Plantae
Vanilla
V. planifolia
Orchidaceae
Asparagales
Monocotyledonae
Anthophyta
Animalia
Musca
M. domestica
Muscidae
Diptera
Insecta
Anthropoda
Animalia
Homo
H. sapiens
Hominidae
Primates
Mammalia
Chordata
corn vanilla orchid housefly human
Figure 19.17Page 318
ConstructingA
Cladogram
Jaws Limbs Hair Lungs Tail Shell
- - - - + -
+ + - + + +
+ + + + + -+ + + + - -+ - - + + -+ - - - + -+ + + + - -
Lamprey
Turtle
CatGorillaLungfishTroutHuman
Taxon Traits (Characters)
Jaws Limbs Hair Lungs Tail Shell
0 0 0 0 0 0
1 1 0 1 0 1
1 1 1 1 0 01 1 1 1 1 01 0 0 1 0 01 0 0 0 0 01 1 1 1 1 0
Lamprey
Turtle
CatGorillaLungfishTroutHuman
Taxon Traits (Characters)
In-text figurePage 320
Constructing a Cladogram
gorilla humanturtlelungfishtrout
jaws
lamprey
lungs
limbs
hair
tail loss
cat
Figure 19.20ePage 320
Evolutionary Tree
extreme
thermophiles
halophilesmethanogens cyanobacteria
ARCHAEBACTERIA
PROTISTANS
FUNGIPLANTS
ANIMALS
clubfungi
sacfungi
zygospore-forming
fungi
echino-derms
chordatesannelids
mollusks
flatworms
sponges
cnidarians
flowering plants conifers
horsetails
lycophytes
ferns
bryophytes
sporozoans
green algae amoeboidprotozoans
slime molds
ciliatesredalgae
brown algaechrysophytes
cycads
ginkgos
rotifers
arthropodsround-worms
chytrids
oomycotes
euglenoids
dinoflagellates
Gram-positive bacteria
spirochetes
chlamydias
proteobacteria
? crown of eukaryotes
(rapid divergences)
molecular origin of life
EUBACTERIAparabasalids
diplomonads(e.g., Giardia)
(alveolates)
(stramenopiles)
chlorophytes
kinetoplastids
extreme
(e.g., Trichomonas)
Figure 19.21Page 321