Transcript Document

Essentials of
Biology
Sylvia S. Mader
Chapter 16
Lecture Outline
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16.1 Macroevolution
•
•
•
Large changes over a very long period of time
Requires speciation – splitting of one species
into 2 or more new species
Species originate, adapt to their environment,
and then may become extinct.
Figure 16.1 Dinosaurs
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The Field Museum of Natural History. Neg. CK9T, Chicago
• Biological species concept
 Members of a species
• Interbreed
• Have a shared gene pool
• Each species reproductively isolated from every
other species
 Not based on appearance
 Gene flow occurs between populations of a
species but not between populations of
different species.
• Flycatchers look similar but are different species
• Humans can look very different but are the same
species.
Figure 16.2 Three species of flycatchers
Flycatchers may look similar and
yet do not interbreed in nature –
are different species.
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Acadian flycatcher,
Empidonax virescens
Traill’s flycatcher,
Empidonax trailli
least flycatcher,
Empidonax minimus
(Acadian): © Karl Maslowski/Visuals Unlimited; (Least): © Stanley Maslowski/Visuals Unlimited; (Traill's): © Ralph Reinhold/Animals
Animals
Figure 16.3 Human populations
Humans can look very different and yet can
interbreed – are the same species.
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a.
b.
a: © Sylvia S. Mader; b: © B & C Alexander/Photo Researchers, Inc.
• The biological species concept only
applies to living sexually reproducing
organisms.
 It does not apply to bacteria that reproduce
asexually or fossils.
• Other definitions of species
 Category of classification below rank of genus
 Species in the same genus share a recent
common ancestor.
• Reproductive barriers
 Isolating mechanisms that prevent successful
reproduction (producing fertile offspring) from
occurring
 Prezygotic – before formation of a zygote
•
•
•
•
•
Habitat isolation
Temporal isolation
Behavioral isolation
Mechanical isolation
Gamete isolation
Figure 16.4 Reproductive barriers
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Prezygotic isolating mechanisms
Premating
species 1
Habitat isolation
Species at same locale occupy
different habitats.
Temporal isolation
Species reproduce at different
seasons or different times
of day.
species 2
Mating
Behavioral isolation
In animal species, courtship
behavior differs, or individuals
respond to different songs, calls,
pheromones, or other signals.
Mechanical isolation
Genitalia between
species are unsuitable
for one another.
Gamete isolation
Sperm cannot reach or
fertilize egg.
Postzygotic isolating mechanisms
Fertilization
Zygote mortality
Fertilization occurs, but
zygote does not survive.
hybrid offspring
Hybrid sterility
Hybrid survives but is sterile
and cannot reproduce.
F2 fitness
Hybrid is fertile, but F2 hybrid
has reduced fitness.
Figure 16.5 Prezygotic isolating mechanism
Elaborate courtship displays
are species-specific
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© Barbara Gerlach/Visuals Unlimited
Postzygotic – after formation of a zygote
•Zygote mortality
•Hybrid sterility
•F2 fitness
Figure 16.4 continued
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Postzygotic isolating mechanisms
Fertilization
Zygote mortality
Fertilization occurs, but
zygote does not survive.
hybrid offspring
Hybrid sterility
Hybrid survives but is sterile
and cannot reproduce.
F2 fitness
Hybrid is fertile, but F2 hybrid
has reduced fitness.
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horse
donkey
mating
Figure 16.6
Postzygotic isolating
mechanism
Mules are infertile due to a
difference in chromosomes
inherited from their parents.
fertilization
mule (F1 hybrid)
Usually mules cannot reproduce.
If an F2 offspring does result,
it cannot reproduce.
(horse): © Superstock, Inc./SuperStock; (donkey): © Robert J. Erwin/Photo Researchers, Inc.; (mule): © Jorg & Petra
Wegner/Animals Animals
• Models of speciation
 Allopatric – speciation model based on
geographic isolation
• Ensatina salamanders in California
 Sympatric – population develops into 2 or
more reproductively isolated groups without
prior geographic isolation.
• Found among plants due to polyploidy
• Formation of bread wheat
Figure 16.7 Allopatric speciation
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Northern ancestral
population
Eastern migration
southward establishes
these populations.
Western migration
southward establishes
these populations.
Central
Valley
Genetic differences
build up between
populations.
In the end, two reproductively
isolated populations cannot
mate in Southern California.
Figure 16.8 Sympatric speciation
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Sterile hybrid
2n = 21
Wild wheat
2n = 28
Wild wheat
2n = 14
Doubling of
chromosome
number
Bread wheat
2n = 42
• Adaptive radiation
 New species evolve from a single ancestral
species.
