Download Biosc 41 Announcements 12/3

Biosc 41 Announcements 12/3
§  Turn in research papers!
§  Evolution review
§  Quiz 10- chapters 22, 23
§  Lecture: chapter 56, conservation biology
§  Lab- presentations
§  Review for final exam
© 2014 Pearson Education, Inc.
Evolution Review
§  What was Darwin’s original phrase for what we now know as
“evolution”?
§  What are the two sources of genetic variation?
§  Can natural selection create new traits?
§  Darwinian snails example: what are two limitations on shell thickness in a
population?
§  Does natural selection select for the same alleles regardless of
environment?
§  Is natural selection based on equal or unequal reproduction?
§  Does natural selection act on genotypes or phenotypes?
© 2014 Pearson Education, Inc.
Evolution Review
§  Is speciation an example of microevolution or macroevolution?
§  Is Hardy-Weinberg equilibrium common in nature?
§  What are 5 conditions of non-evolving populations?
§  No mutations
§  Random mating
§  No natural selection
§  Very large population size
§  No gene flow
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Evolution Review
§  In the Darwinian snails lab, what conditions prevented evolution
of the snail population?
§  No variation in shell thickness in the population (note- mutations can lead
to evolution under these conditions!)
§  Shell thickness was not heritable
§  Crab was not selective of shell thickness
§  In the Darwinian snails lab, what conditions led to evolution of
the snail population?
§  Variation in shell thickness in the population
§  Heritability of shell thickness
§  Crab was selective of shell thickness
© 2014 Pearson Education, Inc.
Evolution Review
§  In a population of 12,000, it is known that 12 individuals have
sickle-cell anemia.
§  What percent of the population is homozygous recessive?
§  q2 = 0.001 = 0.1%
§  What percent of alleles in the gene pool are recessive?
§  q = √0.001 = 0.03 = 3%
§  What percent of alleles in the gene pool are dominant?
§  p = 1-q = 0.97 = 97%
§  What percent of the population is homozygous dominant?
§  p2 = 0.972 = 0.94 = 94%
§  What percent of the population is heterozygous?
§  2pq = 2 x 0.97 x 0.03 = 0.06 = 6%
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Evolution Review
§  In the case of sickle-cell anemia, what factors influence whether
the recessive sickle-cell allele remains in the population?
§  Presence of malaria leads to selection of heterozygotes
§  Wet climates = more mosquitos = more malaria
§  Is the sickle-cell allele likely to decrease and/or disappear in wet
regions?
§  Is the sickle-cell allele likely to decrease and/or disappear in dry
regions?
© 2014 Pearson Education, Inc.
Evolution Review
§  Describe 4 mechanisms of microevolution:
§  Mutations
§  Genetic drift: bottlenecks, founder effects- bigger influence
in smaller populations
§  Gene flow: migration- reduces genetic variation between
populations
§  Natural selection, including nonrandom mating
§  Directional
§  Disruptive
§  Stabilizing
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Imagine a species of bird in which females prefer to mate
with brightly colored males. However, males with bright
backs are more often preyed upon by hawks. Assuming that
a wide variety of genetic variation exists in the species,
which do you think is the most likely evolutionary outcome?
a.  Males will be selected to be brightly colored.
b.  Females will be selected to choose drab males.
c.  Males will be selected to have bright chests and
dull backs.
d.  Females will not mate.
e.  The species will go extinct because the hawks catch all the
males.
© 2014 Pearson Education, Inc.
Imagine a species of bird in which females prefer to mate
with brightly colored males. However, males with bright
backs are more often preyed upon by hawks. Assuming that
a wide variety of genetic variation exists in the species,
which do you think is the most likely evolutionary outcome?
a.  Males will be selected to be brightly colored.
b.  Females will be selected to choose drab males.
c.  Males will be selected to have bright chests and
dull backs.
d.  Females will not mate.
e.  The species will go extinct because the hawks catch all the
males.
© 2014 Pearson Education, Inc.
