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Henley hit by 'mutant super rat' invasion
Researchers found the picturesque riverside Oxfordshire area has been inundated with dozens of the pests,
which carry a poison-resistant gene.
Experts say that despite appearing the same as their non-mutant counterparts, they are resistant to pest
controls because of their genetic mutation.
"All rats tend to carry various diseases,” said Dr Alan Buckle, from the University of Reading.
“The reason we need to get rid of them is because they transmit diseases from themselves to humans and
farm animals.
Dr Buckle, who led the study, added: "These anticoagulant-resistant rats carry the same diseases as other
rats carry but are very difficult to control."
The team used new DNA techniques to determine the prevalence of rats with the poison-resistant gene.
Dr Buckle, a research fellow, said there stronger poisons would control the super-rats but were currently
illegal.
"We're not allowed to use them because the regulatory body is worried about their effects on wildlife,” he
said.
Dr Buckle said this caused the greatest concern because the rats carry illnesses such as Weil's disease, which
can be passed on to humans.
It has flu-like symptoms initially but can lead to jaundice in the kidneys.
He added: "If Weil's disease is not treated it's very serious. About 40 to 50 people in the UK catch it every
year."
Weil's disease is a waterborne bacterial infection linked to the urine of infected rats, which killed Andy
Holmes, the Olympic rowing champion in 2010.
But animal welfare groups believe poisons, or rodenticides, are detrimental to wildlife.
It is estimated that there are up to 10.5 million rats in Britain and in areas in which resistance exists almost
three in four carry the rodenticide resistant gene.
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Biology
Concepts and Applications | 9e
Starr | Evers | Starr
Chapter 17
Processes of Evolution
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17.1 What is Microevolution?
• Individuals of a population share
morphological, physiological, and
behavioral traits with a heritable basis
• Variations within a population arise from
different alleles of shared genes
– Dimorphic: a trait with only two forms
– Polymorphic: traits with more than two distinct
forms
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What is Microevolution?
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What is Microevolution?
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What is Microevolution?
• Mutations
– The original source for new alleles.
– Lethal mutation
• Mutation that drastically alters phenotype
• Causes death
– Neutral mutation
• A mutation that has no effect on survival or
reproduction
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What is Microevolution?
• Mutations
– Occasionally, a change in the environment
favors a mutation that had previously been
neutral or even somewhat harmful
– Through natural selection, a beneficial
mutation tends to increase in frequency in a
population over generations
– Mutations are the source of Earth’s staggering
biodiversity
© Cengage Learning 2015
What is the Effect of Directional Selection?
• Peppered moths
– The peppered moth’s coloration camouflages
it from predatory birds
• When the air was clean, trees were light-colored,
and so were most peppered moths
• When smoke from coal-burning factories changed
the environment, predatory birds ate more white
moths – selection pressure favored darker moths
• By 1850s, dark-colored moths were more common
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What is the Effect of Directional Selection?
A
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B
What is the Effect of Directional Selection?
• Wafarin-resistant rats
– Rats thrive there are people
– Wafarin became popular in 1950s
– Spreading poison exerts directional selection
– Exposure caused 10 percent of urban rats to
become resistant to Wafarin by 1980s
© Cengage Learning 2015
17.6 How Does Natural Selection Maintain
Diversity?
• Selection pressures that operate on
natural populations are complex; an allele
may be adaptive in one circumstance but
harmful in another
• Any mode of natural selection may
maintain two or more alleles in a
population
© Cengage Learning 2015
How Does Natural Selection Maintain
Diversity?
• Sexual selection
– Mode of natural selection in which some
individuals of a population out-reproduce
others because they are better at securing
mates
– The most adaptive forms of a trait are those
that help individuals defeat same-sex rivals
for mates, or are the ones most attractive to
the opposite sex
It is NOT always “Survival of the Fittest”
© Cengage Learning 2015
How Does Natural Selection Maintain
Diversity?
• Sexual dimorphism
– Males and females are different in size or
another aspect of their appearance
– Individuals (often males) are more:
• Colorful
• Larger
• More aggressive
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How Does Natural Selection Maintain
Diversity?
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How Does Natural Selection Maintain
Diversity?
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How Does Natural Selection Maintain
Diversity?