 Galápagos Islands finches
 Populations on different islands subjected to
founder effect involving genetic drift, genetic
mutations and the process of natural selection
 Each population became adapted to a
particular habitat on its island.
 New finch species do not interbreed.
Figure 16.9 Darwin’s finches
Each species adapted to eating
a different type of food.
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Warbler
finch
Woodpecker
finch
Cactus
ground
finch
Sharp-beaked
ground finch
Small
ground
finch
Small
insectivorous
tree finch
Large
insectivorous
tree finch
Vegetarian
tree finch
Medium
ground
finch
Probing
beaks
Grasping
beaks
Parrot-like
beaks
Crushing
beaks
Large
ground
finch
16.2 The fossil record
• Fossils – traces and remains of past
life or any other direct evidence of past
life
• Paleontology – science of discovering
and studying the fossil record and
making decisions about the history of
species
• Geological timescale
 Humans have only been around 0.04% of
the history of life
Figure 16.10 Fossils
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a.
b.
c.
a: © Carolina Biological Supply/Phototake; b: © Alfred Pasieka/SPL/Photo Researchers, Inc.; c: © Sinclair Stammers/SPL/Photo Researchers, Inc.
Figure 16.10 continued
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d.
e.
f.
d: © Gary Retherford/Photo Researchers, Inc.; e: © Scott Berner/Visuals Unlimited; f: © Steven P. Lynch
Table 16.1 The Geological Timescale: Major Divisions of
Geological Time and Some of the Major Evolutionary
Events That Occurred
Table 16.1 continued
Table 16.1 continued
• Pace of speciation
 Gradualistic model
• Darwin thought evolutionary changes occurred
gradually.
• Often shows evolutionary history as an
evolutionary tree
• Difficult to indicate when speciation has
occurred because of transitional links
 Punctuated equilibrium
• Period of equilibrium (no change) is punctuated
(interrupted) by speciation.
• Transitional links less likely to form fossils and
less likely to be found
 Difference between models are subtle –
“sudden” in geological time may be
thousands of years.
Figure 16.11 Pace of evolution
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Time
Change
a. Gradualistic model
Figure 16.11 continued
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Time
Change
b. Punctuated equilibrium model
• Mass extinctions of species
 Disappearance of a large number of species
or a higher taxonomic group within a relatively
short period of time
 Occurrence of 5 mass extinctions
• End of Ordovician, Devonian, Permian, Triassic,
and Cretaceous periods
• Significant mammalian extinction at the end of the
Pleistocene epoch
 Many factors contribute
• Continental drift – movement of continents can
lead to massive habitat changes
• Impact of meteorites – proposed as primary cause
of Cretaceous extinction
Figure 16.12 Plate tectonics
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Continental plates meet
along a fault line, shift,
and cause earthquakes.
fault line
Continental plate
is folded into
mountain range.
rift
ocean trench
Oceanic plate
Spreads laterally
and cools.
plate
ocean
volcanic
islands
volcano
plate
Rising plumes of
molten magma
create volcanoes.
Earth’s crust
mantle
Oceanic plate sinks beneath
continental plate and melts
into magma again.
Hot magma rises
to the surface
and cools.
subduction
zone
Figure 16.13 Continental drift
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Eurasia
North
America
Equator
South
America
Africa
India
Antarctica
Pangaea:
Late Paleozoic, 250 MYA
a.
Australia
Figure 16.13 continued
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North
America
Eurasia
Equator
Africa
South
America
India
Australia
Antarctica
Most modern continents
had formed by the end of
the Mesozoic, 65 MYA
b.
16.3 Systematics
• Study of evolutionary relationships
between all organisms, past and present
• One goal is to determine phylogeny.
 Evolutionary history of a group of organisms
• Taxonomy – identifying, naming and
classifying organisms
 Ideally organisms are classified according to
our present understanding of evolutionary
relationships.
• Linnean classification
 Binomial system – genus and specific epithet
• Naming rules – genus capitalized, italics, genus
can be abbreviated
• Cypripedium acaule
 Hierarchical system – higher the category, the
more inclusive
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Domain
Bacteria
Domain
Archaea
Domain
Eukarya
Figure 16.14 Taxonomy
hierarchy
Kingdom
Plantae
Phylum
Anthophyta
Class
Monocotyledones
Order
Asparagales
Family
Orchidaceae
Genus
Species
Cypripedium
Cypripedium
acaule
• Phylogenetic trees
 Diagram that indicates common ancestors and
lines of descent (lineages)
 Common ancestor at the base of the tree has
traits shared by all the other groups in the tree.
Figure 16.15 Classification and phylogeny
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Ovis aries
(sheep)
Ovis
Bos taurus
(cattle)
Cervus elaphus
(red deer)
Bos
Cervus
Bovidae
Cervidae
Artiodactyla
Rangifer tarandus
Species
(reindeer)
Rangifer
Genus
Family
Order
• Tracing phylogeny
 Use a multitude of data to discover
evolutionary relationships between species.