Using the Galápagos finches example from the book, which
of the following best explains the Darwinian reason why the
insect-eating finch has such a long, narrow beak?
a.  Variation existed in the finch population. Those that naturally had
longer, narrower beaks could reach their food more easily,
allowing finches with these features to survive and reproduce
more often than those that did not.
b.  Every day, finches who needed to eat insects would squeeze
their beaks into tiny holes to reach insects, eventually changing
the shape of their beaks, which then got passed on to future
generations.
c.  Those with longer, narrower beaks carried the dominant gene for
that, which is how they evolved.
© 2014 Pearson Education, Inc.
Using the Galápagos finches example from the book, which
of the following best explains the Darwinian reason why the
insect-eating finch has such a long, narrow beak?
a.  Variation existed in the finch population. Those that
naturally had longer, narrower beaks could reach their food
more easily, allowing finches with these features to survive
and reproduce more often than those that did not.
b.  Every day, finches who needed to eat insects would squeeze
their beaks into tiny holes to reach insects, eventually changing
the shape of their beaks, which then got passed on to future
generations.
c.  Those with longer, narrower beaks carried the dominant gene for
that, which is how they evolved.
© 2014 Pearson Education, Inc.
MRSA infections are occurring at alarming rates. One
reason for this could be that people do not finish their
antibiotics. Which of the following is the most likely reason
that this could lead to something like MRSA?
a.  Antibiotics take awhile to start working, giving the bacteria time to
mount defenses against the antibiotics over a few days.
b.  Because antibiotics are often taken when there is no bacterial
infection, the antibiotics aren’t using their medicinal/antibacterial
properties and are losing them.
c.  The first few days of antibiotics kill off the weak bacteria, making
people feel better. Then, when people stop taking the antibiotics, the
strong bacteria that survived have been selected, breed with one
another, and create a stronger population.
© 2014 Pearson Education, Inc.
MRSA infections are occurring at alarming rates. One
reason for this could be that people do not finish their
antibiotics. Which of the following is the most likely reason
that this could lead to something like MRSA?
a.  Antibiotics take awhile to start working, giving the bacteria time to
mount defenses against the antibiotics over a few days.
b.  Because antibiotics are often taken when there is no bacterial
infection, the antibiotics aren’t using their medicinal/antibacterial
properties and are losing them.
c.  The first few days of antibiotics kill off the weak bacteria,
making people feel better. Then, when people stop taking the
antibiotics, the strong bacteria that survived have been
selected, breed with one another, and create a stronger
population.
© 2014 Pearson Education, Inc.
In evolutionary terms, an organism's fitness is
measured by its ________.
a.  stability in the face of environmental change
b.  contribution to the gene pool of the next generation
c.  genetic variability
d.  mutation rate
e.  health
© 2014 Pearson Education, Inc.
In evolutionary terms, an organism's fitness is
measured by its ________.
a.  stability in the face of environmental change
b.  contribution to the gene pool of the next
generation
c.  genetic variability
d.  mutation rate
e.  health
© 2014 Pearson Education, Inc.
Indicate what type of selection is occurring in the
example here: Due to less snowfall in an area,
white mice are predated on more than intermediateor dark-colored mice.
a.  directional selection
b.  disruptive selection
c.  stabilizing selection
© 2014 Pearson Education, Inc.
Indicate what type of selection is occurring in the
example here: Due to less snowfall in an area,
white mice are predated on more than intermediateor dark-colored mice.
a.  directional selection
b.  disruptive selection
c.  stabilizing selection
© 2014 Pearson Education, Inc.
Which of the following evolutionary mechanisms
increases the amount of genetic variation in a
population?
a.  genetic drift
b.  mutation
c.  sexual selection
d.  directional natural selection
e.  stabilizing natural selection
© 2014 Pearson Education, Inc.
Which of the following evolutionary mechanisms
increases the amount of genetic variation in a
population?
a.  genetic drift
b.  mutation
c.  sexual selection
d.  directional natural selection
e.  stabilizing natural selection
© 2014 Pearson Education, Inc.
