Transcript Darwin PowerPoint

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SWBAT define evolution
SWBAT explain Charles Darwin’s theory of
evolution by natural selection in their own words
SWBAT describe the role of genetic variation
and adaptation in the process of evolution by
natural selection
SWBAT identify examples of natural selection
and explain how they demonstrate natural
selection
SWBAT demonstrate the process of natural
selection through an inquiry demonstration.
What determines which organisms survive
and which do not?
 Do species ever change?
 How do scientists believe all of the species
that exist today were formed?
 What evidence is there to support
evolution?
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Have the species of organisms (bacteria,
plants, animals, humans) that exist today
always existed?
Are they exactly the same as they were
many years ago?
OR have organisms changed over time and
have new species of organisms appeared?
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Humans have been
manipulating other
animals and plants
for many years.
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Think of different
breeds of dogs:
Pitbulls, Rottweiler,
Dachshunds,
Bulldogs, Labrador
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Artificial selection or selective breeding
occurs when humans breed other animals
and plants for specific and desired traits
(examples: Dogs, horses, vegetables).
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However, organisms have been changing
for millions of years.
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This topic was studied by a
scientist named Charles Darwin
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Darwin studied plants and
animals throughout South
America and the breeding of
animals in England
 Finches
 Artificial breeding
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From his studies, Darwin
determined that groups of
organisms can and do
change over time
 Evolution!
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He proposed that
sometimes these changes
may even lead to the
appearance of new species
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Evolution is the gradual change in a population
of organisms over time
 Population=all organisms of a species in one area
 Charles Darwin and many scientists have since
agreed that this happens in nature
 Individual organisms do not evolve.
Instead, evolution occurs in populations.
Charles Darwin concluded that evolution
often occurs through a process known as
natural selection
 There are 4 main principles of natural
selection
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Natural Selection
1. All organisms in a population have
different traits due to genetic variation
 Genetic Variation = differences in DNA and
traits
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Example: Most deer mice in North America
are dark brown, but some are light brown
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Why are all deer mice in Sandhills, Nebraska
light brown?
Let’s look at what happened…
Not all organisms in a population can survive.
Organisms with adaptations to their
environment are most likely to survive and
reproduce
 Review: What are adaptations?
 Which mice do you think survived more easily in
the sandy hills? Why?
 Example: Light brown color was an adaptation
(camouflage), so these mice survived
2.
Organisms that survive and reproduce
pass on the genes for their adaptations
 Example: The few light brown mice had
more time to survive and reproduce. They
passed on the gene for light brown color to
their offspring.
3.
Eventually all organisms in the population
inherit the genes and express the
adaptation
 How did the deer mice population evolve?
 What do you think the population is today?
 Example: Over time, all of the deer mice
born were light brown. Today, the whole
population of deer mice in the sandy hills
in Nebraska is light brown
4.
Over time, adaptations are inherited by all
organisms in a population
 Organisms with specific adaptations are
“naturally selected”
 Natural selection causes a population to
evolve, but it may or may not create a new
species
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 The deer mice population evolved from almost all
dark brown mice to all light brown mice.
 However, this did not form a new species
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Evolution also occurs through sexual
selection in which members of the same
species must compete for a mate in order to
successfully pass on genes.
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http://www.bing.com/videos/search?q=birds+
of+paradise+mating+dance&go=&qs=bs&for
m=VBREQY#view=detail&mid=591C6AB5C5
DA7F0168CF591C6AB5C5DA7F0168CF
African elephants typically have large
tusks. The ivory in the tusks is highly
valued by some people, so hunters have
hunted and killed elephants to tear out
their tusks and sell them (usually illegally)
for decades. Some African elephants have
a rare trait -- they never develop tusks at
all. In 1930, about 1 percent of all
elephants had no tusks. The ivory hunters
didn't bother killing them because there
was no ivory to recover. Meanwhile,
elephants with tusks were killed off by
the hundreds, many of them before they
ever had a chance to reproduce.
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. The result: As many as 38
percent of the elephants in
some modern populations
have no tusks [source: BBC
News]. Unfortunately, this
isn't really a happy ending
for the elephants, since
their tusks are used for
digging and defense.
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Pesticides are chemicals used to kill
insects that eat crops. Most insects are
not pesticide-resistant (protected),
but some insects are pesticideresistant
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What is the cause of these differences??
 Genetic variation! (different genes)
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When farmers spray pesticides on their
crops, most of the insects that eat the
crops will not survive.
What trait would be an adaptation?
Pesticide-resistance
Which insects will NOT survive?
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What do the organisms with the adaptation
do?
Insects with pesticide resistance reproduce and
pass on genes for pesticide-resistance to their
offspring
What happens to the rest of those without
the adaptation?
More of the insects without pesticide resistance
die as farmers continue to spray the crops
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Eventually what happens?
What trait do all of the surviving insects have?
 All surviving insects are pesticide-resistant
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How did the population evolve?
 From being mostly not pesticide-resistant to being
all pesticide resistant
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What is this process called?
 Natural selection!
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What problems might this cause for farmers?
Most birds on an island have fragile, thin
beaks and a few have strong, thick beaks.
 What is the cause of these differences??
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 Genetic variation!
Chunk 1: Parent Generation
Chunk 2: Environmental
disturbance
 Chunk 3: Generation 1
 Chunk 4: Remainder/Analysis
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Expectations:
 Follow along with the
procedures
Procedures
1. Ms M. will assign you to a station. Each station represents a different food
source.
 2. As a group decide which feeding implement each member will have. Each
group member should have a different feeding implement and a Dixie cup.
 3. You are now a very hungry bird. The tool you have selected is your “beak”. You
can only use your beak to pick up food.
 4. The cup is your stomach. It must remain upright at all times. You must hold
your beak in one hand and your stomach in your other hand, close to your body.
Only food that is placed in the cup by the beak has been “eaten”. No scooping
is allowed and no fighting over food with other birds.
 5. When Ms. M says “Go” you will have 30 seconds to feed (or until the food runs
out). Collect as much food in your stomach as possible until Ms. M says “Stop”.
 6. When Ms. M says “Stop”, you will empty your stomach and count the contents.
Record data in the Individual Data Table. Replace food items.
 7. Rotate to a new station upon Ms. M’s instruction. You may bring your beak with
you!
 8. Continue steps 4-7 until each group has visited each food station.
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