 Morphological data
• Homologous structures are related to each other
through common descent – forelimbs of
vertebrates.
• Sometimes difficult due to convergent evolution
 Acquisition of the same or similar traits in distantly
related lines due to adaptations to the same environment
 Analogous structures – same function but no recent
common ancestor
 Molecular data
• The more closely related species are, the more
similar their DNA.
• Ribosomal RNA changes little and can be a
reliable indicator.
Figure 16.16 Molecular data
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Millions of Years Ago
(MYA)
0
10
20
30
40
Galago
Capuchin
Green monkey Rhesus monkey
Gibbon
Chimpanzee
Human
• Cladistics
 Way to trace the evolutionary history of a
group by using shared traits derived from a
common ancestor to determine relationships
 Cladogram – depicts evolutionary history of a
group based on available data
• Outgroup – not part of study group
• Ingroup – part of study group
• Parsimony – least number of assumptions is the
most probable
 Construct cladogram that minimizes number of assumed
evolutionary changes
• Shared derived traits – homologies shared by only
certain species of the study group
• Ancestral trait – present in common ancestor to
ingroup and outgroup
Figure 16.17 Constructing a cladogram
Notochord in embryo
Vertebrae
Lungs
Three-chambered heart
Internal fertilization
Amniotic membrane in egg
Four bony limbs
Long cylindrical body
a.
lizard
snake
newt
eel
lancelet
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• Outgroup – lancelets
are not vertebrates.
• Ingroup – members of
study group
• This cladogram has 3
clades.
• Following principle of
parsimony, this is the
sequence traits must
have evolved.
 Any other arrangement
would be more
complicated.
Figure 16.17 continued
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amniotic egg,
internal fertilization
lungs,
three-chambered heart
vertebrae
b.
• Linnean classification versus cladistics
 Linnean classification places birds in their
own group but cladistics places them in a
clade with crocodiles.
 May modify Linnean classification or construct
an entirely different system
Figure 16.18 Cladistic classification
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mammals
turtles
Snakes
and lizards
crocodiles
gizzard
epidermal scales
hair and mammary glands
amniotic egg,
internal fertilization
birds
• 3 Domain system
 5 kingdom system changed based on rRNA
sequencing data
 Domain Bacteria
• Arose first, prokaryotic cells
 Domain Archaea
• Arose next, also prokaryotic cells
 Domain Eukarya
• Last to evolve, eukaryotic cells
• Kingdoms for protists, plants, fungi and animals
Figure 16.19 Three-domain system
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cyanobacteria
Bacteria
• Prokaryotic, unicellular
organisms
• Lack a membrane-bounded
nucleus
• Reproduce asexually
• Heterotrophic by absorption
• Autotrophic by
chemosynthesis or by
photosynthesis
• Move by flagella
heterotrophic
bacteria
z
prokaryotes
common ancestor
Figure 16.19 Three-domain system
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cyanobacteria
Bacteria
• Prokaryotic, unicellular
organisms
• Lack a membrane-bounded
nucleus
• Reproduce asexually
• Heterotrophic by absorption
• Autotrophic by
chemosynthesis or by
photosynthesis
• Move by flagella
heterotrophic
bacteria
z
prokaryotes
common ancestor
Archaea
• Prokaryotic, unicellular
organisms
• Lack a membrane-bounded
nucleus
• Reproduce asexually
• Many are autotrophic by
chemosynthesis; some are
heterotrophic by absorption
• Unique rRNA base
sequence
• Distinctive plasma
membrane and cell wall
chemistry
Figure 16.19 Three-domain system
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eukaryotes
fungi
plants
animals
Eukarya
• Eukaryotic, unicellular to
multicellular organisms
• Membrane-bounded
nucleus
• Sexual reproduction
• Phenotypes and nutrition
are diverse
• Each kingdom has
specializations
• Flagella, if present, have a
9 + 2 organization
protists
cyanobacteria
Bacteria
• Prokaryotic, unicellular
organisms
• Lack a membrane-bounded
nucleus
• Reproduce asexually
• Heterotrophic by absorption
• Autotrophic by
chemosynthesis or by
photosynthesis
• Move by flagella
heterotrophic
bacteria
z
prokaryotes
common ancestor
Archaea
• Prokaryotic, unicellular
organisms
• Lack a membrane-bounded
nucleus
• Reproduce asexually
• Many are autotrophic by
chemosynthesis; some are
heterotrophic by absorption
• Unique rRNA base
sequence
• Distinctive plasma
membrane and cell wall
chemistry