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4.1.2-.4 Natural Selection Evolution of mammals
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http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html
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Darwin and Evolution
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Evolution are the changes in the gene pool of a population over time.
Natural selection process by which individuals that are better suited to their environment survive and reproduce most successfully.
Adaptation is an inherited characteristic that increases an organism’s chance of survival.
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Isabela
Darwin
Wolf
Pinta
Marchena Genovesa
Fernandia
SantiagoBartolomé
RåbidaPin zon
SeymourBaltra
Santa Cruz
Santa Fe
Tortuga
Española
San Cristobal
Floreana
EQUATOR
GalåpagosIslands
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Land Iguana
Marine Iguana
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FOUNDER SPECIES
insect and nectar eatersfruit and seed eaters
KAUAI AKIALAOA
AMAKIHI
IIWI
APAPANE
KONA FINCH extinct
LAYSAN FINCH
AKIAPOLAAU
MAUI PARROTBILL
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Based on his observations,
Darwin proposed that
EVOLUTION occurs by NATURAL
SELECTION.
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Darwin’s Postulates
•Variation within populations.•Overproduction of offspring.•Struggle for existence.•Unequal survival and
reproduction rates.
http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html
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Population of organisms
Limited resources leads to a struggle for survival
between offspring.
Overproduction of offspring
Survivors reproduce more successfully.
Mutations & Sexual reproduction
produces variations among offspring.
Population changes over time.
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Evolution of Mammals
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Fig. 27.19d, p. 471
DISPERSAL OF HIGHLY EVOLVED PLACENTAL MAMMALS
South America
Extinctions of many marsupials and early placental mammals
About 5 million years ago, during the Pliocene
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Nonvertebrate chordates
Jawless fishes
Cartilaginous fishes
Bony fishes
Amphibians
Reptiles
Birds
Mammals
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Fig. 27.19a, p. 471
North America
MONOTREMES, MARSUPIALS EVOLVE AND MIGRATE THROUGH PANGEA
South America
Antarctica
AustraliaIndia
Africa
Eurasia
About 150 million years ago, during the Jurassic
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Spiny anteater
MONOTREMES
Platypus
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Koala
MARSUPIALS
Tasmanian Devil
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Fig. 27.19b, p. 471
PLACENTAL MAMMALS EVOLVE; ADAPTIVE RADIATIONS BEGIN
Isolation of the early
monotremes, marsupials on
this land mass
Between 100 and 85 million years ago, during the Cretaceous
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PLACENTAL MAMMALS
Walruses
Bat
Manatee
Arctic Fox
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Beaver
NORTH AMERICA
Muskrat
Capybara SOUTH AMERICA
Coypu
Beaver
Muskrat
Beaver andMuskrat
Coypu
Capybara
Coypu andCapybara
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Fig. 27.19c, p. 471
North America
ADAPTIVE RADIATIONS OF MORE EVOLVED PLACENTAL MAMMALS
South America
Antarctica
Africa
Eurasia
Continued isolation of early monotremes
and marsupials
Extinctions of mammals
About 20 million years ago, during the Miocene
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Fig. 20.10, p. 319
RACCOON RED PANDA GIANT PANDA
DIVERGENCE approximately 40 million years ago
DIVERGENCE 15-20 million years ago
SPECTACLED BEAR
SLOTH BEAR
SUN BEAR
BLACK BEAR
POLAR BEAR
BROWN BEAR
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What is a Species?A group of potentially or actually
interbreeding populations, with a common gene pool, which are reproductively
isolated from other groups
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The problem with the species definition
The species concept is a human construct used to make sense of the natural world.
While extraordinarily helpful in understanding life, it fails to capture the
full complex reality of continually evolving populations of organisms.
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Sibling SpeciesSpecies that can’t interbreed, but have
no significant differences in appearance.
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Very different appearance that can interbreed?!
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Two tigons (male to the left, female to the right)
•
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A Liger-Lion/Tiger
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A "boblynx" -- a hybrid of bobcat and lynx;
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A "zonkey" -- a hybrid of zebra and donkey;
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• The "Toast of Botswana", -- a hybrid of a female goat to a male sheep;
A "cama" -- a hybrid of camel and llama;A "yakalo" - a hybrid of buffalo or bison and yak;A "cattalo" (or "beefalo") -- a cross of a bison with a domestic cattle;A "coywolf" -- a hybrid of coyote and wolf; A "wholphin" -- a hybrid of a bottlenose dolphin mother and a false killer whale father. Same situation like with the "pumapard" (parents belong to different genera).
Some intraspecies hybrids (both genders fertile):
A "wig" -- a cross of a wild and a domestic pig;An unnamed cross of a Siberian and a Manchurian tiger.
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tulips