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© Cengage Learning 2015
Irish Elk
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Charles Darwin (1809-1882)
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Darwin in 1840
Great
Britain
Europe
Asia
North
America
ATLANTIC
OCEAN
HMS Beagle
Africa
Galápagos
Islands
PACIFIC
OCEAN
Pinta
Marchena
Equator
Genovesa
South
America
Equator
Santiago
Daphne Islands
0
40 km
Santa Santa
Cruz
Fe
Florenza
San
Cristobal
PACIFIC
OCEAN
Española
Cape of
Good Hope
Andes
Isabela
0
Australia
Pinzón
Fernandina
Tasmania
Cape Horn
New
Zealand
40 miles
Tierra del Fuego
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Figure 13.3
HMS Beagle
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Figure 13.3b
Galápagos
Islands
PACIFIC
OCEAN
Pinta
Genovesa
Marchena
Equator
Santiago
Daphne Islands
Pinzón
Fernandina
Isabela
0
0
© Cengage Learning 2015
Santa
Santa
Cruz
Fe
Florenza
40 km
San
Cristobal
Española
40 miles
Figure 13.3c
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© Cengage Learning 2015
© Cengage Learning 2015
Figure 13.4
Giant Tortoises of the
Galápagos Islands
Pinta
Tower
Marchena
Pinta Island
Intermediate shell
Fernandina
James
Santa Cruz
Isabela
Santa Fe
Hood Island
Floreana
Isabela Island
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Dome-shaped
shell
Hood
Saddle-backed shell
Lonesome George : Died June 2012
Age?
Cells frozen to Clone?????
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© Cengage Learning 2015
17.8 How Do Species Attain and Maintain
Separate Identities?
• Speciation: one of several processes by
which new species arise
• Reproductive isolation
– Absence of gene flow between populations
– Always part of speciation
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How Do Species Attain and Maintain
Separate Identities?
• Reproductive isolation
– Gene flow does not occur between
populations
• Different genetic changes accumulate
• Reinforces differences between diverging
populations
• If pollination or mating cannot occur, or if zygotes
cannot form, the isolation is prezygotic
• If hybrids form but are unfit or infertile, the isolation
is postzygotic
© Cengage Learning 2015
How Do Species Attain and Maintain
Separate Identities?
• Seven mechanisms of reproductive
isolation
– Temporal isolation
• Some populations can’t interbreed because the
timing of their reproduction differs
– Mechanical isolation
• Size or shape of an individual’s reproductive parts
prevent it from mating with members of another
population
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Temporal Isolation
Skunk species that mate at different times
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Figure 14.4a
Mechanical Isolation
Snail species whose genital openings cannot align
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Figure 14.4d
How Do Species Attain and Maintain
Separate Identities?
– Ecological isolation
• Populations adapted to different
microenvironments in the same region may be
physically separated
– Behavioral isolation
• In animals, behavioral differences can stop gene
flow between related species
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Habitat Isolation
Garter snake species from different habitats
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Figure 14.4b
Behavioral Isolation
Mating ritual of blue-footed boobies
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Figure 14.4c
How Do Species Attain and Maintain
Separate Identities?
– Gamete incompatibility
• Even if gametes of different species meet, they
often have molecular incompatibilities that prevent
them from fusing
• Primary speciation route of animals that release
free-swimming sperm in water
– Hybrid inviability
• If genetic incompatibilities disrupt development, a
hybrid embryo may die, or hybrid offspring that
survive may have reduced fitness (e.g., ligers)
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Gametic Isolation
Sea urchin species whose gametes cannot fuse
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Figure 14.4e
POSTZYGOTIC BARRIERS
Reduced Hybrid Viability Reduced Hybrid Fertility
Hybrid Breakdown
Horse
Donkey
Mule
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Figure 14.5
How Do Species Attain and Maintain
Separate Identities?
– Hybrid sterility
• Some interspecies crosses produce robust but
sterile offspring (e.g., mules)
© Cengage Learning 2015
17.9 What is Allopatric Speciation?
• Allopatric speciation
– Speciation pattern in which a physical barrier
that separates members of a population ends
gene flow between them
– Geographic barrier arises
– Genetic divergences then give rise to new
species
© Cengage Learning 2015
What is Allopatric Speciation?