A high proportion of the cats on Key West (a
relatively isolated island) have extra toes
(polydactyly). What is the most likely explanation?
a.  high rate of mutation
b.  founder effect
c.  bottleneck effect
d.  directional selection for extra toes
© 2014 Pearson Education, Inc.
A high proportion of the cats on Key West (a
relatively isolated island) have extra toes
(polydactyly). What is the most likely explanation?
a.  high rate of mutation
b.  founder effect
c.  bottleneck effect
d.  directional selection for extra toes
© 2014 Pearson Education, Inc.
Quiz 10
1.  Describe two factors that led to evolution in Darwinian
snail shell thickness.
2.  Describe two factors that prevented evolution in
Darwinian snail shell thickness.
3.  Describe two factors that limit maximum shell thickness
in Darwinian snails.
4.  Would you expect the frequency of sickle-cell alleles to
be higher in dry or wet regions of Africa?
5.  Describe two mechanisms of microevolution.
© 2014 Pearson Education, Inc.
Conservation Biology and Global Change
(chapter 56)
© 2014 Pearson Education, Inc.
HOW many species??
§  Scientists have named and
described 1.8 million species
§  Biologists estimate 10-100
million species exist on Earth
§  Tropical forests contain some of
the greatest concentrations of
species and are being destroyed
at an alarming rate
§  Humans are rapidly pushing
many species toward extinction
© 2014 Pearson Education, Inc.
§  Conservation biology, which seeks to preserve
biodiversity (the variety of life), integrates several
fields:
§  Ecology
§  Physiology
§  Molecular biology
§  Genetics
§  Evolutionary biology
© 2014 Pearson Education, Inc.
Three Levels of Biodiversity
Genetic diversity: source of variations that enable
populations to adapt to environmental changes
Species diversity: important in maintaining
structure of communities and food webs
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Ecosystem diversity: provides life-sustaining services
such as nutrient cycling and waste decomposition
§  The local extinction of one species can have a
negative impact on other species in an ecosystem
§  For example,
flying foxes (bats)
are important
pollinators and
seed dispersers in
the Pacific Islands
© 2014 Pearson Education, Inc.
Philippine eagle
Yangtze River
dolphin
Benefits of Species and Genetic Diversity
§  Species related to agricultural crops
can have important genetic qualities
§  Ex: plant breeders bred virusresistant commercial rice by
crossing it with a wild population
§  In the U.S., 25% of prescriptions
contain substances originally derived
from plants
§  For example, the rosy periwinkle
contains alkaloids that inhibit
cancer growth
© 2014 Pearson Education, Inc.
§  The loss of species also
means loss of unique
genes and genetic diversity
§  The enormous genetic
diversity of organisms has
potential for great human
benefit
© 2014 Pearson Education, Inc.
Ecosystem Services
§  Ecosystem services encompass all the processes
through which natural ecosystems and their species
help sustain human life
§  Some examples of ecosystem services:
§  Purification of air and water
§  Detoxification and decomposition of wastes
§  Cycling of nutrients
§  Moderation of weather extremes
© 2014 Pearson Education, Inc.
Threats to Biodiversity
§  Most species loss can be traced to four major
threats:
§  Habitat loss
§  Introduced species
§  Overharvesting
§  Global change
© 2014 Pearson Education, Inc.
Introduced Species
§  Introduced species are those that humans move
from native locations to new geographic regions
§  Without their native predators, parasites, and
pathogens, introduced species may spread rapidly
§  Introduced species that gain a foothold in a new
habitat usually disrupt their adopted community
§  Ex: Lionfish
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Invasive lionfish in the Atlantic
§  Likely introduced by aquarists
§  Very few predators
§  They are voracious predators!!
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Overharvesting
§  DNA analysis can help conservation biologists identify
the source of illegally obtained animal products
§  For example, DNA from illegally harvested ivory can be
used to trace the original population of elephants to
within a few hundred kilometers
© 2014 Pearson Education, Inc.
Can Extinct Species Be Resurrected?
