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Natural Selection
Natural Selection
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What is natural selection?
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In 1858, Darwin and Alfred Russell proposed the
same explanation for how evolution occurs
In his book, Origin of the Species, Darwin
proposed that evolution occurs by natural
selection
Natural selection is the process by which
individuals that are better adapted to their
environment are more likely to survive and
reproduce than other members of the same
species
Natural Selection
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What is natural selection?
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Factors that affect natural selection
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Overproduction – Most species produce far more
offspring than can survive
There are not enough resources – food, water, living
space, for them all to survive
Natural Selection
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Type I curves
 High age-specific survival probability in early and
middle life,
 Rapid decline in survival in later life.
 Humans, large mammals
Type II curves
 Between Types I and III
 Constant mortality rate/survival probability is
experienced
 Some birds and some lizards.
In Type III curves
 Greatest mortality is experienced early in life
 Low rates of death for those surviving this bottleneck.
 Insects, marine organisms
Natural Selection
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What is natural selection?
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Formation of new species
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Isolation can cause a new species can form.
Over a long period of time, an isolated group of
individuals of a species can evolve different traits that
prevent reproduction
Natural Selection
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What is natural selection?
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Variation – a difference between individuals of
the same species
Competition – organisms compete to survive
since they must compete for living space, water
and food
Selection – some individuals are better suited for
their environment
Environmental change – a change in the
environment can affect an organism’s ability to
survive and therefore lead to natural selection
Natural Selection
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What is natural selection?
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Darwin proposed that, over a long time, natural
selection can lead to change
Helpful variations may accumulate in a species,
while unfavorable ones may disappear
Natural Selection
Environmental Change
When copper contaminated the soil surrounding the monkey
flowers, the environment changed. What do you think the area will
look like in ten years?
Natural Selection
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What is natural selection?
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Genes and natural selection – Without
variations, all members of a species would have
the same traits and same chance of surviving and
reproducing
Variations can result from changes in genes
Only traits that are inherited, or controlled by
genes, can be affected by natural selection
Natural Selection
Natural Selection
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Evolution of Man
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Years back to common ancestor of humans and *
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All humans – about 140,000 years ago
Chimpanzees – about 6 mya
Gorillas – about 7 mya
Orang utans – about 14 mya
Gibbons – 18 mya
Old World monkeys – 25 mya
New World monkeys – 40 mya
* From “The Ancestor’s Tale – A Pilgrimage to the Dawn of Life”
Richard Dawkins, 2004 by Weidenfeld & Nicolson
Natural Selection
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Evolution of Man
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Years back to common ancestor of humans and
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Rodents and rabbitkind – 75 mya
Monotremes – 180 mya
Birds – 310 mya
Sponges – 800 mya
Plants - 3600 mya
Natural Selection Classwork
1.
2.
3.
4.
5.
How do life forms change over time?
How does genetic variation contribute to the
diversity of organisms?
How long ago did the common ancestor of
all humans live?
How long ago did the common ancestor of
humans and chimpanzees live?
How long ago did the common ancestor of
humans and rodents live?
Biodiversity and Extinction
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What is biodiversity?
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The number of different species in an area is its
biodiversity
Biodiversity and Extinction
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What factors affect biodiversity?
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Area – a large area will support more species than a small
one
Climate – areas with more rainfall and higher temperatures
have more biodiversity than those with less rainfall and
lower temperatures
Diversity – diverse traits exist in individuals in a healthy
population (example: color, size). These organisms have
genes that are shared and genes that are different
Niche diversity – a niche is the role that an organism
plays in its habitat. Diverse ecosystems have more niches
Biodiversity and Extinction
The map
shows
the ranges of
Kaibab and
Abert’s
squirrels.
Biodiversity and Extinction
Park Size
The dark green area represents three different
park plans. Which plan supports the most biodiversity?
Biodiversity and Extinction
Differences in
Biodiversity
 Biodiversity tends to
increase as you
move toward the
equator because
temperatures tend
to be warmer.
Number of mammal species
in each country
Biodiversity and Extinction
Differences in Biodiversity
 Ecosystems with the highest biodiversity usually
have warm, moist climates.