• Geographic barrier can block gene flow
– Depends on how an organism travels
• e.g., by swimming, walking, or flying
– How it reproduces
• e.g., by internal fertilization or by pollen dispersal
• Example:
– When the Isthmus of Panama formed, it cut
off gene flow among populations of aquatic
organisms in the Pacific and Atlantic oceans
© Cengage Learning 2015
What is Allopatric Speciation?
Alpheus nuttingi (Atlantic)
Isthmus
of Panama
Alpheus millsae (Pacific)
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What is Allopatric Speciation?
• Speciation in archipelagos
– Archipelagos are isolated island chains
formed by volcanoes, such as the Hawaiian
and Galápagos Islands
– Archipelagos were populated by a few
individuals of mainland species whose
descendants diverged over time
– Selection pressures within and between the
islands can foster even more divergences
© Cengage Learning 2015
What is Allopatric Speciation?
• The first birds to colonize the Hawaiian
Islands found a near absence of
competitors and predators and an
abundance of rich and vacant habitats,
which encouraged rapid speciation
– Honeycreepers, unique to the Hawaiian
Islands, have specialized bills and behaviors
adapted to feed on certain insects, seeds,
fruits, nectar, or other foods
© Cengage Learning 2015
What is Allopatric Speciation?
© Cengage Learning 2015
17.10 Can Speciation Occur Without a
Physical Barrier to Gene Flow?
• Sympatric speciation
– Populations sometimes speciate even without
a physical barrier that bars gene flow between
them
– Can occur instantly with a change in
chromosome number – many plants are
polyploid (e.g., wheat)
© Cengage Learning 2015
Can Speciation Occur Without a Physical
Barrier to Gene Flow?
• Examples of sympatric speciation
– Lake Victoria cichlids (sexual selection)
• In the same lake, female cichlids of different
species visually select and mate with brightly
colored males of their own species
– Warblers around the Tibetan plateau
(behavioral isolation)
• Two populations overlap in range, but don’t
interbreed because they don’t recognize one
another’s songs
© Cengage Learning 2015
Can Speciation Occur Without a Physical
Barrier to Gene Flow?
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17.11 What is Macroevolution?
• Macroevolution
– Evolutionary patterns on a larger scale
• There are five patterns of macroevolution
– Stasis
– Exaptation
– Mass extinction
– Adaptive radiation
– Coevolution
© Cengage Learning 2015
What is Macroevolution?
• Mass extinction
– Extinct: refers to a species that has been
permanently lost
• Simultaneous losses of many lineages
• 99 percent of all species that have ever lived are
now extinct
– Fossil record indicated that there have been
more than 20 mass extinctions
– Five catastrophic events in which the majority
of species on Earth disappeared
© Cengage Learning 2015
17.12 Why Do We Study Evolutionary
History?
• Instead of trying to divide the diversity of
living organisms into a series of taxonomic
ranks, most biologists are now focusing on
evolutionary connections
• Phylogeny
– Grouping species on the basis of their shared
characters
– Like a genealogy
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Why Do We Study Evolutionary History?
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Why Do We Study Evolutionary History?
• Cladistics
– Method of determining evolutionary
relationships
– Group species into clades based on shared
characters
– Results in a cladogram
• A type of evolutionary tree used to visualize
evolutionary patterns
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cladogram
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17.4 Directional Selection
• Superbad superbugs
– Are we overutilizing antibiotics?
• Bacterial species are able to survive after
exposure to antibiotics
• Pathogens resistant to multiple antibiotics are
considered multidrug resistant (MDR) or
superbugs
• Serious and growing phenomenon in
contemporary medicine
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Directional Selection
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What is Macroevolution?
Notochord Lobed fins
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Long gestation
Rostral organ
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Missing
Link?
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© Cengage Learning 2015
From left: Eric Hunt, JLB Smith, the DC3's pilot, a local French
governor, and several Comorans surround the "second"
coelacanth that established the Comoros as the first home of
the famous "living fossil" in 1952.
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At a stopover on the way back to South Africa, a
nervous JLB Smith sleeps next to the "second"
coelacanth in its travel box!
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Coelacanth
Latimeria
chalumnae
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What is Macroevolution?
• Stasis
– A lineage which persists for millions of years
with little or no change
– Example: Coelacanth
• Ancient lobe-finned fish
• Thought to be extinct
• Rediscovered in 1938
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