§  Species recovery may be possible through cloning
technology if frozen tissue is available
§  Current research is underway to determine if ancient
extinct species frozen in Arctic ice can be
successfully cloned
§  Resurrection of extinct species raises ethical
questions
© 2014 Pearson Education, Inc.
Population conservation focuses on population
size, genetic diversity, and critical habitat
§  Biologists focusing on conservation at the
population and species levels follow two main
approaches
§  The small-population approach
§  The declining-population approach
© 2014 Pearson Education, Inc.
Small-Population Approach
§  The small-population approach studies processes that
can make small populations become extinct
§  A small population is prone to inbreeding and genetic
drift, which draw it down an extinction vortex
§  The key factor driving the extinction vortex is loss of
the genetic variation necessary to enable evolutionary
responses to environmental change
§  Small populations and low genetic diversity do not
always lead to extinction
© 2014 Pearson Education, Inc.
Figure 56.13
Small
population
Inbreeding,
genetic
drift
Lower reproduction,
higher mortality
Loss of
genetic
variability
Lower individual
fitness and
population adaptability
Smaller
population
© 2014 Pearson Education, Inc.
Case Study: The Greater Prairie Chicken and
the Extinction Vortex
Results
§  To test the extinction vortex
hypothesis, scientists imported
birds from larger populations
§  The declining population
rebounded, confirming that
low genetic variation had been
causing an extinction vortex
150
100
Translocation
50
0
1975
1980
1995
Year
(a) Population dynamics
1985
1970
1980
1985
Years
1990
90
80
70
60
50
40
30
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1970
100
Eggs hatched (%)
§  Populations were fragmented
by agriculture and found to
have decreased fertility
Number of male birds
200
1975
1995
(b) Hatching rate
1990
Minimum Viable Population Size
§  Minimum viable population (MVP) is the minimum
population size at which a species can survive
§  The MVP depends on factors that affect a
population’s chances for survival over a particular
time
© 2014 Pearson Education, Inc.
Declining-Population Approach
§  The declining-population approach
§  Focuses on threatened and endangered populations
that show a downward trend, regardless of population
size
§  Emphasizes the environmental factors that caused a
population to decline
© 2014 Pearson Education, Inc.
Case Study: Decline of the Red-cockaded
Woodpecker
§  Red-cockaded woodpeckers require living trees in mature pine
forests
§  These woodpeckers require forests with little undergrowth
§  Logging, agriculture, and fire suppression have reduced
suitable habitat
Red-cockaded woodpecker
Forests
with
© 2014(a)
Pearson
Education,
Inc.
low undergrowth
(b) Forests with high, dense undergrowth
§  Red-cockaded woodpeckers take months to excavate
new nesting cavities
§  In a study where breeding cavities were constructed,
new breeding groups formed only in these sites
§  Based on this experiment, a combination of habitat
maintenance and excavation of breeding cavities
enabled this endangered species to rebound
© 2014 Pearson Education, Inc.
Weighing Conflicting Demands
§  Conserving species often requires resolving conflicts
between habitat needs of endangered species and
human demands
§  For example, in the U.S. Pacific Northwest, habitat
preservation for many species is at odds with timber
and mining industries
§  Managing habitat for one species might have positive
or negative effects on other species
© 2014 Pearson Education, Inc.
Landscape and regional conservation help
sustain biodiversity
§  The structure of a landscape can strongly
influence biodiversity
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Fragmentation and Edges
§  The boundaries, or edges,
between ecosystems are
defining features of
landscapes
§  An edge has its own set of
physical conditions, which
differ from those on either side
of it
§  Some species take advantage
of edge communities to access
resources from both adjacent
areas
© 2014 Pearson Education, Inc.
Corridors That Connect Habitat Fragments
§  A movement corridor is a narrow strip of habitat connecting
otherwise isolated patches to promote dispersal and help
sustain populations
§  In areas of heavy human use, artificial corridors are sometimes
constructed
§  Corridors can also be harmful by facilitating the spread of
disease between populations
© 2014 Pearson Education, Inc.