 In fact, tropical regions contain two-thirds of all
of Earth's land species.
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Costa Rica is a tropical Central American country
about the size of West Virginia.
Yet it is home to as many bird species as there are in
the United States and Canada combined.
In addition, there are biodiversity hot-spots that
do not depend on latitude
Biodiversity and Extinction
Why is biodiversity important?
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For people, it provides food, medicines, and
many products.
Furniture and buildings are made from wood and
bamboo.
Fibers made from cotton, flax, and wool are
woven into clothing.
Every species on Earth plays a certain role and
is necessary in the cycling of matter.
As a result of biodiversity, soils are richer,
pollutants break down, and climates are stable.
Biodiversity and Extinction
Humans Need Biodiversity
 Biodiversity can help improve food crops.
 Crossbreeding a small population of Mexican wild
corn with the US corn crop yielded a strain of
corn resistant to a new fungal disease
 Biodiversity strengthens an ecosystem.
In a vineyard, vines grow close together,
and a disease infecting one grapevine
could easily move to another plant,
infecting the entire vineyard.
Planting alternate rows of different crops
can help prevent disease and reduce or
eliminate the need for pesticides.
Biodiversity and Extinction
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Humans Need Biodiversity
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Medicines
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Most medicines used today originally came
from wild plants
Scientists still are discovering new species.
The next plant species discovered could be
the cure for cancer.
Pacific Yew
Source of drug taxol used to treat
ovarian cancer
Biodiversity and Extinction
Extinct species
 a species that was once present on Earth but
has died out.
Endangered species
 a species in danger of becoming extinct
Threatened species
 a species is likely to become endangered in
the near future
Biodiversity and Extinction
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Why do species go extinct?
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Once the population of a species drops below a
certain point, it may not be able to recover
One way that this can happen is if a species
becomes isolated, cut off geographically from
others of its species
Another way is habitat loss, when land area
available for a species to live decreases due to
human activity
Biodiversity and Extinction
Factors affecting biodiversity
 Native and non native species
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Native species are the original organisms in an
ecosystem.
An introduced (non-native) species is one that
moves into an ecosystem as a result of human
actions.
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They often have no competitors or predators in the new
area, so their populations grow rapidly.
They become invasive species when they crowd out or
consume native species.
Biodiversity and Extinction
Factors affecting biodiversity
 Native and non native species
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Competition
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Non-native species compete for the same resources
(food, water, air, nesting sights, etc.) as native species
Limited resources
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Non-native species may use up scarce resources which
will then not be available for native species.
Biodiversity and Extinction
Factors affecting biodiversity
 Non-native species
The Australian pine was introduced
in the 1800s for lumber and erosion
control.
Because it can tolerate saltwater and
out competes many native plants,
it has taken over.
Biodiversity and Extinction
Factors affecting biodiversity
 Non-native species
The red lionfish is a
venomous invasive species
on the east coast of the US
and in the Caribbean. It has
few natural predators, “high
rates of prey consumption, a
wide variety of prey, and
increasing abundance of the
fish”
Sources: Florida Natural History Museum,
Biodiversity and Extinction
Factors affecting biodiversity
 Non-native species
The Cuban treefrog preys
upon smaller native
treefrogs and may reduce
their populations via
competition and predation
Source: Florida Fish and Wildlife Conservation Commission
Biodiversity and Extinction
Factors affecting biodiversity
 Non-native species
The Burmese python preys
upon native species and may
reduce their populations
locally.
Source: Florida Fish and Wildlife Conservation Commission
Biodiversity and Extinction
Factors affecting biodiversity
 Habitat loss
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When habitats of some species become smaller
or disappear completely due to human activity.
Habitat loss may be due to divided habitats,
when a habitat is divided by roads, cities, or
farms.
May reduce biodiversity.
Biodiversity and Extinction
Factors affecting biodiversity
 Habitat loss
The Key Largo cotton
mouse has become an
endangered species.
The building of houses,
roads, and hotels is
reducing the mouse's
habitat (and pythons).
Biodiversity and Extinction
Factors affecting biodiversity
 Habitat loss
The Florida black bear
is the only subspecies of
black bear living in a
subtropical region.
