Transcript Natural Selection

Natural Selection
& Evolution
• TSW investigate and understand how
populations change through time,
including:
– How variation of traits, reproductive strategies,
and environmental pressures impact on the
survival of populations
– Recognizing how adaptations lead to natural
selection
– How new species emerge
Charles Darwin
• On the Origin of Species
• Sailed with the HMS Beagle
• Observations made in the Galapogos
Islands
• These observations helped him form the
theory of how species change over time
called natural selection
Voyage of the Beagle
During his travels, Darwin made numerous
observations and collected evidence that led
him to propose a hypothesis about the way
life changes over time.
That hypothesis has become the theory of
evolution (aka theory of natural selection).
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Living Organisms and Fossils
•Darwin collected the
preserved remains of ancient
organisms, called fossils.
•Some of those fossils
resembled organisms that
were still alive.
•Others looked completely
unlike any creature he had
ever seen.
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Darwin's Observations
The Galápagos Islands
Darwin observed that the Galápagos Islands were close together
but had very different climates.
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The Journey Home
Darwin observed that the characteristics of
many animals and plants varied noticeably
among the different islands of the Galápagos.
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The Journey Home
Darwin wondered if animals living on different
islands had once been members of the same
species.
These separate species would have evolved
from an original South American ancestor
species.
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Natural selection vs Evolution?
Fact:
Evolution- process by
which modern
organisms have
descended from ancient
organisms.
TheoryNatural Selection- based
on the principles of
genetics.
*Note-A scientific theory
is a well-supported
testable explanation of
phenomena that have
occurred in the natural
world.
Evidence for Evolution
• Fossil record
• Anatomy
– Homologous structures
– Analagous structures
• Vestigial structures
• Embryology
• Molecular biology (DNA differences)
What is a Population?
• Populations are groups of interbreeding
individuals that live in the same place at the
same time
• Individuals in a population compete for
resources with each other.
• Populations evolve over many generations,
individuals don’t.
How Does Evolution Work?
• Populations produce
more offspring than
the environment can
support
• The unequal ability of
individuals to survive
and reproduce leads
to the gradual change
in a population over
many generations.
Mechanism for change in a population
of organisms.
• Animals who have greater fitness survive in
environment and live to reproduce
• Random changes (mutations) can lead to
greater or less fitness
• Adaptations allow an organism to survive
better in their environment
What is an Adaptation?
Evolutionary process by
which an animal
becomes better suited
for its environment.
Physical
Behavioral
Physical Adaptations
• are body structures that allow an
animal to find and consume food,
defend itself, and to reproduce its
species.
toad
Physical adaptation
Camouflage
(use of color in a surrounding)
The chameleon can change its color to match its
surroundings. Can you do that?
Physical adaptation
Mimicry
(looking or sounding like another living organism)
The Viceroy butterfly uses mimicry to look like the
Monarch butterfly. Can you tell them apart?
I’m the Viceroy!
Not poisonous
Poisonous
I’m the
Monarch!
Physical adaptation
Chemical defenses (like venom, ink,
sprays)
Physical adaptations
Body coverings & parts (claws, beaks, feet,
armor plates, skulls, teeth)
The elephant’s trunk is a physical adaptation that
helps it to clean itself, eat, drink, and to pick things up.
Behavioral
Adaptations…
Behavioral Adaptations allow animals to
respond to life needs. They are the animals’
actions.
Behavioral Adaptations
Instinctive
These behaviors
happen naturally &
don’t have to be
learned.
Methods of
gathering & storing
food
Finding shelter
Defending oneself
Hibernating
Raising young
Learned
These behaviors
must be taught.
Adaptations
• Can arise in response to
environmental
pressures
– Temperature
– Antibiotic resistance in
bacteria
– Pesticide resistance
– Morphological changes
in peppered moths
Darwin Video
• Show Darwin Video
http://www.pbs.org/wgbh/evolution/educators/teac
hstuds/unit2.html
• Answer Questions:
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Who is Darwin?
What college did he attend? What did he study?
What book did most people read that explained creation?
How many years was he on the Beagle? How old was he?
What was the name of his book?
What was his Mechanism of change called?