Preserving Biodiversity Hot Spots
§  A biodiversity hot spot is a relatively small area with a
great concentration of endemic species and many
endangered and threatened species
§  Biodiversity hot spots are good choices for nature
reserves, but identifying them is not always easy- and
they may change over time/ with climate
Equator
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Earth’s terrestrial (■) and marine (▲) biodiversity hot spots
Urban Ecology
§  The field of urban ecology examines organisms and their
environment in urban settings
§  A critical area of research centers on urban streams, which
experience rapid water fluctuations after rainfall
§  Restoration of Guichon Creek, near Vancouver, British
Columbia, has allowed for the successful reestablishment
of cutthroat trout
© 2014 Pearson Education, Inc.
Earth is changing rapidly as a result of human
actions
§  Human-caused changes in the environment include
§  Nutrient enrichment
§  Accumulation of toxins
§  Climate change
§  Ozone depletion
© 2014 Pearson Education, Inc.
Nutrient Enrichment
§  Human activity often removes nutrients from one part
of the biosphere and adds them to another
§  Harvest of agricultural crops exports nutrients from
the agricultural ecosystem
§  Agriculture leads to the depletion of nutrients in the
soil
§  Fertilizers add nitrogen and other nutrients to the
agricultural ecosystem
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§  Critical load is the amount of added
nutrient that can be absorbed by plants
without damaging ecosystem integrity
§  Nutrients that exceed the critical load
leach into groundwater or run off into
aquatic ecosystems
§  Agricultural runoff and sewage lead to
phytoplankton blooms in the Atlantic
Ocean
§  Decomposition of phytoplankton
blooms causes “dead zones” due to
low oxygen levels
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Toxins in the Environment
§  Humans release many toxic chemicals, including
synthetics previously unknown to nature
§  In some cases, harmful substances persist for long
periods in an ecosystem
§  One reason toxins are harmful is that they become
more concentrated in successive trophic levels
§  Biological magnification concentrates toxins at
higher trophic levels, where biomass is lower
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§  Pharmaceutical drugs enter freshwater ecosystems
through human sewage and agricultural runoff
§  Estrogen used in birth control pills can cause
feminization of males in some species of fish
Pharmaceuticals
Farm animals
Toilet
Humans
Manure
Sludge
Farms
Treated effluent
Sewage
treatment plant
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Lakes and rivers
Agricultural
runoff
Greenhouse Gases and Climate Change
§  One pressing problem caused by human activities is the
rising level of CO2 and other greenhouse gases in the
atmosphere
390
380
370
Temperature
360
350
340
CO2
330
320
310
300
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1960
1965
1970
1975
1980
Year
1985
1990
1995
14.9
14.8
14.7
14.6
14.5
14.4
14.3
14.2
14.1
14.0
13.9
13.8
13.7
13.6
2000
Average global temperature (°C)
CO2 concentration (ppm)
§  Due to burning of fossil fuels and other human activities,
the concentration of atmospheric CO2 has been steadily
15.0
increasing
400
§  Climatologists can make inferences about past
environments and climates
§  Pollen and fossil plant records reveal past vegetation
§  CO2 levels are inferred from bubbles in glacial ice
§  Chemical isotope analysis is used to infer past temp
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§  Many organisms may not be able
to survive rapid climate change
§  Some ecologists support assisted
migration, the translocation of a
species to a favorable habitat
beyond its native range
© 2014 Pearson Education, Inc.
Climate Change Solutions
§  Global warming can be slowed by reducing energy needs
and converting to renewable sources of energy
§  Stabilizing CO2 emissions will require an international effort
§  International negotiations have yet to reach a consensus
on a global strategy to reduce greenhouse gas emissions
§  Reduced deforestation would also decrease greenhouse
gas emissions
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Sustainable Development
§  Sustainable development can improve human lives
while conserving biodiversity
§  Sustainable development is development that meets
the needs of people today without limiting the ability of
future generations to meet their needs
§  Sustainable development requires connections
between life sciences, social sciences, economics, and
humanities (interdisciplinary)
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