Habitat loss and bears
being injured or killed by
motorists is another
threat to regional
populations.
Source: Wikipedia/wiki/Florida_black_bear
Biodiversity and Extinction
The Bartram scrubhairstreak butterfly is
endangered because
its habitat, the place
where it lives, is being
destroyed.
One place where this
butterfly lives is the
Richmond Tract, a pine
rockland next to
MiamiZoo.
Biodiversity and Extinction
The Florida
bonneted bat, also
endangered, lives
in pine rocklands
The Miami Blue
butterfly is
endangered
because its coastal
habitat is being
destroyed by
development.
Biodiversity and Extinction
The Miami Tiger
beetle, also
endangered, lives
in pine rocklands
only in Miami
An endangered
plant species, the
deltoid spurge, is
a pine rockland
resident.
Biodiversity and Extinction
The Florida Key
Deer is
endangered; they
live mostly on Big
Pine Key.
Biodiversity and Extinction
The Florida
Panther’s habitat is
being lost and it is
endangered.
Biodiversity and Extinction
Slow Down for Panthers!
Road signs such as this one warn drivers in Florida to watch out for
panthers in the road.
Update
As of November 2014, 19 panthers had been killed by cars in
South Florida
Biodiversity and Extinction
Florida Panthers
This pie chart shows the causes of death for Florida panthers
between 1997 and 2007.
Mass extinctions – past and present
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Over the geologic time of the Earth, there
have been five mass extinctions
In a mass extinction, there is a widespread
and rapid decrease in the amount of life
on Earth
Here is a list of the five and their possible
causes
Cretaceous–Paleogene extinction event (K-Pg event;
formerly K-T event)
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66 mya
Likely Cause: Impact event
About 17% of all families, 50% of all genera and
75% of all species became extinct.
In the seas it reduced the percentage of sessile
animals to about 33%.
All non-avian dinosaurs became extinct during that
time
Mammals and birds emerged as dominant land
vertebrates in the age of new life.
Triassic–Jurassic extinction event
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200 mya
Cause: Global warmimg
About 23% of all families, 48% of all genera (20% of
marine families and 55% of marine genera) and 70% to
75% of all species went extinct.
Most non-dinosaurian archosaurs, most therapsids, and
most of the large amphibians were eliminated, leaving
dinosaurs with little terrestrial competition.
Non-dinosaurian archosaurs continued to dominate
aquatic environments, while non-archosaurian diapsids
continued to dominate marine environments.
Permian–Triassic extinction event
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251 mya
Cause: Massive volcanism? Sea level fall? Global
cooling?
Earth's largest extinction killed 57% of all families, 83%
of all genera and 90% to 96% of all species
(53% of marine families, 84% of marine genera, about
96% of all marine species and an estimated 70% of land
species, including insects).
Ended the primacy of mammal-like reptiles.
In the seas, the percentage of animals that were sessile
dropped from 67% to 50%.
"Great Dying".
Late Devonian extinction
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375 – 360 mya
Cause: Sea level fall? Anoxic event?
A prolonged series of extinctions eliminated about
19% of all families, 50% of all genera and 70% of all
species.
This extinction event lasted perhaps as long as 20
Ma, and there is evidence for a series of extinction
pulses within this period.
Ordovician–Silurian extinction event
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450–440 Mya
Cause: Sea level fall? Global cooling? Anoxic
event?
Two events occurred that killed off 27% of all
families, 57% of all genera and 60% to 70% of all
species.
Together they are ranked by many scientists as the
second largest of the five major extinctions in
Earth's history in terms of percentage of genera that
went extinct.
Holocene
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Ongoing
Cause: human activity
Sometimes called the Sixth Extinction
Proposed to describe the extinction event of species that
has occurred during the present Holocene epoch (since
around 10,000 BCE) mainly due to human activity.
The large number of extinctions span numerous families
of plants and animals including mammals, birds,
amphibians, reptiles and arthropods.
The present rate of extinction may be up to 140,000
species per year.
Biodiversity and Extinction Classwork
1.
2.
3.
How do new species form?
What factors affect biodiversity?
What are the ways in which a species can
become extinct?